Re: Standard Valve PA Stages


Mike Gathergood, G4KFK wrote:

On 23 Jun, 16:11, "John" <m...@xxxxxxxxxxx> wrote:
"Nick B." wrote in message

I'm told that someone was asking for a reference to a standard valve
PA design.
There was a time when one had to be able to draw the circuit diagram
for one, from memory, in order to pass the _REAL_ RAE.

73 de G3NYY

What, with no 'prior authority' for the design ;-)

It's certainly in my 1971 copy of Radio Amateurs Examination Revision
Notes (G L Benbow G3HB). I'll reproduce the appropriate section here just
in case anybody wants to print it out and stick it to the top of their
FT-101E :^)

"Transmitter tuning:

Implies resonating all tuned circuits at required frequency. Tune anode
circuits to minimum anode current or maximum grid current of following
stage. PA tuning requires connection of dummy load (70 ohms). Adjust
tuning capacitor to minimum anode currentwith loading capacitor at
maximum. Decrease loading capacitor until PA is drawing anode current to
give input power desired (probably necessary to readjust slightly the
tuning capacitor)."

The accompanying circuit showing an 807 with 375V HT on the anode and a
pi-tank output circuit.

Thats no good. The FT101E didn't use 807s.- Hide quoted text -

- Show quoted text -

... but 6146s are beam tetrodes, just like 807s.

Easy peasy lemon squeezy - we had 12 year olds tuning up my FT901DM on
last year's JOTA. Can't see why a grown man and experienced "ham"
would struggle with it.

73
Mike G4KFK/A6 (it ain't 'arf 'ot Mum)

Well, that's done it for him, then.

Clearly, the original enquirer has not grasped that knowledge of
standard valve PAs, including their design, operation, and tuning, was
part of the RAE syllabus that he should have studied.

This was the style of RAE that he holds dear in his stance on
'maintaining standards'. It is a pity he could not maintain - or given
the nature of his responses, perhaps it should be 'attain' - the
standards the he asserts others should meet. Had he done so, he should
have been able to tune up his FT-101E on transmit. The procedure
mentioned in the RAE syllabus has been quoted above.

To introduce, at this late stage, claptrap about 'prior authority',
preselector tuning, and shack clearances is an indication of
desperation in covering up his original ignorance of the subject:
side-stepping and bullshitting, simple and clear.

I suggest the original enquirer returns to the syllabus he should have
been familiar with, and reacquaint himself with what he should have
already known. A discreet silence on 'maintaining standards' would
also be appropriate, but if things run true to form, there will now be
a plethora of postings, pleadings, self-justifications, personal
attacks disguised as 'rights to reply', and attempts to shift
goal-posts. Anything, in fact, to deflect attention from that which he
should have known.

He claims forty years in Amateur Radio - and has little to show for
it. Clearly a candidate for the new multi-part exam - one easy (PA)
stage at a time.
--
from
Aero Spike
.

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