All About Baluns (Ask Dave #73)
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- เผยแพร่เมื่อ 30 ก.ย. 2024
- I get lots of questions about baluns. This video explores baluns and gives demos. A balun is a device to convert a balanced transmission line to an unbalanced transmission line and vice versa. Subscribe: / davidcasler . Ask Dave Playlist: goo.gl/inaQeB. Tip Jar: ke0og.net/tip-jar
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Some really great info here, and presented at a level that you don't need to be a Broadcast Engineer to understand. Well done and thanks from KM2U ;)
You don't say where it's better use a voltage or current balun, so if I understand correctly, it's a free choice. You just see what works best?
You said that you don't know why the two to four ratio of ballon Transformer is used quite a bit, but I would guess that it's probably for the same reason high voltage power lines are used to transmit electricity across country. With a higher voltage, you lose less power to heat when they get put through the line.
Thanks man, informative as always!
Thanks for the info.
Is all this applied to reception only antennas or only to transmision ?
All of this helps reception some. But the primary purpose of careful matching is for transmitting.
Excellent job Dave, explanation is clear and concise. I have one question however; I am moving my shack and as such need to run a new schedule 40 underground feed aboiut 150 feet to the tower. You mentioned balanced feed line vs unbalanced. I have LMR 400 now, but it is not bury flex and not long enough, which would mean that I would need to have a union installed along the run. So is there an advantage to running the REAL ladder line in the underground conduit vs bury-flex LMR 400? Disadvantages ?
Burying ladder line doesn't work. It needs to be out in the open away from other metal. Call Ray at USAcoax.com and he'll get you set up.
Thank you Dave. I will check out USACOAX.com (Ray). I am confused however by your comment that it needs to be away from other "metal". The ladder line would be buried 18" in the ground in Schedule 40 PVC electrical conduit, not metal conduit. I should have made that clearer, my bad. ISo would ladder line be Ok in PVC conduit buried ?
Ladder line is easily unbalanced by what surrounds it. You can contrary to popular belief run it close to metal pipes or panels but ideally each conductor should be equal distance from that object. IE you could run a ladder line down a metal tower on stand offs. to preserve the characteristic impedance the spacing from that conductive structure should be much greater than the spacing of the conductors in the feedline. I suspect that your scheme to bury it in PVC conduit would be very lossy due to the localized rf fields in the ground. I am sure ladderline could be laid underground in a huge duct but it is far from easy. I think the way forward in your project would be the best coax you can afford.
Dave, what kind of verticle do you use?
It's a Butternut HF-9V. I did a recent video on it.
Dave, you are a blessing! Thank you for sharing your experience and wisdom!
David, thanks for the video. I noticed that your explanation is in contradiction with the article by W7EL you are refering to. The current flows in both directions inside the coax cable, through the inner conducter and the inner surface of the shield, the same way it does in the symmetric feed. A balun prevents the current to flow on the outer surface of the shield. According to your video the current flows only through the inner conducter, which doesn't seem to be right.
In a proper coax, with all impedances matched, the current is unbalanced. The inner shield is ground, and the current on the inner conductor is AC, back and forth. If there is an imbalance, or impedances are not matched, then things change. I think what I've shown in the video is correct.
@@davecasler The fact that the shield is ground only means that we consider it a zero voltage reference. It doesn't mean that there is no current in it. The reason why bifilar 1:1 current balun works is that there are two currents with 180 degree shift flowing through it, one through the middle part of the cable and one through the inner part of the shield. Magnetic fields of these currents cancel each other, thus balun doesn't stop them. The current could choose to flow through the outher part of the shield (because from current's point of view there is no difference where to flow at the end of the cable - through the antenna or through the outer part of the shield). However this would turn the balun to the coil (choke) because now there is no opposite current to cancel the magnetic field. This fact creates high impedance for this patch.
My understanding is this; if an antenna is not balanced, current (or signal/RF/voltage it's all the same idea) flows back along the shielding of the cable (or one leg of a feedline) to the transceiver. This back flow produces a high SWR reading which can damage the receiver if not corrected. Makes sense so far?
A balun which is an RF choke, a line wrapped around a toroid core, absorbs and dissipates this RF before it returns thereby producing an acceptable SWR reading.
The reason there are different ratios of baluns is because the amount of turns, equaling RF absorption, is different depending on how unbalanced the antenna is.
More unbalanced=more windings around the core=more RF absorbed. That's it!
Fantastic video - I learned a lot - Thank you @David Casler - btw, animations that show what's happening 'in the wires' is really helpful!
I'm confused by the coaxial cable graphic where there is no current in the shield because it's ground...I thought ground serves as the return path...and hence the shield really does carry current...what am I missing?
There is current on the inside of the shield. Hopefully it isn't also on the outside of the shield.
This is the video that got me to connect the dots from my electrical knowledge to my lacking antenna/balun knowledge. Thank you sir.
I have a novice argentine license (LU5ARC), an extra american licence (AC1DM) and a foundation british one (M6UON) and only just now watching this video I understood choque baluns. Thank you Dave.
How do you determine how many turns of cable to make a choke on different bands...
4:1 is because TV's expect 75 ohms on the coax input, but TV antennas are usually 300ohm.
Simply freaking awesome! I just learned a ton of new stuff!
Dave, you are a real asset to Amateur Radio. N7KHH 👍🏾
Some 50 years ago when I got my first call sign, we used to make baluns out of coil of coax. Why nobody uses them anymore? They were wideband transformers not dependent on the frequency and were capable to transfer kilowatts of power. Now with all these different ferrite toroids who knows what performance they'll have all over the spectrum and what loss of power is going to be transformed into heat?
@John Cliff No sir, I wasn't talking about the RF choke made of coax. Some almost 50 years ago, in our radio club YU5CEF back in Macedonia (Z37CEF now) Europe we bought a fabricated (I don't know who made it though) multiband antenna W3DZZ. It had a balun made out of coax to match the balanced dipole to the unbalanced coax. I remember bot hot sides of the coax loop were connected to both sides of the dipole while the connecting coax was connected to one side and the shield were all connected together. We were not aware of toroid baluns at the time. (de W5DMA)
From one grey bearded ham to another, "very well presented. Thanks." I'll be watching more. After almost 60 years in the field, and 40 years of not operating at all, baluns have always eluded my understanding of them. Hardly ever needed one but I'm back building antennas and I have no idea what I'll be trying next. Now with the internet sleep will be my only distraction. I finally picked up an MFJ Z-bridge like you show and that will be a lot of fun to play with. 73's OM.
Thanks for breaking this down. I still want to learn more about baluns and ununs, but this video got me thinking about them in a different way. I understand so much more about antennas now.
Dave is the best of Elmer's. 👷
Awesome! Pure gold, thank you very much, now I finally understand what it is, what it's for and where/how to use one. 73 from NL
Thanks Dave. I’m scratching my head while trying to match my 20m efhw vertical (SpiderBeam) antenna. Maybe I’ll jot you down a quick question and maybe you could make a video. All my best to your sound and camera person (XYL). She does an awesome job. I just watched your 1000th video. Congratulations. Keep up the good work. 73!
No Dave! The coax MUST have return current on the inside wall of the shield! You see 1:4 baluns a lot because it just naturally comes out with 2 windings or 4 windings, as you showed.
Hmm... I wonder, in addition to the comment by @laserhobbyist19751 and I saw someone else with one... but still -- those old TV baluns we'd see on the backs of our sets to go from the 300-ohm twin lead screws to a 75-ohm RG-59 coax to our rooftop aerial for the UHF channels... those would be 4:1, would they not? I wonder, what would the maximum power be to use one of those where a 4:1 would be called for in amateur practice? Or, would they even be usable? I remember reading about that, but I suspect they'd only be good at QRP... Thoughts?
Of course, that was typed at only 8:36 or so into the video....
I will definitely have to watch this one several times...
Dave you did a awesome job on a very complicated subject, l do however have a couple, dare I say, squabbles :o) , perhaps more like friendly advice. First, you should always use a 1:1 current balun when connecting an unbalanced radio to a balance antenna such as a dipole to prevent current from running back down the outside of your coax shield and the other was your advice on building your own. It is a little bit more complicated then just wrapping some wire around a big toroid. Peter from the TRX Bench did a wonderful 4 part series on Baluns, just search youtube for TRX Bench balun (videos 100, 101, 105 and 131) and if you want more information as to why the type of wire matters (actually it is the diameter) just do a wiki on telegraph equation. After viewing these videos you will be able to build a Balun better than anything you could buy at a fraction of the cost and you will be able to customize them to your needs. Peter has an awesome channel and his balun videos are must see for any ham. 73
Thanks for the TRX que. I'm currently building a 3 element yagi (my first antenna build. Also, the first time I've used a milling machine!) tuned to 144mhz. I was hoping I could use it for an experiment in RX on 143.050 and the lower end of the 2m band for TX. As I'm building it, I've been wondering about a balun. A yagi It is just a dipole with clothes on, but I've been scratching my head about how to implement it.
Excellent work OG - I think your best work is with these advanced concepts, thorough and nuanced.
Hi, Dave
If I were to put up a shortwave dipole, each leg 12', without balun/transformer/impedance matcher, which bands should I expect to receive?
Many thanks and 73
N4ANO
Hi Dave,
In your animation starting at 1:38, you show current flowing back and forth on the center conductor, but no current flowing on the shield. However, there is current flowing on the INSIDE of the shield, and it is equal and opposite to the current on the center conductor. So there should be two arrows going in opposite directions INSIDE the coax. There must be a return path somewhere, and we don't want it on the OUTSIDE of the shield. That's why we might want to use a choke balun.
Keep up the good work! 73 de kc0tw.
Would it hurt anything to just wind a choke at the dipole connection regardless of whether you know if you have RFI or not?
If not, are there specific ummm...Specifications of how many winds/how large of a loop for each band/meter?
The best SWR you can achieve without any balun. Say how to proper measure and calculate the CMRR of a 1:1 current balun with a two port VNA. The current balun itself is a three port device.
The statement of how the current behave in a coax cable, is really misleading. Every one who has the ARRL handbook should take a look at chapter 20.1.1.
There must be a return path for the current. And for the coax, the return current flows on the inner surface of the shield.
Current doesn't always stay inside coax. It is best of it does and is called differential mode current, but sometimes a portion of it also flows on the outside of the coax called "common mode current". If a dipole exhibits an imbalance for some reason like one side somewhat closer to ground or close to metalic objects such as a metal roof, then common mode current can and will flow on the outside of the shield. Thats where a good, 1:1 current balun should be used!
Great discussion Dave. However, in this video and the other you did about "Do I Need a Balun?", you discussed that incident where you couldn't get the antenna to tune with the balun and when you removed it, it worked fine. You didn't explain why the balun didn't work in that case. Please explain.
I made a 20M Dipole Antenna. I will not be using this 20M dipole for any other frequencies other than the 20M that it was made for. Is a balun needed for this a 20M Dipole antenna? Again I will not be using this 20M dipole for any other frequencies other than the 20M that it was made for. I also have an isolator. Would I need both? Do they pretty much do the same job?
An estate sale yielded two baluns. A 1:1 and a 4:1
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They look identical but I'm not sure how they work..
Why don't we call transformers "inductifiers" and call rectifiers "transformers"?
Dave - I think you should review your statements regarding coax starting around 2:30. The shield in fact is the second conductor in this RF AC circuit; you have to have at least 2 conductors in a circuit. You can't have a single conductor simultaneously being the supply and return path. RF current equal and opposite to the current in the center conductor does flow on the 'shield'. Ideally, the shield current will be confined to the inner surface of the shield due to skin effect- the surface that can 'see' the center conductor
And all that aside, this was a very good presentation. Nicely done.
Thanks a lot!! Now I understand choke balinés from matching baluns. So a 1/4 vertical antenna is unbalanced, right?
Great lesson, pretty much serve the same purpose just a difference in winding. So, here's my question.
When it is appropriate to use a current or voltage balun?
What about a advantage and disadvantage between the two?
hi mr david am real new about the balum thing.. what you think here is my project 140 ft wire loop try ing to use it on cb band ch 20 and 7 meter 7263 balum 4.1 home made type best it will match is 2.1 swr need lower 1.2 is my desired swr what you suggest
Rubbish, Coax does the same....but you need to remove the outer-currents, all the rest is bullshit. Coax with a good choke is the same. Where do you get this bullshit?
Balun=to a balanced antenna, UnUn=to an unbalanced antenna to start.
The real mystery to me is the fact that twin lead has less loss than coaxial cable.
while discussing current-baluns 11:35 he says: "If you want that kind of current, that's fine." and he leaves it at that. but i'm still studying for the technician class license and dont know that means? i was hoping to learn WHY a balun would be used in this situation but the discussion went in another direction. i must have missed something... i usually do:)
Baluns are used when transitioning between a balanced system (like a dipole antenna) and an unbalanced system (like a coax transmission line). Properly done, it keeps RF where it's supposed to be (inside the coax, and radiated only from the antenna).
if only you believed in miracles, baby, you could have Marty's Balun
I love your videos. I feel like I'm learning from Obi-Wan himself.
Wow, great job. Thank you. 73 Pascal VA2PV
A wealth of knowledge. thank you :)
Very informative, thanks for teaching complex subjects. 73 de N5EVD
So Dave, You said in the beginning you would tell the difference between voltage and current baluns and when to use each type. I love the way you compare voltage balun to current balun but....you do lack the idea of when to use each. I have been spending the past 5 years looking up when to use each and have run into too many formulas. so, when is the case for a current balun and when is the case for a voltage balun?That is what the beginner and me stop at because there is no explanation on exactly when to use each without multiple formulas and very very technical articles. could you please find out the reason for the use of each and not just "Use it when necessary and you have to compute..."' there should be some easy explanation on when to use them because of the lack of electronic experts in us hams. Thanks for the video and keep them coming. 73, ad0am
Hi Adam, very interesting question. I don't know the answer. If you find anything definitive (and I'm not sure there is much), send me a link.
David Casler will do. thanks.
Adam Rennison
Nice video Dave! Explanation on choke balun needs more information. Winding few turns of the coax should add inductance on both inner and outer segments of the coax and that should act as common mode choke, which should be same as 1:1 current balun. Assume if it was adding only inductance on the outer braid, then that should be limiting the onward signal from the TX also.
No. What goes on inside the coax is independent of what happens on the outside. The signals inside the coax, going either way, are not affected by the coax loop. Only the current flowing on the outside of the coax is affected. The transmitted signal will not be on the outer braid. The ARRL Handbook and the ARRL Antenna Book both explain this in some detail.
Newly licensed Tech and planning on taking my General next month, so forgive the basic question. Doesn't the extra 25' of coax that you used to make the inductor add to the losses in the feed line (due to the extra length)? Because of that, is it more beneficial to use the choke with the ferrite beads? Thanks.
Yes you are correct, in theory. It's a cost trade-off between the co-ax and ferrite beads. You can go either way. At HF the extra 25 feet of coax doesn't add that much loss
Thank you. Watched all of your tech exam videos prior to my test and got a perfect score. Just finished watching all of your general exam videos. Great stuff and much appreciated.
A lot to take in but we’ll explained thank you
with reference to 8:17 I think the reason is same as why power lines use very high voltages. High voltage means smaller currents. With long cables the I squared losses will reduce the power to the end of line. But using a transformer to convert the signal to a high voltage means proportionally lower current, this 4:1 hence reduces those I squared losses. eg P=IxIxR. My guess is at the arial end, that 4:1 is simply converted back to 50ohms. It means you can have much longer cable as far less I squared losses will occur.
But that is a wild guess as I know bugger all about transmission lines.
All of my questions answered. Thank you Sir. Steve GJ6WRI
Glad to help
Nice presentation on a confusing subject to a lot of people. I like the , "if you need one they are great"!!!
New subscriber and now working my way through every video. Awesomeness.
Welcome to the channel!
what is a symptom of RFI in the shack? i have an IC 7300 and not sure what i am looking for WRT RFI noise in the shack.
For example, the radio locks up, or you hear a buzz in the computer speakers, or you get a zap when you touch the radio. These are some symptoms. Basically anything that behaves in ways they shouldn't.
mysterious signals on your computer speakers, all of a sudden shutdown of equipment when you did not hit the power button, and the most obvious TVI.
Wow, I'm an EE and I've been wondering what all this talk of voltage balun vs current balun is all about. Translated back to conventional engineering lingo, I now know that this is just an autotransformer vs a conventional transformer with two isolated coils. I still don't quite get why this is called "voltage" vs "current" in ham land, but at least I know what they are now!
Yeah, I didn't spend a lot of time on voltage vs current. Basically a voltage balun balances the voltage at the output, and a current balun balances the currents regardless of the voltage.
In technical literature. a voltage balun would be different voltage and a current balun would make a different current. the impedance stays the same but multiple of the turns ratio time the inverse square so to speak. hope that helps some in understanding even tho this is not technical video. i mean that the only real change is in ohms law aspect of voltage and current.
73, ad0am
4:1 Baluns are useful between balanced lines for center fed Zepps, Off-center fed (OCF) dipoles with coax, G5RV antennas, full wave loops, NVIS dipoles that are close to ground and have impedance levels near 200 ohms or high impedance feeds for log periodic beams.
Hi Dave, Is there a way to calculate how many ferrites are needed in a coax going to a 2m Jpole? I think this method would look cleaner than a bunch of loops of coax in my neighborhood. I am using RG-8X for a 40' run. Otherwise, barring this.. can one estimate the number of turns of 8X of, say 4-5" diameter ??
This explains a lot for me and answers my questions. I'm building a 2m j-pole that I intend to mount on my semi (modern semi bodies are terrible for ground plane antennas. Not very flat and they have a LOT of fiberglass). Instructions I find say I need a balun just below my antenna, but no one seems to agree on how many turns or diameter. So I suppose I can just coil SOME coax a few turns? Anything is better than nothing?
Hi Dave, great video which I really enjoyed. The only one thing I'm confused with is when or what antenna situation would you decide to use a 4:1 voltage or current balun? Say a Doublet for 80-10m, I would be very grateful if you could help me with this 'voltage or current' choice, does it depend on the type of open line balanced antenna? Many thanks for the informative video.
I saw a video showing how to make an antenna that should cover 40 M through 6 M I think may have been just up to 10 M. But it had the wires out with 600 ohm ladder line coming down connected to RG8 and a coil of coax. I don't remember the length of the wires and the ladder line. But I was thinking that it would help if there was a balun in there to help change from the 600 ohm to 50 ohm. I am new to this and learning. But I think something like a 4:1 balun would make the ohms match better. If I wanted to make one of the antennas what would be a good balun to try in there? They say it isn't needed that the 600 ohm ladder line will make it 600 ohms to the antenna. I am new at this but I don't understand how that would work.
Smart Man right here, reminds me of my Father silent key (k6hzh) who was also a amature extra and a radar engineer for Lockheed Aircraft from 54' to 78' these guys are the pioneers of the ham radio hobby!🇺🇸⚡
TRX Bench #101 Balun part 2 describes the wire and Ferrite Toroid to use for an accurate Balun. Beware of the Ferrite Material being sold - I purchased what was to be an F114-43 Toroid Core after forming the Balun it only has a low SWR on the 13Mhz Frequency a true 43 Composition Ferrite Toroid will produce a low SWR on all bands when used with 18 Stranded Teflon Wire.
This was not the first video on this subject I should have watched-more confused now. I’m going to check out David’s earlier videos. Sheesh! 🤦🏼♂️
Hi Dave, thanks for the video. I understand the need of impedance transformer what ever they call them. However, I'm not quite understand 1:1 balun. Based on this video they are two type, the transformer (1:1 transformer, of cause) and the choke balun. What is the different between them in term of function and performance?
Very nice presentation. I appreciated that you pronounced the word BALUN correctly. Sometimes they are called “balms” (that’s an ointment) or “balloons” which only adds to the confusion about these devices.
I've been subscribed for awhile and watching. I was looking at you older videos and was surprised to see you had a flying broomstick. Why do you want a plain? To many bugs in the face I'm guessing. Love the channel, keep up the good work. You've been very helpful to me as I'm a new ham. KF0ALT
in the beginning you said there is no current on the outer shield of the unbalanced line, then later you talk about the dipole and then you say there is current coming out of the shield. you didn't really explain the difference between voltage and current balance, you didn't write down the voltage and current anymore like you did in the beginning.
Minute 11:02 you show the phyiscal balun and i think you saybit matches the previous diagram you had.
the physical one seems to have two separate loops? and has 8 turns each side. diagram was a single 4 turns.
i am confused by this.
Also why are you able has you said to operate a dipole with no Balun sometimes?
How would you use a twin lead as a dipole for the Balun?
The so-called "folded dipole" is made with twinlead. It's a balanced antenna, hence often fed with ladder- or window-line. You'll need to provide a balun somewhere in the system.
nuts dave now i need to learn more about it because now i want to see if a balun would improve my Rx antennas for fm radio on 3 meters and for aviation band and one for 1090mhz ads-b. the aviation band i made a Rx ground plane half wavelength, its real fun just to see the extra Rx range i get from home made antennas. the dutch government wants ham's to pay 35 bucks a year these days to just be a licensed ham so i will stay with Rx.
Baught a qrp tuner kit wating for delivery. Have a few hand wound units. That was given by my Elmer. At W8FT.
Ha ha. Yes I've used in the army a beer can as a form for a choke=6 turns then remove the can. tape down the coil and make fast to the mast. Off to the radio we go with tolerable SWR. TKS
Hi Dave I was looking at a video you did on Chinese radios, no place to comment, Baofengs have proven to be more reliable and legit than Yasuo. Kenwood firm ware is identical to Baofeng.
Thank you Dave!
73's
KP4OSP
I think it is a very bad idea to ground the coil on the balanced side
One nice thing about grounding the center of the coil on the balanced side is that there's a direct DC path for wind-created static to drain off.
Brilliant Dave - you make the subject matter real fun to learn. 73s GI8WFA.
Could you please give information about a transformer balun used for uhf band antennas... 🙏
I've not seen baluns used at VHF/UHF. But there will be some method of tuning the antenna. If that is a gamma match, very common, it acts as a balun.
@@davecasler Sir, could you please provide detailed informations about 'Gamma Matching' for uhf band antennas... 🙏 it would very kind of you..
Very well explained. Thanks again Dave!
Can I see a Picture of a built Toroid with 200 ohm resistor please, Cant figure out where the resistor goes
Dave I should have added I am making 2 meter quad antennas so am using sleeve chokes due to light weight and less windloading.
Get it well tightened down Dave, 3.5kW is a lot of current!!
All right words are there, but many explanations are missing.
Thanks for sharing. It really helps in understanding how balun worked in CCTV.
please use both feet while walking ….. Love It like the man said before me nice presentation.
Great info Mister Casler, thanks a lot. Very Very helpful for us *hams* in EL81mt
Perfect explanation on a rarely explained topic...73...Roger / NQ8RP
Would it make a difference if you used Carbon composition resistors for your tests?
The folded dipole, like in a yagi-uda antenna, has an impedance of 200 ohms
So the turns ratio makes sense, but I never know how many turns to make the primary in the first place... say 50 ohm (real) coax, what should I design the impedance of the primary to be? 50 ohm (imaginary) as well? please help me understand that :/
You're getting into design issues. You should start with existing designs and go from there. You need fewer turns as the frequency goes up, but I don't know the exact equations.
Thanks for the information. I use a 10 turn loop of coax at the junction of coax and ladder line of my 40 mtr G5RV and I wound a transformer/balun [49:1] for my EFHW 40-10 wire antenna.
I understand this was about baluns, but now I am confused about both sides of the dipole antenna radiating RF signal or not. I have been using a coax choke balun for my 40M dipole fed with all coax. Are both sides radiating? If not, will a 1:1 balun make it more efficient by making it radiate from both sides?
Both sides of a dipole radiate. A choke balun helps keep that power in the antenna so it doesn't creep back down the outside of the coax and cause the coax to radiate. Sounds like you're set up properly.
no. all the 1:1 balun would do is make sure the currents are equal. but remember, a dipole is 75 ohms and coax is 50 ohms at the 1/4 wavelength of that particular frequency. when used as multiple band it is alot more complicaed
Thank you. You're the boss Dave.
Adam, correct me if I am wrong, but in the case of an inverted vee the feed point impedance is lowered as the elements are angled down, as well as lowering the whole antenna. as in NVIS. Right? This is more about confirmation of being on the right track than an argument. I promise.
correct
Great explanation of the topic. Even though I had a basic idea of the topic , I learned something. Thank you. David Byrd KN4BHS
Remembering Navy & college I got my Extra (AG7MW) on the first try. That doesn't mean I know something. I have a MFJ-9200 QRP with a SWR, tuner, then 50 feet of RG-8X going to an MFJ mini G5RV. I understood that I needed an isolation balun, so I did. Should I have gotten another? What tape do you recommend to keep the rain out of the connector? It might be too late.
Sounds like you have everything you need. Just add perseverance and you'll have lots of contacts! Re the rain, electrical tape is fine for the short term. Look at DX Engineering's web page for sealing tapes.
nice