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Re: System Gain
- Subject: Re: System Gain
- From: Dave Sublette <arrl.net; k4to@xxxxxxxxxxxxxxxx>
- Date: Fri, 21 Dec 2007 15:23:41 -0500
Guy, et. al.,
I am getting absolutely no decrease in noise to the K2 or the SDR-14
when the IF cable is removed. So, I don't think the SDR has a problem.
Both the SDR and the k2 are very sensitive and detect very weak signals
I just believe that with a little more post conversion gain in the IF at
the top of the tower would improve the system even more.
I remember when I did the original design of the setup, I was cautious
about over driving the K2. My rule of thumb is that the noise should
increase when you hook up the transverter, but the S-meter should not
morve or at least should move only to S-1 or so in order to keep from
over driving the IF radio in contest conditions.
Now admittedly, I don't live in an area that has heavy microwave
activity, but I still feel that following this guideline will result in
a near optimum system response.
> I'm not sure exactly how the SDR-14 differs in architecture from my
> or how Leif has implemented the control of gain/attenuation through
> or indeed how the 144MHz input works - presumably through a converter
> down to 28MHz.
> But ... the first thing I would be checking is that you are not
> inadvertently using some
> front-end attenuation in the SDR-IQ, as I found I was with the SDR-IQ.
> When I unplug the 28MHz input to my SDR-IQ, the Linrad noise floor
> drops by about 17dB.
> My 2p-worth.
> 73 Guy VK2KU
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