[hpsdr] ADC Overload (again)
phil at pharman.org
Sun Aug 2 00:45:14 PDT 2009
No need to be concerned. The ADC Overload indicator just lets you know that
you are most likely going to see spurious signals in the bandscope. In fact
the ADC appears to overload quite gracefully, you can run well into the
overload region without too many adverse effects.
With a reasonable antenna you should not need the preamp on below 17m - in
fact with my HF beam I don't use a preamp until 15m.
I'm fortunate to have a prototype Alex board so can use that if I have
problems with broadcast stations causing overload. Mostly the natural
selectivity of my antenna and ATU etc is sufficient to eliminate out of
You may want to try KK and look on the wideband bandscope to see what
signal(s) is causing the overload. If it's a local broadcast station then a
simple HPF will most likely do the trick.
The front end of Mercury does have overload protection which we know does
work - one of our users accidentally transmitted into the Mercury input
connector and the protection network saved the day!
----- Original Message -----
From: "Richard Ames" <richard at ames.id.au>
To: "HPSDR list" <hpsdr at lists.openhpsdr.org>
Sent: Sunday, August 02, 2009 3:20 PM
Subject: [hpsdr] ADC Overload (again)
> ***** High Performance Software Defined Radio Discussion List *****
> Phil -
> In this message:
> You said "you may see smoke from the preamp" when the ADC Overload is
> flashing. Here in Sydney I occasionally see it flashing when the
> attenuator is out of the circuit ('Preamp on'). I suspect this is due to
> generally high noise level + broadcast transmitters about 10kms away.
> This afternoon with 80m having S9 noise - it was on all the time.
> How concerned should I be??? I often need the 'preamp on' in the
> amateur bands.....
> Regards, Richard.
> HPSDR Discussion List
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