[TowerTalk] 9913 coax

[K8RI on TowerTalk]

> It bothers me that 9913 coax gets a bum rap in the amateur radio
> field. I personally have used a 130' run for over 15 years to feed
> one tower and to date, there is no moisture in the cable. The key to
> use is proper waterproofing which is in the realm of all amateur's

I knew some one would comes to 9913's defense, but "to me" there is no such 
thing as proper water proofing for it. Certainly there are going to be more 
happy users than dissatisfied, but to me it only takes once.

> capabilities. The same holds true of Davis's Buryflex which has a
> foam dielectric. (Or any other coax for that matter.) You need to
> properly weather seal the connection to make sure water stays where
> it belongs, outside the coax.
>
> FWIW, I have never had a customer either complain or return a 9913
> order for or due to water ingress.

I had multiple runs of 9913 and all carefully waterproofed. They were up for 
quite a few years with nary a problem and the stuff was still bright and 
shiny inside.  (I checked)  Then one day we had a thunderstorm.  Lightning 
hit the tower and blew off every bit of water proofing at the top. Less than 
15 minutes after the strike I had water running out of one rig onto the 
operating desk. As soon as the weather broke I was removing coax and 
replaced it all with LMR 400.   I threw away nearly 800 feet of 9913 and 
will never use the stuff again.

You could do the perfect job waterproofing connections, but the potential is 
there if something causes that water proofing to fail, be it mother nature 
or critters (two or 4 legged). That potential and the one failure makes the 
cost of trusting it far too great.

>
> Any combination of tape, liquid tape, self vulcanizing tape, duct
> seal, coax seal or Scotch-kote, to name a few products, will ensure
> water stays out of your coax.

Nothing can ensure that if it loses its integrity.

My choice for coax would be the flooded (buriable) LMR-600 were I still 
working and I may go that route with just two runs and remote switches. 
Unfortunately due to multiple stations operating at the same time I would 
still need a minimum of four runs at 200 feet each just to reach the top of 
the tower. The costly part is each run takes 5 connectors at roughly $25 USD 
each.

We're not even in an area considerd as a high lightning hazard, but my 
current tower still gets hit on average of three times a year. I have five 
confirmed for this year. All ocurred early  in the summer.  These are 
confirmed strikes.  How many times it actually gets hit, I don't know but 
it's most likely more than the number visually confirmed.

I would note that the connectors on the coax and remote HF antenn switch 
appear to have been etched from electrical discharge.  The thing is about 4 
years old and looks as if it's been up there for 20 years.  There's no coax 
seal left up there, but *most* of the liquid electrical tape is still in 
place.  Had the current cables been 9913 instead of LMR 400 I'd already be 
replacing it again, or rather I'd probably have been doing so the first 
year.

Roger Halstead (K8RI and ARRL 40 year Life Member)
N833R - World's oldest Debonair CD-2
www.rogerhalstead.com (Use return address from home page)
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