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Re: [TowerTalk] Recommendation for heat gun for shrink wrap

To: <towertalk@contesting.com>
Subject: Re: [TowerTalk] Recommendation for heat gun for shrink wrap
From: "Roger (K8RI)" <K8RI-on-TowerTalk@tm.net>
Date: Sat, 25 Aug 2007 14:25:32 -0400
List-post: <mailto:towertalk@contesting.com>


>
> You're all talking about using hot melt glue under the shrink tubing.
>
> Why not use silicone grease for the flood material ?   It will stop water
> from seeping in and absolutely stop all corrosion.

Two reasons at least for me.
The flooded heat shrink tubing adds a lot of mechanical strength and it too 
if properly applied will keep moisture out. I've never had one leak yet. 
Adding the grease is just one additional step that buys me nothing as far as 
I can see. I can't speak for all flooded tubing, but the MMM variety has 
plenty of flooding compound to give a good, strong, mechanical, water proof, 
connection.

Using Silicone grease requires a lot of care.Get it on your hands and any 
place you touch becomes "stick proof" Applied under heat shrink tubing and 
there is no mechanical bond or strength. This also allows the coax and heat 
shrink tubing to move in relation to each other giving the grease the 
capability to work over time out leaving voids. (I speak from unhappy 
experience )Hence the need to apply only enough to do the job.  Even at the 
top of the tower grease leaking out will soon pick up a lot of dust and dirt 
and look like it had been dragged through a sand pile. When working on those 
connections your hands soon pick up a lot of gritty grease that gets on and 
into just about every thing you touch.  A thin coat of grease on the 
connector will keep it shiny and allow easy removal of the flooding (hot 
melt) compound, but I prefer to have the flooding compound stick. As I've 
said before, that grease is a *very* effective dirt magnet. Once you put the 
Silicone grease on or in the connector you have to keep it clean. Drop it in 
the dirt and it may well be back to installing a new connector.  I've thrown 
a good many PL-259s away for that very reason. It's just too difficult to 
clean sand and dirt out of the threads. Also even a tiny blade of grass or 
dirt coud act as a leakage point for current between the shield and center 
conductor in the future, particularly if you run high power and or VHF/UHF

When it comes to small cables like RG-58 I use the smaller tube at the rear 
of the connector and then the larger over the back of the connector and out 
onto the smaller tube that I shrunk onto the RG-58. This gives a *strong* 
and weatherproof seal. It also eliminates the need for additional hot melt 
glue.

Having said all that, I do on occasion flood connectors such as the ones 
connecting to a matching network at the base of a vertical. Moisture can get 
into the matching network and through the chassis connector into the coax. 
In those cases I flood the connector to create a barrier to keep that 
moisture out of the coax. OTOH if all connectors are flooded and sealed on 
the outside, changes in temperature and pressure will cause the coax to try 
to breathe. This is particularly pronounced on long runs and with larger 
coax. In some instances enough of the flooding compound may be drawn out of 
the connector and into the space between the jacket and dielectric to open 
that barrier. Quasi air-core cables are particularly bad at this. Hence, if 
necessary flood the connectors at the far end and leave the rest all the way 
to the shack without flooding. If you look near the bottom of 
http://www.rogerhalstead.com/ham_files/tower.htm there are a series of 
photos on the installation of my half sloper for 160.  This is pretty much 
the same procedure I follow when connecting to matching networks.

One example, I have a Hy-Gain AV640 on top of a 32 foot tower at the West 
end of my shop. The PL-259 that attached to the matcing network was flooded 
and then sealed with flooded heat shrink tubing. the coax was 9913 (the only 
piece I had left). When I took the antenna down recently, I had to remove 
the matching network due to an invasion of Wasps.  This involved cutting the 
heat shrink tubing lengthwise and peeling it off. Other than a bit of glue 
left on the connector is was shiny. However, the center conductor of the 
9913 was rough and green at the connector. The corrosion tapered off  to the 
point of the center conductor being clean in about 18 inches. That was with 
a flooded connector.

73

Roger (K8RI)

>
> Roger
> KC8HZ
>
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