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Re: [TowerTalk] Measuring Coax Loss-Dealers - Response DAVIS R

To: "Tower and HF antenna construction topics." <>
Subject: Re: [TowerTalk] Measuring Coax Loss-Dealers - Response DAVIS R
From: "Roger (K8RI)" <>
Reply-to: "Tower and HF antenna construction topics." <>
Date: Wed, 24 Feb 2010 21:12:23 -0500
List-post: <">>

jimlux wrote:
> Roger (K8RI) wrote:
>> My problem is neither the loss per connector or number of connectors. It 
>> is the breakdown voltage when running QRO into a very high SWR at the 
>> band edges on 75 and 160.
>> I standardized on N connectors, but they don't have the voltage ratings 
>> to handle that kind of voltage. I see at much as 8:1 at the band edges 
>> on 75 and even higher on 160 so I've had to go back to UHF connectors on 
>> the HF bands. IT's not a problem or hasn't been on 40 through 10, or 
>> 3ven far.  But I need to have higher voltage ratings for 
>> at least 160 and 75 and the only way I can see doing that is with true 
>> UHF connectors even on LMR-600 even if I have to resort to "Clamp type 
>> connectors"
> Have you actually had breakdown occur?  
> The "databook" ratings for 
> connectors are quite a bit less than the actual AC breakdown voltage, 
> for a variety of reasons.  For instance, PL-259/SO-239 gets used for 
> 20kV all the time, although the spacing is wider on that connector, 
> particularly across the face.  There's also lots of different kinds of 
> N, in terms of the dielectric construction. 
I've blown out Amphenol, silver plated, double female connectors. It was 
the first thing I checked and the last thing I found...not at the same 
time.  I pulled out the connector and it measured fine with an ohmmeter 
but with it in the swr under load was very high. I even removed the 
balun. Finally I did what I should have in the first place and tested 
that connector by substitution. The new connector worked fine, the old 
one was shorted.

I've also blown out a few of the male N-connectors at the antenna.  
Running QRO and an SWR on the band edges of 8:1 or greater.  160 is even 
worse.  I haven't lost a UHF connector yet.  OTOH I've misplaced a few.

I've never had a problem with N-connectors on VHF or UHF either, but 
there the SWR is usually quite low even on some fairly wide excursions 
on 6-meters.  2-meters seems to be capable of covering the CW and FM 
portions of the band. On 440 I live too close to Canada so power is not 
a problem for the antenna system unless I can get a special issuance for 


Roger (K8RI)

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