RADIO RELAY
Based on the success of the Wireless Set No. 10 (Beam Wireless) and the ability for any Officer who knew how to use a telephone, to talk over it to HQ without needing to tell an operator what to send, the army decided the needed a similar full duplex radio relay link.
The Larkspur C-41 / R-222 radio relay station was actually being developed during WW2 but built in numbers for use in 1948 (years before Larkspur) where it was known as wireless set No. 86. It was mounted in a Commer Q4 or later Bedford RL and used as a vehicle based medium radio relay station for brigade, division or corps communications.
The C-41 Transmitter is a wide band VHF FM “Frequency Modulation” multi-channel duplex radio transmitter. Frequency range 50-100 MHz selected by fixed crystal or with built-in variable Synthesizer. Low / High Power “LP/HP” facilities. Output power 4 to 10 Watts Low Power or 18 to 35 Watts High Power into either a VHF Yagi or into a Helical Coil antenna both mounted in parallel pairs for full duplex working. It operated from 240V AC mains or Generator needing about 900 Watts for the TX, using the supply unit’s rectifier “Tx PSU” and about 350 Watts, using the combined “Audio Amp / Rectifier Rx-PSU”.
The R-222 Receiver is designed to be used exclusively with the C-41 Transmitter. The receiver is a wide band VHF FM radio with a Frequency range of 50 to 100 MHz and is crystal controlled.
Using the transmitter with YAGI antennas gives nominal link range of 20 to 30 miles. Wide band unloaded range of 7 miles. Narrow band loaded range of 12 miles. LoS (Line of Sight)
The picture below shows (left to right, top to bottom) the four main units of the C41 Top row, Left, the C41 Transmitter, Right, the R222 (or later R442) Receiver, Bottom row, Left, PSU / Rectifier No.22, and Right, the PSU / Rectifier No.23.
Another unit used with the C41 is the Channel unit and quad line terminal known as the “CST 1+4 Number 3 “
Installed in a wireless Box Body (WBB) the set looks like this...
The yagi antennas are held on top of the set when they were not in use.
and outside on a Bedford RL looked like this...
Views of this Radio Relay platform on other vehicles can be found in the vehicles sections
The D11 Transmitter has a frequency range of 2.0 to 22.0 MHz. (less than the complimenting R-230, 231 or 234 can cover) It has an RF output of 100W DSB (AM R/T voice), 300W CW (morse) and 350W SSB (voice). Range (mobile) is about 60 miles. But with a good dipole and height world wide communication just like Ham radio, is quite possible.
There is a D13 version of this transmitter, as a high powered version of the D11 and uses the same cabinet. It is for long range communications. It has the same frequency range 2-20MHz, But the RF output is 250 Watts DSB, 700 Watts CW, and 1kW SSB. By using dual diversity reception (R231) it was suited for RTTY (Teletype) operation. Which is what I used it for.
The R-230 (and 234 as a single Frq. version of the 231) Rx is a high frequency “HF” double super-heterodyne communications receiver (the stack on the right above) is made up of five units which are housed in a robust hammer finish painted aluminum cabinet fitted with shock absorbent mountings.
The receiver covers the frequency range of 2.1 to 27.0 MHz and operates from 110-240V AC. Mounted with the D11 Transmitter in an Austin K9 truck, it provided facilities for communication by DSB (Double Sideband), Lower and Upper SSB (LSB, USB, Single Side Band), ISB (Independent Side Band), and Suppressed SB, CW (Continious Wave also known as “Morse”) and FSK (Frequency Shift Keying). Same as the civilian sold (for land based Maritime or Shipboard) Marconi HR27 Rx.
Reception Set R231 was a dual diversity HF SSB version of the R230 receiver. Effectively it contains two separate R234 recievers. Same as the civilian sold (for land based Maritime or Shipboard) Marconi HR28 Rx.
Reception Set R234 was a HF SSB receiver, principally half a R231 and similar to the original R-230, i.e. no dual diversity feature.
The units could be dismounted individually, or the entire frame unbolted from the floor and fold up and out handles on both these racks front and rear sides be carried out of the truck and into the stores or workshop in one piece. The Stores for such equipment were always upstairs to make it more fun...
Tuning up could throw you from the roof of the K9, or if you were up adjusting the cam nets when someone inside hit the send button... But you could also carry a Neon strip light tube as a torch (without wires or power) to light up the area during an emergency “Crash” move, or to amaze German farmers and visiting British Tankies alike.
