Carl sez:
>I have never operated a QRO RF oscillator but have picked up many for
>parts or conversion. These go from single 4-400A's up to 14KW water
>cooled triodes. Not one has ever had a parasitic suppressor. Is there a
>reason for this? Many/most were built by well known and competent
>commercial companies..
Aha! That is an Oxymoron, competent commercial companies (CCC)! Yes, there
are some, but then again, there are probably as many who aren't. RF
dielectric heating equipment and induction heaters (eddy current heating)
can be extremely simple. Tuned plate tuned grid, get the phase right, and
whamo, it's an oscillator. The worse the tube is for linear communications
service, the better (at least it seems). Like that Philips/Amperex 5868
that was mentioned here a few months back (same as the Seimens RS1016), a
horrible old bottle for an amplifier, but great for a rugged industrial
noise maker.
The lack of parasitic suppressor in these beasts maybe due to the fact that
the designers figured that the thing would only take off on one freq, the
desired one. There is so much feedback in them, that they are bound to
always start, and always lock on the main frequency. But then again, if you
get an arc in the circuit (not from a parasitic - but from a small fly or
gnat or a piece of dirt), you just grounded the circuit in a new place, and
the thing jumps frequency to oscillate in a new mode.
This is all academic here, as the forum is about amateur amplifiers for the
most part. I was just wondering about experiences with oscillators that
also make parasites. Yes, sounds like it happens, in more than one
oscillator. But those guys (the industrial RF'ers) don't really care if the
unit goes burp, slapzzz, groan, pop, as long as it starts back up after the
spark trips a relay and clears. Wonder how they get by?
John
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