Czech RF-10 Military Radio
© Brooke Clarke 2008
RF-10 Battery Box Empty Opened
|RF-10 Approximately Full Size
From time to time Sportsman's Guide
gets european military radio equipment and offers it at a very
attractive price. I missed out on the VHF low band mast and
antenna about a year ago. But did get this radio, which was out
of stock, then finally did arrive.
Translation of part of web page provided by Bill Howard:
I had a friend translate the Czech web site on the RF 10 radio set. Here is his translation for anyone interested in Czech radios.
CZECH RF-10 Radio Set
For some time I have looked for info on this set which is serving in
our army. What I could find was very general and for me insuficient.
After half a year I was lucky to buy a pair of units and I started
getting practical experience.I started to write a short summary on
RF-10 and later I wrote this essay. Lately there was a large increase
in apearance of those sets on the air. In this section I would be glad
to introduce this communication device made by Company TESLA from
In the 70's there was planned a replacement of obsolescent R-105 and
R-109 which were large, heavy, and used obsolete electronics which
produced loud continous noise during reception. Constructors from TESLA
produced an item of real quality. The technology employed significantly
outdistanced other competitors. For example our enemy USA in the 70's
used PRC-77 which the RF-10 greatly surpassed in smaller size,
usefullness, lower weight, etc. In those days Czech Army used RF-10
mainly for communication on company level, but the utility did not end
there, thanks to its adaptability they were mounted in the vehicles,
served as telephone relays,allso they found use in fire fighting.
In storage and for transportation RF-10 is stowed in polyester boxes,
and that fits into a waterproof container provided to keep out moisture
fe. during descent in a helicopter or during immersion in water. In the
boxes the parts of the set include radio set propper, microphone and
head set, short and long antennas, hanging and directional antennas
bags and harness for the set, spare bateries, cables and a box of spare
parts. In some cases a charger box was provided to alow keeping
batteries in fully charged state for battle readiness, the weight of
the charger was on the order of 3 to 4 kg. Operating the set is simple
and error free, if however the operator still did not understand
something there is onthe side of transmitter short manual of operating
On the top pannel of the set there are 2 connectors, one is for 0.5m or
1.5m Whip antennas, the other a BNC for a 5 m. hanging or 30m
directional antennas. By the whip antenna connector there is an eylet
connection for a grounding wire to provide image plane for the
antennas. Care should be taken that both whip and long wire
antennas are not connected to the set at the same time. The whip
antennas are very stiff so their ends have a plastic ball with a white
line for safety of people working around the station. Hanging
antenna consists of two gold colloured wires connected to a coil
assembly in the center, from the coil assy. a green colour coax
connects to the antenna connector on the set. For the installation of
the long wire antenna the gold single conductor wires should be
stretched vertically to ground, the green coax may be routed as
convenient. Directional antenna provides for sending in a
specific direction, its whole length is stretched in a backward
direction at a height of 1 meter above ground.
Under the antenna conectors there is a 6 position operating mode
selector switch. One position marked with a triangle activates the
"Noise Compressor" stage. This is usefull if the operator has to send a
message in whisper, compressor than increases the gain of microphone
input circuit for small signals. The listener hears the message as if
transmitted with normal loudness. In this mode operator has to watch
thattransmitting loud messages and orders is not attempted as that can
lead to overloading of transmitter stages which leads to modulation
dropouts. Next two positions give two levels of loudnes in the
headphones, the microphone sensitivity is set for standard voice
level. Sensitivity of "Noise Gate" is set for a quiet location.
Proper functioning of the noise gate (squelch) is in RF-10 is a great
improvement in comparision with previous equipment. In the fifth
position of the selector switch the noise gate is disabled, this is
preffered when receiving a very weak signal, headphone volume is set
high Sixth position is test, a green light lights on the front pannel,
and noise is heard in the headphones. For this test it is not neccesary
to connect an antenna as the set input is routed to a dummy antenna.
Next three sellectors set operating frequency. First sets from 44Mhz to
53Mhz in 1Mhz steps. Next sets Kiolohertz in 1Khz steps. Last Hertz
with values 00, 25, 50, 75 Hz (probably meaning 000,250 500 750 hz). In
addition on the front pannel there is an discharged batteries alarm
(red light), a headphones and microphone connectors, and two
pushbuttons for adjusting the call tone which may allso be used for
Now some info about power supply. Battery consists of 5 rechargeable
NICD D size cells of 1.2V at 4 Ah. Charging may be provided in a number
of ways: Most common method is thru use of "konzervatory", a trickle
charger designed for maintaining 30 units in readiness for immediate
use. Another is by using a field charger called "one hour charger"
which indeed can completely charge a flat battery with high current in
about an hour. Third method is by using box A of the RF-10 complet,
this will provide a charging current of 450 mA. The Transmitter has an
output of 1 W, which is not that much, so for a weekend practice
sessions battery discharging is no problem.
The mode switch uses icons. Here
is an image you can print then tape on the radio until you learn the
This connector with 19 contacts plus
the shell has a lot more terminals than the US U-229
family which has 6 contacts plus the shell. Functions supported
by the U-229 family include normal analog audio, retransmission, Crypto
Fill and digital data modes. But some radios may use multiple
connectors to achieve this, for example the RT-1439
radio has three connectors for a
total of 18 pins and more
panel area than the RF-10 is using. But the functionality of the
connector is yet to be determined.
The RF-10 audio connector seems to support not only the normal Mike,
Speaker, PTT and ground but also two additional momentary contact push
I've just assigned numbers since there does not seem to be any already
printed on the connector. This is the RADIO connector. The
handset will have the mirror image numbering.
Number 1 is the outside pin close to the large key way and the numbers
go counterclockwise 1 to 12,
then step to the inner circle with pin 13 between pin 1 and the center
pin (19) and go counterclockwise,
the center pin is 19.
|PTT (nc) *
Battery Minus = Gnd
* note: the switches use pin 19 as a common
Connector on Radio
Connecotor on Handset cord
These audio connector pinouts by Bob Nickels are slightly different
from those in the table above and may be more accurate. Bob has
also made a battery box from double sided PDB material, see photos
Note from Bob: The mic audio gain
(deviation) control is the trimpot on the small PC board just
behind the audio connector.
Home Brew Battery Box
I came home from Dayton determined to
get some green radios on the air for next year. Top of the pile is the
Czech RF10 that I bought from Sportsmans Guide, but which came without
the slide-on battery pack. Inspired by one I saw at Dayton I thought
I'd fool around making a battery box out of double-sided PC board
material (G-10, FR-4 or what-have-you). It came out good enough that I
determined it would be a keeper, and took some photos that may be of
interest to others who need a solution for powering their RF10.
A few comments to go along with the photo captions:
- I recommend using five brass screws, as brass machines and solders
easily. I machined off the tops of four fillister head screws for the
slide-on studs, and left one intact to use as the 12 volt power
contact. I used 8-32 because I had them, 6-32 pan heads should work -
just make sure your studs will slide easily in and out of the RF-10
- Layout of the four mounting stud locations is VERY critical, if you
are off very far you won't be able to slide the box in position. Drill
and tap threads for the screws you are using and adjust the height of
the stud for proper engagement in the latches, and when you can slide
the assembly on and off easily, solder the studs in place on the back
- Locate the center of the +12 volt supply contact spring with the
assembly in proper position, then isolate a copper pad on both sides.
The RF10 case is the 12v return.
- I used copper tape to hold the outside box corners in place,
tack-soldered and checked for squareness, then soldered all the
seams. If you scrub the copper with steel wool or a Scotchbrite
pad and use a bit of flux, soldering is quick and easy. After you
solder the fixed side piece in place, the box becomes quite rigid. An
easy way to cut the copper clad material is to score each side deeply
with a utility knife and then break it over a sharp corner. File the
edges smooth and square.
- Use your imagination when it comes to attaching the removable side
and selecting the type of battery that meets your needs. I mainly
wanted to show the construction method using the double sided PCB
material, which can usually be found at most hamfests for little or
Good luck and 73,
29 May 2008 - I thought I'd add that I've since upgraded the battery
pack to 4 D cells. The Radio Shack plastic 4D holder fits just fine -
the current drain of the RF-10 is really too high for the AA cells I
used to prove out the concept.
9 Ded 2008 - a web
showing how to make a radio DC powr connector by modifying the
plastic battery safety covers.
The box arrived with a hole, not sure if it's poor packing or UPS abuse.
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