Czech RF-10 Military Radio

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.

Bill Howard

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 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
instructions.

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.

Description

The carry bag is 19" wide, 6¼" deep and 14¼" high and has a shoulder strap. Weight is 12 pounds.
I've added a new column to the packing list so that English names can be matched with the items (RF10PckLstEn2.pdf 1.8 MB)


System Bag Front	System Bag End

Styrofoam Open Antennas in lid Radio & Accessories in base	Radio bag, Radio & Manual
	Pouch (battery or battery box?) Wide strap for radio bag. Metal box with universal tool and misc. small parts. Padlock. 3 each - Wire on spool handset The accessory pocket has a bunch of stuff. Need to do inventory Pouch at top of photo probably is for battery box which is missing.
	The Handset has in addition to the normal Push To Talk switch two additional pushbutton switches. The Connector has 19 female contacts and no marking on the face or anywhere else. The Microphone is of the noise canceling type so your lips need to be touching the front of the mike when using. There are two screws at the top and bottom that would allow opening the handset for repairs. It's not a throwaway like the H-250.
	The top of the battery has 4 pins with notches that fit into the 4 "d" holes. the fifth pin near the right center end snaps into a hole in a spring locking the battery in place. The two contace electrical connector may be the same as the connector on the rear of the radio, only installed upside down. If you have a source for these, even with dead batteries, please Let me know.
photo supplied by Daniel
photo supplied by Daniel	I think the round silver item it to allow the gas from a venting battery to escape. It has the same look and feel as the ones on the FS5000 Spy Radio. But then why would there be one on the bottom of the radio?
photo supplied by Daniel	There's a pin in the upper left corner of the lid that mates with a socket in the lower left corner of the box bottom.
RF-10 Battery Box Empty Opened - holds 5 rechargable D" cells (5 * 1.2 = 6 Volts) Thanks to Petr Ourednik for finding it for me. 16 May 2010 - Five Ni-MH "D" cells with tabs are on order.
RF-10 Battery Pack

18 May 2010 - Pack assembled by soldering tabs toghther (rough surface, use flux). A hole was made so that the red wire can be routed to the bottom side (the factory pack probably had a long tab on one end). The assembly shown above is first installed in the battery box, then the plain plastic part is installed next.

Mode Switch

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.

http://picasaweb.google.com/RANickels/RF1002 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,
Bob W9RAN

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 page showing how to make a radio DC powr connector by modifying the plastic battery safety covers.

Needed

Links

11631 hits since February 26 2008 page created 26 Feb. 2008. List of all my web pages in alphabetic order.

Pin	Description
1	Chassis Gnd
2
3	Chassis Gnd
4
5
6	Battery +
7
8
9
10
11
12
13	Button 2 (no) *
14	Mike (when PPT pressed)
15	PTT (nc) *
16	Spkr (260 Ohm DC)
17	Button 1 (no) *
18	Audio Common
19	Switch Common *


RF-10 Audio Connector on Radio	RF-10 Audio Connecotor on Handset cord