[Elecraft] OT: pwr rating of RG6, etc

[Samuel Strongin]

I have a great idea don't use the proper cable at all just use the cheapest 
piece of junk and try to justify it. The fact of the matter 1.5 does 
matter.For example Icom radios fold back when seeing a swr of 1.5 to one. 
CHEAP is not a reason to use something yes it will work so what. Is it the 
proper cable to use no.  Rg6 gives you a starting loss at 1.5. Rg 59 will 
work to on 75 meters it will even handle some power would I use it No.
       Good luck using the wrong cable. We don't have pi networks any more. 
Solid state devices want to see the proper load. They arn't rated 50-75 
ohms. Yes it will work so will a coat hanger with a tuner as antenna.
----- Original Message ----- 
From: "Don Wilhelm" <w3fpr at embarqmail.com>
To: "Samuel Strongin" <kf4yox at embarqmail.com>
Cc: "DOUGLAS ZWIEBEL" <dougzzz at gmail.com>; <elecraft at mailman.qth.net>
Sent: Tuesday, November 13, 2007 9:10 AM
Subject: Re: [Elecraft] OT: pwr rating of RG6, etc


> You use it because of 2 characteristics.  1) It has lower loss than an 
> equal physical size 50 ohm cable - and that is true even considering the 
> added loss due to mismatch.  2) It is conviently available and 
> inexpensive.
>
> Considering the added loss due to a 1.5 SWR, look at the charts.  If the 
> matched line loss is 2 dB, the loss when the SWR is 1.5 is only 2.1 dB. 
> Even if the matched line loss is 10 dB, having an SWR of 1.5 adds only 0.2 
> dB to the total loss.  A 1.5 SWR is insignificant when considering line 
> loss, especially at HF.
>
> The facts do not support the popular view that an SWR any higher than 1.0 
> is a bad thing.  In most cases, a transmission line SWR of 2.0 or below 
> will work fine.
>
> Now, there is another part to consider - the feedpoint impedance at the 
> output of a transceiver may have to be transformed to something closer to 
> 50 ohms for proper, full power operation of the PA - but that is the job 
> of a tuner, it has nothing to do with feedline loss beyond the tuner. 
> Unfortunately, these two parameters get mixed together and the result is 
> 'numerical soup'.
>
>
> 73,
> Don W3FPR
>
> Samuel Strongin wrote:
>> RG6 is 75 ohm cable. Why would you buy a great radio and worry about 
>> performance,then go use the wrong cable. You start out at a 1.5:1 swr. 
>> Idon't get it.
>>                  kf4yox
>>