As mentioned before a suitably rated single transformer with a center tapped secondary will suffice if you want to build your own linear psu. I use a 2 amp 25.2 volt center tapped transformer (along with a bridge rectifer, filter caps, 3 terminal regulators, fuse holder etc.)
I don't losse any sleep over the 5 volt regulator having to dissipate several watts more than it would if I had a differrent transformer. On Mon Feb 14th, 2011 1:31 PM EST Larry McDavid wrote: >I think you should look at the specifications for the noise-rejection >capability of those three-terminal regulators. They are simple and inexpensive >but not particularly good at noise rejection. Some of the noise from the >switcher supply will pass through. Is it enough to cause a real problem? >Unknown to me as yet. > >The power requirements of the Thunderbolt are not the usual ones you see >standard supplies designed to meet. I have yet to find a small linear supply >that is adequate that does not absolutely dwarf the Thunderbolt itself! > >Back in The Day, one could find a good assortment of multiple-secondary power >transformers that would allow us to build a simple linear supply with the >three-terminal regulators; there would no switcher to generate noise. Alas, >these transformers are no longer easily available today. I think it can be >done with two separate transformers but with the filters, regulators and >actual wiring, this adds up to a lot of work! > >TAPR does offer a 13 vdc input, three-output power supply kit for their >software-defined radio kits, but its -12 vdc output comes from a switching >dc-dc inverter. That -12 vdc does supply the Thunderbolt OCXO so I have some >concern about noise on that power feed. > >One could get a custom-designed PC board mount transformer and develop a board >to supply adequate power. I doubt there is enough interest or purchase volume >to justify this, however. > >So, I'm still looking for a compact linear power supply. I welcome your >suggestions! > >Larry W6FUB > > >On 2/14/2011 10:06 AM, [email protected] wrote: >> Yes I am doing it with some very low cost switchers off ebay, followed by >> linear regulators as I mentioned previously. Works great. >> Bert Kehren >... > >-- Best wishes, > >Larry McDavid W6FUB >Anaheim, CA (20 miles southeast of Los Angeles, near Disneyland) > >_______________________________________________ >time-nuts mailing list -- [email protected] >To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
