[hpsdr] ADC overload problems.

[Jeff Cook]

I raised this point a few weeks back and received various suggestions on 
how to solve my problem; unfortunately I have got absolutely nowhere.  
Rather than go back over old ground, I'd like to approach this from the 
receive point of view, perhaps if I can crack this then the transmit 
problem may also be solved.

I use an octagonal magnetic loop made from 28 mm copper pipe, tuned by a 
50 pF vacuum capacitor, it works surprisingly well on 20 through to 10 
m.  I also use a long wire (20 m in length) fed at its far end via an 
automatic ATU, this for use on 160 through to 30 m. If I attempt to use 
the long wire on any of the amateur bands at all with PowerSDR's preamp 
on (or more accurately its attenuator switch in the off position) then I 
get the flashing red/yellow ADC overload warning, and I'm talking 
receive only here.  Given that ADC overload occurs only at -12 dB's 
(preamp on), and at +8 dB's (preamp off), and given that I'm nowhere 
near any high power transmitting equipment, I'm at a loss to know why 
this should be happening.  Now I realise that this can be misleading but 
looking at signals and noise levels as displayed in the pan adapter, I 
have a typical noise level of around -100 dB's and rarely do I see a 
signal topping -50 dB's.

Given the ADC problems that I've got in receive it's little wonder that 
in transmit I have to limit myself to little more than QRP levels.

Is it plausible that I'm receiving a false ADC overload warning?

Jeff Cook, G0AFQ.