Jerry's
Ham Receiver Petting
Zoo
I have been licensed
since January 1971 originally as WN6FQL, later (and currently) as
WB6FQL.
One of the activities I
have particularly enjoyed has been taking old receivers and making
them like new, or modifying them to work better than original,
differently than original, or performing evil experiments upon them.
It all started when I was studying for my ham license, and realized
my two-tube regenerative Knight Span-Master was not adequate for ham
use. Wandering through a swap meet, I found a Hallicrafters S20-R
for $8.00. After talking the owner down to $5.00, I tied it to the
rack on the back of my bicycle and walked it 5 miles home.
(Barefoot. In the snow. And that was in the summer!) This was in
the middle of 1970.
Shortly after getting
my license, I became aware of the shortcomings of this receiver.
Lack of sensitivity on the highest band, lack of selectivity -- this
receiver has no crystal filter, lack of stability -- drifting and
mechanical instability all made me yearn for something better. My
first attempt to rectify this situation was to build a combination
preselector and T-R switch copied from an old (1940-something) QST
magazine. At that time, I owned a bunch of QST and CQ magazines from
1941 'till 1959. Wish I had them now. Next, I soldered a piece of
wire from the plate of an IF tube and hung it near the grid
connection, creating a regenerative IF, and increasing the
selectivity by a lot.
In 1971, I was a junior
in high school. A chance conversation with another kid in the locker
room during PE unearthed my second receiver, a BC-224 which cost me a
princely $2.00. However, when I plugged it in, it smoked! Opening
it up revealed a burnt resistor. Don't remember where it was in the
circuit, but I remember my father (who had run a TV shop in the '50s,
and earlier, when he was a youngster was the person who all the other
hams in town came to to keep their rigs running when they couldn't
figure out what was wrong) said: "Before replacing the resistor,
find the shorted capacitor which caused it to burn out in the first
place." Sure enough, there was a bypass capacitor which was shorted,
the replacement of which (along with the burned out resistor),
brought this set back to life. The advantages of this receiver were
better stability and a crystal filter. The disadvantages were a
somewhat noisy front end (which brought about some evil experiments
-- such as converting the first RF to a 6AK5 from a 6K7, etc),
backlash in the tuning due to extreme wear in the tuning gears -
especially in the ham bands, a really geared down dial (takes about
90 turns to get from one end of the band to another), and, on this
receiver an exposed set of contacts, some with over 250 volts on
them, in just the right spot for an unwary kid to lean on them (only
once, that was all it took to learn my lesson).
Next came a Hammarlund
Super-Pro. This was my most expensive old receiver, costing $15.00.
It was also probably the biggest project, the IF and audio stages
having been gutted. Since I had no crystal filter, I cannibalized an
old '30s or '40s table radio for an IF transformer, and built up a
utility audio stage to drive a speaker or headphones. The addition
of a Heathkit Q-Multiplier gave me adequate selectivity, and the heft
of this receiver gave me the mechanical stability I wanted. Since
the receiver only went up to 20 MHz, I was unable to use it on 15 or
10 meters. This wasn't a big problem, since I usually used 40 or 80
meter CW anyway.
A military version of a
National NC-100 was another addition for a while -- my biggest
modification was to put some padder capacitors in series with the
tuning capacitor, bandspreading the receiver and making a ham-band
only set out of it.
Coming
Soon...
More receivers,
pictures, etc.