Ben Nock’s
valve & vintage
Ben Nock G4BXD took advantage of a brief spell of good weather to test several new arrivals at the ‘Kidderminster Kollection’.
big hello once again as I open
the doors to the Valve and
A
It’s been a good few weeks for the
Kidderminster Kollection and some
interesting German Second World
War sets and the odd Eddystone or
two have arrived. But this month I’ll
describe the recent addition of several
military man-pack radios that have
been delivered.
the idea of man-packs. There’s always
the thought we will rush off into the
hills and sit working the DX while
chomping on the buttered scones,
although in reality, military man-packs
are not as great as they fi rst sound!
Being military, weight never seems to
be a consideration. It might well take
three men to carry the complete radio
kit, not a problem when you have an
army to employ– but for a single, unfi t,
overweight civilian, well, it can get too
much!
Vintage (V&V) shop for August!
Many military radio collectors like
Then there is the fact that 10W or
Fig. 1: The PRC-74 operating controls.
so to a short whip does not go far. So,
to work any distance the operator will
need a pole or two and a few feet of
wire, cable, guys, pegs, radials, etc.,
again all adding to the weight.
Battery Problem
Then there’s the battery problem! The
man-pack battery (when new) might
have lasted 20 hours or so, but that’s
for short military type messages not
prolonged Amateur Radio QSOs!
Nowadays though, with old batteries
(if they’re available), or new Nicads
fi tted in their place it’s amazing just
how quick they run down when out in
the fi eld.
So, the modern user either needs
to carry extra battery packs – again,
this isn’t a problem if a three tonne
truck is available – or fi t sockets on the
set so external batteries can be fi tted,
all adding to the weight once more.
Finally, there’s the tuning as
many military sets employ dial-
up tuning, that is they have
six or more knobs to set the
frequency. Not a problem
when the frequency is
allocated on a military
net – but trying to tune
around the band can
really hurt the fi ngers as
I know from blistering
experience!
However, even
after mentioning
all the problems
for the modern
68
Fig. 2: View showing the PRC-74’s modular construction internally.
Practical Wireless, August 2008
Fig. 3: The SEG-15D, with a clean front panel layout.
user, readers will realise I’m one of
the collectors who loves the military
man-pack despite all its failings! So
it was really nice when three new
ones arrived for the Kidderminster
Kollection in a very short space of
time. An American PRC-74 arrived
along with an East German SEG-15D
and a Belgian BDR-510C. A search on
the Internet throws up loads of info on
the ‘74 and 15D but very little on the
‘510.
Ben Nock G4BXD
62 Cobden Street
Kidderminster
Worcestershire DY11 6RP
E-mail: military1944@aol.com
Fig. 4: The BDR-
510C, with the solid
construction on this set
clearly visible.
The American PRC-74
This PRC-74 man-pack, Fig. 1, has
a really exciting history as it was
widely used in Vietnam during the
confl ict there and I have found some
interesting information and pictures
on the web detailing its use. Basically,
the set tunes 2 to 18MHz and puts
out a good 15W of upper side band
(u.s.b.) or Morse (c.w.) signal from a
12 – 15V battery supply.
The series started with the PRC-74
that tuned 2 to 12 MHz, the 74A had
a similar range while the 74B and 74C
tuned up to 18MHz. Various battery
boxes were available and allowed for
different battery combinations, one
box even taking several wet cells.
Other boxes used Ni-cads and various
pre-packed units.
Although the transmitter generates
u.s.b., the unit can be altered for l.s.b.
in a couple of ways. The best method
is to replace the internal fi lter, these
are available but fi nding one is hard.
The other method is to shift the carrier
oscillator, presently on 1750kHz to
the other side of the existing fi lter
and make it about 1747kHz. The
latter method would throw out the
frequency calibration but there’s
a way of correcting the error. The
photograph, Fig. 2, shows the internal
layout of the set.
On the one sunny day we seem to
have had so far this summer (at time
of writing this) in Kidderminster, I took
the set to a nearby hill. Using just the
whip antenna, I heard USA, Japan,
Africa and many European station
whilst working several Europeans and
a couple of Scandinavians with good
reports on 14MHz. On the next sunny
day I intend to take a pole and some
wire with me.
East German SEG-15D
The East German SEG-15D set tunes
2 to 12MHz although it can easily be
modifi ed to tune up to 15MHz thus
adding the 20 metre band coverage.
The set, Fig. 3, generates 3 or 15W of
amplitude modulation (a.m.), l.s.b.,
u.s.b or c.w. signal from a 24V battery
supply. By the way, its model number
is derived from SendEmpfangGerate,
or transmitting receiving equipment,
15 for 15W of course and the D stands
for digital.
This set was manufactured by
the East Berlin company RFT VEB
Funkwerk Kopenick between about
1975 and 1988. It was intended
for both military and civilian use,
including – apparently – the infamous
Stasi secret police.
The set has at least three battery
boxes, one taking Ni-cads, one to
power the set from an external 12 or
24V supply as in a vehicle for instance
and a mains power unit running of
220V. Luckily, my set came with all
three boxes, so I’m well covered and
there’s also a mention on the Internet
about a hand generator as well.
The set is very easy to use,
the tuning controls are quite light
– probably too light for serious military
use – but very easy on the fi ngers
when tuning round an Amateur band.
Output is either to a telescopic whip
or a BNC type 50Ω socket. A large
roller coaster tunes the r.f. output to
the antenna, with the panel meter
showing either battery state or the
output tuning.
There’s a very good German web
site which details many modifi cations
for this set including the frequency
extension. I intend to fi t this mod at
a later stage to give access to the
14MHz band.
With the mains power unit and the
external amplifi ed loudspeaker fi tted
the set works well as a shack mounted
transceiver and I’ve made several
good contacts. The set’s lightweight
construction, light gauge metal, little
reinforcing, makes it look somewhat
amateurish compared to the solid
make up of the PRC-74.
The BDR-510C
The BDR-510C is made by MBLE in
Belgium and the set tunes 2 to 12MHz
and generates 10W of a.m., c.w., u.s.b.
signal from a 12-15V battery supply. I
acquired this set, Fig. 4, along with its
Practical Wireless, August 2008
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