[Amps] Pin Diodes

[R at contesting.com]

On Mar 7, 2006, at 9:19 PM, Rob & Terri Sherwood wrote:

> It is interesting that Alpha threw in the towel on PIN diodes with the
> upcoming 9500.  Tech support told me the yield on a batch of diodes was
> terrible, possibly as low as 30%.  That is a shame, as my Alpha 89
> (manual-tune version of the 87A) has PIN diode switching, and is a
> wonderful QSK amp.  I don't believe an amp with vacuum relay T/R
> switching can be considered a full QSK amp.

Quite true, but 2mS R/T, T/R switching is not exactly lethargic.

> Yet Alpha advertises the
> 99 and the 9500 as full QSK.

Does Alpha use a speedup circuit with their vacuum relays?

> I run my 99 in semi-breakin only. How
> long can a vacuum relay last in full QSK mode?   There must be a 
> maximum
> keying rate and a typical cycle life for anything mechanical.  Are they
> banking on the fact that semi-breakin is usually adequate?
>
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Rich Measures, 805.386.3734, AG6K, www.somis.org