Waterprofroofing a two piece antenna.

[ChrisL]

 I would like some advice for sealing a Comet CA-712EFC antenna where the top and bottom come together In the middle. The manual mentions sealing this area for a permanent installation but there is no sealant or tape mentioned in the parts list. I have seen a few ideas online about this topic but it wasn't easy to find and nothing that made me feel confident about the advice. I simply want the center of the antenna to be waterproof and I don't want to do anything that will compromise the SWR measurement.

 I ordered from the Antenna Farm for just about $160 and am excited about the project.

 Thanks for all your advise and yes I did search the forums here and couldn't find an answer.

 Take care,

 Chris

 

[berkinet]

Did you check the Antenna Farm website? They list a number of sealing and weatherproofing tapes that should work. Or, you could put some silicon plumbing grease on the threads. If you will never dismantle the antenna, you could use silicon sealant instead.

[Jones]

http://coaxseal.com/products/

 

Coax-Seal brand tapes.  The original.  The best.

[gortex2]

I just ran into this on my Diamond antenna I got for my APRS Digi. I went to Home Deport and purchased heat shrink that would fit over the center section and put that on. It shrink well and did not appear to affect the SWR at all. My hopes is to never remove the antenna unless its being replaced.

[berkinet]

...I went to Home Deport and purchased heat shrink that would fit over the center section and put that on. It shrink well and did not appear to affect the SWR at all. My hopes is to never remove the antenna unless its being replaced.

 

While shrink tubing is waterproof itself, water can wick in through any exposed ends. So, should you ever have to remove the antenna, you might wish to reseal the connection by smearing some silicon caulk inside the shrink tube before you heat it. Or, try something like this adhesive lined shrink tubing.

[RickW]

Had an embarrassing thing happen last year. I had installed a GP-9 antenna (three sections) only 2 or 3 years ago and one day I looked up and saw the top section wire just hanging loose in the wind. The top fiberglass radome had fallen to the ground. At first I thought it was all over for that antenna, but I took it down and except for a slight bit of chipping on one of the molded plastic inserts that helps the wire maintain its complicated folded positions, it seemed to be reasonably intact. It did not snap the wire, but if I had let it swing around for much longer it likely would have. I put it back together and screwed the top back on.This time I wound several turns of good quality electrical tape (Scotch 88 I think) over the joint of the top and middle section after securely screwing them together. Same with the still intact lower to mid section joint.

 

I would not again install such an antenna without using some kind of tape or heat shrink to insure it can not come undone. There is a gasket to seal the sections, so I was not worried about any water ingress. Antenna seems to work about as well as before. I use if for GMRS, even though it is not ideal because the SWR approaches 2:1 on the 467 MHz channels.

[gortex2]

While shrink tubing is waterproof itself, water can wick in through any exposed ends. So, should you ever have to remove the antenna, you might wish to reseal the connection by smearing some silicon caulk inside the shrink tube before you heat it. Or, try something like this adhesive lined shrink tubing.

 

The heat shrink I got is the stuff with sealer used for underground well lines. The glue is pretty tough. I have used it in the past and it works really well. Made by T&B. Hopefully mine is only up until spring and i start my tower install.

[kipandlee]

have used this stuff on lots of projects holds up well in the extremes lasts for years  https://www.lowes.com/pd/ZIP-System-90-ft-Panel-System-Tape/50373856

[n4gix]

I used glue-filled heat shrink myself. My Comet CA-712EFC antenna has been up now for five years and still checks out just fine.

[ChrisL]

Thanks guys for your experienced recommendations. I have some large diameter glue filled heat shrink but will need to wait for the antenna to arrive to see if it would fit over it. I have a feeling this project will take mare than a weekend to complete but I want to be sure to cover all the bases.

Thanks for every ones help.

 

'

[ChrisL]

Wow, just noticed how I spelled Waterproofing in the subject line. Maybe my next post will be about proofreading.

Cheers

[WRAF213]

I've gone through enough Flex-Shot to name a radio after it.

[gman1971]

I recommissioned an old rusted TRAM antenna using Deoxit and by purchasing a thin PVC pipe/cap that was used as a sleeve/radome for the entire antenna, so nothing in the antenna is exposed now. (required a slight tuning adjustment to account for the radome velocity factor) but never had any issues with that antenna ever again.

 

Tape and all that other stuff is just a mess that can, and will fail over time, plus it looks really cheap. A PVC pipe covering the antenna will require a hurricane to damage and will look like a professionally made antenna.... For exposed UHF connectors I used to use STUF dielectric grease. Unfortunately, UHF(SO239/PL259) connectors only seem viable if you live in the desert, in my case all those developed a lot of corrosion in WI weather, and now I am all about N connectors, the connection section is sealed both ways, and I went with either made out of tri-metal or silver plated... which seem to hold up on rough weather way better than the cheap nickel plated stuff (which given my current RFI situation, those are PIM generators too)

 

G.

[WRAF213]

UHF connectors shouldn't even be used at GMRS frequencies since they don't present 50 ohms above 100ish MHz.

[BoxCar]

UHF connectors shouldn't even be used at GMRS frequencies since they don't present 50 ohms above 100ish MHz.

Let me see if I understand what you are stating correctly. You state Ultra High Frequency connectors shouldn't be used even at Very High Frequencies because they don't present a 50 ohm impedance somewhere above 100 MHz. I guess following that logic they should only be used at frequencies usually referred to as being in the high frequency range. Did I capture this correctly?

[RCM]

I don't always even use RF connectors - or for that matter, RF feedline - at HF. And I've even been known to not use RF connectors as high as 927 MHz!

[gman1971]

BoxCar,

 The biggest issue with UHF connectors, regardless of higher frequencies impedance issues (which will reduce the power output of the radio due to mismatch), is that they are PIM magnets. Once they get dirty and corrosion sets in after being exposed to inclement weather, you'll have a massive noise generator that will take a lot of detective work to track down. I've been fighting noise on my UHF setup for months and I've finally narrowed it down to three things: LMR400 cable, nickel plating and UHF connectors. Once I moved to 1/2 Heliax, white-bronze N connectors the noise dropped dramatically. Even silver plated UHF connectors will eventually get corrosion on the threads if exposed to the elements long enough. LMR400 cable in a high wind situation is basically a noise generator for VHF and UHF, specially if its been sitting outside for a few months as well. Having the giant Candelabra tower pumping thousands of watts made the problem even worse.

 

RCM, so, what do you use? Magic? heh. (j/k)

 

G.

[WRAF213]

UHF connectors have been around for almost a century, back when VHF was called UHF because we didn't have enough frequencies above HF to need a distinction. They're cheap to make and handle a lot of power (a well-constructed connector will handle full legal power on HF amateur), so they remain popular. Unfortunately, they remain popular on radio equipment designed for frequencies well above what the UHF connector is designed for. Avoid the connector wherever possible on 220, 440, and GMRS equipment. N is a much better connector both in RF performance and weather resistance. Regardless of connector choice, pay attention to your connector's plating as well to avoid PIM. PIM shouldn't matter a whole lot unless you're full duplex, transmitting on two radios simultaneously, in a generally poor RF environment, or monitoring open channels for weak signals (like with emcomm).

[BoxCar]

Connectors, no matter the type will always degrade as they represent a break in the electrical path and a mechanical restoration of the circuit. The mechanical pieces will ALWAYS introduce less than perfect electrical properties and a less than perfect mating of the parts, The only connection I am aware of that does not result in a break in the electrical path is a fused connection where two conductors are fused together. That doesn't imply there is no loss or impedance introduced due to impurities or misalignment in the fusion process. 

[RCM]

BoxCar,

 The biggest issue with UHF connectors, regardless of higher frequencies impedance issues (which will reduce the power output of the radio due to mismatch), is that they are PIM magnets. Once they get dirty and corrosion sets in after being exposed to inclement weather, you'll have a massive noise generator that will take a lot of detective work to track down. I've been fighting noise on my UHF setup for months and I've finally narrowed it down to three things: LMR400 cable, nickel plating and UHF connectors. Once I moved to 1/2 Heliax, white-bronze N connectors the noise dropped dramatically. Even silver plated UHF connectors will eventually get corrosion on the threads if exposed to the elements long enough. LMR400 cable in a high wind situation is basically a noise generator for VHF and UHF, specially if its been sitting outside for a few months as well. Having the giant Candelabra tower pumping thousands of watts made the problem even worse.

 

RCM, so, what do you use? Magic? heh. (j/k)

 

G.

Just solder, sometimes. Feedline disconnects, indeed feedline itself is at best a necessary evil. Why mess with it in applications where it is not necessary? For example, pop the cover from your radio and see what the board connection looks like. The fact is, the only time connector impedance really matters very much is when it is actually somewhere along the feedline. At the ends there is an impedance bump regardless of what connector you use.

 

I've been known to build radios (uhf included) that don't even have what most people consider an antenna connector.

[gman1971]

Wasn't implying that, but in some connector types that process only takes a few months, whereas other types will take years; N connectors seem to hold up a lot better in bad weather than UHF, even sealed with STUF grease, especially the outer threads.

 

G.

 

Connectors, no matter the type will always degrade as they represent a break in the electrical path and a mechanical restoration of the circuit. The mechanical pieces will ALWAYS introduce less than perfect electrical properties and a less than perfect mating of the parts, The only connection I am aware of that does not result in a break in the electrical path is a fused connection where two conductors are fused together. That doesn't imply there is no loss or impedance introduced due to impurities or misalignment in the fusion process. 

[gman1971]

Been tempted about replacing the Mini-UHF on my VS radios... seems like a pretty poor connector, but then again, I could be wrong.

 

G.

 

Just solder, sometimes. Feedline disconnects, indeed feedline itself is at best a necessary evil. Why mess with it in applications where it is not necessary? For example, pop the cover from your radio and see what the board connection looks like. The fact is, the only time connector impedance really matters very much is when it is actually somewhere along the feedline. At the ends there is an impedance bump regardless of what connector you use.

 

I've been known to build radios (uhf included) that don't even have what most people consider an antenna connector.