[hpsdr] Demeter = HPSDR power supply(?)

[k5nwa]

At 11:29 AM 6/8/2007, Chris Albertson wrote:
>***** High Performance Software Defined Radio Discussion List *****
>
>
>I'm thinking recently about a project like HPSDR in that it also
>uses cards and a backplane and of course it to will need a power
>supply.  This project will use a 50 pin ribbon cable as a backplane
>so there are no DC power connectors on the backplane as with Atlas.
>So the power supply, or at least parts of it will be built on one
>of the cards.  I think that idea could work for HPSDR too.
>If you are going to communicate voltage and current levels and
>accept a digital command to "shut down", the power supply needs to
>be connected to the buss which means you need a card.  Once you are
>committed to using a plug-in card you may as well make it as large
>as the specification allows, Smaller cards don't make for a
>smaller system as the enclosure must be spec'd for the largest card.
>
>So on the card you could mount some DC-DC converters for the voltages
>other than +12 and a regulator to take +13.8 to +12 then you feed
>your new card only 13.8V from either a lead acid battery or a
>standard "ham" power supply that most of us might already own.
>I don't see much reason to use the DC connector that is on the
>Atlas board if you are using a plug in card.  The new power supply
>card would plug into Altals and have just an Anderson Power Pole
>connector and a fuse on it's exposed side.
>

The card has a couple of disadvantages that are hard to deal with.

1. Coupling of noise to the other cards is easier since they are 
right next door, and most likely with no shielding.

2. On a separate power supply you can put the whole thing on a steel 
case and keep the magnetic fields from the power supply components 
from affecting other boards, you filter the living daylights out of 
any line coming in or out of the little box, and all the noise stays 
inside that little prison.

Since the purpose of all these projects is exceptional performance, a 
switcher no matter how clean can and will contaminate weak signals if 
given a chance, sealing up the power supply is your best bet, even an 
analog power supply would need the magnetic fields from it's 
transformers kept for contaminating signal lines.


Cecil
K5NWA
www.softrockradio.org www.qrpradio.com

"Blessed are the cracked, for they shall let in the light." 


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