Grumpy The Mule wrote:
Howdy,

Heh! I didn't look at the url for that schematic, it's an SW3!
I love National Radio gear. I had two HRO-500's, sold one, and
there's an FRR-59 in my basment. I regret having sold my pristine
RBL receiver which beat the pants off either the HRO-500 with LF10
or the Racal RAL7 with RA237 for LF/VLF work. My highschool's club
had an NCX-1000 which I lusted after... er, but only in my heart.

But back to the SW3. I recall padder capacitors mounted on the
top of the RF stage coil former. I don't know the value of the
dual gang tuning capacitor but armed with that, Wheeler's formula
and these sites, you could calculate the effect of the grid circuit
to some extent.

http://www.io.com/~nielw/sw3coils.htm
http://www.antiqueradios.org/gazette/swevol.htm


73,
Grumpy
IIRC the SW3 used a dual 100uuf capacitor. It's a weird one that
tunes through 270 degrees of rotation.

Hmmm, looks to me like that tapped tank is the oscillator set up for
the super regeneration...

denny ... k8do

On Nov 10, 3:30*pm, Denny wrote:
Hmmm, looks to me like that tapped tank is the oscillator set up for
the super regeneration...

denny ... *k8do

And a second thought is see the same thing on the second stage, where
the top portion of that tank is in series between the tank and the
control grid... Redraw that circuit in your head so that the top
portion of coil is bent over at a right angle to the tank... I wonder
if the grid to cathode capacity is too high for comfort and the
series section of coil is for taming that... We do that for
amplifiers on 10 meters where the plate capacity is too high for
comfortable tuning... A small series coil between the plate and the
tank calms that down...