[Amps] FW: Zener Bias Replacement

[Bob Maser]

Try K2AW in the back of QST.

Bob W6TR
----- Original Message ----- 
From: "Larry Carman" <lncarman at swbell.net>
To: <amps at contesting.com>
Sent: Tuesday, November 07, 2006 4:32 PM
Subject: [Amps] FW: Zener Bias Replacement


> OK... you all have sold me on the idea of using zeners instead of standard
> diodes. At least by using standard diodes I have determined the bias 
> voltage
> I need. Now I have to find a zener supplier that will accommodate a poor
> mans budget.
> Regards to all and thanks for the info.
> Larry N5BIP
>
> -----Original Message-----
> From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] On
> Behalf Of Marv Gonsior
> Sent: Tuesday, November 07, 2006 2:08 PM
> To: amps at contesting.com
> Subject: [Amps] Zener Bias Replacement
>
>
>>
>>>I've been following this string with a great deal of interest as
>>>some years ago, W6GNX and I made bias measurements on three
>>>different legal limit 8877 amps.  Two were home brew and one was a
>>>Henry 3K Classic X.  All were measured up to 1A of anode
>>>current.  We no longer have the data but the diode strings were by
>>>far the worst regulators as compared to a Zener and a simple
>>>transistor regulator.  The developed 12V from the diode string
>>>continuously rose with the current like a rubber band and,
>>>obviously as now a number of inputs have shown, the t.c. is part of
>>>the problem let alone having ~20 diodes to assemble for an
>>>8877.  The suggestion of two 6V Zeners seems like a very good choice.
>>
>>In my case, with the two different 8877 amps, the Henry was pretty
>>bad and it used a  Semtech diode pack (replaced with a 50W Zener on
>>a good heat sink) and the rise was in the order of several volts at
>>peak anode current.  Obviously, this leads to current and power
>>limiting and IMD generation.  In my opinion the diode string is the
>>worst thing one could do for biasing!  In a number of times, in the
>>past. when I have read where someone extolled the virtues of doing
>>this, I have written and asked for a measurement but never had a
>>reply.  I have to wonder why.  It is refreshing to see the current
>>interest in this area and it would be a real benefit to all to see
>>some additional, meaningful measurement data being published.
>>
>>>73,
>>>
>>>Marv, W6FR
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