[TowerTalk] isolation and SWR

[Pete Smith N4ZR]

190 feet of LDF4-50.  Antenna switch and 80m array switch are in series.

73, Pete N4ZR
The World Contest Station Database, at www.conteststations.com
The Reverse Beacon Network at http://reversebeacon.net, blog at reversebeacon.blogspot.com,
spots at telnet.reversebeacon.net, port 7000 and
arcluster.reversebeacon.net, port 7000

On 9/10/2012 6:34 PM, Jim Lux wrote:
> On 9/10/12 8:03 AM, Pete Smith N4ZR wrote:
>> Just now, I was fiddling with my homebrew 80m array switchbox.  I have
>> only two dipoles on it at the moment, both reasonably well matched.
>> Accidentally I switched to one of the unterminated positions, and got an
>> SWR on the order of 4.5:1 (feeding the dipole switchbox through my
>> Ameritron RCS-10.  By comparison, if I disconnect the feedline inside
>> the shack, the SWR is in excess of 25:1, and if I switch the RCS-10 to
>> an unused position, I get 4.5:1.
>>
>
> So, the RCS10 has mostly good matches on most of the outputs, and one 
> that's unterminated.  When you switch to the unterminated one, you get 
> 4.5:1, and 1:1 if you switch to the others?  And this is at 3-4 MHz?
>
> 4.5:1 is a return loss of about 4 dB.  That is.. if you had a 2 dB pad 
> in line and a dead short, that's what you'd see.    How long is the 
> coax to the RCS-10?   Is 2 dB of loss plausible?
>
>
>
>
>
>> Is there even an approximate relationship between these various SWR
>> numbers and the degree of isolation afforded by the two switchboxes? And
>> probably an even dumber question.  If you have two devices in line and
>> each has (say) 30 dB isolation between a line in use and an unused one,
>> both of which pass through them both, is the resulting isolation 27 Db?
>> Some other number?
>
> Are you talking two switches in series?
>
>>
>> Be gentle - I was a liberal arts major.
>>
>
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