Re: [amsat-bb] Preamp / SWR issue

[Nate Duehr <nate@xxxxxxxxxxxx>]

Tony wrote:
> All:
>
> Just installed a new Mirage preamp and noticed a jump in SWR from 1:1 
> to almost 3:1
>
> I tried different lengths for the coax jumper, but the result is the 
> same.
>
> Any ideas?
>
> 73, Tony KT2Q
Adding a preamp on receive shouldn't have done that.  Especially 
assuming you're switching it out of the RF path during TX??

Did you mean Mirage AMP?  (Not Pre-Amp)

One for the books, although it probably isn't your problem, but remember 
that SWR as seen at your transmitter is the reflected power that makes 
it back down through your co-ax to the transmitter.  If your return loss 
coming back down the co-ax is high (thus, losing you received signals 
too) if you add a large amp, you can sometimes now "see" a lot more 
reflected power make it back down through the lossy co-ax cable. 

Not likely to be your problem from your description, but folks do forget 
to check SWR at the antenna feedpoint... and forget that return-loss is 
a factor...

(Example: You could put 50W into the cable... did it all make it to the 
antenna?  How much is reflected right at the antenna?  How much makes it 
back down the cable to your transmitter?)

It's worth measuring if you're going for maximum "smoke" in and out.

Nate WY0X
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