"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."
What's shouting? Is that when I hit the paddle a bit harder?
;)
----- 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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