[hpsdr] Fwd: Two Questions

[Jim Sanford]

Additional information:

As I lower the signal generator output, the dbm meter tracks within 1 db.

The lower the signal level gets, the greater disparity between the 
panadapter and the meter.  At -113 dbm input (including 10 db attenuator 
in that level), the panadapter display is now 30 db lower.

Any suggestions on what is going on would be gratefully appreciated.  I 
suspect that this is some artifact of the way the software works, but 
would very much like to understand it.

Thanks and very 73,

Jim

wb4gcs at amsat.org




-------- Forwarded Message --------
Subject: 	[hpsdr] Two Questions
Date: 	Tue, 29 Mar 2022 21:44:21 -0400
From: 	Jim Sanford <wb4gcs at wb4gcs.org>
Reply-To: 	wb4gcs at amsat.org
To: 	hpsdr at lists.openhpsdr.org <hpsdr at lists.openhpsdr.org>



***** High Performance Software Defined Radio Discussion List *****

All:

I am building a second Atlas-based HPSDR. Going well. One question:  If 
IAMBIC is deselected, where do you connect hand key or WinKeyer?  I know 
this can be done, but it would be a lot of disassembly to open up the 
first HPSDR to see how it is connected.  I can't find this info in 
either Metis or Penelope manuals.  Any help??

Second, in calibrating frequency and "S-meter", I'm noticing some 
interesting things.  I have calibrated the radio in frequency and 
amplitude.  When I feed it a signal from a calibrated signal generator, 
the radio is dead-on in frequency and level.

Here's what's wierd:  The S-meter and dbm meter agree with what I'm 
providing (accounting for attenuators).  When I disable the RF OUT from 
the signal generator, the meters drop to -121 dbm and corresponding 
S-meter reading for the noise floor.  Interestingly, the panadapter 
shows the noise floor at -150 dbm or so.  There is also a birdie about 8 
KHz lower in frequency at about -120 dbm. SO, I'm wondering, why the 
difference?  Any ideas?

I'm wondering if perhaps the meters are integrating the entire 192 KHz 
spectrum??

Any thoughts?  Ideas most appreciated.  This is not a problem, radio 
seems to be working fine, but would like to understand what I'm seeing.

Thanks and very 73,

Jim

wb4gcs at amsat.org



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