"Cecil Moore" wrote in message
...
Reg Edwards wrote:
So we need something different from and more sophisticated than
the
conventional automatic tuner with its relatively simple magnitude
and
phase-searching abilities.

If you remembered what frequency the mag loop had been tuned
to last time, would that alleviate the need to know phase?
The reason I ask is that is how I auto-tune my screwdriver
without knowing phase.
--
73, Cecil http://www.qsl.net/w5dxp
========================================

Cecil, while you are tuning your screwdriver, which is not a magloop,
phase and magnitude does not enter your head. Forget all about it!
---
Reg

"Cecil Moore" wrote in message
.. .
Reg Edwards wrote:
If I can't do it when the transmitter is ON then neither can an
automatic ATU. It would have to be more clever than I am.

It would be relatively easy to use the SWR meter driving
current from an MFJ-259 to control the ATU motor.
--
73, Cecil http://www.qsl.net/w5dxp

================================

Cecil, I keep telling you, there's no such thing as an SWR meter.
---
Reg.

Reg Edwards wrote:
Cecil, while you are tuning your screwdriver, which is not a magloop,
phase and magnitude does not enter your head. Forget all about it!

Watching the SWR meter while tuning my screwdriver while driving
had always bothered me. I first installed an audio VCO so I
wouldn't have to watch the SWR meter. Next I installed a flip-flop
so I only had to get the screwdriver started in the right direction
and didn't have to hold down the toggle switch. When the SWR starts
dropping, an LM-339 shuts off power to the screwdriver motor. And
it's all done while my IC-706 is in reduced power tune mode.
--
73, Cecil http://www.qsl.net/w5dxp

Reg Edwards wrote:
Cecil, I keep telling you, there's no such thing as an SWR meter.

The folks over on sci.physics.electromag disagree.
--
73, Cecil http://www.qsl.net/w5dxp

Reg, G4FGQ wrote:
"The transmitter is OFF when I do it manually and I tune for maximum
noise in the receiver."

As Reg said, reciprocity rules.

You can also satisfactotily tune an antenna to resonance by adjusting it
for maximum output. When I was in Tierra del Fuego we had Land Rovers
and boats equipped rith RCA single-sideband HF radios.

The Rovers had whip antennas atop fiberglass boxes containing loading
coils and motor-driven tap-changing switches. The coil base-loaded the
whip.

I routinely tuned the whips by switching my multimeter to the a-c range
(it used germanium rectifiers) and tuning for a maximum meter
indication. I chose meter-probe positions for a convenient scale
indication.

The above was accomplished with the transmitter ON and fed with a test
tone driving it to put out some power. The whip was mostly
non-directional so it made little difference where the r-f sensing
antenna was placed. The tuning procedure worked fine even with the
multimeter in the near-zone laying on the bonnet (hood) of the Rover.

The capacitor tuning a high-Q loop could also be tuned for maximum
output because that is your goal. The sampling antenna could be located
almost anywhere but probably not in a null of the loop.

Best regards, Richard Harrison, KB5WZI

Richard Harrison wrote:
The above was accomplished with the transmitter ON and fed with a test
tone driving it to put out some power.

I don't know much about small loops. Modern transceivers,
like my IC-706, have such good protection circuitry that
it can be tuned into any load at full power. Is there
anything in the design of a small loop that would prevent
full power plus foldback tuning?
--
73, Cecil, http://www.qsl.net/w5dxp

Reg, G4FGQ wrote:
"Cecil, I keep telling you, there`s no such thing as an SWR meter."

Terman says in his 1955 edition, page 99:
"The standing-wave ratio S is one means of expressing the magnitude of
the reflection coefficient;---."

This, Terman illustrates can go either way via formulas. Rho is
convertible to SWR and SWR is convertible to Rho.

Why should an indication proportional to SWR not be so calibrated and
called ?

Best regards, Richard Harrison, KB5WZI

Cecil, W5DXP wrote:
"Is there anything in the design of a small loop that would prevent full
power plus foldback tuning"

Maybe off-resonance operation. The small loop is always inductive but
its reactance is high and its resistance is low, so it has a high-Q. It
has almost uniform current thoughout, so this produces nulls on its
axis.

Best regards, Richard Harrison, KB5WZI

Reg Edwards wrote:
So we need something different from and more sophisticated than the
conventional automatic tuner with its relatively simple magnitude and
phase-searching abilities.

I'll believe it when I see one which works.

Reg, I just opened up my 2006 MFJ catalog. They have
an "Automatic LoopTuner(TM)", the 300w MFJ-937. It's
designed for approximately 1/10WL loops.
--
73, Cecil, http://www.qsl.net/w5dxp

On Mon, 10 Oct 2005 11:33:48 +0000 (UTC), "Reg Edwards"
wrote:

....
At higher frequencies
there's usually enough space to erect a dipole or an inverted-L which
will perform at least as well. (Ian, you could perhaps do a useful
article on the subject.)

....

I wrote an article on the Inverted L with a remote autotuner (designed
for end-fed wires) some time ago. The configuration, it is frequency
agile, very convenient when integrated with transeiver auto-tune
controls, and works a treat. The most significant downside (like most
Marconi, Windom, Long Wire etc configs) is from an EMR safety point of
view, it has a radiator within reach of people standing on the ground.
The article is at
http://www.vk1od.net/InvertedL/InvertedL.htm .

With the experience of using such a configuration, I reckon that a
magloop with an remote autotuner designed specifically for a magloop
would be a great option for people with very little space, better than
Echolink!

Reg, if you have an expression for the loop inductance and resistance
as a function of frequency, and we could make the assumption that the
coupling coil is a broadband ideal transformer with a fixed z ratio or
otherwise characterise the transformation as a function of frequency,
I could do a software simulation of an autotuner... be an interesting
project.

BTW, the tuner values in the article above are found through
simulation of an automated L tuner, but the 3 variable binary
searching algorithm used for performance would not work for a loop.

Owen
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