At 10:53 PM 10/14/98 +0100, you wrote:
Hi John and Crew
>John Fielding wrote:
>Hi everyone - It seems us "VHFer's" know a bit more about using grounded
>grid triodes than the "DC boys".
>
I think enough has been said about that.
>
>For many years we have been using active shunt voltage stabilisers to
>maintain a very constant cathode to grid bias, irrespective of the cathode
>current. Net result virtually no change in cathode-grid voltage with drive
Yes the shunt voltage stabiliser will improve IMD by a few points but at
what price. More parts in the machine are more parts to break. Allow me to
pass along this annecdote. When I was a tot in the late 70s with my shiney
new Extra Class ticket I did quite abit of DX Contesting from W2PV. Jim
used Alpha products exclusively. At the time he had Alpha 70s, the steamer
version, at every station. The first 77Dx had just come in. I believe that
the 70s employ a voltage stabiliser. Dick, if your listening, correct me if
I'm wrong. My memory is vague but I do remember Jim having a conversation
with Fred Lass on Sunday afternoon of an ARRL DX or a CQWW. They were
discusssing one of the Amplifers and I distinctly remember the phrases
Distortion and the failure of a Darlington Pair being used. Whether it was
an outright failure or conjecture over a bad signal report I don't
remember. I must say however this was the only amplifier failure that I
noticed during several years of contesting at Jim's place. The Alphas were
impressive the way they withstood the abuse we put them through.
John get back to my original point unnecessary complexity can lead to
unnecessary headaches. The IMD Spectral plots for the current generation of
Transceivers as they appear in QST are disgracefull. I'm talking about the
Icom 746 and the Yaesu 920. Yet the FCC over type approves them and the
ARRL editorial shines the results of their own tests. Which leads me to ask.
Why are we banging our heads against the wall?
73s
Bob K1TA
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