On Fri, 17 Apr 1998 16:30:53 -0600 John Lyles <jtml@lanl.gov> writes:
>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
Academic, not really John. Many hams use those oscillators as the basis
for an amplifier ( not with the 5868, but the socket is the same as the
3-1000Z and 4-1000A). There are many 3-3000A7 units showing up for real
cheap $$ and I was just wondering why I never noticed suppressors. Tnx
for the plausible answer.
73 Carl KM1H
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