The Semtecc diode string in question appears to be a 10 diode unit.
>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.
>I've done it with a Henry 3K Classic X, using and 8877,
>and the bias soared about 6V from zero to full signal.
6V sounded a bit high, 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?
> I couldn't
>wait to dump Henry's Semtec diode pack and put in a 50W,12V Zener. IMHO,
Humble ?
>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
The red herring.
>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?
>
>73,
>
>Marv, W6FR
- R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
www.vcnet.com/measures.
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