Hi Micheal Jerry lynn Parks here" KM4GNC The Slim-Jim I got from you is the best I've ever seen! I mounted it 30 ft up and it's picking up station's my hy-gain VB 12 element beam is! Really clear! I was amazed what a great antenna! Thank you" and 73s For a super made Slim-Jim antenna everything perfect on my 2 meter" picking up stations 100 miles away on about a 4 never did that with my 15' diamond antenna! Really pleased! Thanks again!
Just purchased the slim jim antenna and was able to make contact from my Qth Rockford, Il. and tripped the K9MBS 2 meter Repeater in Bloomington, Il. At 125.15 statute miles away at only 14ft. off the ground. 09/03/2020 using a Kenwood TS-711A at 25 watts when the band was wide open...go figure... does it work or does it work!!! , I'm sold, and that's my comment....and I'm sticking with it! Thanks Michael, KB9VBR. Rick. H (KD9QDP).
I'm not quite understanding your description, could your antenna be damaged in shipment? If you wish, you can email a couple of pictures to kb9vbr@jpole-antenna.com
@@KB9VBRAntennas I guess the question comes down to: is the top of the antenna supposed to be open, when the other ends show professional-level soldered caps ? [thank you for the quick response !!!]
When I build mine, I solder a cap on the top of the antenna and leave the bottom open for drainage. But a cap on the top is purely cosmetic and its lack thereof won't affect performance.
Michael Thanks for your videos, I have a J-Pole antenna that I purchased several years ago at a HAM show several years ago and I am pretty sure this is one of your antennas and I just hooked it up to my TS2000 after both the antenna and the radio have been sitting in storage for about 5 years. I have it hooked to my VHF port right now (works great) and was wondering if this antenna is also good for the 70cm UHF band? If so I will purchase a switch to use it as well instead of purchasing another antenna for UHF only. Thank you! Bob-KN4JLT
Hey Michael, I bought your Marine 155 - 159 MHz j-pole antenna a few years back. Great scanner antenna! I using LMR-400 coax about 30 to 35' long with coax balun 18" from the SO-239 connector on the antenna. I have the coax grounded right before it runs inside my house with a 6' grounding rod. My mast is a 2" pvc with hose clamps. My question is would I actually gain anything switching to a slim jim antenna? I'm using a uniden bcd536hp scanner. Thanks again.
Why am I constantly being told that J-Pole antennas have no gain and sometimes a negative gain? I am new to ham radio and just trying to learn about antenna designs. Thanks Michael for your informative videos.
It depends on what the antenna is compared to. Commonly gain is calculated based on the relative radiation of an isotropic radiator. This is a theoretic antenna that radiates uniformly in all directions. An antenna is said to have gain as its design compresses the RF radiation signal so more of it is focused in a particular direction or plane. So if an isotropic antenna has 0 db of gain, a J-Pole, which is a 1/2 wave antenna, would be said to have 3 db of gain. More of it's energy is focused towards the horizon. But to make things confusing, some people will compare the antenna to a 1/4 wave dipole or ground plane antenna. 1/4 wave antennas have about 1.5 db of gain when compared to the isotropic antenna. So if you compare a J-Pole to a 1/4 wave, the relative gain amounts will be less.
Simple answer: those who talk down a J-pole are selling something else, or bought something else and never tried one. Don't believe what you read always. Try a J-pole, they've been around for a very long time for good reason. Also, unlike any 1/4 wave, there is zero need for grid or ground radials or to be "over good ground". 1/2-wave antennas are not sensitive to such. 1/4-wave are. I've always found a j-pole to out-perform a 1/4 wave. Last one I built was of 450-ohm feedline and cut for 6-meters. I use it portable. Pull it up into a tree and you're on the magic band!
Thanks for all the great videos, this might be a newbie question but can you mount two of these on one mast given that your only using one at a time, each with its own feed line? I bought your slim jim a while back and now as I get ready to finally mount it I am faced with lots of new questions. Including what if I wanted to do 70cm or 6M without having to put up another antenna mast and still have that performance of the slim jim for 2m.
Sir, how many watt of transmitter this jpole antenna can carry? Or is this jpole antenna can carry the 200w power output of the transmitter? Please reply. I am interested this jpole antenna
Hello Michael. How is it possible to solder the SO239 connector to the copper pipe? Yesterday I wanted to solder such a connector to a HB9CV, and the solder didn't stick. Do you have an advice for me? Thank you!
I use a propane torch so I can apply a lot of heat very quickly. Then cool it with a wet rag. Also surface prep by cleaning the copper and using a good amount of flux helps too.
@@KB9VBRAntennas Okay, thank you, I'm just afraid of melting the plastic part inside the SO239 connector by using the intense heat, because for soldering I have to heat the connector too. I think, you know what I mean.
@@KB9VBRAntennasOkay Michael, thank you, but the Amphenol connectors have a plastic insert too, so I think, it will melt anyway. But thanks for your help and 73 to the USA.
I probably wouldn't use Plasti-Dip to cover the antenna as it could detune it and alter the antenna's performance. But you can paint the antenna with clear lacquer or a non-metal spray enamel without any loss of performance.
With the two piece antennas, I like to put some dielectric grease such as OxGard or NoAlox on the threads and put the two pieces together finger tight so that they don't seize up.
On break down antennas, you are using a standard 1/2" male and female pipe thread to solder joint adapter. Since they are NPT, the threads are tapered. This means that you can vary the overall length of the element by 1/4 to as much as 1/2" in length, depending on how tightly you crank those threads down. Does this affect tuning?
No it doesn't. When I build the antennas I take into account the space taken up by the threaded connectors. My recommendation is to thread the two pieces together 'finger tight' and to use a bit of anti-oxidant like Noalox or Oxgard to aid in making a good connection. Once you do that a couple of times, pieces will consistently thread to about the same spot.
Michael, Just a curiosity, has anyone yet requested cophase coax(harness) to combine, oh, say three or four slim jims straight up a pole @ say 465mhz. I just placed an order for this antenna, will be needing another(going mobile). But I had on my mind the cophased loops from the old systems up at the Natnl Guard Armory/State Police Posts/UHF loops. Talk about some ears man. Anyway, pretty sure amagonna love the antenna. Thx ahead from KY have a great day
I periodically get requests for co-phased J-Pole and Slim Jim antennas. It is certainly doable, and I've researched putting a system together. I just haven't had the production capacity to add that item to my catalog.
@@KB9VBRAntennas Antenna arrived timely, undamaged and is now sitting on top of 100ft. LMR600 with a fine brillo polished sheen. The antenna works quite well indeed (knew it would) and a satisfied customer is what you have here. Thanks KB9VBR! And I'm not quite done yet. Will be hollering at ya as future projects are realized(off grid ammo can repeaters for uphill deployment) is my aim. Thanks again Michael.
@@KB9VBRAntennas I gotta say, I absolutely cannot wait to get out into the county here and run a pair of 50 watt radios through a pair of KB9VBR slim jims. It should be quite interesting. Only have 1 rig though, gotta build out a mobile now. I did send my son to work with an old value little silver uniden bubble wrap 5 watt radio, 4 miles through an industrial park & in a hole he sounded like he was right next to me. Solid. Phenominal. It's not even 10 feet above the roof now. I've got up to 70 feet to go which will put it well over the dirt and into the regional airwaves, should put a grin on my face in a month or two. I plan to use a sat dish mount low on back of the tool box, which might not get the SJ up over the cab(tundra) but should be well out of the bed, close to over the cab roof anyway. Will let you know how it all pans out for me, but I have to think a base SJ will talk to a mobile SJ just dandy. I was looking at high gain, base loaded trams/brownings, Motorola but what you get these days, a lot of it's just China junk or knock off. Now, one thing I do know, this copper pipe here, is NOT china junk. It's anything but. Good Day Sir!
I am new to ham and at this time don't want to perforate my home to mount an antenna outside to run in a cable. Therefore I have a 1/4 wave ground plane in my second story. I able to get into my nearby repeter just fine. My question is if you would please recommend either of these antennas for an inside use like I described. If mounted outside, how do you protect the coax from water intrusion? Does it make a difference if it is mounted vertically or horizontal? Thanks you!
The J-Pole is 69 inches from tip to tail and the Slim Jim is 58 inches. Both antennas are great choices for placing them in your attic and I've had countless customers do that with excellent results. You can protect the coax by sealing the connection with high quality electrical tape or amalgamated tape. The antenna is a vertically polarized antenna, so you should mount it vertically for best performance.
Michael, I have a question as a complete antenna idiot... I was looking closely at your J-Pole building schematics, but thought the center lead of the coax was supposed to be connected to the longer radiating section of the antenna, and the outer shielding of the coax was connected to the matching or shorter section of the antenna... I am studying at HamRadioPrep for my Technician currently and have not as yet built any...
As you have probably found out by searching online, there are plans that attach the center conductor of the coax on either side of the antenna. I have experimented with attaching the center connector of the SO-239 to the stub and to the main radiator. I have not found a difference in signal quality or performance. I choose to mount the edge of the connector onto the main radiator because I believe it makes a better mechanical connection. A J-Pole style antenna is comprised of three sections. First is the mounting section where the antenna is attached to a mast or support. The second section, which is 1/4 wave long, is the impedance matching section. The two pieces of the antenna that run parallel to each other change the impedance from the 50 ohms at the feedpoint to about 300 ohms which is the impedance at the start of the third section. The third section, which is 1/2 wave long is an end-fed dipole radiator. With end-fed antennas, the impedance is high at the ends and low in the middle. With the 1/4 wave section, the impedance is low at one end and high at the other. So the two parts of the antenna can work in harmony. Interestingly enough, in the Rothammel's Antenna Book (13th ed english translation, page 777) the author states that feeding both the short and the long sides of the antenna are electrically equivalent, yet a configuration where the short side is direct fed provides improved overvoltage protection because the half wave section is directly grounded via the outer cable conductor. (parenthetically, this method also helps lower the overall noise floor of the antenna, by dissipating static to ground). Since a J-Pole is considered a balanced antenna- it is a half wave antenna by design; the RF energy will travel up the matching section and then radiate from the resonant part of the antenna. Hence it really doesn't matter which side the connector is attached to.
@KB9VBRAntennas Thank you!!! Can't tell you how much I appreciate your explanation!! I know electricity and RF have different properties and whatnot, but this kinda distilled that fact for me... BTW, I'll be looking up that antenna book and reading more, since I am determined to graduate from antenna idiot to antenna moron (or better yet) antenna wizard...LOLOL Thanks again, Michael!!!
Can I ask about your bottom of your base at T area .If you measured for frequency then why is there more copper extended on T area ?.Shouldn't it be non inductive ?.
Would there be much difference between using 1/2" copper and 3/4" copper? I've heard it provides wider bandwidth, but no specs on how much more... Thoughts?
Michael, i just came across your channel and website. i was wondering the separating style of j-pole, is it just the 2 meter or can it be gotten in 70cm, 6m or the murs band?
The 2 piece separating, or break-away J-Pole is available in the 2 meter version, and I can also supply it for the VHF MURS, marine, or public safety frequencies. The break-away for MURS isn't in the catalog, but you can order the 2 meter break-away and request that it be tuned for MURS. As for 6 meters, that antenna comes standard in 2 pieces otherwise it would be two long to ship. I don't offer a 2 piece UHF antenna as their shorter length really doesn't require the need to be broken down. I hope this helps you out. Michael
Hi Michael ,I'm really new to this and trying to learn ,are either of these antennas capable of working on vhf and uhf frequencies without having to add other antennas. I'm probably asking a lot but I'm looking for an antenna that I can hook to my hand held without having to mount multiple antennas but use both bands. Kind of like a temporary base station until I can upgrade to bigger and more advanced equipment . thank you for the video and 73s till next time.
VHF/UHF is line of sight propagation. I usually tell people that the sweet spot is about 20-30 feet. You can put it higher or lower, but 20 feet is an easily attainable height that offers good reward.
I have a question, why does it look like the centre pin is connected to the quarter wave part of the antenna. Should the centre pin connect to the half-wave part and the outer part of the socket hit the quarter wave part?
I'm no matching guru, but It is my understanding that it will work both ways. If you're building your own, try it both ways to see which works better for you. But the design has been around for 100 years seems like. So there is ample testing and in-service antennae out there to look at, as well as dozens of diagrams and calculators online. Look around. I don't even know which way mine are connected, I have a handful of j-poles I've made over the years, both of copper and of parallel feedlines. I've also seen them made of aluminum and stainless.
Not really. I've got one that's been on the air consistently for at least 10 years. It still works great. I checked the connectors a couple years ago‚ the connection was nice and clean with no water penetration.
Hey Michael,, I mounted my J Pole in a rubber isolator,,,,Did I do wrong, PS I am on my HT most of the time, tied into Western Reflector and the local reflector. On week ends I get on my base unit, connected to the JPole
I have a question that nobody seems to ask but, if there are slim jim antennas, why would anyone ever build j poles anymore since in many videos it says that the slim jim is in so many cases better. Or is it simply to spare an extra bit of copper pipe. What is the pros and cons of both antennas or do they have their respective purposes for certain applications. What I'm really asking is...why build a jpole if you can spend a tiny bit of extra money for a slim jim? Any explanation would be greatly appreciated
J-Poles are a good choice if you are mounting the antenna at a lower mast height, or if you live in an urban area or valley. The omnidirectional radiation pattern and higher takeoff angle makes it easier to get a signal out if you are surrounded by buildings or rough terrain. Also, with the base of the antenna at DC ground, you can mount it on a metal or non metal mast with affecting the antennas performance. It also has a very low noise floor which makes the J-Pole an excellent receiving antenna for weaker signals. The Slim Jim has a lower takeoff angle and more compressed radiation pattern. These two features of the antenna gives you about twice the gain as a standard J-Pole. A little more gain will make up for some of the feedline losses you’ll receive at VHF frequencies. Plus it will help stretch your signal out a little further. To really realize the benefits of the Slim Jim, you need to mount it in the air at about the 20-30 foot level. It will work well at lower heights, but the antenna shines when you get it up in the air.
Cheap SO-239 connectors will melt when you apply heat to them. The ones you don't want are those with the white dielectric material. I use Amphenol brand connectors. Those have a heat resistant insulator that won't melt if you work fast in soldering the connector.
@@KB9VBRAntennas Thanks Mike, yes am using a torch to heat it but had some luck with those cheap 239s, i made a jpole yesterday for my airband receiver, the nanoVNA works great on analyzing the antenna.. centered the freq to 125mhz. Thanks for the details of your videos. Am thinking of 6M right now.
You'll always have your best performance with an outdoor antenna, but often that can't be done for whatever reason. Fortunately the GMRS J-Pole is quite short, so if you can't put it outside, you may be able to place it in a window, on a deck, or in your attic.
I realize this is a question that isnt easily answered, but what type antenna would you recommend wide band use for an sdr? Im new to ham....tech licensed in April 2020, and taking my general next week, August 2020. Ive got a gp-3 atop a 24’ mast I put up last week. Now looking for a good general purpose antenna for an sdrplay. Thanks for your time.
I bought this for my baofeng r5. Is there any trick to making this work? I can not seem to pickup anything that my default little 4inch antenna does. I'm new to this so pardon ignorance. Thanks
There are a lot of variables that could affect how the antenna performs. Is it inside or outside. If outside, where is it located and how high up is it. Are there other buildings or large objects that could shade it. What type of feedline are you using and how long is it. Are the connectors good on the feed line? A short circuit in the cable can cause performance issues. My list of Frequently Asked Questions has some tips that may help you: www.jpole-antenna.com/faq/
on other j pole builds the coax centre is connected to the long section but yours seem to be opposite. does it actually matter or is it relevant for certain situations, would appreciate your help please
The 2 meter J-Pole antenna also works quite well on the 440 band. The SWR at 445 MHz is about 1.5:1 or so. The 70cm band is a frequency multiple of the 2 meter band so that's why this antenna can work for dual band operation. The antenna works great for local repeater contacts and such on the UHF band.
The antenna would work somewhat for TV, but television channels are spread widely between 50-700 Mhz, so this antenna would be a poor choice for the UHF channels.
You need wide band-width for various stations as they're all on different frequencies. It will receive but they are tuned for a specific (small) frequency range. If you're near the stations you want to receive, could be good.
Yes. The 2 meter J-Pole antenna also works quite well on the 440 band. The SWR at 445 MHz is about 1.5:1 or so. The 70cm band is a frequency multiple of the 2 meter band so that's why this antenna can work for dual band operation. The antenna works great for local repeater contacts and such on the UHF band.
Hi Micheal Jerry lynn Parks here" KM4GNC The Slim-Jim I got from you is the best I've ever seen! I mounted it 30 ft up and it's picking up station's my hy-gain VB 12 element beam is! Really clear! I was amazed what a great antenna! Thank you" and 73s For a super made Slim-Jim antenna everything perfect on my 2 meter" picking up stations 100 miles away on about a 4 never did that with my 15' diamond antenna! Really pleased! Thanks again!
Just purchased the slim jim antenna and was able to make contact from my Qth Rockford, Il. and tripped the K9MBS 2 meter Repeater in Bloomington, Il. At 125.15 statute miles away at only 14ft. off the ground. 09/03/2020 using a Kenwood TS-711A at 25 watts when the band was wide open...go figure... does it work or does it work!!! , I'm sold, and that's my comment....and I'm sticking with it! Thanks Michael, KB9VBR. Rick. H (KD9QDP).
Great antennas! Precisely tuned. I've got the J-pole
John Stuart We
Hat type of range do you get from your J pole? Trans \ Receive
Just ordered the gmrs version. Really excited to get it.
I love mine, it's been working as you said it would.
Beautifully made antenna. Thank you !
I'm not quite understanding your description, could your antenna be damaged in shipment? If you wish, you can email a couple of pictures to kb9vbr@jpole-antenna.com
@@KB9VBRAntennas I guess the question comes down to: is the top of the antenna supposed to be open, when the other ends show professional-level soldered caps ? [thank you for the quick response !!!]
When I build mine, I solder a cap on the top of the antenna and leave the bottom open for drainage. But a cap on the top is purely cosmetic and its lack thereof won't affect performance.
Love a J-pole, those look great, but I made all of mine. 73.
this are great.. at this price is not even worth to go make your own. keep up the good work
These are very good antenas. I made one myself but not so strong as yours. Good work!!!
Michael Thanks for your videos, I have a J-Pole antenna that I purchased several years ago at a HAM show several years ago and I am pretty sure this is one of your antennas and I just hooked it up to my TS2000 after both the antenna and the radio have been sitting in storage for about 5 years. I have it hooked to my VHF port right now (works great) and was wondering if this antenna is also good for the 70cm UHF band? If so I will purchase a switch to use it as well instead of purchasing another antenna for UHF only. Thank you! Bob-KN4JLT
Hey Michael, I bought your Marine 155 - 159 MHz j-pole antenna a few years back. Great scanner antenna! I using LMR-400 coax about 30 to 35' long with coax balun 18" from the SO-239 connector on the antenna. I have the coax grounded right before it runs inside my house with a 6' grounding rod. My mast is a 2" pvc with hose clamps. My question is would I actually gain anything switching to a slim jim antenna? I'm using a uniden bcd536hp scanner. Thanks again.
Is it possible to ship to Japan?
Why am I constantly being told that J-Pole antennas have no gain and sometimes a negative gain? I am new to ham radio and just trying to learn about antenna designs. Thanks Michael for your informative videos.
It depends on what the antenna is compared to. Commonly gain is calculated based on the relative radiation of an isotropic radiator. This is a theoretic antenna that radiates uniformly in all directions. An antenna is said to have gain as its design compresses the RF radiation signal so more of it is focused in a particular direction or plane. So if an isotropic antenna has 0 db of gain, a J-Pole, which is a 1/2 wave antenna, would be said to have 3 db of gain. More of it's energy is focused towards the horizon.
But to make things confusing, some people will compare the antenna to a 1/4 wave dipole or ground plane antenna. 1/4 wave antennas have about 1.5 db of gain when compared to the isotropic antenna. So if you compare a J-Pole to a 1/4 wave, the relative gain amounts will be less.
Simple answer: those who talk down a J-pole are selling something else, or bought something else and never tried one. Don't believe what you read always. Try a J-pole, they've been around for a very long time for good reason. Also, unlike any 1/4 wave, there is zero need for grid or ground radials or to be "over good ground". 1/2-wave antennas are not sensitive to such. 1/4-wave are. I've always found a j-pole to out-perform a 1/4 wave. Last one I built was of 450-ohm feedline and cut for 6-meters. I use it portable. Pull it up into a tree and you're on the magic band!
Very nice and well done
Do you still have to make a choke on this antenna?
Thanks for all the great videos, this might be a newbie question but can you mount two of these on one mast given that your only using one at a time, each with its own feed line? I bought your slim jim a while back and now as I get ready to finally mount it I am faced with lots of new questions. Including what if I wanted to do 70cm or 6M without having to put up another antenna mast and still have that performance of the slim jim for 2m.
Thanks Michael for swiftly mailing our 6 meter J-Pole on 12/24/2018! 73s kk4ztg
Michael, on the slim jim, if I put a PVC coupler or something else non-conductive in the gap to add stability, would that affect performance?
Do you have the folded version for 6m too?
Sir, how many watt of transmitter this jpole antenna can carry? Or is this jpole antenna can carry the 200w power output of the transmitter? Please reply. I am interested this jpole antenna
Hello Michael. How is it possible to solder the SO239 connector to the copper pipe? Yesterday I wanted to solder such a connector to a HB9CV, and the solder didn't stick. Do you have an advice for me? Thank you!
I use a propane torch so I can apply a lot of heat very quickly. Then cool it with a wet rag. Also surface prep by cleaning the copper and using a good amount of flux helps too.
@@KB9VBRAntennas Okay, thank you, I'm just afraid of melting the plastic part inside the SO239 connector by using the intense heat, because for soldering I have to heat the connector too. I think, you know what I mean.
Yes I do. I use Amphenol brand UHF connectors specifically because they have a heat resistant dielectric that will stand up to torch soldering
@@KB9VBRAntennasOkay Michael, thank you, but the Amphenol connectors have a plastic insert too, so I think, it will melt anyway. But thanks for your help and 73 to the USA.
saw your listing on ebay!
If i were to spray it with plasti dip (plastic paint) so the copper doesn't maintain exposed will it affect the performance of the antenna?
I probably wouldn't use Plasti-Dip to cover the antenna as it could detune it and alter the antenna's performance. But you can paint the antenna with clear lacquer or a non-metal spray enamel without any loss of performance.
sir is it possible to have a twin slim jim antenna?
Does anyone use this just for scanning radios? I'd love to see a demo on how well it receives.
That's my plan; just built one. Will see how it works next week.
Do you recommend anything for putting the 2 m antenna together such as dialectic grease
With the two piece antennas, I like to put some dielectric grease such as OxGard or NoAlox on the threads and put the two pieces together finger tight so that they don't seize up.
Most excellent
On break down antennas, you are using a standard 1/2" male and female pipe thread to solder joint adapter. Since they are NPT, the threads are tapered. This means that you can vary the overall length of the element by 1/4 to as much as 1/2" in length, depending on how tightly you crank those threads down.
Does this affect tuning?
No it doesn't. When I build the antennas I take into account the space taken up by the threaded connectors. My recommendation is to thread the two pieces together 'finger tight' and to use a bit of anti-oxidant like Noalox or Oxgard to aid in making a good connection. Once you do that a couple of times, pieces will consistently thread to about the same spot.
Michael, Just a curiosity, has anyone yet requested cophase coax(harness) to combine, oh, say three or four slim jims straight up a pole @ say 465mhz. I just placed an order for this antenna, will be needing another(going mobile). But I had on my mind the cophased loops from the old systems up at the Natnl Guard Armory/State Police Posts/UHF loops. Talk about some ears man. Anyway, pretty sure amagonna love the antenna. Thx ahead from KY have a great day
I periodically get requests for co-phased J-Pole and Slim Jim antennas. It is certainly doable, and I've researched putting a system together. I just haven't had the production capacity to add that item to my catalog.
@@KB9VBRAntennas Antenna arrived timely, undamaged and is now sitting on top of 100ft. LMR600 with a fine brillo polished sheen. The antenna works quite well indeed (knew it would) and a satisfied customer is what you have here. Thanks KB9VBR! And I'm not quite done yet. Will be hollering at ya as future projects are realized(off grid ammo can repeaters for uphill deployment) is my aim. Thanks again Michael.
@@KB9VBRAntennas I gotta say, I absolutely cannot wait to get out into the county here and run a pair of 50 watt radios through a pair of KB9VBR slim jims. It should be quite interesting. Only have 1 rig though, gotta build out a mobile now. I did send my son to work with an old value little silver uniden bubble wrap 5 watt radio, 4 miles through an industrial park & in a hole he sounded like he was right next to me. Solid. Phenominal. It's not even 10 feet above the roof now. I've got up to 70 feet to go which will put it well over the dirt and into the regional airwaves, should put a grin on my face in a month or two. I plan to use a sat dish mount low on back of the tool box, which might not get the SJ up over the cab(tundra) but should be well out of the bed, close to over the cab roof anyway. Will let you know how it all pans out for me, but I have to think a base SJ will talk to a mobile SJ just dandy. I was looking at high gain, base loaded trams/brownings, Motorola but what you get these days, a lot of it's just China junk or knock off. Now, one thing I do know, this copper pipe here, is NOT china junk. It's anything but. Good Day Sir!
I am new to ham and at this time don't want to perforate my home to mount an antenna outside to run in a cable. Therefore I have a 1/4 wave ground plane in my second story. I able to get into my nearby repeter just fine. My question is if you would please recommend either of these antennas for an inside use like I described. If mounted outside, how do you protect the coax from water intrusion? Does it make a difference if it is mounted vertically or horizontal? Thanks you!
The J-Pole is 69 inches from tip to tail and the Slim Jim is 58 inches. Both antennas are great choices for placing them in your attic and I've had countless customers do that with excellent results. You can protect the coax by sealing the connection with high quality electrical tape or amalgamated tape. The antenna is a vertically polarized antenna, so you should mount it vertically for best performance.
Thank you, Thank you, Thank you.
Michael, I have a question as a complete antenna idiot... I was looking closely at your J-Pole building schematics, but thought the center lead of the coax was supposed to be connected to the longer radiating section of the antenna, and the outer shielding of the coax was connected to the matching or shorter section of the antenna... I am studying at HamRadioPrep for my Technician currently and have not as yet built any...
As you have probably found out by searching online, there are plans that attach the center conductor of the coax on either side of the antenna. I have experimented with attaching the center connector of the SO-239 to the stub and to the main radiator. I have not found a difference in signal quality or performance. I choose to mount the edge of the connector onto the main radiator because I believe it makes a better mechanical connection.
A J-Pole style antenna is comprised of three sections. First is the mounting section where the antenna is attached to a mast or support. The second section, which is 1/4 wave long, is the impedance matching section. The two pieces of the antenna that run parallel to each other change the impedance from the 50 ohms at the feedpoint to about 300 ohms which is the impedance at the start of the third section. The third section, which is 1/2 wave long is an end-fed dipole radiator. With end-fed antennas, the impedance is high at the ends and low in the middle. With the 1/4 wave section, the impedance is low at one end and high at the other. So the two parts of the antenna can work in harmony.
Interestingly enough, in the Rothammel's Antenna Book (13th ed english translation, page 777) the author states that feeding both the short and the long sides of the antenna are electrically equivalent, yet a configuration where the short side is direct fed provides improved overvoltage protection because the half wave section is directly grounded via the outer cable conductor. (parenthetically, this method also helps lower the overall noise floor of the antenna, by dissipating static to ground).
Since a J-Pole is considered a balanced antenna- it is a half wave antenna by design; the RF energy will travel up the matching section and then radiate from the resonant part of the antenna. Hence it really doesn't matter which side the connector is attached to.
@KB9VBRAntennas Thank you!!! Can't tell you how much I appreciate your explanation!! I know electricity and RF have different properties and whatnot, but this kinda distilled that fact for me... BTW, I'll be looking up that antenna book and reading more, since I am determined to graduate from antenna idiot to antenna moron (or better yet) antenna wizard...LOLOL Thanks again, Michael!!!
Can I ask about your bottom of your base at T area .If you measured for frequency then why is there more copper extended on T area ?.Shouldn't it be non inductive ?.
Can you use the 2m antenna for 70cm/440 for tuning?
Would there be much difference between using 1/2" copper and 3/4" copper? I've heard it provides wider bandwidth, but no specs on how much more... Thoughts?
Michael, i just came across your channel and website. i was wondering the separating style of j-pole, is it just the 2 meter or can it be gotten in 70cm, 6m or the murs band?
The 2 piece separating, or break-away J-Pole is available in the 2 meter version, and I can also supply it for the VHF MURS, marine, or public safety frequencies. The break-away for MURS isn't in the catalog, but you can order the 2 meter break-away and request that it be tuned for MURS. As for 6 meters, that antenna comes standard in 2 pieces otherwise it would be two long to ship. I don't offer a 2 piece UHF antenna as their shorter length really doesn't require the need to be broken down. I hope this helps you out. Michael
Hi Michael ,I'm really new to this and trying to learn ,are either of these antennas capable of working on vhf and uhf frequencies without having to add other antennas. I'm probably asking a lot but I'm looking for an antenna that I can hook to my hand held without having to mount multiple antennas but use both bands. Kind of like a temporary base station until I can upgrade to bigger and more advanced equipment . thank you for the video and 73s till next time.
Very much interested in gmrs, i will be getting in touch
I am a new ham how high does the J pole need to be for 2 meters?
VHF/UHF is line of sight propagation. I usually tell people that the sweet spot is about 20-30 feet. You can put it higher or lower, but 20 feet is an easily attainable height that offers good reward.
I have a question, why does it look like the centre pin is connected to the quarter wave part of the antenna. Should the centre pin connect to the half-wave part and the outer part of the socket hit the quarter wave part?
I'm no matching guru, but It is my understanding that it will work both ways. If you're building your own, try it both ways to see which works better for you. But the design has been around for 100 years seems like. So there is ample testing and in-service antennae out there to look at, as well as dozens of diagrams and calculators online. Look around. I don't even know which way mine are connected, I have a handful of j-poles I've made over the years, both of copper and of parallel feedlines. I've also seen them made of aluminum and stainless.
Why the center conductor pass thrue 19 inches stub. Why not in long tube 58 inches? That is vhf design?
Hello Michael,, I acquired on of your solid J Poles 3 years ago.. Do you recommend replacing the antenna after so long ?
Not really. I've got one that's been on the air consistently for at least 10 years. It still works great. I checked the connectors a couple years ago‚ the connection was nice and clean with no water penetration.
Are you ever on your radio, like do you ever talk to other hams?
I'm on the radio all the time. Here's a recent Parks on the Air activation that I did: th-cam.com/video/OkKBPc-AhEk/w-d-xo.html
Hey Michael,, I mounted my J Pole in a rubber isolator,,,,Did I do wrong, PS I am on my HT most of the time, tied into Western Reflector and the local reflector. On week ends I get on my base unit, connected to the JPole
I have a question that nobody seems to ask but, if there are slim jim antennas, why would anyone ever build j poles anymore since in many videos it says that the slim jim is in so many cases better. Or is it simply to spare an extra bit of copper pipe.
What is the pros and cons of both antennas or do they have their respective purposes for certain applications.
What I'm really asking is...why build a jpole if you can spend a tiny bit of extra money for a slim jim? Any explanation would be greatly appreciated
J-Poles are a good choice if you are mounting the antenna at a lower mast height, or if you live in an urban area or valley. The omnidirectional radiation pattern and higher takeoff angle makes it easier to get a signal out if you are surrounded by buildings or rough terrain. Also, with the base of the antenna at DC ground, you can mount it on a metal or non metal mast with affecting the antennas performance. It also has a very low noise floor which makes the J-Pole an excellent receiving antenna for weaker signals.
The Slim Jim has a lower takeoff angle and more compressed radiation pattern. These two features of the antenna gives you about twice the gain as a standard J-Pole. A little more gain will make up for some of the feedline losses you’ll receive at VHF frequencies. Plus it will help stretch your signal out a little further. To really realize the benefits of the Slim Jim, you need to mount it in the air at about the 20-30 foot level. It will work well at lower heights, but the antenna shines when you get it up in the air.
I built my own, but looking at your website, I'd have to say your prices are very reasonable.
Are these strictly 2 meter or do they dual band 70cm? I noticed some do and some dont depending on the 1/4 wave matching side.
Do you have VSWR and impedance figures for the 2m band Slim Jim. (I ask as the original design by Fred Judd resonated above 146 MHz).
Hi Mike, quick question.. what brand of SO-239 are you using? Mine easily melts when i solder it.. thanks w1mdm
Cheap SO-239 connectors will melt when you apply heat to them. The ones you don't want are those with the white dielectric material. I use Amphenol brand connectors. Those have a heat resistant insulator that won't melt if you work fast in soldering the connector.
@@KB9VBRAntennas Thanks Mike, yes am using a torch to heat it but had some luck with those cheap 239s, i made a jpole yesterday for my airband receiver, the nanoVNA works great on analyzing the antenna.. centered the freq to 125mhz. Thanks for the details of your videos. Am thinking of 6M right now.
If I can not get an antenna outside my house for various reasons , would be operating on gmrs reasons ...... what would you recommend?
You'll always have your best performance with an outdoor antenna, but often that can't be done for whatever reason. Fortunately the GMRS J-Pole is quite short, so if you can't put it outside, you may be able to place it in a window, on a deck, or in your attic.
What about a true dual band VHF/UHF j-pole? Not just a 2m j-pole that happens to resonate at 70cm.
hi do you make slim jims tuned for the UK and are they available with coax as I will need about 30' to run from my eves to my shack.
cheers Phil M6PGU
I realize this is a question that isnt easily answered, but what type antenna would you recommend wide band use for an sdr? Im new to ham....tech licensed in April 2020, and taking my general next week, August 2020. Ive got a gp-3 atop a 24’ mast I put up last week. Now looking for a good general purpose antenna for an sdrplay.
Thanks for your time.
A good discone for receiving would be ideal. They're great for scanners or SDRs, but lack for transmitting.
I bought this for my baofeng r5. Is there any trick to making this work? I can not seem to pickup anything that my default little 4inch antenna does. I'm new to this so pardon ignorance. Thanks
There are a lot of variables that could affect how the antenna performs. Is it inside or outside. If outside, where is it located and how high up is it. Are there other buildings or large objects that could shade it. What type of feedline are you using and how long is it. Are the connectors good on the feed line? A short circuit in the cable can cause performance issues. My list of Frequently Asked Questions has some tips that may help you: www.jpole-antenna.com/faq/
KB9VBR Antennas thanks I started getting better signals in front of house. Posted message from back of house. Crystal clear reception with antenna.
I'm glad to hear you found a better spot for the antenna. There must be something in the back yard affecting the antenna.
on other j pole builds the coax centre is connected to the long section but yours seem to be opposite. does it actually matter or is it relevant for certain situations, would appreciate your help please
Can you tune J pole for CB radio ?
No
how about a dual bander?
Am I able to run 440 on this antenna?
The 2 meter J-Pole antenna also works quite well on the 440 band. The SWR at 445 MHz is about 1.5:1 or so. The 70cm band is a frequency multiple of the 2 meter band so that's why this antenna can work for dual band operation. The antenna works great for local repeater contacts and such on the UHF band.
KB9VBR Antennas thank you very much!
Hello
Can someone tell if this construct the ANTENNA
I will work on my own radio which is Baofeng UB-5P?
Thanks
Anyone build and test one for over the air TV?
The antenna would work somewhat for TV, but television channels are spread widely between 50-700 Mhz, so this antenna would be a poor choice for the UHF channels.
You need wide band-width for various stations as they're all on different frequencies. It will receive but they are tuned for a specific (small) frequency range. If you're near the stations you want to receive, could be good.
Oi amigo manda esquema dessa antena
Thank you for your video. N0QFT
So the first jpol e for 34,00 will work on uh f and vhf?
Yes. The 2 meter J-Pole antenna also works quite well on the 440 band. The SWR at 445 MHz is about 1.5:1 or so. The 70cm band is a frequency multiple of the 2 meter band so that's why this antenna can work for dual band operation. The antenna works great for local repeater contacts and such on the UHF band.
I love j.pole more then slimjim.sir