How do I design an automatic antenna tuner?
 

I recently built a 100W HF amplifier by modifying existing designs.
Now I'd like to build an automatic antenna tuner. Where can I find some
good articles / web sites on theory, practical design, and tuning
algorithms for the switching circuit. Has anyone published all the
details including source code.

I recently built a 100W HF amplifier by modifying existing designs.
Now I'd like to build an automatic antenna tuner. Where can I find some
good articles / web sites on theory, practical design, and tuning
algorithms for the switching circuit. Has anyone published all the
details including source code.

QST published a (two-part?) article on an "Easy Tuner" design a couple
of years ago. As I recall it's a microprocessor-controlled tuner of
the T configuration, with a switched tapped shunt inductor, and two
air-variable series capacitors driven by small motors.

I believe that source code was available.

I suspect that most of the ATU-control code out there is proprietary,
and that which isn't is likely at least somewhat specific to a
particular ATU design. Designs using motor-driven capacitors are
going to be at least somewhat different from those which use
relay-switched capacitor sets.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

The best software for any self-respecting _REAL_ Radio Ham is
that which he writes for himself. It is CBer who buy such things
off-the-shelf.

It is very much the case with software that you can manufacture a much
better
product than any you can buy for a very small percentage of the cost.

"WA3LTJ" wrote in message
news:fzORd.27956$uc.2859@trnddc08...
Has anyone published all the
details including source code.

"Airy R.Bean" wrote in message
...
The best software for any self-respecting _REAL_ Radio Ham is
that which he writes for himself. It is CBer who buy such things
off-the-shelf.

It is very much the case with software that you can manufacture a much
better
product than any you can buy for a very small percentage of the cost.

Oh, so we can be sure that you wrote the operating system and mail program
that you are using to access the newsgroup? Or do you have no self respect?

Perhaps you have enough time to generate the software for the rest of us
that don't have the time to spend even more time coding than we have to
already. Unless you are a professional coder, then don't disrespect the
profession by suggesting that anyone can hack up a program for lower cost
with better performance. If you are a professional coder then considering
your posts, perhaps anyone could output code that is better than what you
are being paid for, so anyone could produce code with better performance
than what you can output.

If you are a professional at anything, then stay with your field of
expertise. Can you cite any accomplishments that you have achieved?
thanks, John.
KC5DWD

WA3LTJ wrote:

I recently built a 100W HF amplifier by modifying existing designs.
Now I'd like to build an automatic antenna tuner. Where can I find
some good articles / web sites on theory, practical design, and tuning
algorithms for the switching circuit. Has anyone published all the
details including source code.

Thanks for all the suggestions. I found the QST article on the switched
automatic tuner at LDG sold (AT-11). The source code was not published
and I think the ARRL has a new policy requiring source code (in most
cases). The article does hint at the algorithm. It was written in
assembler on a Motorola 'HC11.

I am interested in building a similar design and playing with the
tuning algorithms. I need a suggestion for a
microprocessor/microcontroller. I am most experienced with the Motorola
'HC08, PIC, and Rabbit Semi 2000 series. I think I would rather code in
C. So here are the basic specs for the processor:
1) low cost C compiler/IDE
2) at least 28 available general I/O bits
3) built in 8 or 10 bit A/D (2 channels are enough)
4) low cost development board or easily constructed one.
5) 16 bit or larger counter

What is the easiest way to have the tuner measure the frequency? Should
I just put a pre-scaler in front of a digital port and sum pulses over
time?

What do you think of this idea? Have the tuner control the
transmitter. Use the combination to completely characterize the antenna
across each band of interest. Then select the tuning "instantly" based
on a large frequency-based lookup table. With enough table space, you
could create a table for each antenna and each band. This assumes that
none of the programmed antennas changes much over time.

Andy WA3LTJ

(remove the b's for address)

In article stM0e.10352$Ax.4673@trnddc04,
"WA3LTJ" wrote:

What is the easiest way to have the tuner measure the frequency? Should
I just put a pre-scaler in front of a digital port and sum pulses over
time?

What do you think of this idea? Have the tuner control the
transmitter. Use the combination to completely characterize the antenna
across each band of interest. Then select the tuning "instantly" based
on a large frequency-based lookup table. With enough table space, you
could create a table for each antenna and each band. This assumes that
none of the programmed antennas changes much over time.

Andy WA3LTJ

(remove the b's for address)

Most of the autotuners use a Lookup table for "Instant Tuning" once
a Frequency has been tuned previously. This causes a lot less wear on
the Cap Contact Points.
1. Measure Freq by looking at period.
2. Lookup tuning canstants in table. If no data jump to tuning routine.
3. Set tuning constants and measure Reflected Power and Phase.
If above Set Level jump to tuning routine. If below, end/shutdown.

Run tuning routine at less than 5 watt level, will also save contacts.
All you need is enough power to allow the period to be measured and for
the Phase and forward and reflected power levels to be sampled.


Bruce in alaska a autotuner betatester from way, way, back........
--
add a 2 before @