FM home brew refurbisment

Sorting out some FM broadcast transmitters for various local stations recently. Here is a typival one. A home brew sort of. Fabricodled using a little 5 Watt Chineezium transmitter as an exciter and a Broadcast Warehouse 300 pallet module. A chunky 48V 10 amp PSU told to stay outside. The unit looks as if it has had a hard life and the power output device was dead. This chip, MRF151G is expensive, around 150€. Problem here is that with such a basic set up, you have no idea as to reflected power and the power output is determined by the setting of the exciter. Little fingers have a habit of winding it up and there ya go! Lucky as it goes, I had a drop in replacement device which when fitted and bias adjusted worked well. Always a bit uncertain as you can get instability silliness going on. A few capacitors replaced and all seems okay.

The power module as said is made by Broadcast Warehouse. Always well made and these units go on forever. I recall some time ago, repairing one of these modules and looking at the PCB under a magnifying glass, I saw a little silk screened image of a man, with a very large how’s your father. Made me chuckle. A while later when I rang BW and spoke to an engineer, I mentioned what I saw. He laughed and was impressed that I saw this. The owner of the business used to lay the PCBs out and it was his messing. That’s what I call a nice touch!

 

 

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