Bob Miller ) writes:

There is absolutely no reason in the world to use a switching supply for
this.

The radio doesn't require much current, but the switching supply will
be far noisier than a linear supply unless it's really carefully filtered
and shielded.

Michael

Well, switching or linear, whatever. The point is, if the Sony AC
adaptor is so hard to find, and it's $100, a small, conventional power
supply would suffice.

A communications-quality switching supply would work (all ham
transceivers nowadays are paired up with such critters), or a standard
linear supply.

But the reason transceivers use switching supplies is because on
transmit a lot of power is needed.

That requirement isn't there for just a receiver.

But the "cost" of a switching supply in the application is the noise,
or the real cost of something carefully filtered and shielded, or
doing it yourself, to keep that noise to a minimum.

But that cost has no return, since the receiver requires so little
current that a linear supply will be small and not heavy, and
efficienty will not be an issue.

Michael

One problem with rectifiers is that they ground and unground the
RF path 120 times a second (60 Hz) and unless bypassed will add a hum
to a received station that has nothing to do with ripple. Many supplies
have this fault.

The effect is that the antenna system is changed 120 times a second.

I say go with batteries.

Having purchased NiMH cells and a charger, they're also useful for
other devices. Get 8 AA cells to start, 4 in the radio and 4 charging.

Don't let them run completely down. The clock in the 7600 will
run them to zero, and unfortunately the weakest cell gets
reverse-charged by the others if that happens, which is not good
for that cell.

--
Ron Hardin


On the internet, nobody knows you're a jerk.

In article ,
Ron Hardin wrote:

One problem with rectifiers is that they ground and unground the
RF path 120 times a second (60 Hz) and unless bypassed will add a hum
to a received station that has nothing to do with ripple. Many supplies
have this fault.

Snip

Wrong theory on the hum but the right solution. I've giver the reason
for this a number of times and I'm not doing it again. Anyone that has
build linear and switching power supplies knows the reason.

--
Telamon
Ventura, California