[hpsdr] Atlas Bus power supplies - Update?

[Christopher T. Day]

Peter,

 

I think I may be the only one who can even try to address this question
as I don't think anyone else has the combination of PSUs and HPSDR
boards. But I live in a very RF noisy environment even without the PS.
So, what I can do is limited. What I have done is the following:

 

1)       Set up my SDR-1000/Janus/Ozy combination and calibrated it
using an Elecraft XG1.

2)       Removed all the audio connections from Janus.

3)       Made a screen capture of PowerSDR at different sample rates
with different PSUs.

 

I have three PSUs available:

 

1)       picoPSU-60WI, which is the size of an ATX connector, can supply
~60W at 5V, and which can be driven by 13.8V, among other supply
voltages.

2)       picoPSU-120, which is the same size, can also supply about ~60W
at 12V, and which must be fed only by regulated 12V.

3)       Sparkle Power Int'l 145W microATX supply, which is a
conventional, small PC supply.

 

I tried sampling at 48ksps and 192ksps. The results are at:

 

1)       http://www.hamsdr.com/personaldirectory.aspx?id=488
picoPSU-60WI @ 48ksps

2)       http://www.hamsdr.com/personaldirectory.aspx?id=489
picoPSU-60WI @ 192ksps

3)       http://www.hamsdr.com/personaldirectory.aspx?id=490 picoPSU-120
@ 48ksps

4)       http://www.hamsdr.com/personaldirectory.aspx?id=491 picoPSU-120
@ 192ksps

5)       http://www.hamsdr.com/personaldirectory.aspx?id=492 Sparkle
145W @ 48ksps

6)       http://www.hamsdr.com/personaldirectory.aspx?id=493 Sparkle
145W @ 192ksps

 

 

I think this has nothing to say about wide-band RF noise. But, since the
current Janus/Ozy combo does not deal with RF itself, the wide-band
noise may be irrelevant. Having the PS generate RFI in other equipment,
e.g., the SDR-1000, is a different problem and amenable to the usual
techniques, I would suppose. The bigger problem would be the PSU feeding
noise directly into the Atlas bus, which would be mush harder to deal
with.

 

To me, the screen shots suggest the problem is minor at best, but I'm no
expert. If others have suggestions for tests I might be able to do, I'd
be happy to do them if I can.

 

 

            Chris - AE6VK

 

P.S. - The manufacturers have announced the picoPSU-120WI-24, and -35
which are wide-input versions that handle 120W from unregulated
supplies, e.g., 13.8V. My quick glance at the specs suggests that what
they've added is a ~6A 12V switching regulator, so it's ~60W at each of
5V and 12V.

 

 

  _____  

From: PETER BUCK [mailto:peteg3lwt at btinternet.com] 
Sent: Thursday, February 08, 2007 6:52 AM
To: hpsdr at hpsdr.org
Subject: [hpsdr] Atlas Bus power supplies - Update?

 

Hi all,

Some time ago there was much discussion about powering the Atlas bus,
including some 12DC input PSUs. At that time the wideband noise produced
by the converter(s) and its effect on attached boards was unknown. Is
there any update on this now that some units approach manufacture and
others are in prototype? I'm delaying powering up as long as possible in
the hope that this issue can be resolved and a "best buy" for a 12V DC
powered unit recommended.

Peter G3LWT 

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