JERSEY-CITY-SPECIAL CRYSTAL SET
Copyright 2015, 2020 - Alan R. Klase - All rights reserved
when your having fun:
I sold my
house in the deep New Jersey suburbs in 2007, and moved to Jersey
City. The crystal set environment here is quite different.
See: The City
Mouse. So it's been a while since I built a serious
crystal radio. For a while now, I've had good intentions of
building a reproduction of this WWI Telefunken Crystal
set. This is a good example of a portable communication
receiver from 100 years ago. And, having been designed for
short-range communications on the battlefield, it is strictly a
medium wave device. The tuning range is 500 to 2000 KHz,
making it much more like a broadcast-band crystal set, than the
better know maritime radios of the wireless-telegraph era.
radio was displayed in the Fort Monmouth
museum..... but now,
it's in here, beside the Lost Ark.
radio is associated with Edwin Armstrong, who's unit in France,
1918, did evaluations of captured equipment..
Signal Corps blueprints came from HERE.
This is one of the earliest radio I know of where the designer was
smart enough to tap the detector "down" on the tuned circuit.
didn't feel up to an accurate reproduction, so I'm settling for a
similar circuit with a few modern tweaks.
you're going to build anything nearly this complicated, you need
to breadboard it first. I used a piece of 1/4" luan
plywood, and a 3/4" base. I added a wooden stiffener to
the top of the front panel.
in mind the signals are strong here.)
primary tuned circuit can be operated in series or parallel
with the antenna-ground system.
better accommodates short antennas.
between Primary and Secondary
primary rotates via the "Coupling" knob.
are stops to limit the rotation.
is a Ben Tongue inspired thing.
two windings are in series for the low band, and in parallel
for the high band.
is an untuned secondary, in keeping with the original
to support Sound-Powered Headsets It's a UTC A-11.
(50uA full-scale) for tuning and comparative measurement
series with the 100K "Benny" resistor for normal
shunted by 470 Ohms for strong signals.
shunted for maximum meter sensitivity.
Phone Jack for Training Purposes. In fact, that was a
feature of the Telefunken set.
my low (25-feet) ham-radio 80-foot doublet connect as a
easily-listenable stations using a sound-powered headset.
output to drive my 1920's horn speaker with sound-powered
driver element on the stronger stations.
approximately -10 to -30 dBm.
WABC, 50KW, omnidirectional antenna, distance = 12
power in the 100K diode load (Benny resistor) = -12 dBm
-22 dBm average.
sign of any signals from outside the metro area.
- Front panel is 1/8" tempered hard board (Masonite)
painted flat back to simulated Bakelite.
- I scanned the penciled-in dial form the prototype, and
used CorelDraw to construct the calibrated secondary dial.
- The detector is a 1N34'ish diode installed in a quartz
crystal holder to ape the Telefunken detector in the German set.
- Cabinet is a vintage piece from the 1920's
I've been playing the set into an modified Atwater Kent horn with an
sound-powered telephone element as a driver.
Video of my presentation to the New Jersey
Antique Radio System