[hpsdr] PowerSDR Request

[Mark Amos]

Graham,

Thanks - yes I typically use 48K for the sharper filters so that's where I
calibrated it.  Good idea on the fake-out!

Also thanks for the additional info on the 10 MHz input work going on!

Mark

-----Original Message-----
From: Graham / KE9H [mailto:KE9H at austin.rr.com] 
Sent: Friday, January 16, 2009 6:47 PM
To: Mark Amos
Cc: hpsdr at lists.hpsdr.org
Subject: Re: [hpsdr] PowerSDR Request

Mark:

You can make a much more accurate calibration by setting the
sampling rate down to 48 K during calibration, which makes the
calibration about three or four times more accurate than at 192K,
since it inherently narrows the FFT bins.

You can also fake it out a little by changing the target.  That is, if
it keeps coming in 3 Hz high, tune to WWV at 10 MHz and tell it that
the target is 9.999997 MHz.  You can adjust that.  Hokey, but will
serve as a work around until you get your 10 MHz local reference
running.

Specs for 10 MHz input on C16 are 10 MHz square wave,
0 to 3.3 V, 2 to 5 ns rise and fall time. (!)

More coming soon on feeding external clock into bus line C16. 
It currently has some of the same problems related to the card
position sensitivity, but is currently being worked very hard.

--- Graham / KE9H

==


Mark Amos wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
> Thanks for adding the frequency calibration facility.  I'd like to be able
> to adjust out that last couple of Hz...  If the correction factor could be
> manually adjusted, I'm sure I'd be able to set it spot on.
>
> Speaking of spot on, I saw that there was an update to the Mercury code
that
> looks like it had something to do with an external clock on C16... I'd
like
> to be able to feed this clock pin from a GPSDO.  I had some notes on this,
> but can't seem to lay my hands on them.  What level should the clock be to
> fed to C16 and does it need to be square or will a nice sin shaped
frequency
> standard do the trick?
>
> I just replaced a horribly noisy ATX power supply with an Astek 16130 that
> seems to be much quieter (I used a little loop pickup and the SDR1000 to
> compare the two - the improvements were obvious.)  Also, a 12 V PC power
> supply fan blowing across the board stack seems to keep the Mercury ADC
> plenty cool. 
>
> What a fun radio.  Thanks!
>
> Looking forward to Alex!
>
> Mark
>
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