[Amps] Zener Bias Replacement

[Marv Gonsior]

>
>>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