Auto Tuner Wish List

[jmeade]

Here is what I would like in an auto tuner.

1. Balanced Output for ladder line - two sets of inductors and one set of
capacitors (like the Rich Measures roller L design). The inductors can step
along in parallel.  No control software changes are needed - just another
set of inductors and relays. The capacitors can switch between the input and
output depending on the load impedance.

2. A current balun on the input side of the tuner driving the 2 sections of
inductors.

3. 160m to 10m operation.

4. Matching range somewhat better than the Johnson Matchbox.

5. A rating for 150W max. power output.

6. A switch for bypassing the tuner and connecting the ladder line directly
to the output of the balun.

7. A peak-reading, illuminated power-output meter.

8. A 4-position input (rig) selection switch.

Right now, I have the following set up:

Outside:
Ladder-line fed Cobra Ultralite 160m to 10m antenna.

On the desk:
Johnson Matchbox for 80m to 10m.
Drake MN75 with Elecraft balun on the output for 160m. It also has a bypass
switch.
Ceramic knife switch to switch the ladder line from one tuner to the other.
Heath coax switch to select one of four inputs (2 rigs and 2 boatanchor
receivers).
Autek WM-1 peak wattmeter.

Everything works fine, but takes up a lot of precious room on the desk.  (I
could put more boat anchors there!).

Having a one-box, balanced auto tuner with those options would be great!

IMHO, of course.

John W2XS
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In defense of the KAT100 Tuner....which I do not believe was being attacked....but, in its defense.....
 
I have come back to the fact that the LC or CL antenna tuner is a very good tuner concept.  See recent articles in QST.  The LC tuner is quite the tuner once you understand what it is doing and how it works to your advantage.  The KAT100 has never missed a match since I have owned it and when I say never missed a match...I am not talking about perfect antennas.
 
It even matched a longwire very well and it radiated too.  In otherwords, I made contacts right and left with the KAT100 matched longwire.  I made the contacts on 160, 80, 40 and 20.  The 130 foot (or so) hunk of wire even matched oon 15 and 10 meters.
 
Yes, it would have been nice for the KAT100 to have a watt meter and extra antenna ports, but I have found it is excellent .... very excellent ... the way it is designed.  Elecraft was very thoughtfull in design...making it easy to use...and it matches a very wide range of impedances.
 
Because of my experience with the KAT100, on my other station I have been foolling around with a high powered LC matching systems that can take 1500 watts.  Again, the matcher tunes in all.  You just have to make sure you use 20 watts or so to find the match because moving the alligator clip from coil turn to coil turn at 1500 watts....hurts.
 
The LC Match is not new...I used it years ago in my college days in my basement appartment to have a station with 70 foot of 18 bell wire using a cold water pipe as ground.  Worked well then too.  Old is still good.....
 
Lee - K0WA
 


Common sense is in short supply - get some and use it  - Lee Buller
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[Don Ehrlich-2]

Funny you should ask.  That is almost exactly what I want except I want mine
to handle at least 500 watts (with *my* antenna anyway) and fit in a K2
case.

I am designing and building my own.  So far I have a fairly neat breadboard
operating and when I am ready all of the assemblies of the breadboard will
fit right into the K2 case.  I am about to order the components for the
controller and should have that built up and installed in two or three
weeks.  The controller will be a Basic Stamp BS-2sx PIC, some octal latches,
an A/D converter and miscellaneous frequency measuring components,
optoisolators, relay drivers, etc.  The breadboard is for verifying that the
capacitors, inductors, and relays can handle the stress.  For testing only
it is controlled by a diode matrix switched by a single pole rotary switch.

My design uses Form A reed switches (the *big* ones) with about 500 turns of
#38 magnet wire wrapped on them to form the relays I need.  There are 32 of
them because each of the capacitors are switched in by a pair of relays, one
at each end of each capacitor to maintain balance by decoupling *both* ends
of each capacitor which is not in use.  The little latching relays as used
by Elecraft would be a whole lot quicker and easier but they would not
handle the voltages I expect at higher power levels.

My design has a homemade balun at the input, two strings of inductors, and a
single set of capacitors to form a 'balanced L-network'   ... at least that
is what I call it.  There are 8 capacitors  with the smallest 5 pF stepping
up binarily (X2 at each step) so that the PIC can switch in any value from 0
to 1275 pF in 5 pF increments.  Each bank of inductors works in the same way
with 0.25 microHenry as the smallest increment.

I have a forward and reverse current monitor at the input identical to the
one in the K2 100W amp but I have not decided if I will go to the trouble of
putting in a LCD display for SWR, power, band/frequency, etc.  None of that
is really needed but it would be kind of nice to duplicate the general
appearance of the K2 with an LCD display.

If anyone is interested in following my progress (or lack thereof) let me
know and I will provide occassional updates.

Don K7FJ

> Here is what I would like in an auto tuner.
>
> 1. Balanced Output for ladder line - two sets of inductors and one set of
> capacitors (like the Rich Measures roller L design). The inductors can
> step
> along in parallel.  No control software changes are needed - just another
> set of inductors and relays. The capacitors can switch between the input
> and
> output depending on the load impedance.
>
> 2. A current balun on the input side of the tuner driving the 2 sections
> of
> inductors.
>
> 3. 160m to 10m operation.
>
> 4. Matching range somewhat better than the Johnson Matchbox.
>
> 5. A rating for 150W max. power output.
>
> 6. A switch for bypassing the tuner and connecting the ladder line
> directly
> to the output of the balun.
>
> 7. A peak-reading, illuminated power-output meter.
>
> 8. A 4-position input (rig) selection switch.
>

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[jmeade]

I was by no means criticizing any other auto tuner with the Auto Tuner Wish
List, including Elecraft's.  The reason for the wish list in the first place
was to express the desire for a BALANCED tuner - by design - not an
unbalanced tuner by design with a balun on the output.  I am sure the KAT100
(etc.) are great tuners, and can match a wide range of loads.  But my wish
is that another set of inductors would be added to make the design
inherently balanced.

The meter and switches are optional, of course, but they were on my "wish
list".

But, as those great philosophers the Rolling Stones say:  "You can't always
get what you want....."  (I used to play that for my kids when they asked
for something).

72,

John W2XS
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[Ben Hofmann K1NT]

John W2XS, I have been wondering about a balanced L
network auto tuner for some time now.  No one is
making one that I know of at this time.  Like you, I
thought it would be great for the Elecraft guys to
produce a kit for it.

And Don K7FJ, I would be very interested in following
your progress in building one of these as you
described in your post.

Here's my wish list.

1)  Balanced output using a balanced L network with 2
set s of inductors and one set of capacitors.

2)  Current balun at input.

3)  Programmable and switchable to be able to use
unbalanced line as well by: switching the balun out of
line, and bypassing one set of inductors to
effectively be the same tuning circuit as the
presently available L network autotuner.

4)  At least 2 antenna inputs (even better 3) each
separately programmable and switchable for balanced or
unbalanced as stated above.

5)  160m - 10m capability.

6)  Bypass function.

7)  150w power handling minimum.

8)  Maybe an option kit to add an analog meter if the
user wants one.

9)  Same algorithm as KAT100, where it searches for
the best match, not just an "acceptable" one.

10)  Function to auto-retune when a certain (user
selectable maybe) SWR threshold is exceeded.

11)  Integration with the K2 "TUNE" and "ANT 1/2"
functions as the KAT100 does

12)  Selectable Ability to use stand-alone with other
non-Elecraft rigs

13)  A kit


So Wayne, Eric, what do you think?

Another idea might be to sell production rights to
manufacture an assembled version.  I bet lots of
people who maybe don't like kits would be interested
in an assembled one.

This thing has the potential to be marketable to a
very much larger customer base than elecraft's current
product offerings.

Of course I'd buy the kit, and use it faithfully with
my K2 (s/n 4429) which is very close to completion by
the way.

-Ben  KB1AHR
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[N8LP]

There is acompany out of Germany that has made such a device for
years... it's very well built, but very expensive.

Larry N8LP



Ben Hofmann KB1AHR wrote:

>John W2XS, I have been wondering about a balanced L
>network auto tuner for some time now.  No one is
>making one that I know of at this time.  Like you, I
>thought it would be great for the Elecraft guys to
>produce a kit for it.
>
>And Don K7FJ, I would be very interested in following
>your progress in building one of these as you
>described in your post.
>
>Here's my wish list.
>
>1)  Balanced output using a balanced L network with 2
>set s of inductors and one set of capacitors.
>
>2)  Current balun at input.
>
>3)  Programmable and switchable to be able to use
>unbalanced line as well by: switching the balun out of
>line, and bypassing one set of inductors to
>effectively be the same tuning circuit as the
>presently available L network autotuner.
>
>4)  At least 2 antenna inputs (even better 3) each
>separately programmable and switchable for balanced or
>unbalanced as stated above.
>
>5)  160m - 10m capability.
>
>6)  Bypass function.
>
>7)  150w power handling minimum.
>
>8)  Maybe an option kit to add an analog meter if the
>user wants one.
>
>9)  Same algorithm as KAT100, where it searches for
>the best match, not just an "acceptable" one.
>
>10)  Function to auto-retune when a certain (user
>selectable maybe) SWR threshold is exceeded.
>
>11)  Integration with the K2 "TUNE" and "ANT 1/2"
>functions as the KAT100 does
>
>12)  Selectable Ability to use stand-alone with other
>non-Elecraft rigs
>
>13)  A kit
>
>
>So Wayne, Eric, what do you think?
>
>Another idea might be to sell production rights to
>manufacture an assembled version.  I bet lots of
>people who maybe don't like kits would be interested
>in an assembled one.
>
>This thing has the potential to be marketable to a
>very much larger customer base than elecraft's current
>product offerings.
>
>Of course I'd buy the kit, and use it faithfully with
>my K2 (s/n 4429) which is very close to completion by
>the way.
>
>-Ben  KB1AHR
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>
>
>  
>

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[Don Ehrlich-2]

Mike,

Trouble with that is you can't predict which of the 8 capacitors will be
connected.  It may be the ones from only one side of the output bus.  My
original breadboard, now scrapped, used just one relay per capacitor and I
found that the circuit was badly out of balance when *no* capacitors were
connected ... just the capacitance of the wires running to one side of all
the capacitors was causing it.

The other reason I use two capacitors, one on each end of each capacitor, is
that it puts two sets of relay contacts in series and so divides the voltage
that each switch experiences.  I worry about voltage breakdown under high
swr conditions when the voltage node occurs near the tuner and the two
switches in series just doubles the ability of the tuner to survive that
stress.

My antenna is a full wave horizontal loop for 160M which is a very forgiving
antenna to match.  I feed it with ladder line and find that with all of that
wire out there the voltages and currents do not seem to build up as badly as
can happen with shorter antennas which are much more of a challenge for a
tuner .. especially when operating at higher power.  What works for me may
not work for others.

Don K7FJ



         < Don,
         < Rather that switching both sides of the caps, what about
alternating which side they are connected to and which side is switched.
That
         < should    keep things fairly well balanced and cut the relay
count in half.
         < 73/72 - Mike WA8BXN


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