[GPS_Standard] -5 to +5 Voltage Source

[Dave Platt]

> I'm having difficulty understanding how to create the proper voltage source
> for the VE2ZAZ control board, -5 to +5 volts.  Any suggestions?

There are several approaches.

If you start with a single-voltage supply (say, a +12 or +24 - whatever
your oscillator requires) you can add an additional regulator to get a
clean +5 supply for the board's oscillator-control output.  Since you
only need a small current, a simple 78L05 regulator and a couple of
filter caps would be all you need.

The -5 is more difficult.  The most straightforward way is to use a
commercially-made or home-made power supply with both positive and
negative outputs... say, a +/- 15 (these are relatively common) and then
use a negative voltage regulator such as a 7905 to regulate the -15 down
to -5.

You could buy a kit such as the Chaney C6895 from Electronics
Goldmine... this has three variable output voltages (positive and
negative up to 15 volts, at 400 mA, and positive up to 21 volts at 1
ampere).  This might be your best bet, if 1 amp is enough to run the
oscillator with its heater and the main VE2ZAZ input - the two
low-current outputs could be set to +5 and -5 and provided to the VE2ZAZ
output circuit.

It *is* possible to start with a single-voltage DC supply, and generate
positive and negative voltages from it.  It's a bit tricky.  One
approach is to use a switching-type "inverting regulator" to create the
negative voltage.  Alltronics has a +12 in, -5 out (Astec AA7600), $8
for two.  These switching inverters might not be a great solution for a
GPSDO where you want really low noise, though.

Another approach is to start with something like a 24-volt DC supply,
and use a 7805 linear regulator to create an "artificial ground" (which
then becomes the "GND" power input to your VE2ZAZ board).

If I were you I'd probably look for a multiple-output DC power supply...
Electronics Goldmine, Alltronics, All Electronics, Marlin P Jones are
all good on-line vendors to check.

And... as an out-of-the-box possibility - although your HP oscillator
has a -5 to +5 tuning range, there's no law that says you have to
actually *use* the whole tuning range.  You could have the VE2ZAZ board
put out a tuning voltage between 0 and 5 (so no negative supply
required) and use the HP oscillator's "FREQ ADJUST" trimmer to
rough-tune the oscillator so that it's right about on-frequency when the
VE2ZAZ is feeding a mid-scale output (2.5 volts) to the oscillator's
EFC input.

This would let you get away with just positive power supply voltages to
the oscillator oven, oscillator input, and VE2ZAZ.