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Re: [Xylo-SDR] power

I'm not so sure we need +- 15volts, a long time ago when op-amps were not tolerant of Vcc variations that was the standard power supply. Today most op-amps will work fine with +-5V.

Power supplies now more commonly have +5V and +-12V so most likely that will be what we end up with.

+12V is a nominal value, the analog cards will regulate that down to +-5, or +-9 for noise elimination. The only place where it will be used is if you have a card with a RF power amplifier, or a Auto tuner, those are application that will use that voltage directly. Any decently designed low power RF amplifier will tolerate 11V but will have slightly lower output power, and most 12V relays will still work at 11 volts..

The +5 volts will consume a lot of current so regulating it from a 12 source will create a lot of heat, and internal parts like the FPGA's run on 3.3Volts and 1.7Volts at high current, regulating those from 12 volts would be insane, so like it or not a noisy switcher will be necessary, a carefully chosen one, with noise suppression will eliminate the problems both electrically and thermally.

At this point it has not been decided if the input to the power supply will be 13.8 volts or a wall plug.

First well decide what voltages we need, then we can shop for power supplies that will fit in the space that is affordable, that will determine the power input options. It could well be that there could be an option as to what the voltage in is by choosing what power supply to stick in the box.

My personal preference is to use a 13.8 volt source as the input power, but that will be quite limiting as to available power supplies. That way the unit could run at the shack, or on a 12 volt battery system. But some don't have a 13.8 Volt power supply in the shack, so they will not like it. All my radios except for one run on 13.8 Volts so it's no problem for me, I have several 13.8Volt high current power supplies around

At 09:45 PM 1/15/2006, you wrote:
a note on the +12, please make that +11 to +15v so i can use solar and charging batteries or marine type stuff with some margin.  the +12 is to narrow. the +5 can be made using a 7805 but the +- 15 looks like more noise generators making the volts from +12.  more comments ???
tom
w0kgw@citlink.net
----- Original Message -----
From: Eric Ellison
To: 'Xylo-SDR Discussion'
Sent: Sunday, January 15, 2006 4:03 PM
Subject: [Xylo-SDR] RFC - Powers

Folks

 

Changed the subject in the header.

 

I hope folks like Bill ? KD5TFD, Phil ? VK6APH, Phil ? N8VB are designing their projects based on some of the constants we are defining are NOT reading all this stuff based on subject. Hopefully they WILL trust that we are commenting and deciding and are keeping their project in mind.

 

What powers do we want coming into the MB?

 

Do we want to create a power board within the enclosure or have power source external to the enclosure?

 

I?ll kick it off.

 

I would like to see us use the ?rest? of our 100 x 156 (ID) x 113 mm enclosure for a powers board.

I would like to see a SINGLE 12 volt input to the back of the enclosure with other voltages derived from that via DC-DC regulators.

On project board regulators should use the power supplied from this slide in board for component power, from the buss.

 

Thoughts for the ?rest of the space? is take +12 Volt input from the back of the enclosure to a DC to DC converter to supply:

 

+12 V ( passthru from back panel regulated, not highly filtered, unlimited current)

5 V

+/- 15 V.

 

 

Comments?

 

Eric

 

 

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Cecil Bayona
KD5NWA
www.qrpradio.com

"I fail to see why doing the same thing over and over and getting the same results every time is insanity: I've almost proved it isn't; only a few more tests now and I'm sure results will differ this time ... "