[Amps] Overdrive protection

[Bert Almemo]

There is a simple solution. I use a 9V battery and a pot to set an
appropriate/fixed ALC voltage to my 746 for the drive power I want. Works
like a charm and no overshoots.

73 Bert, VE3NR



-----Original Message-----
From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] On
Behalf Of Joe Subich, W4TV
Sent: Thursday, July 26, 2012 10:51 PM
To: amps at contesting.com
Subject: Re: [Amps] Overdrive protection


> 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.
>
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