[hpsdr] ADC overload problems.

[David McQuate]

Hello Jeff,
   If you're using Power SDR you don't have the possibility of using 
Mercury's wide bandscope.  I'd suggest trying Kiss Konsole, and turning 
on the Wide Band spectrum display, that shows signals from 0 to 55 MHz.  
That way you'll know if you are receiving some huge low frequency 
signals, rather than just guessing that they are not present.  If you 
see a high signal strength low-frequency signal, you could use a 
high-pass filter to attenuate it.  Alternatively, I suppose it could be 
somewhere else in the 0 to 55 MHz spectrum.

73,
Dave
WA8YWQ


On 10/14/2012 11:27 AM, Jeff Cook wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
> 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.
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