25mhz

[vanlifeson]

I have a MK3 transmitter that is putting out on 25 MHz! Any ideas what the heck is up wit dat?

[2600]

Somebody tweaked the alignment adjustments and got it wrong. Looked at the wattmeter, but not at a counter.

If a Mark 3 transmitter goes dead, you look to see which one of the three oscillators has shut down. The 5.645 carrier, the 5.045 offset and the selected channel crystal.

Most of the time, you'll find that one of these three has quit. Maybe because of a dirty tube socket, and rocking the tube around makes the transmit "kick in" briefly. A bad crystal is not all that common, but the older the radio gets, the more often you see it.

Kinda like "my car won't start". Just one symptom, more than one possible cause.

It's possible to produce just a Watt or so of power at oddball frequencies when one of the three oscillators has quit, and produce a feeble wattmeter reading. But to do this, at least two or three of the alignment adjustments has to be drastically out of proper tune.

Sounds as if the transmitter quit, and then someone tweaked and tweaked until they got an upward flicker on the wattmeter.

Again, like "my car won't start" the first thing to do is establish which parts of the system are not broke, like seeing a spark, fuel pressure etc.

Do you have any kind of shortwave or HF receiver that can tune in the three crystal frequencies inside this transmitter? Eavesdropping on them each in turn also lets you peak internal adjustments without having to see a wattmeter reading.

But this is what it sounds like, out-of-control tweakeritis.

73