Balanced Tuner Help

[W1QWT]

Hi,
I built a balanced tuner out of a 1955 ARRL Handbook.
The design uses a big 3.5 inch diameter 34 turn coil (measures as 12.5 uh) with a 5 turn primary wound
in the center. The input went into the primary through a 300 pf air variable and the other
side of the primary coil is grounded. This made a series tuned input.
The secondary was equally tapped for both sides of the ladder line at 5 places and the tap was
selected with a strapping ceramic rotary switch. The selected taps then went through RF ammeters to the ladder line. The secondary also has a dual air variable (130 pf each section) with their centers grounded.

Ok so it works great on 40 meters. Input tunes, output tunes and I have almost an amp of antenna
current with 100 watts. Also seems to work on 6 meters.
Twenty meters so so but the other bands don't seem to tune.
One thing I am wondering about is the grounded dual cap on the secondary. That doesn't seem to be referenced to anything? Is the chasis of the tuner supposed to be grounded?
Do I need to tap the primary for each band? The one in the book used a different plugin coil configuration for each band and both the primary and secondary had different num of turns. I would have thought that the variable cap on the input side would accommodate anything but maybe I should have done the math.

Regards
Q

[k4kyv]

You don't have to ground the split stator capacitor.  In fact, grounding it may cause common mode currents on the open wire line, making the whole thing work like a Marconi antenna referenced to ground, which will result in feedline radiation and unbalanced current in the feedline.  Another thing you don't want to do is connect the midtap of the coil to the frame of the capacitor.  Just let both float.  If the antenna is properly balanced, the tuner will also be balanced.  You cannot force-balance the feedline by grounding the tuner.

If the transmitter end of the feeder is at a voltage loop (high rf voltage point), the feeders should go right to the ends of the coil, connected directly to the capacitor (parallel feed).  If the end of the feeders is at a current loop (voltage null), the feedline must be series fed.  The way to do that with a split stator cap is to split the secondary coil and strap the feeders across the gap.

If the impedance is somewhere between a voltage and current loop, you may be able to tune it by tapping down on the coil, but sometimes that doesn't work well.  It is better to make the feedline length such that the tuner is looking into a voltage or current loop, or else tune the feeders with a series capacitor or series inductor in each side of the  feedline to tune out the reactance, so that the tuner is looking into as little reactance as possible.

I have used a link coupling coil with 4 turns all the way from 160 through 20.  The series capacitor will tune the  link on all bands except 160.  On that band I had to come up with a more complex circuit to get enough coupling.  I always used plug-in coils in my tuner, but you can use one coil and tap it with clips or use a hv rf switch.

[flintstone mop]

Hello my friend,
Could I save you some grieve and ask you to look at a posting in the tech forum on PAGE 10. "BLISS TUNER SICK" PAGE 2 of this thread was a sheezo and discussion and my pictures of the tuner I built from help from Tom, K1JJ. It's a truly balanced tuner and I love it to pieces. The easiest tuner I ever built and so easy to tune with my MFJ 259. Please consider what I went through, and you will have a very simple tuner and it will handle "LEGAL LIMIT" and beyond easily!!!
Fred

[ve6pg]

...SOMEWHERE ON THIS SITE IS A PIC OF THE K1JJ TUNER...WERKS FB,I BUILT ONE,AND POSTED TOM'S DWG ON HERE...TAKE A LOOK,TO SEE IF YOU CAN FIND IT,AND COMPARE....TIM....SK..

[flintstone mop]

Check PAGE 10 of the Technical Forum and look for th title of "BLISS TUNER SICK".
Page 2 of  "BLISS TUNER SICK" is the schematic and pictures of the tuner.

[W1QWT]

Check PAGE 10 of the Technical Forum and look for th title of "BLISS TUNER SICK".
Page 2 of  "BLISS TUNER SICK" is the schematic and pictures of the tuner.

Can you put the actual URL on here or email it to me?
I have been looking and so far have not been able to find it.
I have built the other tuner from the 55 handbook and it might be easier at this point to modify that but if the one you refer to is not too complicated I might consider changing it especially since you give it good reviews.

Best Regards
Q

[flintstone mop]

Hey buddy,
I was hoping this would be easy. At the top of the listings of topics in the TECHNICAL FORUM there are page numbers. CLICK on page 6 so you can get to PAGE 10 and the click on the title "BLISS TUNER SICK" CLICK on PAGE 2 of that thread and you will see the schematic of the tuner and pictures.
Good luck
Fred

[w3jn]

The SEARCH functionon this forum works FINE BUSINESS to dig up older topics like this.  10 seconds with the search function yielded this thread:

http://amfone.net/Amforum/index.php?topic=5931.0

73 John

[K1JJ]

Right on John!  You can find......anything you want... in Big G's Resturant.

Here's some shots of Tina's Tuner which appears to be the same simple floating design. Notice he made the input link switchable. This gives an even wider adjustment range. Or, a variable 1400pf cap, receiver broadcash type, in series with the input link will do a similar range.  Most don't use anything, since the range using the four taps is quite wide, able to match anything as is.

Note that the big coil is mounted on fiberglass insulators. They look like metal, so don't be fooled and start a fire... 

The advantage of this tuner is that you can use any SINGLE-Ended capacitor, like a nice vac variable. Use an insulated shaft.

Try the tiny flashlight bulb trick, as described in the thread, to get a perfect current balance, thus total feedline cancellation.

73,
T




CLOSE -UPS of Tina's Tuner:
https://home.comcast.net/~w1ia/

[flintstone mop]

It's a heck of a tuner that won't break!!!!
Fred

[Vortex Joe - N3IBX]

Try this link for the double balanced tuner I built. It works very well and can take all the power I can put into it.
Regards,
           Joe Cro N3IBX


http://members.aol.com/yardleyite/tuner.html

[WA1GFZ]

Hey Joe,
Nice tuner. The 40 UH inductors are a great value. I designed my tuner one day in '82 sitting in my LA apartment and built it when I came East and rejoined the human race in '83. I never heard of Rick Measures. My tuner is a pair of 22 UH 5 KW broadcash inductors and a pair of 300 pf 10 kV cardwells. I feed it with a 1:2 broadband transformer on the 50 ohm side. I run out of inductance at the low end of 160 meters. This is by far the best turner I have ever built so there was no reason to change it. The biggest problem is finding a matched pair of inductors. one could build a pair of copper tubing inductors with a band switch. No link to mess with and tunes over a wide range of l/c ratios. I have tried the coax balun on my network and it works just as well. My transformer use to warm up slightly during 4X3 strap fests. the right kind of coax might hace slightly less loss. I was thinking of RG393 teflon if I swapped it out. gfz

[W2VW]

I use a tuner based on the Measures article.
Originally used a pair of BC-939 roller inductors. They got HOT on 160 feeding the 75 metre dipole.

When you try to feed short antenna, stuff has to be large or power will change to heat.

Switched to ice maker supply line homebrewed coils.

Last photo is 50 Ohm hardline coiled to make BalUn. Anyone who pronounces this as bail-on should be required to stick his tongue on one while it is being used.

Who needs roller inductors. They drive the price of homebrewing a tuner WAAAAY up.

After using 4 different versions of these tuners an interesting thing comes to light. I've been able to operate 2 different  ham bands (40/80 or 160/80)  with minimal circuit changes in the tuner.

Hammy Hambone tuners sold today are either crap or very expensive. Homebrew or be PW.

[WA1GFZ]

Dave,
The strap in my inductors is 3/16 by 3/8 I've seen it warm up a bit. I agree copper tubing will send the price way down.
BTW I have put AC amp meters on my feeders and my johnson flash box produces the same feeder current as the balanced tuner. The balanced tuner has much wider range though.

[flintstone mop]

Hey Guys
Not to offend any one but the K1JJ tuner looks so much simpler to adjust. Just change the taps evenly on the big coil and adjust the vac variable. I don't have any heat at all on mine. Running legal limit.
Just $.021/2 cents worth
Fred

[W2VW]

Hey Guys
Not to offend any one but the K1JJ tuner looks so much simpler to adjust. Just change the taps evenly on the big coil and adjust the vac variable. I don't have any heat at all on mine. Running legal limit.
Just $.021/2 cents worth
Fred

No offense taken. Try that tuner into a 123' centerfed dipole @ 1885 kcs with 1500 Watts and let me know how it works. I will try your configuration sometime in the future myself but for now I can stuff plenty of R.F. into a small radiation resistance.

[WA1GFZ]

Fred,
I agree with Dave no link to adjust is much easier. Been there done that and bought the tee shirt.   JJ works great, balanced works great, flash box works great.
I beleive the balanced gives you more options as long as the inductor conductors are big enough.. choose your weapon..

[VE7 Kilohertz]

Some very nice looking tuners here and some great designs.

Here is my implementation of a balanced tuner. Two 22 uH rollers and a 750 pF vacuum. Balun (which is made up of the 2 words "BALanced - UNbalanced" hence the correct pronunciation is as Dave described  ) anyway, the balun is simply 30' of RG-213 wound on a piece of 4" black ABS pipe. Even with a KW of fully modulated AM going thru it for 10 minutes, only makes the balun slightly warm with a 160M loop on 75M. If it's the other way around, running a 160M signal into a 75M loop, more heat would be generated in the components.

I still need to put on the toothed gears and cog belt to synch the rollers. Now that I have a autotune PA, I may just make the tuner motorized as well.





cheers

Paul

[WA1GFZ]

Paul,
I'm also running 22 UH but a lot less C. I dropped a couple trees in the yard and now can't tune up on 1885 but ok on 1945. Guess I need more C.
fc

[flintstone mop]

Hey Paul,
with th two variable inductors and Tom's little light bulbs on each leg (loosely coupled) of the ladder line you can achieve that balance for good cancellation of the RF.
Pretty hefty design, but yous guys over the border are allowed the full KW OUT!!!! DAM!!!
How did we fall into that @#* P.E.P. thing!!!!!
Whats' 4dB???

fred

[W2VW]

Paul,
I'm also running 22 UH but a lot less C. I dropped a couple trees in the yard and now can't tune up on 1885 but ok on 1945. Guess I need more C.
fc

One way to work around this with your situation would be the addition of an inductance in parallel with the opposite ends of the matched coils. If your tuning cap is across the output then try some L across the junction of the input BalUn and inductor pair. Reverse works also. This will increase circulating current so recheck stuff for heat. The shunt inductor is used on 160 here.

My tuner works on 75 and 160 with the addition of this shunt inductance and only a small change in the vac variable setting. The matched coil L remains unchanged.
My pictures show a roller inductor in this position but that has since been stolen for another tuner.

Sorry but I can't suggest a starting value except to say that it seems like a much smaller number than I'd expect. Using 5-1/4 turns, 3" I.D., 2-1/4" long. Value is extremely touchy with my antenna. It takes genuine patience to find these numbers using the Edison method. The K3L tuner was similarly cornfigured on 75 last summer and was not easy to set.

[W2VW]

I still need to put on the toothed gears and cog belt to synch the rollers. Now that I have a autotune PA, I may just make the tuner motorized as well.

cheers

Paul

Nice tuner. Anyone looking at your coils thinking about buying some might benifit from knowing that there are quite a few similar looking inductors which have different turns counts. Be careful to get ones which match. This one got past me and I landed up using dissimilar rollers. It still works but adds even more to the frustration of initial Edison tuning.
I never did get to hook up and gears to match roller inductors. Always counted turns when changing bands. Saying numbers aloud keeps them in memory easier. The tuner is next to the laundry area and my wife no longer questions me standing in the corner mumbling to myself.

[W1QWT]

Hey Don,
Thanks for the advice of not grounding the split stator on the balanced side.
I ungrounded it today and now I can tune up ok on 40 thru 6 meters.
Before it only really seemed to work ok on 40.
On 75 I can just get it under 3:1 but on 160 I can't get the SWR below too high!
With a hundred watt rig I get no higher than about 1 Ampere of RF current on each leg.
Some bands show as low as 1/4 amp. The RF ammeters are 0- 3 AMPS

Regards
Q