[hpsdr] ADC overload problems

[John Petrich]

Jeff,

 

I agree with Shel that your problem might be from the aggregate RF power
from BC band signals.  I had that problem when my 80 meter dipole and 80
meter loop.  I installed a 3 element HP filter with a cut off starting about
1.9 MHz resulting in a total attenuation of only 16 dB at 700 KHz and the
problem is completely solved.

I think it is important to remember that the ADC is a broadband power
sensor.  The aggregate power accumulated from, say, the BC band and HF BC
and the occasional local ham station at the same time can add together in
the ADC and result in an overload indication.  There are elaborate
multi-pole HP filter designs available, but in my experience with a couple
of similar front end designs, the rather relaxed filter profile that I
outlined above is more than sufficient to reduce the aggregate BC band RF to
a level that the ADC is happy with.

I can provide specifics if you are interested.

 

Regards,

John, W7FU

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