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, ewkeh...@aol.com 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)
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