>>>At 08:01 AM 7/19/02 -0700, Richard Measures wrote:
>>>
>>>>The Semtecc diode string in question appears to be a 10 diode
>>>>unit. No, it was a 10V unit, according to Henry and the Semtech p/n
>>>>was their SA5534. So, now we are talking about an ~18 diode device as
>>>>used in the Henry 3-K Classic X.
>>>
>>>> >I would like to ask the proponents of series rectifier diode strings if
>>>> >they have ever measured the developed bias between the minimum and full
>>>> >power conditions?
>>>>
>>>>Yes. Please tell us about the results.........one 5408,
>>>>or? Previously, when I asked you for test data on your recommended
>>>>diode biasing , your response was that I "didn't need no stinkin'
>>>>data." Why now?
>>>>
>>>> >I've done it with a Henry 3-K Classic X, using and 8877,
>>>> >and the bias soared about 6V from zero to full signal.
>>>>
>>>>V sounded a bit high, You bet it was high and you can't compare a
>>>>Semtech assembly with a sample of one 5408. BTW, the early Henry 2-Ks
>>>>used a 50W, 6V Zener.
>>>
>>>>so this morning I tested a 1n5408/3A diode for fwd
>>>>V-drop using 8877-sized currents, assuming a ZSAC of 0.1A and a signal
>>>>max Ik of c. 1.2A. At 0.1A, the V-drop was 0.734v. At 1.2A, the V-drop
>>>>was 0.813V. Thus, with a 10-diode string, the change in bias V for an
>>>>8877 would be 0.79V from zero-sig to max-sig. For improved IMD, and
>>>>less chance of overdrive with more than 78w drive, add a few ohms in
>>>>series with the diode-string to increase V-drop at max sig.
>>>>
>>>> >Read that power limiting that must result in additional distortion
>>>> products.
>>>>
>>>>A diode has more V-drop as current increases. A resistor has even more
>>>>V-drop as current increases. A resistor can be added in series with the
>>>>cathode to create RF-NFB. (which I read in Svetlana, Eimac, and RCA
>>>>pubs).
>>>
>>>>- Marv - Does more RF-NFB increase or decrease IMD? We all know the
>>>>answer to that one but you have to know the net effect of the ratio of
>>>>the biasing distortion to the negative feedback afforded by the resistor.
>>>>
>>>> > I couldn't wait to dump Henry's Semtech diode pack and put in a
>>>> 50W,12V Zener. IMHO,
>>>>
>>>>Humble ? Yes, humble and it is not obvious that you know much about that.
>>>>
>>>> there is nothing worse than diode strings as a biasing element.
>>>> > Further, just ask the G-land 6M ops what they think of the bricks
>>>> >that find their way into cluttering up the band with relatively high
>>>> levels
>>>>of splatter resulting from diode bias. Ian et al, are you listening?
>>>>
>>>>The red herring. Now, don't tell me that you've gotten into fishing?
>>>
>>>73,
>>>
>>>Marv, W6FR
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