Tuna X-treme       





"The genesis of the Super Massive Tuna!"

Due to Piss Poor Tuner manufacturer's Design and Quality,
to the Condescending and rude Customer Service,
and to the lack of a High Power, Balanced Tuner for the Hammy Radio Community,
This Super Massive Tuner has been created for use at Studio "X".
This creation is called a Link Coupled Tuner, or an LCT.

it's HUGE, with BIG Honkin components!!
No sissy tuners are allowed in Studio "X".

scroll down the page to see this massive construct...

The Super Massive Tuna!

The Super Massive Tuna opened.


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So what is a LCT?

The Link Coupled Tuner, or LCT, is an inductively coupled tuner that uses 2ea tuned Tank Circuits to
inductively couple an RF signal from the Transceiver to the Antenna System, and also in reverse.
The design of this tuner matches the unbalanced 50 ohm impedance of
the Shack Equipment to the balanced feed line impedance of the Antenna System.
This is a truly Balanced Antenna Tuner. It is used with a balanced feed line.

There are many different configurations and styles of the LCT tuner to match different feed line impedances.
One of the best places for detailed information about this type of tuner is at L.B. Cebik's site.
Being that he has accumulated and archived so much theory and information on the LCT Tuner,
I'm not going to get into any of that. I will only detail my build.






The Design

I chose a Parallel Secondary type LCT because of the Antenna System I was using.
My system consists of a 288' 160m Doublet fe
d with 600 ohm Balanced Ladder Line.
I wanted to use this Antenna System on all bands, so the feed line impedance range I needed to match
would probably range from around 50 ohms to over 1200 ohms.

The LCT configuration that was built here, is using a Low Pass, Series Resonant Input Circuit Primary.
This consists of an inductor, with a capacitor in series to ground. The Inductor on the Input is called the 'Link'.
This is identified as L1 in my schematic, and I will tell you more about the inductors later.
The input series capacitor is identified as C1.


The WZ5Q LCT Schematic.

The Output uses a Parallel Resonant Circuit Secondary, which consists of
an inductor with a capacitor in parallel across the ends of the inductor.
This inductor and capacitor are designated as L2 and C2 in the schematic.
The feed lines are connected to the secondary via taps on the L2 coil.
There is a ground reference Tapped to the center of L2.

I had searched the world over looking for high voltage capacitors
in both the Split Stator and Dual Differential varieties.
I am talking about in the 9kv range, BIG ones!! These are cherished by those who have them.
Needless to say they are hard to find, and I found NONE.
After some redesigning of the circuit I wanted to build, I decided to use Vacuum Variable Capacitors.
They are small in size, high in Voltage Ratings, and high in Capacitance Value.
I found 2ea Comet Vacuum Caps on ePay,
A 20 - 2000pf range at a 3KV Continuous/5KV Intermittent voltage rating for the input.
The other, a 10 to 500pf range at a 9kv Continuous/15KV Intermittent voltage rating for the output.
These would work nicely for a High Power Tuna!!

The Inductors were designed by WW8J, Richard Flake.
I found his web site while researching my design, and just LOVED the Plug-In style coils he was using on his LCT.
I had to have some of those monsters!! They were Massive, hand wound from 1/4" copper tubing and B - I - G!!
I emailed Richard asking all kinds of questions about his tuner.
He was very friendly, knowledgeable, and speedy with his replies.
This started a correspondence that is still ongoing today. He is a very knowledgeable fellah.
His Tuner design actually came from his uncle and mentor, W8MAS(silent key 1970).
I am very PROUD to be able to use it in my Tuner, Thank you W8MAS and WW8J!
I've got a Legacy in my Tuna!

I had the design for the Tuner, along with the type of inductors and caps I was going to use.
Now I needed a plan for the enclosure, and where I was going to put it.
Being the coils were of the Plug-In variety, access to the unit was a must.
I decided to build it inside my existing shelving, on a slide out drawer, with heavy duty tracks.
I also decided to make the enclosure out of Acrylic Plexiglas.
That would be fun as I have never worked with it before.

Now on to the Construction Phase of this project...





Building the Super Massive Tuna

I really liked the way Richard, WW8J made his coils as Plug-In Modules.
This was really going to make the Tuna look Old Buzzardly!
To build my Coil sets, I used the Data from Richard's web site.
To keep this data safe for prosperity, I have mirrored it on my web site as well.
It can be accessed on the Tuna Inductor Coil Data page.

Lets build a Super Massive Tuna!!

I have added all the pics that were taken making the LCT Tuner, to this photo gallery page:
The LCT Picture Gallery
They are in pretty good resolution so you can see the details.


I decided to build the biggest coil first.
This would allow me to get the dimensional data for the rest of the tuner components placement.
I used a cardboard concrete form that was purchased at Lowe ´s Hardware.
This form measured about 8.5" and would have to modified to the correct diameter.
I cut the form length wise, and removed small slices until the ends would have the correct dimension when butted together.
Then the form was duct taped together, we were ready to wind a coil.


Cardboard Concrete Form Modified.


Cardboard Concrete Form Modified for correct Diameter.
Here you see the Form is at the correct diameter, then duct taped.


Winding the Coil on the form.
The 1/4" copper tubing is wound tightly on the form to the correct amount of turns, 18 in this case.


Red Oak Coil Spacers.
These are the Hardwood coil spacers for the 160m L2 coil made from Red Oak.
I liked this idea from Richard, WW8J web site so I followed suit.
The only difference is that I did not split mine down the middle, I left them intact.
I didn't like the idea of having to have to glue them, then try and get the coil symmetrical.
I left the spacers whole and then 'Wound' the coil into them.


Winding the Coil into the Spacers.
This is a shot of how I wound the Coil into the spacers.
Note: One of your spacers will have to have an extra hole drilled in it to capture all the bottom turns.
If you have an 18 turn coil, then there are 19 at the bottom.
This spacer is threaded on FIRST!


Spacers almost there!.
When you get to this point, its getting a little tight.
You have to finesse and wiggle and move the coil around to get them to move.
You will know when you get the sweet spot because they will all give way and slide easy.
DON'T FORCE IT! You will split the spacers!


The L1 Link installed in the L2 Coil.
Here is the L1 Link coil. It is made the same way, just on a smaller form.
It is slid into the L2 coil.


Coil Disconnects are made.
The Coil mount/disconnect were made next. The Design is from Richard, WW8J. The Pin spacing is 1.25"
These were made from 1/4" Acrylic Plexiglas and solvent welded together.
The Banana Plugs are P/N 3264 made by Pomona, and the Jacks are P/N 108-0740-001 made by Emerson/Johnson.
I liked Pomona Plugs because they used Beryllium for the contact spring.
I liked the Johnson Jacks because they had a real deep chamfer for alignment.
Note: What you don't see is the Ground Reference Jack that was added to the coil mounts in order to allow the
center of L2 to be tapped to ground. This is shown latter.


The 160m coil mounted.
Here you see the 160m coil installed on the plexiglas mount.


The Coil Disconnect Base installed.
Here the Coil Disconnect Base is installed onto the pull out shelf.


The 160m Coil Completed.
Here is the completed 160m coil with all the taps wired.


The 160m Coil Completed.
Here is the completed 80m coil with all the taps wired.


The Pull Out Tuner Shelf.
I installed some 100lb capacity tracks for the 1/2" Lexan shelf.
This is were all the components will be mounted.


The 2ea Vacuum Caps installed.
Here I installed the 2ea Vacuum Capacitors. The cap mounts are made from 1/4" plexiglas.
You can see the E.F. Johnson ceramic couplers installed on the shafts.


The Front Plexiglass Panel is installed.
The Front Panel was installed in this pic. It is another piece of 1/2" piece of Lexan.
I had to screw these together as the solvent weld (Mythelyne Cloride) just wouldn't take to the Lexan.
I personally don't like to work with Lexan poly carbonate, I like the Acrylic Plexiglas better.
The Lexan has too much moisture in it and will bubble too easy when you Flame Polish it with the torch.


Holes drilled for controls.
I drilled and cut the holes for the controls and milli ammeters in the Lexan in this photo.


Meters and Turns Counters Installed.
Here you will see the Marion Milli-Ammeters and the Turns Counters installed in the Front Panel.
A Handle was also installed to be able to pull the Tuner out of the shelf.


The Rear Shelf Panel.
This is the Rear Shelf Panel that holds the Toroidial Current Transformers.


The X-former Carrier Installed.
I installed the Transformer Carrier Shelf onto the Pull-Out shelf.
This will engage the Banana Jacks on the rear panel when the shelf is closed.


Wrapping the Toroid with PTFE Teflon.
These are the Iron Powder Toroids I will be using to pick the Current Readings off of the Feed lines for the Milli-Ammeters.
They are P/N T-520-2 from Micrometals. I wrapped 2 layers of PTFE Teflon Plumbers Tape on each Toroid.
Yes there Big!! I didn't want any chance of arcing happening. I also wanted minimal reaction to there presence on the feed line.
This idea came from W5JGV, Ralph's web site. He used a -26 core, the yellow one.
I changed that to a -2 core for more broad banded response as his design was for 166.5kc.


Toroid being Kapton Tape wrapped.
This pic shows the PTFE wrapped Toroid, covered in Kapton Tape.
This polyamide tape is a very high dielectric Tape.


The Toroid with the Secondary wound.
Here is the Toroid with the secondary wound.
It consists of 30 turns of #26 enabled wire. A phono plug was soldered on the end.
You must PAY ATTENTION to the phase of your secondary winding, be sure and mark it.
The winding must be wrapped in the same direction as the signal going thru the primary winding (the feed line).
Then I wrapped a layer of Kapton tape over the winding.


Rear Panel Installed.
The Rear Panel is installed in this pic. The Pull-Out Shelf interconnects to this when closed.


Backside of Rear Panel.
This is the backside if the Rear Panel. You can see the 50 ohm Input, and the Balanced Line Output.
Please excuse the scratches as I didn't have the wood touched up yet when I took the pics.
You can see how the Pull-Out shelf connects to the Rear Panel in this pic.


Tuna wired complete.
This pic shows the Input Wiring for the Primary.
The coax is RG400 Teflon insulated coax, and the white wire is PTFE Teflon Insulated, 6 AWG tinned wire


Tuna wiring complete.
Here is a pic showing a top view of the wiring.
All the white wire is PTFE Teflon Insulated, 6 AWG tinned wire.
If you look closely, you can see the added Ground Reference Jack for the coils in the middle of the Coil Base.
This is to allow the L2 coil center to be tapped to ground.


Tuna wiring complete.
This pic shows another view of the completed Tuna wiring.


Tuna Finished!!
The Tuna is now Finished! This is the 160 meter coil installed.
I haven't wired the meters in yet as I'm still waiting on parts for them.


Side View of Finished Tuna.
Here is a side view of the finished Tuna with the 160m coil installed.





Finishing up

Well that's it, The Tuna is operational now and is working flawlessly.
I haven't wired the Marion Meters in yet, as I'm still waiting on the parts to build the circuits.
I also have to build and optimize a 40m coil set.

Keep checking back for more info.




'Tuning' the Tuner

OK, so the LCT Tuner is all put together and your ready to throw some RF thru it.
You hook up your O'scope to monitor the Balance and Phase of the Feed Line...
Key down the Transmitter and throw about 10 watts into the Antenna System...
You tune the tuner for the best 1:1 SWR on the Input...
Whaaaaa???? what's this? the outputs not balanced?? What gives??
Wait....it doesn't even tune the top of the 80m or 160m bands to a 1:1...huh.

Well, that's what happened to this Tuner.
Our Antenna System has a little bit of asymmetry to it that cannot be helped. So, It was time to 'Tune' the Tuner.
We will go through the process using the 80m coil set.

The Feed Line Taps needed to be moved around on the L2 coil for the best tuning bandwidth,
Then the Ground Reference Tap needed to be moved around on the L2 coil for the best Balance on the Feed Line.

NOTE:
This is optional as you can let the L2 Secondary 'Float' from ground.
I could not because of the unavoidable slight asymmetry in my Antenna System, I needed the Ground Reference.

First you need to adjust the Feed Line taps on the L2 coil to get a good tuning solution across the band.
You start with each feed line tap at the very extreme ends of the L2 Inductor coil.
Check the Tuning Solution at 3.5, 3.6, 3.7, 3.8, 3.9, & 4.0mc and record the SWR at each of these frequencies.
On our Tuner, everything looked good until we got up to 3.9mc and the SWR wouldn't get below a 1.5
On 40.mc the SWR couldn't be brought down past 3.0 with the C2 cap running out of capacitance.
This told me that the Feed Line Taps needed to be brought in a Turn on each side of the coil.

NOTE:
Be sure to try and keep the taps symmetrical on the coil.
If you note in the pics, you will see the feed line taps are on opposite sides of the coil to retain symmetry.
Also only move the feed line taps in and out on the coil an even amount of turns, or you will skew the output phase.

Now run thru the Frequencies again and record the SWR.
3.9mc tuned to a 1:1 SWR now, but 4.0mc still ran out of capacitance.
So I had to move each feed line tap in toward the center of L2 again.
This made it better, but still not good enough, still not a good sharp 1:1 dip.
I moved the feed line taps in yet another turn toward the center of L2.
This made the feed line taps now 3 turns in from the ends of L2.
(Well, 3 1/4 turns to be exact as 1 turn wound up at the very bottom of the coil and I couldn't tap there.)
That did it! I had a good Tuning Solution across the entire 80m band.

For the next procedure, You will need to be able to monitor the balance and phase on the feed lines.
I used a dual trace Oscilloscope with some 10x probes, and clip them to the insulation on the feeders.
You have to 'calibrate' the probes to one side of the feed line feeder waveform.
This is done by connecting both probes to the same feeder and adjusting the waveforms to match perfectly on the O'scope.
Reference the following pics...


Calibrating the feeder waveforms.
I attach the probes to the same feeder, trying to keep the probes oriented 90 degrees to the feeder.
Clip the probes ground leads to the station ground.


Before probes calibrated to same feeder.
Key the Transmitter with about 10 watts or so.
You will see 2 waveforms on the screen almost superimposed on each other.
Adjust the Channel 1 waveform vertical amp control to where the sine wave is filling about 50% to full screen.
Adjust the Channel 1 vertical position control to center the trace up and down.
Adjust the Channel 2 vert amp to the same settings.
Now take the VAR out of its detent on the channel that is higher in amplitude then the other,
and adjust it to perfectly superimpose itself over the other trace.
You might have to adjust its vert position control as well.
Now pick a good setting on the Horiz Amp to display a few waveforms in the screen.


After probes calibrated to same feeder.
This is what the waveforms should look like after the 'calibration'. They look like one trace.


Probes connected to read Feed Line Balance.
Now that the probes and vertical amplifiers of the O'scope are 'calibrated',
Remove one of the probes from the feeder and connect it to the opposite feeder.


O'scope showing unbalance.
Key the Transmitter with about 10 watts or so.
You can see that there is an unbalance in the amplitudes of the sine waves, but the phase is perfect at 180 degrees.
If there was a phase shift on either side of 180 degrees,
you would see the the sine wave peaks closer and farther away from each other horizontally
thereby making the intersection of the waveforms above and below the center line.



Well, the above picture was the out of balance condition I was seeing across the 80m band.
What isn't shown was that I had a slight out of phase condition as well at first.
The waveforms were not showing a perfect 180 degrees out of phase as it should. I was at about 175 degrees or so.
I swapped the feed line feeders on the back of the tuner, re calibrated the probes, and the phase was perfect then.

NOTE:
When your optimizing your antenna system for a perfect match, everything can affect it.
What you can't fix at one end, lets say the Aerials, you can usually fix it by changing another parameter at the Tuner.
You have to be careful though, sometimes it might change other parameters as well.
It's defiantly a balancing act.

It was time to start adjusting the Ground Reference Tap position on the Center of the L2 coil.
I moved it over one turn to the right of center, WOW! Way out ...wrong way for sure.
I then moved it 1 turn to the left of center, perfect.
There was now balance, and it was acceptable throughout the entire 80m band.
Best balance was optimized on the lower part of the band from 3.6 to 3.8mc, where I operate the most.
From about 3.9 to 4.0mc there was some phase shift and out of balance, but it was acceptable to me.

Oscilloscope Balanced Output Waveform Trace on 3.7mc.
This is an Oscilloscope Trace of the output waveform on 80m at 3.7mc.
You can see the Amplitude and Phase are balanced almost perfect.
The 'ADD' function of the O'scope takes the difference of amplitude and phase from both channels and adds a third trace.
The flatter this trace is the better, and you can see that trace is FLAT!


Oscilloscope Balanced Output Waveform Trace on 3.9mc.
This is an Oscilloscope Trace of the output waveform on 80m at 3.9mc.
You can see the Amplitude and Phase are slightly out of balance.
This amount is acceptable to me, as I am still not getting any RFI or RF Hot Spots in the shack with it.
I also hardly ever Transmit up there.


Oscilloscope Balanced Output Waveform Trace on 1.8mc.
This is an Oscilloscope Trace of the output waveform on 160m at 1.8mc.
You can see the Amplitude and Phase are balanced very well.
You can see the third trace is pretty flat. Very acceptable.


The 160m coil set was the next to go thru the optimization process.
I was able to get the 160m band balanced almost perfect through the entire band. See the picture above.
I still have to build the 40m coil set, but when that's accomplished it will go through the same procedure.


There are a few things I would like to say about the Ground Reference Tap and the wire lead that goes to it.
It matters a great deal on the route this lead takes going thru or around the inductor to get to the tap point.
The routing thru the magnetic field of the coils changes the Balance of the output.

Lets say you have the Tap Point directly on top of the coil
If you bring the Ground Lead up the left side of the coil and measure the Balanced on the Feeders,
Then remove, and reroute the Ground Lead up the right side of the coil, the Balance on the Feeders will change.
This holds true even coming up thru the center of the coils.

The best routing for me on the 80m coil set was to bring the lead up around the right side of the coil.
The routing on the 160m coil set was best going straight up the middle of the inductors.

One would ask, but what if I want to use and tune more then just one antenna system with this tuner?
In that case I would say to just keep the Ground Reference Tap exactly in the middle of the L2 coil.
Or don't use a Ground Reference Tap at all and 'Float' the Secondary.
This should be fine if your Aerials and Feed Lines are symmetrical.
The ultimate solution would be to make a separate coil set that is optimized for each Antenna System.
Your going to have to play with it in your own application to see what works the best.

Also, according to Richard, WW8J,
He said that all of his antennas can be tuned flat with the Feed Line Taps at the ends of his L2 inductor.

All Stations, and Antenna Systems tend to be unique in there characteristics due to near field influences and what have you.
So the best thing to do, is to experiment, and experiment well!!!!

Take Care Ya'll,
WZ5Q








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