Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KD9NSL, Dec 10, 2019.
What value of resistor do you recommend, Glen?
The "balun" is allready a "dc short"
Adding a resistor is a wa$te of money.
If there is a balun near the equipment end, and that balun presents a DC short, then a resistor is probably not needed. However, for other antenna installations, I would use something between around 27K-ohm to 100K-ohm at 2-watts. If running low power, a lower value resistor would work, something like 4.7K-ohm to 10K-ohm.
The purpose of the resistor is to "bleed off" the charge that builds up on the antenna and not for any lightning protection.
Not Glen but no less than 10X the impedance. Example 500 ohms or more. Anything less and you start affecting the impedance of the antenna. As Glen said 4.7 to 10 is just fine to bleed static'. In fact for static you can go much higher. Take away nothing less than 10X.
But my balun isn't a DC short, which is why I asked.
Then what you have is likely just a common mode choke, (likely some ferrous beads on a length of coax)... not a balun...
I used to install UHF systems and standardized everything with N connectors and AVA5-50A hardline. I would order in bulk so we had all the same stock. What is described here is what I used at the top of towers. I would use fiberglass verticals with LMR-400 Ultra feeders (usually 5-10ft). The feeder coax had N-M's on both ends. Then the AVA5-50A had an N-F on it. The theory was to keep the hardline straighter and from making any unnecessary bends. The LMR-40o Ultra was a lot easier to weave around to where the antenna was mounted. Usually within 2-3ft from the top of the hardline is where I put the ground clamp. Sometimes I couldn't get right to the top so it was installed below a ways, but that was the theory.
One important note with this method of cutting through the sheath on the outside of the coax - and any coax (hardline, meaning a solid shield, included) is the integrity of the weatherproofing. If you are putting an install in that is to be permanent for decades you have to take care in sealing your connections (all connections - coax to antenna, coax to ground buss, ground clamp on the coax, you name it - if it is outside it needs proper sealing).
The weatherproofing method pictured here is to wrap with tape. That is impossible to get an acceptable seal with. The reason being you can't get a 100% seal around the wire you are using to ground with. Tape won't make that form. This is where CoaxSeal comes in to play. I tried some commercial stuff (I think the Andrew connectors come with some actually) but I didn't have much luck with it so I always bought cases of CoaxSeal - the wide rolls (at the time they weren't sold individually, only the narrower rolls). This is really great stuff to use - provided you are working in relatively warm weather (the colder it is the stiffer the stuff gets and harder it is to mold).
My method for sealing is to wrap a layer of 3m Super 33+ black electrical tape sticky side OUT (backwards) first. The reason for the backwards wrap is to keep the goo off the coax and everything that is being wrapped**. Once the wrapping is complete, apply a layer of CoaxSeal and knead it to form to the coax and in between the coax and ground wire (important note - you need the CoaxSeal behind the ground wire as that is the space you can't get tape to seal!!!). Then wrap a layer of electric tape sticky side down against the CoaxSeal to finish off the job.
**The first time you have to cut in to one of your connections to sweep test a 300ft run of hardline or to inspect components you will learn real fast how much better it is to have the wad of tape and CoaxSeal roll right off and have shiny connectors to work with, not old tape goo'd up junk to smear in your hands.
Don't skimp on tape, don't skimp on CoaxSeal. On the last wrap of tape - don't wrap too tight, but pull the slack out of the tape so it is taught and doesn't wrinkle. If you wrap the tape tight in hot weather the CoaxSeal will ooze between the tape layers until the pressure equalizes. I've never had that be a huge problem, but the idea of the outside layer of tape is to keep the connection clean and with exposed CoaxSeal everything blowing past sticks to it and accumulates. Plus the job looks good and professional when its nice and clean!
And he dosn't have a "G5RV", just a random collection of wires and coax.
In that case op, since you are hooking things up at random, ju$t add more part$ at random till you run out of ca$h.
You are wrong with your assumption that using tape for weatherproofing is faulty!
What is used is the very cheap black plastic tape. After a week, or 2, in the sun, that tape congeals into a waterproof mass which has to be cut off to remove it. Better quality tape often does not congeal. Of course, there are also specific tapes made for weatherproofing.
For decades, the original Decibel Products, manufacturer of commercial two-way antennas especially base station types, included a roll of this cheap black plastic tape with every base station antenna sold. The tape was intended for weatherproofing the connection of the feed-line to the antenna. Many tower men also used this tape for weatherproofing any connections in the antenna system.
I have personally removed, from Heliax, coaxial cable, even antennas themselves, this tape that had been applied years before, in some cases, decades before. In every case, the connectors looked like the day that they were installed.
One does NOT just put on a single layer of this tape because that can certainly not weatherproof. At least 3-layers of tape are required. The first layer covers the connection and at least a half-inch on the cable on either side. The second layer covers the first layer and at least a half-inch additional on either side. The third layer covers the second layer and at least a half-inch on either side. Longer lengths on each side are even better.
To speed up the congealing process, some installers would spray clear Krylon over the tape.
Today there are a number of products specifically made for weatherproofing. However, those products can be fairly expensive. Using the really cheap black plastic tape, although definitely not "high tech", does do an excellent job at a very low price.
Can you give an example (preferably with pictures to show) where tape will seal underneath the ground wire so the connection to the coax underneath is completely sealed?
Hence my comment from my previous post (highlighting the most pertinent part of the comment):
I am not doubting what you are saying 100%, you may have used materials that have worked for this purpose whereas I found my previously mentioned process to work well for me. I'm just curious to see the results of another process.
Edit - I just noticed this. Look at the pictures early on in this thread of the hose clamp method against the braid of the coax. The top step shows the "sealed" package, however the ground wire is placed underneath the coax so all you see is the tape seating nicely around the clamp and cable. What does the space between the ground wire and coax sheath look like? That is the space (small, yes) that the CoaxSeal in my example is great at sealing as it can knead in to that space like smearing caulk in between tiles.