[Elecraft] K3 and Expert 1K-FA

[Paul Christensen]

> So, please do not advise someone with a solid state amp to disconnect 
> their ALC- unless you want to assume the cost of repairs.

Overall, I agree with that assessment.  However, I do no not make use of the 
K3's ALC line with my SPE solid-state amp.  In looking at the SPE's 
protection circuitry, a fault buss is created that applies a high level of 
bias to the power MOSFETs when any of about 6-7 different fault conditions 
occur.  The response time is exceptionally fast to the point where if I 
deliberately blast the SPE with full power from the K3 without ALC connected 
(don't try this at home - I'm a risk taker but did so only after reviewing 
the circuit), the SPE detects the presence of high input power and applies 
enough MOSFET bias to keep output power below about 1100 watts.  How 
instantaneous?  I have not measured the response time but it does respond 
well to the leading-edge power spike from another well-known transceiver. 
Today, a solid-state amp should be smart enough to know when it's being 
overdriven.

Also, an unknown with the SPE amp is what happens to amplifier linearity 
when the bias protection circuitry begins to engage to keep power from 
exceeding 1KW?  But the same question must be asked of any transceiver that 
interfaces to an amp while using an ALC line.  I like to think that when an 
amp and transceiver come from a common manufacturer, the ALC circuitry is 
probably optimized since the designer knows exactly what's needed at the ALC 
"meet me" point between the amp and transceiver.

Paul, W9AC