[hpsdr] Demeter PSU design

[Jeroen Bastemeijer]

Dear Doug, and others,

Doug, thank you for your thoughts! The situation you are describing is 
totally correct. Maybe I should clarify the Demeter and Tiny Demeter 
project:

Last year we started with the Demeter project. At that time we wrote 
down a list of specifications (wishes). This made Demeter a rather 
complicated power supply, but it allows a broad range of input voltages 
(e.g. batteries with a low output voltage). So, Demeter would be very 
suitable to run from a (car)battery during a field-day.
A couple of weeks ago, during the Teamspeak session, the idea was 
discussed to build a simple power supply. It was picked up as Tiny 
Demeter. The main design objective for Tiny Demeter is simplicity, hence 
we want to keep the HP (High Performance) from HPSDR. Therefore, Tiny 
Demeter is intended to be used in a better conditioned environment e.g. 
the shack. In the shack a 13.8V power supply doesn't have to be a problem.

So, if you are looking for a power supply to use HPSDR in the field, you 
should wait for Demeter (or find a good source for a 13.8V power 
supply). If you only intend to use the HPSDR in the shack: Tiny Demeter 
could/would/should be your friend. ;-)

Hope this clarifies the (Tiny) Demeter project a little bit more.

73 Jeroen PE1RGE

Doug Bade schreef:
> While not exactly part of the discussion at hand but a lower input of 
> say 11v might be worth planning ??? as batteries at field day rarely 
> yield 13.8v :-)
> Many HF rigs seem to give it up under 12.5v.... pretty sad as we are 
> sort of expected to work of sources besides a regulated 13.8v...and 
> unless the charger is running , getting 13.8 at a source, let alone at 
> the radio is tricky at best....
>
> Just my thoughts.... :-)
>
> Doug
> KD8B
>
>
> At 10:33 AM 6/26/2008, you wrote:
>> ***** High Performance Software Defined Radio Discussion List *****
>>
>> Dear Phil,
>>
>> Thank you for your comment. I think we all are very curious to see 
>> how Mercury behaves in general, and for (Tiny) Demeter, in 
>> combination with a switching power supply. Is the SMPSU you are using 
>> a PicoPSU? Or are you using another type of SMPSU?
>>
>> You are right about the efficiency of a linear regulator. Worst case, 
>> the dissipation would be around 12 Watts. Another option would be to 
>> use a switch-mode preregulator to approx 6V and then use a linear 
>> regulator for a clean 5V. Dissipation of the lin. regulator will be 
>> around 1.5Watts in that situation.
>>
>> The switcher for -12V is always necessary (if we want to run from the 
>> 13.8V station supply).
>>
>> 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?
>>
>> 73 Jeroen PE1RGE
>>
>> Phil Harman schreef:
>>> ***** High Performance Software Defined Radio Discussion List *****
>>>
>>>
>>> Hi Jeroen,
>>>
>>> Good to see this discussion on Demeter. We are very close to seeing 
>>> how well the small switching power supply that plugs directly into 
>>> the ATX  connector on Atlas works with Mercury i.e. the picoPSU-120.
>>>
>>> I am using switching regulators on all my HPSDR supplies and have no 
>>> problem with noise etc.
>>>
>>> I suggest you review the use of a switching regulator to provide +5v 
>>> and -12v  from 13.8v after the results of the above test are completed.
>>>
>>> I am concerned that a linear regulator for the 5v supply will be 
>>> very inefficient.
>>>
>>> 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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