[hpsdr] Jan/Ozy Spurious Signals

[Joe Barger]

Hi Tommy,


> Joe:
> I saw very similar signal levels to yours when I first got my Janus and 
> Ozy
> running.  I was using a standard PC supply plugged into Atlas.  As a test 
> I
> plugged in a couple of old lab supplies and saw the noise drop 
> dramatically.
> See the attached photo.  I am converting to all analog supplies.  The
> difference seems to be quite remarkable.

Thanks for your observations.

I finally got some time to think about what's going on.  I believe the 
PicoPSU is switching at about 22KHz and that's whats causing the 22KHz spike 
and the odd harmonics (i.e., the fundamental and odd frequency components of 
a square wave).  I sent an email to the PicoPSU support guys asking what the 
switch freq is but haven't heard back yet.  Unfortunately I don't have 
immediate access to any analog supplies now to confirm my theory, but I'm 
working on it.

Once I connect everything into the nominal configuration the background 
noise is above the 22KHz spike (an industrial area with lots of power line 
leaks), so the spike isn't a factor yet.  When (if) I get the noise level 
down to a resonable level I'll worry about beating the spikes down.

The Janus frequency response thread seems to explain the "hump" issue I 
mentioned.

> One additional detail that I have not seen anyone mention is the status
> lights on the OZY.  With everything working perfectly and analog supplies; 
> I
> see the same LEDs as everyone else. (D12 on, D9 and D10 flashing, D5 
> through
> D8 on) When I plug in the PC switching supply I suddenly have some
> additional LEDS on.  Currently it is D1 and D3.  I have also noted the 
> LEDs
> that are on have changed over the last few weeks when I fixed other
> problems.

I must admit I haven't paid much attention to the LEDs (since I'm not sure 
what they are all supposed to mean anyway).  As far as I remember they have 
been consistent with what's expected, but I haven't played with many 
different Ozy configurations.

joe n6kk 



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