[Amps] Mismatch loss

[Jeff DePolo]

That sure sounds Maxwellian to me (Walt, not James Clerk :-)

			--- Jeff WN3A 

> -----Original Message-----
> From: amps-bounces at contesting.com 
> [mailto:amps-bounces at contesting.com] On Behalf Of Carl
> Sent: Thursday, May 03, 2012 8:46 PM
> To: garyschafer at comcast.net; jim at audiosystemsgroup.com; 
> amps at contesting.com
> Subject: Re: [Amps] Mismatch loss
> 
> Who's version of a conjugate match is that, Brune or Maxwell? 
> I get them 
> mixed up.
> 
> Carl
> KM1H
> 
> 
> ----- Original Message ----- 
> From: "Gary Schafer" <garyschafer at comcast.net>
> To: <jim at audiosystemsgroup.com>; <amps at contesting.com>
> Sent: Thursday, May 03, 2012 7:47 PM
> Subject: Re: [Amps] Mismatch loss
> 
> 
> > "Mismatch loss" may or may not cause a system loss. It 
> depends on the
> > generator.
> >
> > As I stated in a previous post if there is no re-reflection 
> (conjugate
> > match) at the generator then mismatch loss will be realized 
> the full 
> > amount.
> > It is a real loss.
> >
> > If you look at a transmitter that has an isolator on its 
> output (typical 
> > of
> > UHF/VHF), any reflected power back toward the transmitter 
> will not be
> > re-reflected to the load/antenna but will be absorbed in 
> the isolators 
> > load.
> > So if your load/antenna or connector presented a 3:1 swr 
> there would be 
> > 25%
> > reflected power. All of that reflected power would be lost in the 
> > isolators
> > load. A 100 watt transmitter would only provide 75 watts to the
> > load/antenna.
> >
> > The same thing happens on the test bench as most signal 
> generators provide 
> > a
> > resistive source and there is never a conjugate match. Any 
> reflected power
> > from the load gets absorbed in the source and does not get 
> re-reflected 
> > back
> > to the load.
> > Any mismatch in impedance results in loss. This is where 
> the term mismatch
> > loss comes from. The mismatch can be the result of a connector that 
> > presents
> > a different impedance than Zo or it can be from the load 
> that is not the
> > same impedance as Zo.
> > In other words any SWR will cause a loss of power reaching 
> the load with
> > this type of generator. No transmission line required.
> >
> > But with a typical transmitter with a tuner at its output 
> that same 3:1 
> > swr
> > load will receive most all of the 100 watts due to the 
> tuner compensating
> > for the mismatch back at the transmitter. It will provide a 
> conjugate 
> > match
> > and most all of any reflected power will be re-reflected 
> back to the load.
> > In this case the only system loss will be that of the 
> transmission line 
> > loss
> > with no SWR plus any additional loss in the line by the 
> reflected power
> > running back and forth on the line.
> >
> > 73
> > Gary K4FMX
> >
> >
> >> What you're calling "mismatch loss" is NOT loss, it is 
> nothing more than
> >> the impedance transformation that occurs in any 
> mis-matched line.  The
> >> only signal LOST is that due to excess attenuation.  What 
> you're calling
> >> "mismatch loss" is entirely the result of where along the line the
> >> signal is sampled or retrieved, and the "mismatch loss" can be
> >> eliminated either by changing the line length or transforming the
> >> impedance.
> >
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