Re: [TenTec] Omni VI and non TT Amp

["Arthur Trampler" <atrampler@att.net>]

"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
>
> _______________________________________________
> TenTec mailing list
> TenTec@contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec