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No FM

Wahhh! I just discovered another victim of the lightning disaster at the ol’ homestead. I have a small FM broadcast band transmitter (1/4 watt) that I use to transmit Christmas music for my computerized light show. Yesterday I discovered it had become  a paperweight.

It was setting among the computer gear on my large desk and was plugged in but turned off using the button on the front. It is powered by one of those plugged in wall warts (transformers) that consume a little energy even when they are not in use. Yeah, as an energy manager (CEM) I know better. I should have unplugged it. The transformer is fine although others in the room were blow out in the strike.

The transmitter has one of those simple tubular old car type push up antennas. It was fully extended up behind the book shelves above the desk and right along side of the window frame, kind of back out of the way.

When I push the “on” button it appears to function properly. The display shows the frequency and all the controls look like they work. Since it is a transmitter I can’t hear anything unless I am feeding it audio and have an FM radio tuned to the output frequency. Since I only use it for the light show and don’t have the audio connected (nothing connected to the failed computer system) I assumed it was AOK.

Well, it isn’t.

There is a broad band amplifier used to bring the signal up to 0.25 watts. It is defunct. There is a very low level FM signal present but I have to stick a receiver inside the case to hear it full quieting. Total range is about one foot. It used to be about 700 feet.  So all the front end components, the microprocessor, display screen, audio components, etc  are OK. What has happened is the E2 EMP (ElectroMagnetic Pulse) came in on the extended whip antenna and blew out the RF amplifier stages. They are the first things in line coming from that direction so they acted like fuses. The final amplifier is SMT (surface mount technology) so is not easily repairable.

It is a $200 kit and repairs are probably $100 minimum including two way shipping. I ordered a new kit.

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