If you look at a current repeater list, you will see that GB3BM is located in Cheshire but the original GB3BM was located at the BT Radio Station, Turner's Hill, Nr Dudley, West Midlands.

It was one of the first 2 Metre Repeaters to come on the air and it's coverage was extensive throughout it's life, being a true 'regional' repeater. This was later supplemented by two more repeaters, GB3AM and GB3BX (still on the air).

GB3BM MK1 was built by G8AMD and comprised a Pye T30FM Transmitter, Pye R18 Receiver, 6 Cavity Duplexer (plus a TDK Circulator for TX isolation), and a highly configurable control system built from discrete TTL logic. It ran from the mid '70s until the early '80s when a voltage regulator failed destroying many of the logic IC's.

GB3BM MK1.1 existed very briefly in the form of the GB3AM hardware under test before installation at Longbridge. It was quickly drafted in to fill the void when MK1 failed.

GB3BM MK1.2 again existed very briefly and consisted of the original RF hardware with a control system based on the processor board from an arcade game. It's operation was rather novel to say the least! Paul (I think) who wrote the software - sorry but can't remember much about you, get in touch at the email address below?

GB3BM MK2 was built by G8PYT and comprised a Pye T100 Transmitter (Ex Post Office/BT Radiofone System 3 base station), Pye R18 Receiver (with modified front end), the original duplexer and a highly configurable discrete CMOS control system. The transmitter had a valve final RF amplifier stage (QQVO640 - later QQVO750). This was capable of delivering 70+ Watts continuously but was actually run at a much reduced power level. This particular model of TX has an extremely clean output making it eminently suitable for use in full-duplex repeater applications. It was equipped with alarms for low forward power, high reverse power and cooling fan failure. The equipment was built into a Pye 7' rack cabinet. Control System Mode Change was by entry of numerical codes from a keypad which was locked by a key-switch (I still have the key somewhere!). There was also a facility for remote control (not used due to licensing restrictions) and also to connect a line controller for RAYNET use in an emergency.

For more information on Pye equipment, see G8EPR's Pye Museum.

Various antenna systems were tried over the years ranging from the original Hustler mounted on a telegraph pole to the final commercial collinear mounted on the gable of the building. Contrary to popular belief, the antenna was never located anywhere on BT's 200 foot mast.

GB3BM ran in total for over 15 years until it was eventually decommissioned in the early '90s - a very sad day.

Little-known fact ... BM had an identical twin installed in the same cabinet and sharing the same antenna system (now you know why the cabinet had to be 7' tall!). It was designed as a standby system for BM or for use by RAYNET in an emergency. Both sets of equipment could operate concurrently, effectively providing two 2 Metre Repeaters with identical wide-area coverage. Either equipment could operate on R3/RV54 (145.675/145.075) or on the notional channels R8 (145.800/145.200) and R9 (145.825/145.225) for RAYNET use. The RF output could be increased to full power on both transmitters under these circumstances. They were never 'fired in anger' in this way but were always ready to go.

Photographs coming soon - if we can find them!.

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