[Elecraft] RE: PowerSDR/IF stage v0.91 Released

[John A. McCabe]

Thanks Scott for such a quick fix on this! While waiting on my K3 and I 
was working on the softrock IF Kit, and I noticed the problem when I was 
setting it up with the PowerSDR IF software.

 I think I have found a supplier for a 32.800 Mhz crystal, which would 
put the softrock at around 8200 and make it a more reasonable 15000hz 
offset.  I hope that this will still be far enough away from the 8215 IF 
to not cause any problems, while making the bandpass a little more 
symmetric.Someone else had mentioned the use of a HPL-4562 opto-coupler 
to provide more buffering for the softrock. I may order one and give it 
a try. If it works, a crystal even closer to the IF may work without 
causing problems. Of course, I won't be able to test any of this until 
my K3 arrives, hopefully in December as I am in the first batch.

Thanks again for your work on this, I know that many, including myself, 
will enjoy using the features of PowerSDR with the K3,

73,

John KD8K



Scott McClements wrote:
> On Nov 25, 2007 10:05 AM, John A. McCabe <johnamccabe at verizon.net> wrote:
>   
>> However, one possible problem
>> that I am seeing with the new version is that the IF frequency offset is
>> limited to a maximum of 20000 Hz and I believe that that Softrock for K3
>> requires a 23000 Hz Offset (8215 K3 IF frequency minus 8192 the softrock
>> frequency).
>>     
> John,
>
> I never noticed that the crystal that comes with Softrock for the K3
> was so far off. The 20000Hz limit is just in the dialog validation
> code, I just changed it to 96000Hz, and the DttSP code seems to have
> no problem using a value more than 20000Hz.  Thank you for pointing
> that out. If someone needs this code right away I will build a special
> patch - please only ask if you intend to use it very soon.
>
> That crystal choice is not ideal, especially if someone can only use a
> 48Khz sampling rate. This means on the panadapter you will basically
> only see 48Khz of band above the frequency you are tuned to. If you
> are able to use a 96Khz sampling rate you will see 24Khz below and
> 73Khz above. I understand Tony, KB9YIG, only buys the readily
> available crystal values to avoid the high cost of getting a custom
> crystal frequency made.
>
> -Scott, WU2X
> http://www.wu2x.com/sdr.html
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