Read Linear Tech www.linear.com 's Application Note 70 -- they have
conquered noise by using slew-control switching techniques. Instead of the
complete circuit used in the ARRL design you can jump off and use a slew
control chip. The prices of the Linear slew control chips are not bad,
probably $5 or $6 from Digikey. (and they can be purchased directly from
Linear in quantities less than 500.)

The other thing I have pondered is using a regular gate driver and a 2nd
order low pass filter to approximate a sine wave. You lose a lot of
efficiency going from a square wave to one which is rounded off, and a
filter has issues all its own issues, but I would think that "noise" or
"hash" would drop tremendously.

Jack

"Richard Hosking" wrote in message
...
Dear all
I want to design a power supply for a low power portable HF SSB rig with
maximum efficiency from a 12V battery
I will need +1.8V at around 200mA, +5V at low current, and +/-12V, with
the +12V at 1A unregulated. I thought of using a MAX1865 SMPS chip which
has multiple outputs with good efficiency. However I am conscious that
in a quiet analogue environment, the SMPS may be a problem with
switching noise. Is this a feasible idea? Should I use several separate
chips? What precautions should be taken? (I have read the Maxim app
notes on PCB layout and noise reduction, but I am not sure whether this
will be sufficient in this environment)

Thanks

Richard