[Amps] Overdrive protection

[Joe Subich, W4TV]

> I don't see why the ALC can't be adjusted so the amplifier is never
> over driven

The problem is that the transceiver ALC time constant is too slow and
the transceiver IF stages have excess gain.  Thus the transceiver makes
"full power" for the few milliseconds *before* the ALC can react and
reduce the gain.

It happens in nearly all brands of transceivers - including Yaesu's
FT-1000D, FT-1000MP, FT-1000MP MKV (I haven't tested an FT-2000 or
5000 yet) and all of the Icom 756 series, 7600, 7700, 7800 *IF* the
If gain adjustments (factory) are too high.  Since many of the rigs
have firmware based, per band gain settings, a given radio can have
tremendous overshoot on one band and be fine on another.

73,

    ... Joe, W4TV


On 7/26/2012 10:27 PM, Ron Youvan wrote:
>     Mike G8TIC/M0VHF Tubby wrote:
>
> /*snip*/
>> I cannot see the point of (over) driving an amplifier and effectively
>> using ALC to "hold it back" ... it just seems to me that if you're doing
>> this then your amplifier isn't big enough in the first place - to this
>> end I have to say I'm with Mr. Measures... a 3CX3000 or 3CX5000
>> under-run at 1500W PEP is just going to be SO SO much nicer than a small
>> amp thrashed to within inches of its life ;-)
>
>     I don't see why the ALC can't be adjusted so the amplifier is never over driven and is kept at
> the desired operating drive level.
> I actually thought that was the idea.
>