|
From: Lou Vermond
VA3AWA/VE3BDV
In 1969, after being on the air for a year, I was given a chance to buy ($5.00) a 1942 Handbook and QSTs from 1922 through 1945. From then on, my primary ham interest has been in the history of amateur radio and the building of "beginners" low power transmitters and receivers using the construction techniques and parts common to the 1920s and 30s. Last winter's project was a
P-P TPTG transmitter built
after one found in the December, 1928 QST (see photo below).
 For my UV-210 version, I used
a circuit that combined that and the
Grammer P-P TNT replacing the fixed grid with a duplicate of
the tank circuit. All very 1929 rules. The rig was
completed around 2:30 on a Sunday morning and worked at the first
press of the key. Surprised me, too...
Most of the manufactured
parts used are well known, but
will discuss one in detail. The grid resister is a tubular
"Guaranteed Non-Inductive" Crescent Lavite. The resister's value was
incorrect so I removed the externally applied resistive material,
inserted and soldered a 10k 2 watt resister, then gave it 6
coats of semi-gloss black enamel to simulate the original
finish. The resister had a paper label, but showing the
wrong value, I asked VE3GRO/AWA to make
a digital mock-up of the original...right font/size etc. I
made sure that the company's address on the label was 1928 appropriate.
(Starting in the mid 20's, Crescent was ever on the move to larger and
larger plants.)
The chassis is
made of hard maple with three coats of lacquer. The variable condensers
are "Patent Applied For" 300 and 500 mmfd. Cardwells, RCA tubes and
Air-Gap sockets, Na-Ald dials and Kurz-Kasch knobs, Brinbach
beehive wall insulators, and 250 mmfd. Sangamos.
The jumper wires are twisted
pair lamp cord with copper
Mueller alligator clips. To
prevent the cloth covering from fraying, I brushed on highly diluted
lacquer just behind the bared wire.
 The RFC is wound with 2
inches of # 30 awg. d.s.c. on
a 1/2'' diameter paraffin "boiled" poplar dowel. (As anyone who
has done so knows, you do not boil paraffin unless you have a
fondness for blackened kitchen walls and frantic XYLs.) I simmered the
dowel at the lowest heat possible and when the air/water
stopped bubbling out of the ends, the job was done.
 Finally, the method for
shorting the RF output
tuning lamp sockets after tune-up is my sole contribution
to the art.
 With 350 VDC on the plate, the rig
delivers an either
blistering 9 watts out. The usual tone report is a 7 with the not
unusual comments of, "Sounds kind of funny tho. U seem to be
moving abt." When monitoring my key-down signal on a windy night, I
can "see" the antenna swaying back and forth with the breeze.
Wonderful...
73, Lou |
