- Power output: 100 watts
- Mode: AM
- Frequency range: 1.5 – 7 MHz
- Output valves: 2x ZB120
- Power requirement: 230V AC single phase
- Manufactured: 1943
- Status: Operational
From the May 2009 newsletter:
AM transmitter no. 873 has been fully serviced and is now operational, although it will not be on the air until the 80m antenna has been serviced. Part of the ladder line is twisted and spacers have deteriorated and need replacing.
Our Collier and Beale 873 transmitter had to have some circuit adjustments to the oscillator and a lot of TLC as the crystal change-over relay was faulty. Being a special low loss type, and no others of its type being available, it was replaced by a standard PO type and seems to be fine.
Like the other transmitters, we found that the output tubes had grown old and were low in emission. We had some others in the store so these were utilised. Two others were donated to the Group for this unit and are our spares. This transmitter runs at 100 watts carrier power and on-air tests on the AM net produced favourable results.
The transmitter has two crystals, which can be remotely switched. This unit was modified to communicate with police cars on 1675 kHz.
The cabinet has a black crackle paint finish, and although this has worn thin over the years it still looks great with all the metering on its facing side. As is common with this type of equipment, there are two sections. Although it is built as one unit the top half is the RF Section and the lower is the power supply unit.
The front has a two-door inspection cupboard and the rear door is from top to bottom. Both of these have safety switches, so the transmitter is rendered safe whilst tinkering with the engine so to speak. The output has been altered from a twin feeder or 600d line to coaxial and this also goes to the antenna patch panel. This gives more flexibility.