"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
--

On Mon, 10 Oct 2005 14:20:09 GMT, Cecil Moore wrote:

....
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
....

I know it is common practice to tune screwdrivers for max power out
from IC706s (tuning for "maximum smoke"), but is that good for the
tuner?

Perhaps that is why Icom incorporated low power tuning of its system
tuners. The AH4 actually presents a very limited range of Z to the
radio, it effectively introduces a small attenuator at the tuner input
when tuning. So the radio is limited to around 10W, the Z excursions
are limited, and the tuner relays operate at quite low power. I wonder
what they know that we don't?

Perhaps it is why Kenwood drops carrier before each relay operation in
autotuning the TS2000 internal tuner. (Some of their earlier models
have a reputation for tuner relay failure.)

It may be that tuning screwdrivers under full power isn't detrimental
(I just don't know), but it is probably not safe to generalise.

Owen
--

Cecil Moore wrote:
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
Hi Cecil, Looking at the MFJ site and trying to reverse engineer the
loop tuners they sell...They monitor the loop current to get resonance,
tune for maximum. Then they have an "L" network to match 50 ohms.
They have a Butterfly style Cap. for HV., and monitor the current as it
is adjusted. Have a 50 ohm cross needle swr bridge to detect a 50 ohm
match, for their matching control. I assume their "auto loop tuner"
looks at the same stuff.
Gary N4AST

Owen Duffy wrote:
I know it is common practice to tune screwdrivers for max power out
from IC706s (tuning for "maximum smoke"), but is that good for the
tuner?

The SG-230 seems to handle 100 watts just fine. It is
interesting to listen to an autotuner tune up a transmitter
equipped with foldback. Clickidy-Click, the signal goes from
S5 to S9. If the foldback circuitry failed, then there would
probably be a bad outcome.

Assuming foldback and reflected power not invading the remote
tuner, I don't see why any harm would be done. 'Course, I'm
suffering from macular degeneration.
--
73, Cecil http://www.qsl.net/w5dxp

Reg Edwards wrote:

"Ian White G/GM3SEK" wrote in
If we're not clever enough to build an automatic ATU for a magloop,
it's
a sign that there's something about magloops we still need to
know...
====================================

We are able to analyse and predict the behaviour of magloops to any
required degree of precision.

What is missing is how both a magnitude-searching and phase-searching
circuit of an automatic tuner works when denied access to the
magnitude-searching component.

Not necessarily... see later.

These paragraphs about a T-tuner are really a digression from this
topic, but worth a comment:

When manually adjusting a tuner it is obvious to the operator that the
controls INTERACT with each other. Both variable controls equally
affect both magnitude and phase. That much can be gleaned from
inspection of the circuitry.

For example, in the case of a T-tuner with two variable capacitors,
the operator cannot concentrate on one variable exclusively to the
other. He continually has to swap from one to the other and obtain a
balance by progressively closer approximations whilst keeping his eyes
on the co-called SWR meter.

An automatic tuner manages to complete the operation by varying both
controls simultaneously. But it is obvious from observation of what
the drive motors are doing, and the time taken to do it, that the
circuit is behaving just like a human operator. Occasionally the
motors even have to reverse and try again.

When denied access to either one of the two variable controls, the
automatic tuner doesn't know what to do next and would become lost.

There are actually three variable controls in a C-L-C T-tuner. For
minimum internal losses (mostly in the L) the inductance needs to finish
up at the smallest value that will allow the two Cs to achieve a match.
To do it right, there should be some stepping of the L, until it won't
match any more, and then a step back to the last set of values that did
match.

If the desired impedance magnitude is known to be 50 ohms and is
somehow inserted in the circuit, this is of little assistance to how
the circuit behaves because when the main loop is off-resonance the
actual resistive component is miles away from 50 ohms yet the
automatic tuner is obliged to do something about it.

Not sure what you mean here (that thing about "inserted in circuit"
wasn't anything I intended to suggest or imply).

Back to loops...

But without the
ability to vary the diameter of the coupling loop, as I say, it is
lost.

Hang on - who varies the diameter of the coupling loop in routine
operation? I thought we were only looking for something that would help
a correctly functioning loop to track up and down the band.... in other
words, to operate the tuning control for us.

Like Owen, I'd still be very interested to learn what "maximum noise" on
receive actually means in terms of R and X and/or phase on transmit.


I trust you are comfortably settling down in your new country. I have
spent happy years, in bits, working in Scotland. It is a most
civilised place.

It certainly is. I wish we were there all the time, but my wife and I
are still only spending about one week in two in our new home, because
the removal from England is still dragging on.

Apologies in advance, but I don't have a newsgroup feed in Scotland yet,
which means I'm liable to disappear suddenly in mid-conversa




--
73 from Ian G/GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek