Re: System Gain

[Dave Sublette <arrl.net; k4to@xxxxxxxxxxxxxxxx>]

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 
readily.

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.



VK2KU wrote:
> Dave,
> 
> I'm not sure exactly how the SDR-14 differs in architecture from my
> SDR-IQ,
> or how Leif has implemented the control of gain/attenuation through
> Linrad,
> 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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