[hpsdr] Demeter PSU design

[Jeroen Bastemeijer]

Dear Phil, Graham and others,

Thank you for all the E-mails with regard to the Tiny Demeter design! I 
will read them and respond to them in the coming days.

Phil, at this moment I'm very curious about the performance of Mercury! 
I would like to give you the following suggestion for doing more 
"scientific" noise measurements on Mercury. It is possible to do these 
experiments with a simple setup.

What you need:
* Power supply (which you already have)
* Signal generator
* Toroid or transformer with two coils (primary and secondary)

The transformer is the most tricky part: with succes I used a, so 
called, common mode choke. These kind of chokes can usually be found in 
the input-filter of switching power supplies. So, if you have an 
old/defective computer power supply there is probably one in there. The 
common mode choke is basically in series with the mains connection. It 
passes the mains-power but it represents a short for "RF"-common mode 
signals on the power line and vice-versa.
These chokes have a pretty high power handling capabillity and they have 
two sets of windings (ratio 1:1). The higher the current handling 
capabillity, the better.

For the measuremnts you can put one side, let's call it the primary, in 
series with the power supply line (e.g. the 5 Volt line). The secondary 
winding can be connected to the signal generator. In this way it is 
possible to inject an AC-voltage on the power supply line. The generator 
will be  loaded with the circuit as well, so, when you turn up the 
output level of the generator, a much smaller waveform will be present 
on the power supply (due to the 50 Ohm internal resistance of the 
generator). By adjusting the frequency, amplitude and the waveform you 
could see if there is any influence on the performance of Mercury.

Hope you are willing to do these tests, this will help us enormously in 
determening the finals specs for (Tiny) Demeter.

One more thing, on one of the boards a LT3080 is used. If I'm correct it 
is used with a gyrator like circuit in series. Is the schematic where it 
is used somewhere online?

Thank you, 73 Jeroen PE1RGE

Hope you are willing

Phil Harman schreef:
>
>>
>> Do you have any means to test the sensitivity of the HPSDR and/or
>> Mercury for noise on the supply lines? Especially for "high frequency"
>> noise (at the switching frequency (and harmonics) of a swicther) on the
>> +5 Volt and the -12Volt rail?
>>
>
> Nothing beyond using it to power Mercury and looking at the bandscope 
> - not very scientific I'm afraid!
>
> I think the picoPSU will be a good test and we should be able to try 
> that in the next few days.
>
> 73's Phil...VK6APH
>
>
>

-- 
Ing. Jeroen Bastemeijer

Delft University of Technology
Department of Electrical Engineering
Electronic Instrumentation Laboratory
Mekelweg 4, Room 13.090
2628 CD Delft
The Netherlands

Phone: +31.15.27.86542
Fax: +31.15.27.85755
E-mail: J.Bastemeijer at TUDelft.nl
GPS: Lat N52.00002 Lon E4.37157 Alt 46.2m


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