[50mhz] [VHF] Replacing coax

Wed Mar 2 11:45:51 EST 2011

For a permanent installation Id go with 50 or 75 Ohm hardline every time and 
then the best flex around the rotator and up. Since I use all 75 Ohms here 
thru 1296 my loop choice is CATV flooded RG-11 foam. Then there is no worry 
about water migration at least thru the cable.

These days even 50 Ohm hardline with connectors is often free for the asking 
as commercial repeaters, pagers, etc continue to fade away.

Carl
KM1H

----- Original Message ----- 
From: "Tim Marek" <K7XC at charter.net>
To: "John Geiger" <aa5jg at fidmail.com>; "50mhz" <50mhz at mailman.qth.net>; 
<6meter at yahoogroups.com>; "'VHF REFLECTOR'" <vhf at w6yx.stanford.edu>; 
<DX-IS at yahoogroups.com>
Sent: Wednesday, March 02, 2011 11:18 AM
Subject: Re: [50mhz] [VHF] Replacing coax

> 12 years is a long time for a piece of "VHF" coax.... (used on VHF
> Fequencies)
>
> The insertion loss goes up as the cables die.. and yes Coax has a shelf 
> life
> like anything else. Their are likely many small cracks in the outer jacket
> exposing the shield to wicking up water causing impedance bumps and
> corrosion.Connectors over time degrade, often filling with water at some
> point in time causing... you guessed it... more corrosion.
>
> What is more important to note are the intangibles that prey on the 
> mind...
> "Would I have worked him if the coax and connector had been of verified 
> good
> quality?" Maybe... maybe not... Testing coax loss isnt rocket science...
> but... the same amount of effort needed to get to the far end to test it 
> can
> be used to replace it as well.
>
> In the past when I was doing the VHF Contest's as a very serious Multi Op,
> Mountain Top, Portable... I would replace ALL the coax run's EVERY year,
> last years set became the spares, and the spares became my archived backup
> with the one they replaced (4yrs old) donated to a local ham club or
> individual.
>
> Why did I do this every year? Those cables took a beating each contest
> season and when your trying very hard to break the existing all time W7
> record in the June contest, new feedlines are cheap insurance against
> failure in a key area of the station, your antenna system.
>
> Now that is been almost 10 years since my last mountain top expedition,
> those cables here in the high desert of northern NV are showing signs of
> weather checking and probably could stand to be replaced.
>
> Now this brings up a interesting question... What to replace them with?
> W/O a doubt, the most bang for the buck, most durable, well built, lowest
> loss, 50 ohm RG8 size coax out there has to be CQ-106 made by "The 
> Wireman".
> That is the only cable I have used for the past 20 years after trying many
> others in the harshest places to operate from, the tall mountains of the
> American West. Its the only one to hold up, time after time.
>
> As one who has been a hard core mountaintop contester since the 80s and
> worked in the 2 way field alot of years, thats my take on it. Your mileage
> may vary...
>
> 73s de Tim - K7XC - DM09nm... sk
> ----- Original Message ----- 
> From: "John Geiger" <aa5jg at fidmail.com>
> To: "50mhz" <50mhz at mailman.qth.net>; <6meter at yahoogroups.com>; "'VHF
> REFLECTOR'" <vhf at w6yx.stanford.edu>; <DX-IS at yahoogroups.com>
> Sent: Tuesday, March 01, 2011 4:39 PM
> Subject: [VHF] Replacing coax
>
>
>>I went out this morning and did a visual inspection on my coax runs, and
>>they
>> all look in very good condition. No cracking on the jacket at all, and 
>> the
>> jacket still looks as good as when new.  One run of RG-11 I have is 12
>> years
>> old, but still looks great.  I don't recognize any signal degradation on
>> the
>> coax runs either, nor changes in SWR.  Now I don't have any complex test
>> equipment to test the coax runs with, just a SWR/power meter built into 
>> my
>> antenna tuner.
>>
>> Given that the jacket on the coax looks ok, and I haven't noticed any
>> change
>> in antenna performance, is it safe to assume that the coax is still good,
>> or
>> is there an age limit for coax after which it starts to deteriorate from
>> the
>> inside?  Is there a rule of thumb on how often coax should be replaced?
>>
>> 73s John AA5JG
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