About Us

Owen Duffy · May 28th 10, 01:08 AM posted to rec.radio.amateur.antenna

Keith Dysart wrote in news:7974e65c-6e3a-442b-
:

You left Class A out of the list. Does this mean that Rp is the source
resistance for a Class A amplifier?

Keith,

Assertions have been made about the Thevenin equivalent source impedance
(Zs) of an RF PA. In the discussions over the years, some people have
imposed some qualifications (eg classes, tuned / untuned etc).

Zs can be measured by a number of methods. It is interesting to note that
in many of the discussions on the 'net on this topic, more focus is given
to dismissing the experiment design for experiments that produce
unfavourable results to some, than questioning the proposition that Zs is
50+j0 or thereabouts.

Whilst Walt has documented a quite rigourous experiment, and it produced
a favourable outcome, it is my view that that in itself is not proof of
the proposition.

Whilst one favourable experiment cannot proove the proposition correct,
just one valid experiment can prove the proposition to be not generally
true. No doubt the reason for the focus on proving experiments invalid.

If you give some thought to what you could use Zs for, then every valid
experiment that is designed around that application must produce a
favourable outcome if Zs is as proposed. If they don't, then the value
assumed for Zs must be wrong.

I posted a simple test earlier that in my experience does not support the
proposition that typical ham HF transmitters have Zs=50+j0 or close to
it. The test is documented so that individuals can try it and make their
own mind up. Some might get favourable results on limited trials... but
in my view, that is outweighed by unfavourable results from valid
experiments.

Owen

Thread Tools	Search this Thread
Show Printable Version	Search this Thread: Advanced Search
Display Modes
Switch to Linear Mode Switch to Hybrid Mode Threaded Mode

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
W2DU's Reflections III is now available from CQ Communications, Inc.	walt	Antenna	53	May 27th 10 09:15 PM
W2DU's Reflections III is now available from CQ Communications, Inc.	walt	Boatanchors	0	April 17th 10 03:33 AM
Reflections on rrap	Ryan, KC8PMX	Policy	2	September 30th 03 09:03 AM
Reflections on rrap	Ryan, KC8PMX	Antenna	0	September 24th 03 06:04 AM
Reflections on rrap	Larry Roll K3LT	Policy	0	September 23rd 03 06:34 AM

Menu

About Us