O/K here's the skinny from me, a guy who has made many Slim Jim antennas for friends involved with emergency preparedness. The ones I make are roll-up versions with a BNC connector on the end of a 15 foot feed line (RG-58). Adapters go from that to connect to the myriad of antenna connections on hand held radios. The first one I made I hung from a hot air duct in the basement of my home in Victoria BC Canada. I hooked it to my Icom 91A hand held and pushed the PTT button on a local repeater. Easy pickings, a piece of wet string should work. It came up fine. I then tried some more distant repeaters and all were good so far. I thought that I would just go and try the Abbotsford repeater in the Fraser Valley about 92 km away. It came up. I asked for a reply for a test and a ham got back to me. He said I was a little noisy but readable. I told him how far away I was and where and that I was amazed he could hear me at all. Anyway me and the fellows I sometimes work with have all had great experience with these. The one I build is made from TV twin lead formerly sold by Radio Shack in the US. It has a thin plastic insulation over a white foam plastic core (too bad the Shack is gone). I have a 500 foot spool of twin lead I got via eBay and have not had success in getting my measurements correct for cutting it so far. Velocity factor is the problem. Different feed lines of the same impedance can vary quite a bit and so cutting lengths have to be adjusted to suit. If you can get a nicely tuned Slim Jim you likely won't be disappointed. A very appropriate thing for a grab and go kit
Based on this great review I bought one. Not the same make, but man, I am impressed with it. To give an idea of why I love it. I get crystal clear reception and transmit from a repeater that is 47 miles away from my home as the crow flies. What makes this impressive is that I live in London, UK. The antenna is suspended out of my second floor bedroom window and the radio is a Baofeng UV5R that cost me £20 from eBay. The Slim Jim cost me £10 sterling including shipping from the States. So the whole set up cost me £30. I did buy a bigger battery for the radio later but I forget how much that cost. It was still cheap and sent from China. This is a fantastic design but it MUST be kept away from metal to work well. So thanks man. You put me onto a terrific antenna. Happy new year to you and all who you love.
I purchased one of these antennas from N9TAX. ARES was called out in my region a week ago. As an ARES member, I was deployed to a hospital to provide emergency communications. I used this antenna exclusively during the deployment and can vouch for it's performance. If I could only pack one antenna for 2 meters/70 cm, it would be this antenna. 73
@12:30 I went and sealed my ends with the liquid electrical tape stuff, and I used another little piece of the shrink wrap tube for the gap. It works great I measured a SWR of 1.0044385:1 lol, return loss of like 52dB so I would say it should work jut fine
@photofudge Congrats on your license. I'm gearing up onmaking a vid about camoflauging the slim jim, or making it hide in plain site. will be experimenting with various pipes and enclosures along with the effects of mounting it close to structures. I'm sort of curious about the subject too. I just gotta find the time that I dont have, but the vids will come. Thanks for watching.
yes, it will work. I've seen professional installations mount their antenna upside down to direct the signal mor in a downward direction. you'll loose a little bit of range but not enough to make a difference. Just make sure the antenna is clear of close objects horizontally, it does not like neighbors. Your profile name gave me a chuckle or two.....
Great video on this antenna! I have had 2 of them for a while and they work great. However, like everyone in Ham Radio, I'm constantly looking to improve my antenna setup. I'm looking at the Diamond X50 base antenna to replace my Slim Jim as the base antenna. Do you think it would perform better than the Slim Jim? Any personal experience with the X-50? Thanks!
Nice review ? What type of cable is provided with this antenna ? Looks like RG-58U, or is it a more expensive cable, like a foam cable or something like that ?
Enjoy video,like your straight forward approach very easy to understand.The only thing I could find wrong with this antenna due to the lower angle of radiation is when used is hilly terrain and your at the bottom of hills surrounding you its a lot harder getting your signal out,that say a quarter wave ground plane antenna mounted low (quarter wave has an higher angle of radiation).But I did find as long as you mount them high up and clear as you said in practice they work really well,I built a 2m (450 ohm ribbon feeder) and was very impressed with performance and got about 10mhz bandwidth in vhf range,that's about 143 to 153mhz.Cant wait too see your antenna enclosure follow up vid,that's something like to try!Cheers!
Could you please make some measurements ? Length of TOP, MIDDLE and BOTTOM section. Length of TRAPS and measurements how far is gap from bottom big that gap is? And how far from bottom is coax cable connected? Thank you very much.
Thank you for these very informative videos. I am purchasing a Yaesu VX-7R as per your recommendations in other videos. I just received my Technician class license and look forward to getting on the air besides through Echolink. I really appreciate this video, due to limited budget and apartment living, this looks like it will be my best option for an external antenna. Please keep the radio videos coming, I would love to see more about maximizing the VX-7R and radio in general. Thanks GG ...73
This seems to be a winner. I am just wondering if you guys know, would it be ok to hoist this thing up inside an old windsurfing mast made out of fiberglass? I have saved a couple of masts since i just couldn't make myself throw them away. Would be nice up on top of the roof of my house. I already have a good mount, while the old satellite tv dish is coming down, ot now sits on the chimney. The fiberglass mast wall is just about 2mm's in thickness. I am new to this, so sorry if this is a silly question. thanks
I love all your videos, bro. However, this one in particular has been very informative and really helped me understand quite a bit. Even though I got my general ticket I'm still very much a novice. Been in fire and EMS four decades but like you said in another video I never really cared for the science of radios, all I needed to do was talk to dispatch and other mobile units. Thanks to yourself, USNERDOC, Comms Prepper and a couple of others, I caught the bug, and now I'm a ham. keep up the great videos. '73. -KD0TLN
I just bought this from you . it doesn't say gmrs on it. It says dule band ??? .my midland mxt 115 gets hot when I use it . I am very confused on what to try next . I joined a repeater club just can reach or after 3 radios later and 4 antennas .please advise thank you much
Great explanation of how it works. I looked into the making of these, and you are right for the cost its a great buy. I am ordering a second one to put up on my house and one and keep one for the bug out kit. Thanks for sharing.
Thanks for this. Just ordered one. Going to use it with my new cheapo Baoefeng when it gets here. Very inexpensive portable setup. Again, appreciate the work and thank you.
Kudos for making a video with so much enthusiasm. I enjoyed it, Though I agree with a lot of what Dan Nelson says regarding keeping the science intact within the hobby and to keep it sacrosanct, I have some major doubts about some of the things he and you both state. For instance, Amateur Radio has NEVER been in danger of dying out. Also, as far as the 'No-Code' licenses now available--that was all a major push by the manufacturers who were all virtually screaming that they could not stay in business because of the limited number of new Hams each year. Obviously, their profits would soar to even higher extremes were there no license requirements at all. But there's something to be said for that as well, since they are making some mighty fine radios these days. I'm in my mid-sixties and have been a Ham for nearly 5 decades now--I am here to tell you that virtually all the whining about anything to do with Amateur Radio/CB/FRS in this country amounts to storms in teacups. As I say though, I agree with much of what Dan has said--since there are many good reasons--including lots of *safety* reasons--why one should have to study to obtain a proper license, with the consequent knowledge one gains from doing so. I still have creepy visions of a trucker who, when busted, was radiating nearly a KW throughout the cab of his big rig, while his wife and daughter sat shotgun, virtually swimming in stray RF. The fellow had absolutely no clue. Again though, thanks for this video--I enjoyed your enthusiasm. Keep up the good work!
safety has nothing to do with why you need to get a license, i used to think that, but the truth is you can be a legally blind and still get your license, anyway just wanted to drop my two since, oh and if they never dropped the code requirements ham really would be dead by now
TexasPrepper86 Garbage. That may be true for Texas, Cletus, but there are dozens of other countries out there that require even tougher testing and Ham Radio is more vibrant than ever--even in places like China, Japan, Philippines, Eastern Europe and on and on. Of course, if you were a Licensed Amateur, you'd know that. As for 'safety not having anything to do with it', sounds like the same logic halfwits with guns keep using even though they keep shooting each other "accidently". Good luck with that cornpone logic there, sport.
You got pretty close with your description. The section below the gap is an impedance transformer from 50ohms to about 3000ohms - this section does not radiate. The top section on 70cm is a single half-wave up to the trap - as you say this is the only radiator on UHF. On 2m the top section is two voltage-fed half-waves in phase, with the 2nd half-wave section folded down parallel with the first one, so as to align the two sine waves, or else they will cancel. The stub cuts off at UHF because it is a shorted 1/4 wave - remember this "a shorted 1/4 wave stub appears open, and an open 1/4 wave stub appears shorted." Connect a shorted 1/4 wave to your analyser and sweep it and you will see. Cut the short off the end and leave it open, and sweep it again - you will see a big notch either high impedance or low impedance. The notch repeats at odd harmonics. Thanks for teaching and showing stuff.
it's a shame the details on the traps were not given, like the printing on the cable and the length they are cut and how they are connected if they are coaxial cable, then it can be replicated
Aye you're right, you've caught me out, you need to notify the man on the video aswell because he's mentioning traps. BTW I now have the details on the antenna construction, it's rg174 coax, and you could make one for less than $22 , here you go chaps...... drive.google.com/open?id=0BwXBqGcnxnlSRktpdWxQTU10TXc
I once made one of these for 10meter. It's hosted up a tree with the top of antenna at approx. 80 feet. It's on top of a mountain here in Washington state. Drive up, park, run a feed to base of tree where you will find a pleasant SO 239 waiting. Worked Spain on FM simplex with it.
Randy S. Sweet, I bet it works extremely well, I have been using a slim Jim for VHF since I was licensed just over 20 years now, i did contemplate modifying it to a super J pole but never did. I always did wonder what a 10m version would work like .
how accurate is that? it appears the 174a traps run on both sides in the n4tax design and they appear to be cut at the same length. the jpg only shows the 174a on the 1/2 wave side
Anything is possible but in this case not practical. The metal of the car will seriously de-tune the antenna. the slim jim folded dipole design like to be free from near objects. I have 2 other videos that show detuning of the antenna when placed near PVC, ABS, fiberglass tubing.
Beware over hyping the gain claims. Search for J-pole antenna on google and read the Wikipedia article which contains solid references to back up the text.
to split some hairs the section below the notched side is about 1/4 wave of 2m and is used for impedance matching. above the notch that is 1/2wave for 2M. www.n9tax.com/Slim%20Jim%20Info.html third image down gives a great explanation.
Beware of na-sayers who come here from ham shops who don't want you to build these yourself. I know that these work because I've been seeing them in many ham shacks since the 70's. I'm a little unsure of the chokes that were used and how they work with this antenna, this is the first time I've seen that. It would have been nice to see an SWR test on this one.
+Grant Aldrich Its alright, sometime we need some nay sayers to keep us in check. It just compels me to follow up with an update video with some A-B comparisons with other antennas to find out what the truth is when it gets warmer. SWR will be included too. Thanks for watching.
I built one of these, it only works when I disconnect the "ground" from the Baofeng, ie with the pl-259 connected to the radio center pin only. Can you tell me why that is happening?
GUERRILLACOMM I took it apart and it turns out the antenna cable I used was shorting inside the connector. It was an intermittent problem and never happened when I used this cable for my CB... you live and learn. Thanks for the reply.
I dunno about the amp, but this unit is rated to 100W so it should be fine if not entirely necessary. I use mine hung up on a balcony with a handheld. Works like a charm.
Dan Nelson said: "The J-pole has since been [modeled] by recognize[d] experts in antenna modeling and these new models have withstood pear review. I urge you to take a look at W8JI's J-pole modeling page and review the data presented. There are many more but that's a good start." They haven't withstood further review by actual professional antenna designers some of which is referenced in the excellent J antenna wiki article en.wikipedia.org/wiki/J-pole_antenna. W8JI makes some relevant points to be sure, but further analysis and actual chamber measurements suggest so long as you heed W8JI's warnings and adequately address feedline and mounting structure current issues, the J antenna works quite well and slightly better than the often referenced 1/4 wave GP monopole antenna. In other words, there is a payoff with the J antenna over a 1/4 GP. To augment Guerrillacomm's observations in this video, we actually did test an N9TAX dual band antenna and will be posting the results at some point. For now I will summarize below... VHF: At VHF the antenna works pretty darn well yielding about 2.5 dBi H-plane gain (freespace) plus or minus the usual small J antenna swing in gain. This jives perfectly well with accurate modeling for SlimJim style antennas. I was suspicious of the ferrite choke working at VHF, but our testing confirms it does mitigate current flow back down the feed line. As there is no conductive mounting structure to worry about, there are zero issues with those, otherwise troublesome, currents. The conclusion of VHF performance is the N9TAX is as good as any dipole in free space with no apparent interactions with the feedline to spoil things. This is the best an antenna of this length can be and it nails it. Bravo N9TAX. UHF: Unfortunately the performance at UHF was questionable. It tunes very well for the 440 band, but even a basic hand test reveals the existence of rf current along the feedline. This suggests the choke just isn't up to the task of functioning at such high frequencies. This is no surprise as ferrite choking at these frequencies is hard and this example proves the point. The other problem found is the Ed Fong inspired inline coaxial chokes in the upper radiator appear to have negligible effect. We found UHF rf currents flowing just fine above the chokes - not good. The measured E plane antenna pattern shows the classic uptilt beam pattern of a 3/2 wavelength antenna. Of course in a pinch the N9TAX dual band antenna will function at UHF, but with reduced gain towards the horizon. N9TAX antenna knowledge in question: While N9TAX knows how to mechanically build an antenna exceptionally well, his actual antenna knowledge beyond copying other designs and how to tune them up is lacking. This is very apparent with his 6 dB gain claim (note the lack of dBi) on his web site and zero antenna patterns of any kind: simulated or measured. The whole SlimJim 6 dB over something-or-other kerfuffle is a myth that just won't go away and Joe is just another victim of it with his parroting of the obviously nonsensical gain claim of what is essentially a simple dipole. In his defense, quelling that myth on the Internet is like playing whack-a-mole. As for the failure of the inline UHF coaxial chokes, Joe is obviously relying on Fong's design to bear fruit so cannot be blamed in trusting Fong's promises. However, if you are selling antennas, you really need to confirm their performance if you are making performance claims in your sales literature. Conclusions: The Fong inspired VHF/UHF rollup antenna by the well intentioned N9TAX, works very well at VHF and has compromised performance at UHF no better than a single band version run at its 3rd harmonic. I always wondered why Fong only showed the "before" antenna patterns and not the patterns of the resulting design in his DBJ-1 and DBJ-2 articles. I was quite surprised at the failure of the UHF chokes and now see this as evidence no one has ever measured and published gain pattern measurements of these antennas. The findings above are reality as best as we can measure them and we are confident in our ability to properly critique and measure any antenna design. It's what we do for a living. The construction quality of the N9TAX antennas is so fantastic, I hope Joe can work through a design change to yield a real dual-band antenna meeting realistic specifications. Until that happens, only his VHF monoband versions function as designed.
What this is, is a JPole. :) I have constructed these for 10 Meter. Pull one up a tree!! Also, as Colinear at 2M. Meaning two 1/2 wave stacked. (The Super Jpole as it is known)
The N9TAX design is based on the SlimJim design which has nearly identical performance (at the lower design frequency) to the J antenna. The lower take off angle myth is based on a now well known misrepresentation of Judd's original article. The wikipedia article en.wikipedia.org/wiki/J-pole_antenna is a well referenced summary.
fiberglass conducts so not good to put slimjim inside i did read its a no no (UPDATED> I was wrong its Carbon Fibers you need to avoid, read below> SORRY!)
+truthseekers666 Hmm well we might want to inform the military and radio manufactures that they don't know how to build antennas or radios. The military and commercial radio services have been using fiberglass radomes for decades. You can take a trip to any marina and see commercial ships with fiberglass enclosed antennas and radars with fiberglass radomes, Or how about the airport or your local police dispatch I'm sure you will see many examples of antennas enclosed in fiberglass radomes.. Fiberglass is actually a very good insulator and is completely transparent to RF. Proof of this is the fact that the PC boards in every radio built today are made from fiberglass.. Carbon fiber on the other hand has graphite in it and should never be used in antenna radome construction and that's where I believe the confusion regarding fiberglass started.
+Dan Nelson Sorry your correct im getting mixed up between my glass fibers and my carbon fibers. Doh. Thanks for pointing that out. I tip my hat to you.
+truthseekers666 Not a problem, it's nice to meet someone on the internet with enough integrity to admit an oversight. I must say it's refreshing. Don't feel bad, unfortunately there is so much disinformation floating around youtube and blogs that it's sometimes hard to know whats fact and whats opinion. Personally if the source doesn't have an ISBN number and published by a reputable publisher then I carefully scrutinize the contents for snake oil. 73 and Good DX.
The focus was the short comings of this antenna design and how it was dealt with by the maker, not the full functioning of the ferrite ring and all its application. For example, Toilet paper is made to wipe my ass, or make cute origami teddy bears in a video about human waste. Stay in context & focus.
Nice video very informative. I have one of those up in my loft, I get some very good reports about it. Just ordered another from eBay so wont be long until it arrives that one will go up in the back garden. M6YMN
6db of gain does not give you 4 or 5 times more anything. It is a good antenna, but not FIVE times anything, and you didn't say 5 times more than what? Six db of gain is 1 s unit....
+Jeff Wimmer (Mustang) If you look at the specification sheet for an antenna, you will typically see units for antenna gain listed in dB, dBi or dBd. dB - decibels. 10 dB means 10 times the energy relative to an isotropic antenna in the peak direction of radiation. dBi - "decibels relative to an isotropic antenna". This is the same as dB. 3 dBi means twice (2x) the power relative to an isotropic antenna in the peak direction. dBd - "decibels relative to a dipole antenna". Note that a half-wavelength dipole antenna has a gain of 2.15 dBi. Hence, 7.85 dBd means the peak gain is 7.85 dB higher than a dipole antenna; this is 10 dB higher than an isotropic antenna. 3 dB is considered doubling. In this case, the claim of 6 dB gain means 3X an isotropic antenna in the peak direction of radiation. or roughly 2X a Dipole.
dB without reference is meaningless and reveals unprofessional antenna specifications either hiding poor performance or, more likely, reveals lack of technical understanding of the writer using such units. The claim "6 dB" does not necessarily mean 4x ( not 3x as you suggest) over an isotropic antenna as the reference is ambiguous. So... dB - they are hiding their ignorance or lack of performance. It's also important to know whether or not a gain figure is in freespace or not.
These antennas are nothing new I remember building my very first slim Jim over 40 years ago, I've learned a lot since then. One of the things I've discovered is that J-pole's and slim Jim style antennas are nothing but snake oil. It has been proven by some of the worlds most well respected antenna authorities, such as Cebic, W8JI, Bill Ore.... that the original J-pole and slim jim antenna models were badly flawed and that the original gain and radiation angles claims were erroneous at best. In other words the performance claims regarding the J-pole and slim Jim style antennas did not pass the peer review system. Unfortunately that doesn't seem to have stopped people from continuing to spread false information based on that original faulty modeling. More accurate antenna modeling and range test performed by well respected experts in the field have proven that a simple 1/4 wave ground plane actually outperforms a J-pole by at least .5 db that's right a J-pole or slim jim actually has negative gain as compared to a simple ground plane antenna, My own testing has backed this up. Ever wonder whey Dr.fong the maker of one of the most popular J-poles refuses to use any real science to back up his advertising claims but rather resorts to snake oil salesmen style tactics such as using questionable "testimonials" Hmm you would think a Dr with a PHD electrical engineering could provide some solid math and science to back up his controversial advertising claims. Also it's nice of you to try and explain antenna theory unfortunately all you've really managed to do is demonstrate your ignorance on the subject. for example your claim that home brew antennas are the reason for common mode or feed line radiation. The reason J-poles suffer feed line radiation has nothing to do with the home brew style antenna but rather that the J-pole/slim Jim is a Marconi style antenna and Marconi style being highly unbalanced antennas with no feed line decoupling are notorious feed line radiators .. The only thing good about a slim jim or J-pole is that they are better then the rubber duck antenna on your HT. the fact that they can be rolled up and stored in a backpack also is a benefit other then that they are a very poor antennas especially for base station type use. One last thing a single Ferrite bead is just barely adequate for 5 watts. On a Marconi style antenna you're going to need a minimum of at lest 7 and more like 10. The problem with using Ferrite beads or whats known as a common mode choke on a J-pole is that it will kill the antennas performance. Considering that feed line radiation is where most of the RF energy is radiated from on a J-pole. By the way I went to ebay and priced out the parts, you can build 5 of these slim jims/ J-pole style antennas for what you spent on one.
+Dan Nelson Damn it, now your gonna force me to run comparison tests between slim & 1/4 wave. It should be a good follow up to prove to myself what's going on instead of taking your word on the subject. For all I know, you could also be regurgitating someone else's opinion on your bit too long post that I almost did not have the patience to read. I did not claim this was the best antenna in the world, only that it was a good inexpensive field expedient antenna that could also serve as a home base antenna for preppers, nothing more. I did mention it was a garbage UHF band antenna. Not preaching to the choir here just translating geek lingo into plain talk for beginners. Not scare them away with technical details, such as your long winded post, that will deter any interested new viewer.
GUERRILLACOMM "such as your long winded post, that will deter any interested new viewer" Good I hope it does, if they have no interest in learning radio, electronics and antenna technology and the math that goes along with it then we don't need nor do want them in the ham radio service. Let them go play cop or solderer of fortune or political activist on FRS and CB where lids and wackos like that belong. We really don't need or what a bunch of political extremest, conspiracy theorists and wannabe cop whackers subverting the ham radio service and destroying our hard earned reputation that took decades to build As the old ham radio saying goes " No Lids, Kids or space cadets" AT one time the ham radio service was well respected for our technical knowledge and electronics skill, The country knew that our skills would be invaluable in times of national emergency. I'm not so sure the same could be said of today ham radio appliance operator who couldn't define resonance or build a dipole without google and who don't seem to understand the difference between subjective personal opinion and fact based on empirical evidence based on scientific testing. Once again the last thing the ham radio service needs is a bunch of cber's and appliance operators subverting the the ham radio service and destroying decades of hard eared reputation. Instead of focusing on dragging a bunch of technically illiterate people into the ham radio service, people who have no interest whatsoever in learning radio electronics and theory we should instead be focused on maintaining our reputation as skilled technicians and that means quality vs quantity. Again I have no issue with people who are electronically illiterate yet sincerely interested in learning the science behind radio. On the other hand I despise people who propagate subjective personal opinion as scientific fact.
+Dan Nelson Well, well, well... The beast reveals itself of its true colors of elitism, condescension, and good old fashion curmudgeon-ness. Listen, if it wasn't for the dropping of the morse code requirement, the ham service would of been less than a quarter of what it is now and the FCC would of had enough justification to gobble up most of the good frequency band from the ham service for profit. I don't exactly see a constitutional right protecting the airwaves like the 2nd amendment protecting the right to bear arms. Us CB'ers, whackos, activist, and my personal favorite and proud card carrying member of the space cadet brigade are here to stay and use your beloved ham service in many ways not intended or fathomed by the traditionalist ham hobby-er just CQing from a shack. Us technically illiterate users breathed new air into a slowly dying hobby and you must admit the numbers will prove that fact. You could also thank the chinese for cheaper access to the ham and public safety frequency band for the uninformed who will undoubtedly stumble upon interfering with those frequencies. I'm here to inform those users on how to operate legally or at least enough to know what not to do to interfere. Whether you or I like it or not, unauthorized use is going to happen, might as well steer the traffic safely out of the way. But no, you prefer to stew, complain, sit back and watch it happen. Now if you don't mind, I have a tin foil Spartan helmet to finish making before I man my patio with my AR15 locked and cocked waiting for the zombie horde.
"and the FCC would of had enough justification to gobble up most of the good frequency band from the ham service for profit." Once again you demonstrate your ignorance, The frequency’s the ham radio service occupies are protected by international treaty and can only be used for either CB or ham radio use.. Hams are allowed exclusive use of most of these frequency’s to practice their “radio art”. At one time this exclusive use was justified because the ham radio service provided a valuable asset to the nation. The dumbing down of the ham radio service has changed all this. The average ham no longer has the tools nor education or skill to provide any value whatsoever to the nation, What’s worse is this new generation of hams have no desire to educate themselves. Many such as yourself wear your ignorance as though it were a badge of honor. So ask yourself what value or asset does the ham radio service today provide to the nation that justifies our existence and use of the valuable frequency’s we occupy and use for free. NONE !! that’s the answer !! Like I said before we’ve seen this happen in the past. If you want a peak at ham radios future All you need to do is look at the joke CB has become. CB is loaded with nothing but a bunch of slackers and right wing illiterate buffoons making idiots of themselves on the air, these CB fools are the reason hams have to deal with antenna restrictions. If we wanted to save ham radio, then we should have focused on science and education in an attempt to maintain an elite reserve of electronics technicians skilled in radio theory, practice and repair that we as American’s could have been proud of and who we count have relied on as an asset in times of emergency, Quality vs quantity that’s what we should have focused on. Instead the ham radio manufactures lobbied the FCC to drop the code requirements and publish the answers to the licensing exams and in the process handing out tickets to people who knew nothing about electronics and had no interest in learning, They did this so they could sell more products. The end result is the ham bands are now loaded with a bunch of lids that couldn’t build a simple dipole or wire j-pole without googling it. Exactly what kind of asset are these people going to provide to the nation during an emergency. The fact that you had to go out and actually buy a J-Pole is testimonial to your own ignorance. I built my first J-pole when I was 12 years old, I built my first tube amp when I was 16. This pursuit of knowledge enabled me to graduate in the top 1 percent in my class at Radioman’s “A” and “C” school The vast majority of new hams today are so technologically illiterate that they are easily fooled by snake oil salesman who easily cons them out of their hard earned cash on antennas that defy the laws of physics using bogus gain claims and testimonials. Anyone with even a shred of technical knowledge should recognize that the information being posted on internet blogs regarding these antennas is nothing but snake oil. Then again we are talking about a group of people who think education is too elitist. As a result they remain so technologically illiterate that they buy into this snake oil hook line and sinker and are proud of it. Yup dropping the code requirement and publishing the answers to the ham test sure did wonders for the service. The influx of new hams are so damn illiterate they have single handedly turned American hams into a world wide laughing stock, What was once a highly regarded radio service is now a world wide laughing stock. As a result American hams for the first time in history are shunned and laughed at by the rest of the worlds hams, So yeah thank you so much.. At one time I was proud of my Extra class ticket now I look at it and realize it’s not worth the paper it’s printed on, At least for the time being I can still be proud of my commercial radio ticket and my MSEE at least they’re still worth something. American hams are so looked down upon and disliked by the rest of the world that It’s the first time in my life I’ve ever heard DX stations and dxpeditions regularly and purposely refuse to work American hams. What ham radio is attracting today is a bunch of slackers who are too lazy to pick up a book and educate themselves, instead they look at blog posts and youtube videos where yet more technologically illiterate people spread subjective personal opinion as scientific fact. Sound familiar ? it should ! it’s CB all over again. " CB'ers, whackos, activist, and my personal favorite and proud card carrying member of the space cadet brigade are here to stay and use your beloved ham service in many ways not intended" Yup everyday the whole world hears these morons making complete idiots of themselves, and yet they can’t figure out why people are laughing at them What sad is that you are so full of yourself that you don't realize the FCC is already planning on removing the licensing requirement for ham radio and reclassifying it as part of the CB radio service. Yup not sure when it’s going to happen, but they just removed the fee for the vanity call so it’s coming soon. Scuttlebutt has it that they plan on opening up the phone bands to everyone. A ham radio ticket today isn't worth the paper it's printed on, Oh wait they stopped printing licenses out this year as well ? Hmm ever Wonder why.. here’s a clue the license to operate Ham radio on phone is going away, thankfully I think they are going to at least preserve the CW sub ands. So while they did away with the CW requirement in effect what’s going to happen is the only modes that’s going to be available to hams exclusively is going to be CW and low bandwidth digital so If you want to continue to use your ham ticket you better brush up on your CW Once again in case you missed it, Rumor has it that the FCC plans on keeping the CW bands for use by licensed hams and that they plan on opening all phone bands from 160m to 70 cm and reclassify it as part of the unlicensed CB service. Once again the CW sub bands will be retained as well as anything above 70cm for ham radio use. Everything else will be reclassified as CB, still not sure if they plan on opening up the whole two meter 70cm bands or just the phone portions of those bands. Either way the writing was on the wall years ago. What did you think was going to happen, the Ham radio service at one time was a valuable asset unfortunately that was back when most hams actually knew something about electronics and radio. As you have demonstrated hams today are nothing more than appliance operators who wouldn't know a base from an emitter or know how to read a smith chart, heck hams today can’t even build a simple dipole yet people like you are proud of your ignorance and yet can’t figure out why the whole world is laughing their ass's off at you. Here’s a clue stope being a slacker quit being so proud of your ignorance and try picking up a book and educating yourself.. But we all know that would never happen because education, skill, knowledge and science is considered far too elitist by neanderthals who glorify ignorance and wear their illiteracy as though it were a badge of honor.
+Dan Nelson I'm done with you sir. Not that its an admit of defeat, you're just not worth the time to waste. I didn't even read your comment. Just go to bed thinking there are thousands of ham radio operators you despise polluting your precious HAM service.
O/K here's the skinny from me, a guy who has made many Slim Jim antennas for friends involved with emergency preparedness. The ones I make are roll-up versions with a BNC connector on the end of a 15 foot feed line (RG-58). Adapters go from that to connect to the myriad of antenna connections on hand held radios. The first one I made I hung from a hot air duct in the basement of my home in Victoria BC Canada. I hooked it to my Icom 91A hand held and pushed the PTT button on a local repeater. Easy pickings, a piece of wet string should work. It came up fine. I then tried some more distant repeaters and all were good so far. I thought that I would just go and try the Abbotsford repeater in the Fraser Valley about 92 km away. It came up. I asked for a reply for a test and a ham got back to me. He said I was a little noisy but readable. I told him how far away I was and where and that I was amazed he could hear me at all. Anyway me and the fellows I sometimes work with have all had great experience with these. The one I build is made from TV twin lead formerly sold by Radio Shack in the US. It has a thin plastic insulation over a white foam plastic core (too bad the Shack is gone). I have a 500 foot spool of twin lead I got via eBay and have not had success in getting my measurements correct for cutting it so far. Velocity factor is the problem. Different feed lines of the same impedance can vary quite a bit and so cutting lengths have to be adjusted to suit. If you can get a nicely tuned Slim Jim you likely won't be disappointed. A very appropriate thing for a grab and go kit
Based on this great review I bought one. Not the same make, but man, I am impressed with it. To give an idea of why I love it. I get crystal clear reception and transmit from a repeater that is 47 miles away from my home as the crow flies. What makes this impressive is that I live in London, UK. The antenna is suspended out of my second floor bedroom window and the radio is a Baofeng UV5R that cost me £20 from eBay. The Slim Jim cost me £10 sterling including shipping from the States. So the whole set up cost me £30. I did buy a bigger battery for the radio later but I forget how much that cost. It was still cheap and sent from China.
This is a fantastic design but it MUST be kept away from metal to work well.
So thanks man. You put me onto a terrific antenna. Happy new year to you and all who you love.
I purchased one of these antennas from N9TAX.
ARES was called out in my region a week ago. As an ARES member, I was deployed to a hospital to provide emergency communications. I used this antenna exclusively during the deployment and can vouch for it's performance.
If I could only pack one antenna for 2 meters/70 cm, it would be this antenna.
73
@12:30 I went and sealed my ends with the liquid electrical tape stuff, and I used another little piece of the shrink wrap tube for the gap. It works great I measured a SWR of 1.0044385:1 lol, return loss of like 52dB so I would say it should work jut fine
@photofudge Congrats on your license. I'm gearing up onmaking a vid about camoflauging the slim jim, or making it hide in plain site. will be experimenting with various pipes and enclosures along with the effects of mounting it close to structures. I'm sort of curious about the subject too. I just gotta find the time that I dont have, but the vids will come. Thanks for watching.
yes, it will work. I've seen professional installations mount their antenna upside down to direct the signal mor in a downward direction. you'll loose a little bit of range but not enough to make a difference. Just make sure the antenna is clear of close objects horizontally, it does not like neighbors. Your profile name gave me a chuckle or two.....
Great video on this antenna! I have had 2 of them for a while and they work great. However, like everyone in Ham Radio, I'm constantly looking to improve my antenna setup. I'm looking at the Diamond X50 base antenna to replace my Slim Jim as the base antenna. Do you think it would perform better than the Slim Jim? Any personal experience with the X-50? Thanks!
Nice review ? What type of cable is provided with this antenna ? Looks like RG-58U, or is it a more expensive cable, like a foam cable or something like that ?
Yes, just RG-58. standard is a piece of about 1 foot. You could order a one piece length of 16'. Thanks for watching.
Enjoy video,like your straight forward approach very easy to understand.The only thing I could find wrong with this antenna due to the lower angle of radiation is when used is hilly terrain and your at the bottom of hills surrounding you its a lot harder getting your signal out,that say a quarter wave ground plane antenna mounted low (quarter wave has an higher angle of radiation).But I did find as long as you mount them high up and clear as you said in practice they work really well,I built a 2m (450 ohm ribbon feeder) and was very impressed with performance and got about 10mhz bandwidth in vhf range,that's about 143 to 153mhz.Cant wait too see your antenna enclosure follow up vid,that's something like to try!Cheers!
Could you please make some measurements ? Length of TOP, MIDDLE and BOTTOM section. Length of TRAPS and measurements how far is gap from bottom big that gap is? And how far from bottom is coax cable connected? Thank you very much.
Who you calling a geek! lol
thanks bro! Just ordered one
Thank you for these very informative videos. I am purchasing a Yaesu VX-7R as per your recommendations in other videos. I just received my Technician class license and look forward to getting on the air besides through Echolink. I really appreciate this video, due to limited budget and apartment living, this looks like it will be my best option for an external antenna. Please keep the radio videos coming, I would love to see more about maximizing the VX-7R and radio in general. Thanks GG ...73
I did a homebrew stuff of this and it really works great!
Hope you return to youtube. Your videos are excellent.
This seems to be a winner.
I am just wondering if you guys know, would it be ok to hoist this thing up inside an old windsurfing mast made out of fiberglass?
I have saved a couple of masts since i just couldn't make myself throw them away. Would be nice up on top of the roof of my house. I already have a good mount, while the old satellite tv dish is coming down, ot now sits on the chimney.
The fiberglass mast wall is just about 2mm's in thickness.
I am new to this, so sorry if this is a silly question.
thanks
I love all your videos, bro. However, this one in particular has been very informative and really helped me understand quite a bit. Even though I got my general ticket I'm still very much a novice. Been in fire and EMS four decades but like you said in another video I never really cared for the science of radios, all I needed to do was talk to dispatch and other mobile units. Thanks to yourself, USNERDOC, Comms Prepper and a couple of others, I caught the bug, and now I'm a ham. keep up the great videos. '73. -KD0TLN
Antennas are ez to make
I just bought this from you . it doesn't say gmrs on it. It says dule band ??? .my midland mxt 115 gets hot when I use it . I am very confused on what to try next . I joined a repeater club just can reach or after 3 radios later and 4 antennas .please advise thank you much
Great explanation of how it works. I looked into the making of these, and you are right for the cost its a great buy. I am ordering a second one to put up on my house and one and keep one for the bug out kit. Thanks for sharing.
Thanks for this. Just ordered one. Going to use it with my new cheapo Baoefeng when it gets here. Very inexpensive portable setup.
Again, appreciate the work and thank you.
Kudos for making a video with so much enthusiasm. I enjoyed it, Though I agree with a lot of what Dan Nelson says regarding keeping the science intact within the hobby and to keep it sacrosanct, I have some major doubts about some of the things he and you both state. For instance, Amateur Radio has NEVER been in danger of dying out. Also, as far as the 'No-Code' licenses now available--that was all a major push by the manufacturers who were all virtually screaming that they could not stay in business because of the limited number of new Hams each year. Obviously, their profits would soar to even higher extremes were there no license requirements at all. But there's something to be said for that as well, since they are making some mighty fine radios these days. I'm in my mid-sixties and have been a Ham for nearly 5 decades now--I am here to tell you that virtually all the whining about anything to do with Amateur Radio/CB/FRS in this country amounts to storms in teacups. As I say though, I agree with much of what Dan has said--since there are many good reasons--including lots of *safety* reasons--why one should have to study to obtain a proper license, with the consequent knowledge one gains from doing so. I still have creepy visions of a trucker who, when busted, was radiating nearly a KW throughout the cab of his big rig, while his wife and daughter sat shotgun, virtually swimming in stray RF. The fellow had absolutely no clue. Again though, thanks for this video--I enjoyed your enthusiasm. Keep up the good work!
safety has nothing to do with why you need to get a license, i used to think that, but the truth is you can be a legally blind and still get your license, anyway just wanted to drop my two since, oh and if they never dropped the code requirements ham really would be dead by now
TexasPrepper86 Garbage. That may be true for Texas, Cletus, but there are dozens of other countries out there that require even tougher testing and Ham Radio is more vibrant than ever--even in places like China, Japan, Philippines, Eastern Europe and on and on. Of course, if you were a Licensed Amateur, you'd know that. As for 'safety not having anything to do with it', sounds like the same logic halfwits with guns keep using even though they keep shooting each other "accidently". Good luck with that cornpone logic there, sport.
***** What gun stuff? You mean when I said "riding shotgun"? It means 'riding in the up-front passenger seat' and has nothing to do with guns LOL!!!
Great review my friend. I am thinking of getting this for my handheld Wouxun Dual Band Radio. It would be great to carry in my pack.
Yes, would leave it outside in its present configuration as well.
Thank you sir. I strive to have a reputation for strait forwardness, integrity, and dependable character in all I do. Your comment means alot to me.
You got pretty close with your description. The section below the gap is an impedance transformer from 50ohms to about 3000ohms - this section does not radiate. The top section on 70cm is a single half-wave up to the trap - as you say this is the only radiator on UHF. On 2m the top section is two voltage-fed half-waves in phase, with the 2nd half-wave section folded down parallel with the first one, so as to align the two sine waves, or else they will cancel. The stub cuts off at UHF because it is a shorted 1/4 wave - remember this "a shorted 1/4 wave stub appears open, and an open 1/4 wave stub appears shorted." Connect a shorted 1/4 wave to your analyser and sweep it and you will see. Cut the short off the end and leave it open, and sweep it again - you will see a big notch either high impedance or low impedance. The notch repeats at odd harmonics. Thanks for teaching and showing stuff.
So the info was super useful, however the piss jugs being used around the KA bar was an incredibly.... unique aesthetic lmaooo
That's not a k near it is a m7 for the m16
after weather proofing the top and bottom would you leave this outside even if it was raining?
Thanks for the heads up on a good antenna, I've already scoped out some PVC to make a stick with, hell with paying 3x as much. Thanks GG. Stay Safe.
Hey MR. what rubber duck you use for your HT?
Is it possible to use this slim jim antenna as a mobile antenna? Any way to fix it to car? Thanks.
Has anybody told you to try 200/psi PVC? It is supposed to radiate better.
Nice job dude! You talk my language lol you really did a superb job. Thank you,
it's a shame the details on the traps were not given, like the printing on the cable and the length they are cut and how they are connected if they are coaxial cable, then it can be replicated
Aye you're right, you've caught me out, you need to notify the man on the video aswell because he's mentioning traps. BTW I now have the details on the antenna construction, it's rg174 coax, and you could make one for less than $22 , here you go chaps......
drive.google.com/open?id=0BwXBqGcnxnlSRktpdWxQTU10TXc
I once made one of these for 10meter. It's hosted up a tree with the top of antenna at approx. 80 feet. It's on top of a mountain here in Washington state. Drive up, park, run a feed to base of tree where you will find a pleasant SO 239 waiting. Worked Spain on FM simplex with it.
Randy S. Sweet, I bet it works extremely well, I have been using a slim Jim for VHF since I was licensed just over 20 years now, i did contemplate modifying it to a super J pole but never did. I always did wonder what a 10m version would work like .
The decoupling stubs are considered traps in some antenna jargon.
how accurate is that? it appears the 174a traps run on both sides in the n4tax design and they appear to be cut at the same length. the jpg only shows the 174a on the 1/2 wave side
Anything is possible but in this case not practical. The metal of the car will seriously de-tune the antenna. the slim jim folded dipole design like to be free from near objects. I have 2 other videos that show detuning of the antenna when placed near PVC, ABS, fiberglass tubing.
Beware over hyping the gain claims. Search for J-pole antenna on google and read the Wikipedia article which contains solid references to back up the text.
to split some hairs the section below the notched side is about 1/4 wave of 2m and is used for impedance matching. above the notch that is 1/2wave for 2M. www.n9tax.com/Slim%20Jim%20Info.html third image down gives a great explanation.
Beware of na-sayers who come here from ham shops who don't want you to build these yourself. I know that these work because I've been seeing them in many ham shacks since the 70's. I'm a little unsure of the chokes that were used and how they work with this antenna, this is the first time I've seen that. It would have been nice to see an SWR test on this one.
+Grant Aldrich Its alright, sometime we need some nay sayers to keep us in check. It just compels me to follow up with an update video with some A-B comparisons with other antennas to find out what the truth is when it gets warmer. SWR will be included too. Thanks for watching.
I built one of these, it only works when I disconnect the "ground" from the Baofeng, ie with the pl-259 connected to the radio center pin only. Can you tell me why that is happening?
perhaps the impedance match is not tuned right. Thats the only thing that i can think of.
GUERRILLACOMM I took it apart and it turns out the antenna cable I used was shorting inside the connector. It was an intermittent problem and never happened when I used this cable for my CB... you live and learn. Thanks for the reply.
That is made Very Good For Homebrewed I will check his site out
Would this be ok to hang in attic with no ground hooked up to amp and ht radio both running on power supplies
I dunno about the amp, but this unit is rated to 100W so it should be fine if not entirely necessary. I use mine hung up on a balcony with a handheld. Works like a charm.
Thanks for the Report....
Dan Nelson said:
"The J-pole has since been [modeled] by recognize[d] experts in antenna modeling and these new models have withstood pear review. I urge you to take a look at W8JI's J-pole modeling page and review the data presented. There are many more but that's a good start."
They haven't withstood further review by actual professional antenna designers some of which is referenced in the excellent J antenna wiki article en.wikipedia.org/wiki/J-pole_antenna.
W8JI makes some relevant points to be sure, but further analysis and actual chamber measurements suggest so long as you heed W8JI's warnings and adequately address feedline and mounting structure current issues, the J antenna works quite well and slightly better than the often referenced 1/4 wave GP monopole antenna. In other words, there is a payoff with the J antenna over a 1/4 GP.
To augment Guerrillacomm's observations in this video, we actually did test an N9TAX dual band antenna and will be posting the results at some point. For now I will summarize below...
VHF:
At VHF the antenna works pretty darn well yielding about 2.5 dBi H-plane gain (freespace) plus or minus the usual small J antenna swing in gain. This jives perfectly well with accurate modeling for SlimJim style antennas. I was suspicious of the ferrite choke working at VHF, but our testing confirms it does mitigate current flow back down the feed line. As there is no conductive mounting structure to worry about, there are zero issues with those, otherwise troublesome, currents. The conclusion of VHF performance is the N9TAX is as good as any dipole in free space with no apparent interactions with the feedline to spoil things. This is the best an antenna of this length can be and it nails it. Bravo N9TAX.
UHF:
Unfortunately the performance at UHF was questionable. It tunes very well for the 440 band, but even a basic hand test reveals the existence of rf current along the feedline. This suggests the choke just isn't up to the task of functioning at such high frequencies. This is no surprise as ferrite choking at these frequencies is hard and this example proves the point. The other problem found is the Ed Fong inspired inline coaxial chokes in the upper radiator appear to have negligible effect. We found UHF rf currents flowing just fine above the chokes - not good. The measured E plane antenna pattern shows the
classic uptilt beam pattern of a 3/2 wavelength antenna. Of course in a pinch the N9TAX dual band antenna will function at UHF, but with reduced gain towards the horizon.
N9TAX antenna knowledge in question:
While N9TAX knows how to mechanically build an antenna exceptionally well, his actual antenna knowledge beyond copying other designs and how to tune them up is lacking. This is very apparent with his 6 dB gain claim (note the lack of dBi) on his web site and zero antenna patterns of any kind: simulated or measured. The whole SlimJim 6 dB over something-or-other kerfuffle is a myth that just won't go away and Joe is just another victim of it with his parroting of the obviously nonsensical gain claim of what is essentially a simple dipole. In his defense, quelling that myth on the Internet is like playing whack-a-mole.
As for the failure of the inline UHF coaxial chokes, Joe is obviously relying on Fong's design to bear fruit so cannot be blamed in trusting Fong's promises. However, if you are selling antennas, you really need to confirm their performance if you are making performance claims in your sales literature.
Conclusions:
The Fong inspired VHF/UHF rollup antenna by the well intentioned N9TAX, works very well at VHF and has compromised performance at UHF no better than a single band version run at its 3rd harmonic. I always wondered why Fong only showed the "before" antenna patterns and not the patterns of the resulting design in his DBJ-1 and DBJ-2 articles. I was quite surprised at the failure of the UHF chokes and now see this as evidence no one has ever measured and published gain pattern measurements of these antennas.
The findings above are reality as best as we can measure them and we are confident in our ability to properly critique and measure any antenna design. It's what we do for a living.
The construction quality of the N9TAX antennas is so fantastic, I hope Joe can work through a design change to yield a real dual-band antenna meeting realistic specifications. Until that happens, only his VHF monoband versions function as designed.
I put mine on PVC 8 feet out my window and still get 1:1 swr... into repeater 29 some miles away
GREAT EXPLANATION!! THANKS!
What this is, is a JPole. :) I have constructed these for 10 Meter. Pull one up a tree!! Also, as Colinear at 2M. Meaning two 1/2 wave stacked. (The Super Jpole as it is known)
The N9TAX design is based on the SlimJim design which has nearly identical performance (at the lower design frequency) to the J antenna. The lower take off angle myth is based on a now well known misrepresentation of Judd's original article. The wikipedia article en.wikipedia.org/wiki/J-pole_antenna is a well referenced summary.
The more you can keep the wires straight, the better you will do with this antenna.
fiberglass conducts so not good to put slimjim inside i did read its a no no (UPDATED> I was wrong its Carbon Fibers you need to avoid, read below> SORRY!)
+truthseekers666 Hmm well we might want to inform the military and radio manufactures that they don't know how to build antennas or radios. The military and commercial radio services have been using fiberglass radomes for decades.
You can take a trip to any marina and see commercial ships with fiberglass enclosed antennas and radars with fiberglass radomes, Or how about the airport or your local police dispatch I'm sure you will see many examples of antennas enclosed in fiberglass radomes..
Fiberglass is actually a very good insulator and is completely transparent to RF. Proof of this is the fact that the PC boards in every radio built today are made from fiberglass.. Carbon fiber on the other hand has graphite in it and should never be used in antenna radome construction and that's where I believe the confusion regarding fiberglass started.
+Dan Nelson Sorry your correct im getting mixed up between my glass fibers and my carbon fibers. Doh. Thanks for pointing that out. I tip my hat to you.
+truthseekers666 Not a problem, it's nice to meet someone on the internet with enough integrity to admit an oversight. I must say it's refreshing. Don't feel bad, unfortunately there is so much disinformation floating around youtube and blogs that it's sometimes hard to know whats fact and whats opinion. Personally if the source doesn't have an ISBN number and published by a reputable publisher then I carefully scrutinize the contents for snake oil.
73 and Good DX.
+truthseekers666 Thank you for correcting that. When I first saw "Fiberglass vs. Radiation" I facepalmed. Nice catching that.
What's with making me sea sick by going up n down with the camera:-(
Just show it to us on the analyzer
Thinking of doing that sometime soon. I have one in my backyard for bout 3 years now. will sweep it to see how its doing.
The function of the ferrite ring as described is nonsense - it will attenuate RF in BOTH directions, not just reflected RF.
The focus was the short comings of this antenna design and how it was dealt with by the maker, not the full functioning of the ferrite ring and all its application. For example, Toilet paper is made to wipe my ass, or make cute origami teddy bears in a video about human waste. Stay in context & focus.
GUERRILLACOMM
Read your rebuttal carefully again... I rest my case!
the ferrite ring is to stop common mode currents from traveling back down the coax...
Nice video very informative. I have one of those up in my loft, I get some very good reports about it. Just ordered another from eBay so wont be long until it arrives that one will go up in the back garden. M6YMN
This guy is bad ass. haha
73's KD2AWT
6db of gain does not give you 4 or 5 times more anything. It is a good antenna, but not FIVE times anything, and you didn't say 5 times more than what? Six db of gain is 1 s unit....
+Jeff Wimmer (Mustang) If you look at the specification sheet for an antenna, you will typically see units for antenna gain listed in dB, dBi or dBd.
dB - decibels. 10 dB means 10 times the energy relative to an isotropic antenna in the peak direction of radiation.
dBi - "decibels relative to an isotropic antenna". This is the same as dB. 3 dBi means twice (2x) the power relative to an isotropic antenna in the peak direction.
dBd - "decibels relative to a dipole antenna". Note that a half-wavelength dipole antenna has a gain of 2.15 dBi. Hence, 7.85 dBd means the peak gain is 7.85 dB higher than a dipole antenna; this is 10 dB higher than an isotropic antenna. 3 dB is considered doubling.
In this case, the claim of 6 dB gain means 3X an isotropic antenna in the peak direction of radiation. or roughly 2X a Dipole.
dB without reference is meaningless and reveals unprofessional antenna specifications either hiding poor performance or, more likely, reveals lack of technical understanding of the writer using such units.
The claim "6 dB" does not necessarily mean 4x ( not 3x as you suggest) over an isotropic antenna as the reference is ambiguous.
So...
dB - they are hiding their ignorance or lack of performance.
It's also important to know whether or not a gain figure is in freespace or not.
73 👍😉
These antennas are nothing new I remember building my very first slim Jim over 40 years ago, I've learned a lot since then. One of the things I've discovered is that J-pole's and slim Jim style antennas are nothing but snake oil.
It has been proven by some of the worlds most well respected antenna authorities, such as Cebic, W8JI, Bill Ore.... that the original J-pole and slim jim antenna models were badly flawed and that the original gain and radiation angles claims were erroneous at best. In other words the performance claims regarding the J-pole and slim Jim style antennas did not pass the peer review system. Unfortunately that doesn't seem to have stopped people from continuing to spread false information based on that original faulty modeling.
More accurate antenna modeling and range test performed by well respected experts in the field have proven that a simple 1/4 wave ground plane actually outperforms a J-pole by at least .5 db that's right a J-pole or slim jim actually has negative gain as compared to a simple ground plane antenna, My own testing has backed this up.
Ever wonder whey Dr.fong the maker of one of the most popular J-poles refuses to use any real science to back up his advertising claims but rather resorts to snake oil salesmen style tactics such as using questionable "testimonials" Hmm you would think a Dr with a PHD electrical engineering could provide some solid math and science to back up his controversial advertising claims.
Also it's nice of you to try and explain antenna theory unfortunately all you've really managed to do is demonstrate your ignorance on the subject.
for example your claim that home brew antennas are the reason for common mode or feed line radiation. The reason J-poles suffer feed line radiation has nothing to do with the home brew style antenna but rather that the J-pole/slim Jim is a Marconi style antenna and Marconi style being highly unbalanced antennas with no feed line decoupling are notorious feed line radiators ..
The only thing good about a slim jim or J-pole is that they are better then the rubber duck antenna on your HT. the fact that they can be rolled up and stored in a backpack also is a benefit other then that they are a very poor antennas especially for base station type use.
One last thing a single Ferrite bead is just barely adequate for 5 watts. On a Marconi style antenna you're going to need a minimum of at lest 7 and more like 10. The problem with using Ferrite beads or whats known as a common mode choke on a J-pole is that it will kill the antennas performance. Considering that feed line radiation is where most of the RF energy is radiated from on a J-pole.
By the way I went to ebay and priced out the parts, you can build 5 of these slim jims/ J-pole style antennas for what you spent on one.
+Dan Nelson Damn it, now your gonna force me to run comparison tests between slim & 1/4 wave. It should be a good follow up to prove to myself what's going on instead of taking your word on the subject. For all I know, you could also be regurgitating someone else's opinion on your bit too long post that I almost did not have the patience to read. I did not claim this was the best antenna in the world, only that it was a good inexpensive field expedient antenna that could also serve as a home base antenna for preppers, nothing more. I did mention it was a garbage UHF band antenna. Not preaching to the choir here just translating geek lingo into plain talk for beginners. Not scare them away with technical details, such as your long winded post, that will deter any interested new viewer.
GUERRILLACOMM "such as your long winded post, that will deter any interested new viewer"
Good I hope it does, if they have no interest in learning radio, electronics and antenna technology and the math that goes along with it then we don't need nor do want them in the ham radio service. Let them go play cop or solderer of fortune or political activist on FRS and CB where lids and wackos like that belong.
We really don't need or what a bunch of political extremest, conspiracy theorists and wannabe cop whackers subverting the ham radio service and destroying our hard earned reputation that took decades to build As the old ham radio saying goes " No Lids, Kids or space cadets"
AT one time the ham radio service was well respected for our technical knowledge and electronics skill, The country knew that our skills would be invaluable in times of national emergency. I'm not so sure the same could be said of today ham radio appliance operator who couldn't define resonance or build a dipole without google and who don't seem to understand the difference between subjective personal opinion and fact based on empirical evidence based on scientific testing.
Once again the last thing the ham radio service needs is a bunch of cber's and appliance operators subverting the the ham radio service and destroying decades of hard eared reputation.
Instead of focusing on dragging a bunch of technically illiterate people into the ham radio service, people who have no interest whatsoever in learning radio electronics and theory we should instead be focused on maintaining our reputation as skilled technicians and that means quality vs quantity.
Again I have no issue with people who are electronically illiterate yet sincerely interested in learning the science behind radio. On the other hand I despise people who propagate subjective personal opinion as scientific fact.
+Dan Nelson Well, well, well... The beast reveals itself of its true colors of elitism, condescension, and good old fashion curmudgeon-ness. Listen, if it wasn't for the dropping of the morse code requirement, the ham service would of been less than a quarter of what it is now and the FCC would of had enough justification to gobble up most of the good frequency band from the ham service for profit. I don't exactly see a constitutional right protecting the airwaves like the 2nd amendment protecting the right to bear arms. Us CB'ers, whackos, activist, and my personal favorite and proud card carrying member of the space cadet brigade are here to stay and use your beloved ham service in many ways not intended or fathomed by the traditionalist ham hobby-er just CQing from a shack. Us technically illiterate users breathed new air into a slowly dying hobby and you must admit the numbers will prove that fact. You could also thank the chinese for cheaper access to the ham and public safety frequency band for the uninformed who will undoubtedly stumble upon interfering with those frequencies. I'm here to inform those users on how to operate legally or at least enough to know what not to do to interfere. Whether you or I like it or not, unauthorized use is going to happen, might as well steer the traffic safely out of the way. But no, you prefer to stew, complain, sit back and watch it happen. Now if you don't mind, I have a tin foil Spartan helmet to finish making before I man my patio with my AR15 locked and cocked waiting for the zombie horde.
"and the FCC would of had enough justification to gobble up most of the good frequency band from the ham service for profit."
Once again you demonstrate your ignorance, The frequency’s the ham radio service occupies are protected by international treaty and can only be used for either CB or ham radio use.. Hams are allowed exclusive use of most of these frequency’s to practice their “radio art”.
At one time this exclusive use was justified because the ham radio service provided a valuable asset to the nation. The dumbing down of the ham radio service has changed all this. The average ham no longer has the tools nor education or skill to provide any value whatsoever to the nation, What’s worse is this new generation of hams have no desire to educate themselves. Many such as yourself wear your ignorance as though it were a badge of honor. So ask yourself what value or asset does the ham radio service today provide to the nation that justifies our existence and use of the valuable frequency’s we occupy and use for free. NONE !! that’s the answer !!
Like I said before we’ve seen this happen in the past. If you want a peak at ham radios future All you need to do is look at the joke CB has become. CB is loaded with nothing but a bunch of slackers and right wing illiterate buffoons making idiots of themselves on the air, these CB fools are the reason hams have to deal with antenna restrictions.
If we wanted to save ham radio, then we should have focused on science and education in an attempt to maintain an elite reserve of electronics technicians skilled in radio theory, practice and repair that we as American’s could have been proud of and who we count have relied on as an asset in times of emergency, Quality vs quantity that’s what we should have focused on.
Instead the ham radio manufactures lobbied the FCC to drop the code requirements and publish the answers to the licensing exams and in the process handing out tickets to people who knew nothing about electronics and had no interest in learning, They did this so they could sell more products. The end result is the ham bands are now loaded with a bunch of lids that couldn’t build a simple dipole or wire j-pole without googling it. Exactly what kind of asset are these people going to provide to the nation during an emergency. The fact that you had to go out and actually buy a J-Pole is testimonial to your own ignorance. I built my first J-pole when I was 12 years old, I built my first tube amp when I was 16. This pursuit of knowledge enabled me to graduate in the top 1 percent in my class at Radioman’s “A” and “C” school
The vast majority of new hams today are so technologically illiterate that they are easily fooled by snake oil salesman who easily cons them out of their hard earned cash on antennas that defy the laws of physics using bogus gain claims and testimonials. Anyone with even a shred of technical knowledge should recognize that the information being posted on internet blogs regarding these antennas is nothing but snake oil. Then again we are talking about a group of people who think education is too elitist. As a result they remain so technologically illiterate that they buy into this snake oil hook line and sinker and are proud of it.
Yup dropping the code requirement and publishing the answers to the ham test sure did wonders for the service. The influx of new hams are so damn illiterate they have single handedly turned American hams into a world wide laughing stock, What was once a highly regarded radio service is now a world wide laughing stock. As a result American hams for the first time in history are shunned and laughed at by the rest of the worlds hams, So yeah thank you so much..
At one time I was proud of my Extra class ticket now I look at it and realize it’s not worth the paper it’s printed on, At least for the time being I can still be proud of my commercial radio ticket and my MSEE at least they’re still worth something. American hams are so looked down upon and disliked by the rest of the world that It’s the first time in my life I’ve ever heard DX stations and dxpeditions regularly and purposely refuse to work American hams.
What ham radio is attracting today is a bunch of slackers who are too lazy to pick up a book and educate themselves, instead they look at blog posts and youtube videos where yet more technologically illiterate people spread subjective personal opinion as scientific fact. Sound familiar ? it should ! it’s CB all over again.
" CB'ers, whackos, activist, and my personal favorite and proud card carrying member of the space cadet brigade are here to stay and use your beloved ham service in many ways not intended"
Yup everyday the whole world hears these morons making complete idiots of themselves, and yet they can’t figure out why people are laughing at them
What sad is that you are so full of yourself that you don't realize the FCC is already planning on removing the licensing requirement for ham radio and reclassifying it as part of the CB radio service. Yup not sure when it’s going to happen, but they just removed the fee for the vanity call so it’s coming soon. Scuttlebutt has it that they plan on opening up the phone bands to everyone. A ham radio ticket today isn't worth the paper it's printed on, Oh wait they stopped printing licenses out this year as well ? Hmm ever Wonder why.. here’s a clue the license to operate Ham radio on phone is going away, thankfully I think they are going to at least preserve the CW sub ands. So while they did away with the CW requirement in effect what’s going to happen is the only modes that’s going to be available to hams exclusively is going to be CW and low bandwidth digital so If you want to continue to use your ham ticket you better brush up on your CW
Once again in case you missed it, Rumor has it that the FCC plans on keeping the CW bands for use by licensed hams and that they plan on opening all phone bands from 160m to 70 cm and reclassify it as part of the unlicensed CB service. Once again the CW sub bands will be retained as well as anything above 70cm for ham radio use. Everything else will be reclassified as CB, still not sure if they plan on opening up the whole two meter 70cm bands or just the phone portions of those bands. Either way the writing was on the wall years ago.
What did you think was going to happen, the Ham radio service at one time was a valuable asset unfortunately that was back when most hams actually knew something about electronics and radio. As you have demonstrated hams today are nothing more than appliance operators who wouldn't know a base from an emitter or know how to read a smith chart, heck hams today can’t even build a simple dipole yet people like you are proud of your ignorance and yet can’t figure out why the whole world is laughing their ass's off at you. Here’s a clue stope being a slacker quit being so proud of your ignorance and try picking up a book and educating yourself..
But we all know that would never happen because education, skill, knowledge and science is considered far too elitist by neanderthals who glorify ignorance and wear their illiteracy as though it were a badge of honor.
+Dan Nelson I'm done with you sir. Not that its an admit of defeat, you're just not worth the time to waste. I didn't even read your comment. Just go to bed thinking there are thousands of ham radio operators you despise polluting your precious HAM service.