On Fri, 25 Jul 2008, Tio Pedro wrote:


"Michael Black" wrote in message
ample.org...
On Thu, 24 Jul 2008, Tio Pedro wrote:

That's the one that's sort of a clone of the S-38?

Michael VE2BVW

It is the clone of the HE-10, which looks like the S-38

I added a voltage regulator, which stopped the oscillator
pulling problems when running the IF gain up and down
(thirty volt swing!). I did a few other simple mods to
get rid of residual hum in the headphones (ground loop
on filament grounding and added one more filter stage
in the PS.) But this drift has me stumped. I tried a
few different osc. circuits, but the design is weird.
It is basically a BS Hartley, except on the highest band
which requires a feedback loop back to the plate to
get it into osc. I suspect it is the nature of the beast.

Pete

I had a Hallicrafters S-120A, which was transistorized, the
only shortwave receiver that I could afford in 1971, and it
has to be the worst receiver ever sold. Not just the usual
faults of bad dial, bad image rejection and bad stability, but
it had the bonus of overloading really badly because they weren't
designing good solid state receivers at the time.

We lived with them because we couldn't afford anything better.
I'd say the experience of having such a bad receiver often
included attempts to improve them, even though they started
out so bad that it was impossible to do much.

The transistorized one, at least when I was 11, was too
undecipherable to do anything to. I did really get a handle
on SSB, since while the receiver had a BFO, it wasn't strong
enough to demodulate SSB. I kept having the feeling that
the receiver was overloaded, that's what the SSB sounded
like, and I think without prompting (but I can't remember
for sure) I got the idea that if I attenuated the incoming
signals I could demodulate the SSB. So I took pot scrounged
out of something and used it as an attenuator between the
antenna and the receiver, and I really could demodulate
SSB. The problem was that I had to attenuate the signals
so much that only the strongest could be received. Of course,
turning down the RF gain was basically what they told you to
do to receive SSB on pre-SSB receivers, so either I discovered
the idea by myself, or did read about it and put it to use,
I can't remember which.

I remember looking in the Handbook at the a filter to keep broadcast
radio out of the receiver, and pricing the toroids placed the project
out of my means. It might not have helped anyway, since the receiver
wasn't really shielded, and it seemed to overload from all the broadcast
signals, AM, FM and TV, while the filter was only a high pass filter
if I remember properly for AM broadcast.

I went from that to a Hammarlund SP-600, you can hardly make
a bigger jump.

Michael VE2BVW