Remember that the ALC is active in the exciter. If the amp is tuned and
loaded correctly with proper drive level from the exciter then the ALC in
the exciter handles the level control chores. Thus ALC in the amp is not
necessary.
Now, if one should take a 200 watt exciter, albeit common today, and drive
the amp designed to be driven to rated power with 100 watts, yes splatter
and etc will abound. Hams are supposed to understand that fact, but do
they? I see more that don't than do.
73
Bob, K4TAX
----- Original Message -----
From: "Dr Gerald N Johnson" <geraldj@storm.weather.net>
To: <tentec@contesting.com>
Sent: Tuesday, October 30, 2007 2:51 PM
Subject: Re: [TenTec] Omni VI and non TT Amp
> On Tue, 2007-10-30 at 10:58 -0400, Paul Christensen wrote:
>> > "Cuz an Omni VI doesn't have ALC jack. Where you going to pug it in?
>> 73 de K1ESE
>> John"
>>
>> There's nothing wrong with the concept of ALC between the transceiver and
>> an
>> amp, but more often than not, the real-world implementation is nothing
>> more
>> than a "feel good" exercise that leaves the operator with a false sense
>> of
>> security.
>>
>> >From what I've seen, the better ALC systems are employed within a
>> >product
>> line under one manufacturer where the designer can calculate the ALC
>> voltage
>> "meet me" point with some semblance of precision. For this reason, ALC
>> within the transmitter section of the transceiver is much easier to
>> manage.
>> Even when some form of ALC voltage adjustment is used between an amp and
>> transceiver of different manufacturers, the ALC transient dynamics may
>> not
>> be optimized. Simply connecting an ALC cable between a transceiver and
>> amp
>> is no guarantee of good linearity and amp protection.
>>
>> For this reason, I have always shunned the use of ALC and try to pay
>> attention to proper amp drive level and loading to ensure maximum
>> linearity.
>
> So you NEVER get excited and shout when chasing DX, so never drive the
> PA to clipping??? If that never happens you are one cool ham.
>
>> A better means of proper amp operations includes the use of a scope in
>> trapezoid X-Y mode between the input and output of the amp.
>
> But it may not always inspire you to keep from a bit of peak
> compression, will it? A little bit of peak compression can show up as a
> lot of higher order intermod, otherwise known as splatter.
>>
>> Until the advent of DSP, an even better method consisted of applying mic
>> audio to one set of scope plates while applying final RF to the opposite
>> set. The benefit is that the entire system from mic to amp antenna port
>> is
>> used to measure total system linearity. However, since transmit DSP
>> introduces latency, even if slight, I've found that method no longer
>> gives
>> an accurate display of linearity.
>
> It didn't work too good in the analog radio either because of phase
> shifts through the audio chain and time delay in the filter.
>>
>> Paul, W9AC
>>
> 73, Jerry, K0CQ
>
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