Czech RF-10 Military Radio
© Brooke Clarke 2008
RF-10 Battery Box Empty Opened
|RF-10 Approximately Full
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.
24 May 2017 - updated information from Petr, OK1RP:
The MHz selector is allowing to set frequency in 1MHz step in between 44-53MHz.
The kHz selectors has two knobs:
left is for setting frequency in 100kHz steps in between 000-900kHz.
right is for setting frequency in 25kHz steps 25/50/75kHz.
So ending frequency in range is 53.975MHz.
Regarding the lights on the top panel:
Left green light with yellow ring is indicating the transmission > in test mode (mode switch to test mode same icon).
Middle white light with white color ring is indication all the time that PLL synthesizer is locked correctly.
Right upper side red light with red ring is indication of the discharged battery pack.
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 Pardubice.
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
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 sending morse.
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 modes.
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
first generation SINCGARS
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
The RF-10 audio connector seems to support not only the normal
Mike, Speaker, PTT and ground but also two additional momentary
contact push buttons.
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.
2 (no) *
(when PPT pressed)
(260 Ohm DC)
1 (no) *
Battery Minus = Gnd
* note: the switches use pin 19 as a common
Audio Connector on Radio
Audio 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
and the comments below.
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 case latches.
- 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 side.
- 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 nothing.
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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