"Mike" <W4EF@dellroy.com> wrote:
> My point is that power dissipation in the source will vary
> depending on the length of that unterminated line since the
> actual impedance presented to the final amplifier could be
> anything on the rim of the Smith Chart ranging from a dead
> short to an open circuit (I am assuming a very low-loss line).
> In other words, which case would you expect to result in a
> higher level of dissipation in the final amplifier, a shorting
> plug placed on the RF output connector, or an open circuit?
> The same goes for more sane levels of VSWR. A 2:1 VSWR,
> for instance, can be represent any value of impedance to the
> final amplifier lying on a 2:1 VSWR circle on the Smith
> Chart. This can range from 25 ohms resistive up to 100 ohms
> resistive with a bunch of other complex impedances in
> between.
>
> 73 de Mike, W4EF..........................
>
Yes Mike.
A lot of this discussion would be eliminated with the use and
understanding of that wonderful tool.
---
Ron
>
> ----- Original Message -----
> From: "Paul Christensen" <w9ac@arrl.net>
> To: "Mike" <W4EF@dellroy.com>; "Gary Schafer"
<garyschafer@attbi.com>
> Cc: "AMPS" <amps@contesting.com>
> Sent: Thursday, March 28, 2002 3:41 AM
> Subject: Re: Bird® 43 Manual
>
>
> > Hi Mike,
> >
> > > The reflected wave combines with the incident wave at the source
> > > such that the source sees a mismatched load.
> >
> > I contend this is true when a conjugate (reactance cancellation)
exists at
> > the source. Typically, this is accomplished by the ubiquitous
transmatch,
> > auto-tuner or Pi-network within the transmitter. The degree of
> re-flection
> > and combining of the reflected wave with that of the forward wave
is a
> > function of that network's ability to cancel system reactance.
> >
> > In the case of a fixed, 50-ohm output transceiver (e.g., my Ten-
Tec Omni
> > Six), I am observing that all reflected power is being returned
back to,
> and
> > absorbed by, my transceiver when the transmitter is feeding an
> unterminated
> > line. This is major point of contention on this thread. When
> transmitting
> > into an unterminated 100-foot length length of transmission line,
my Bird
> 43
> > displays 100-watts forward and very close to 100 watts reflected.
Under
> > this condition, my transmitter draws 20-amperes DC at 13.8 volts.
This is
> > not a trivial point. Watt's Law still applies: power is being
generated
> and
> > dissipated. Notwithstanding any line loss power, the vast
majority of
> that
> > power must be absorbed in the transmitter's PA. Thoughts on this
point?
> >
> > -Paul, W9AC
> >
> >
> >
> >
>
>
>
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