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@contesting.com [mailto:amps-bounces@contesting.com] On
Behalf Of Marv Gonsior
Sent: Tuesday, November 07, 2006 2:08 PM
To: amps@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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