PTR-175 Radio
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Recently, I've had a few requests for help with these aircraft radios, so thought I'd start sharing some technical information about the PTR-175 radio itself and how it integrates with aircraft.
What is a PTR-175 Radio?
It's a beautifully engineered Cold-War era VHF & UHF communications radio, used in a lot of RAF aircraft from the 1960's to the early 1990's, and some are still flying privately today.
It was derived from the earlier UHF-only ARC-52 radio.
The technology is electro-mechanical, and is based on: thermionic valves; crystals; variable capacitors; rotary inverter power supply; and carbon-pile voltage regulators. Re-tuning is via a wonderful mechanical clunking, whirring function of gears and motors, introducing different crystals into circuit, and re-tuning variable capacitors.
It weights a ton and produces, at best, about 5 Watts of AM RF.
Main PTR-175 Transmitter / Receiver (TR) Unit
Cockpit panel mounted Control Unit, details of controller here
Frequency Ranges
50KHz channel spacing, frequency ranges as below:
| VHF: | UHF: |
|---|---|
| 117.50MHz to 135.95MHz | 225.00 to 399.95Mhz |
| 370 channels | 3500 channels |
System
On it's own, the main Transmit / Receive Unit (T/R Unit) isn’t of much use, as it relies upon some other key components to build up a system to integrate with an aircraft:
- T/R (Transmitter / Receiver) unit.
- Control unit.
- Interconnecting Box (or other interconnecting means).
- Antennae and associated selectors and cabling.
- Interfacing cabling and connectors for power, mic / tel, panel lighting etc..
- Integration with navigation equipment.
- In a a multi-seat aircraft, integration with an intercom system.
Typically a whole aircraft radio system would also include a standby radio, and emergency power supplies for either radio. Also included would be other audio signals from navigation and warning equipment.