[Amps] Sequencing an Alpha 87a

Paul Christensen w9ac at arrl.net
Wed May 23 22:05:48 EDT 2007

> Paul, does the 7800 really have delicate finals and/or a fold-back circuit
> that can't protect them?


I can speak only of my own experience with the 7800 and to date, I have not 
run into any PA issues.   Over the past few days, there's been a related 
discussion on the Yahoo 7800 group.  Over a ~ 1.7:1 VSWR, the power begins 
folding back.  OTOH, perhaps there's some bizarre load combination that 
results even when VSWR isn't extreme.

The 7800 has been around for three years now and with the exception of a 
minor occurrence here and there, only recently has this issued really 
surfaced.  Component Q/C may be another variable at work here that did not 
manifest in earlier production units.  All of this is pure conjecture 

Through a menu command, one can select a high-voltage MOSFET or a relay to 
key an external amp.  I have always set mine on the former and have not run 
into any timing issues with any of my three amps.

Paul, W9AC 

More information about the Amps mailing list