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Commercial Radio Transmitter Question

landtuna

landtuna

In the Navy of the 1960's we used LF, MW, HF and UHF. All our transmitters below UHF were frequency tuneable. All our UHF transceivers/transmitters were crystal controlled.

What is the state of today's commercial transmitters? Can their frequency be changed "on the fly" or do crystals and/or other circuits need to be changed out?
 
Most modern FM Exciters are changeable by setting a series of dip-switches....or changing the freq in software. Solid state rigs can pretty much be put on any FM channel. Of course, to be a good neighbor, you should look at the spectral purity of that transmitter after a frequency change. I wont get into whether the the antenna is broad enough for such frequency hopping.
 
HGR1290 said:
Most modern FM Exciters are changeable by setting a series of dip-switches....or changing the freq in software. Solid state rigs can pretty much be put on any FM channel. Of course, to be a good neighbor, you should look at the spectral purity of that transmitter after a frequency change. I wont get into whether the the antenna is broad enough for such frequency hopping.
Click to expand...

Thank you. That would be a lot easier than manual tuning or changing crystals. Of course we tended to change freq's very often, unlike a civilian transmitter.

And you reminded me of the tuning coils we had on all but the UHF transceivers. They were the weak link and burned out fairly often. Even with all the rocking and rolling of a destroyer and firing of the guns (almost daily) we had very few transmitter failures. Most of our stuff was tube-based and that was even more amazing. Never could figure out why they put one of our big dipoles right on top of the forward mount though. We went through insulators on that antenna by the dozen.
 
Many new transmitters use the clock pulses from GPS satellites to lock the internal crystal oscillator.
 
No, but it assures that the transmitter is on frequency. For AM stations, that's + or - 20Hz. For FM stations, that's + or - 2,000 Hz.
 
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