[Elecraft] [K3] Tokyo Hy-Power HL-1.2KFX amp interfacing (to ALC or not to ALC?)

[Don Wilhelm]

John,

I don't know what other folks do, and I don't have an amplifier, BUT ---

Using amplifier ALC is a good way to create splatter on the bands, so it 
should not be used if you are to present a clean signal.  ALC can be 
used as a crude means of power control - the amplifier is overdriven, so 
ALC activates and the drive power is reduced at the driving 
transceiver.  That is the "bad" use of ALC.  I know of at least one 
amplifier manufacturer which instructs the user to run the driving 
transceiver at full power and let the amplifier ALC control its power 
output - don't do that, it causes splatter on the bands because that 
control mechanism is not instantaneous - you go into an overdrive 
condition before the power can be reduced.

However, some solid state amplifiers also use it as a means to shut down 
the driving transceiver if it detects a fault condition.  The use of ALC 
for that purpose is justified IMHO.

Most amplifiers have a control which can set the ALC level.  So if you 
choose to use the ALC line for amplifier fault protection, then set that 
level well above the point where ALC will be activated by the amplifier 
for power control purposes - otherwise just adjust the drive power of 
the K3 to drive the amplifier to the desired power output and do not 
connect the ALC.

Just a point of opinion, I think the amplifier designers who like to 
depend on ALC for amplifier fault protection should find a different 
way.  If the amplifier is in a condition where it needs to reduce the 
power, that should be done in the amplifier itself without reliance on 
any external device, and that includes sending ALC to the driving 
transceiver.

73,
Don W3FPR

On 3/28/2016 4:51 PM, John Shadle wrote:
> I'm considering adding a THP HL-1.2KFX solid state amp to the K3S station I
> have, and was wondering how others have done this. There seems to be
> conflicting info on the "right way" to do things.
>
> 1. The THP manual states that ALC should be used to control the amp, but
> 2. Elecraft support (and documents) suggest that ALC should not be used for
> any amps.
>
> Of course, that begs the question "Why is ALC included at all on the
> K3/K3S?", but...anyway.
>
> Elecraft support suggested I ask the reflector what other folks do, so I
> am. Looking forward to your replies.
>
>