Tuners... Who uses what and the best type to homebrew...

[WA4WAX]

Here is what to do:

1) Get a pair of 300 ohm carbon comp (or other noninductive) resistors, and string them in series.  Match them well.  1 watt is fine. The junction of the two will be your neutral point.  Bond the two free ends to the tuner's balanced output.  Looking into the tuner's 50 ohm input with noise bridge, VNA, etc., find 50 ohm match at frequency of interest. You might want to apply a low level RF signal to the tuner's input, say enough to give you a couple of RF volts across the load.  Get a VTVM with RF probe, or a scope with probe.  Using the junction as a neutral point (ground lead or clip), check the voltage on each output terminal.  The two voltage should be very close if balance is good.

2) Once this is done, HANDS OFF the tuner controls.  Remove the 600 ohm load, and connect the 600 ohm OWL to the tuner on one end, and to the trial feed point on the Zepp feeder.  Slide the short bar up and down, noting where you cut the real axis of the Smith chart.  Move the feed point up or down, until you get your 50 ohm match back at the tuner input.

3) Have fun!

[K1JJ]

I have used a similar technique, but even simpler...

Start with a 70 ohm hardline or 50 ohm coax from the shack out to the OWL antenna area.  I once had a 36 element wire 20M Sterba curtain array (with reflectors) all fed with openwire. 150' wide by 90' high.  And also had a 75M Zepp fed with open wire... it makes no difference.  

Now, how to easily go from a "whatever" OWL impedance to a 50/70 ohm coax to the shack?

Use a 2" donut toroid (or a few stacked to increase power capability) and wind a 1:1 balun.  Unblanced to balanced.

Connect the coax to the unbalanced balun side and then connect the balanced toroid side across the antenna openwire. The toroid will hang right at the OWL. Use the same shorting bar and balun tap experiment that WA4WAX describes to find a perfect 1:1 50 ohm tap on the OWL.  The taps and shorting bar must be changed for each band, of course, but there is just one unbal to bal interface from 50/70 ohms to 50/70 ohms on the OWL  - plus no tuner needed.  Using the shorting bar technique I have always been able to find a perfect 1:1 50 ohm match for the 1:1 balun tap no matter what the OWL antenna may be. Just have enough bare OWL to work with so you can find the proper tap points. It may mean adding some to find 50 ohms.

If you set up the OWL run properly, the coax length can be very short and tap right outside the shack.

Using an MFJ 259 antenna analyzer makes the two adjustments quick and simple by expeimentation.

T

[Steve - K4HX]

Sure. Makes complete sense. This is not how most people and MMR for sure, will run their open-wire fed dipole. So, large impedance swings will occur across the bands.

The Zepp feeder is shorted at 1/2 wave or 1 wave if the feedpoint of the doublet is less than 600 ohms at frequency of interest.  If higher, short at 1/4, 3.4, etc.  Tap into the feeder end to side with 600 ohm OWL.  The feder itself is OWL, with the bottom 25 to 35% bare copper so you can connect anywhere.

Pick a connection point, and slide the short bar around until you hit the real axis.  Move the feed point up or down, and slide the bar again until you eventually hit 600 ohms, or something close.  For each band, you will have a short bar position and a feed point above the bar.  That is the drawback: A trip outside when you want to change bands.

The 600 ohm line will present 600 ohms to the tuner.  For a balanced L with a good current balun on the input, this is within reach. 

You will quickly recognize this as the stub matching problem with a shunt, shorted stub.  Instead of looking for a 50 ohm match, you are looking for a 600 ohm match.

Make sense?

[N7ZDR]

I have posted this picture before but thought I would again-- Why! because these simple tuners work great and are very fast to tune. I have two (2) Palstar balanced tuners and both are sitting in the closet. Fiddling with the dual roller inductors and buttons on the Palstar was a pain in the butt. Once I got use to using this type of "JJ tuner" going to anything else was a burden. No flashing leds or blinking lights required and you can count on most, if not all your power will be transferred to your antenna.

[K1JJ]

I have posted this picture before but thought I would again-- Why! because these simple tuners work great and are very fast to tune. Once I got use to using this type of "JJ tuner" going to anything else was a burden.

Hi Larry,

Looking closely at your picture, I see you have THREE separate "JJ tuners" with three separate antennas. Cheap and easy way to pull it off. Quick band-switching. Very cool.

BTW, just to be clear for the record....  The original schematic came from an old Handbook from the early 1930's. Back in the 1980's I was looking for a design where I could build five tuners cheaply that would handle multi-KW with good efficiency. I used open wire for all antennas back then. Wanted instant band-switching.

There is nothing unique about the current design except the implementation of the single section vacuum  variable cap and the big copper tubing coil you can wind yourself. The 50 ohm input link variable cap is optional, though most use them and they are small variable air caps. All easily available parts.

What other design will handle 5KW+  using one single section vacuum variable cap? Single section caps are very common and vac caps are ALL single section. They can handle the high voltage easily whereas an equivalent air cap is rare and huge and may lack the capacitance to do the job on 75/160M.  

We are paid well for using a highly efficient tuner, even with a 1 watt QRP rig. DB loss is dB loss no matter what power we are running.

It could just as easily be called a link coupled balanced tuner, but the "JJ Tuner" nickname and implementation simply caught on as a convenient reference after I used them for many years - guys started building them and referring to them on the air this way.

The only downside is that the harmonic rejection is not as high with the single floating HV cap - as with tuners having (dual) caps to ground, but in this day and age with pi-networks,  more harmonic rejection is not needed.  I believe we are talking about -25 dB vs: -40 dB or so.

T  

[KC2ZFA]

neat tuners shown here...one question though:

so if I have two 3" diameter, 4TPI, 10AWG, each 9.5" long airdux'es I shouldn't use them for a balanced L ?

[WA4WAX]

That AirDux would be just fine, as long as your are not attempting large impedance transformation ratios.

With a 600 ohm Zepp feeder scheme, you will be fine.  Loss will be negligble.

You will be shooting for a Q of around 4.

[WA4WAX]

Remember:

Current balun on the input side!  Balun should have at least 6K of CMR.

:-)

[Steve - K4HX]

What antenna system will you be "tuning" with it?

neat tuners shown here...one question though:

so if I have two 3" diameter, 4TPI, 10AWG, each 9.5" long airdux'es I shouldn't use them for a balanced L ?

[w9jsw]

My little experimental balanced L Airdux tuner is working fine with a 220ft doublet fed with 100ft of 300 ohm ladder. I pre-tune it at low power. Running 700 watts CW with no arcing. My coils are 1.5in in diameter and 3.25 in long at 10 tpi. I measured them at around 20uH. I am using a commercial DX Engineering 1:1 Current Balun that I was previously using with my lower wattage commercial tuner. 300pf breadslicer. Won't tune 160M. I am sure it would arc if I tried. I used my MFJ-259 analyzer to preset the tuner to get it close on 3.885 and 7.290. Once you set the taps the cap tuning is smooth and fairly wide.

I would think your larger ones should work just fine if you have a well behaved antenna. Give it a try, nothing to lose.

John

[KC2ZFA]

What antenna system will you be "tuning" with it?

right now I have a 67 foot doublet up at 40 ft fed with window line and tuned with the smaller Johnson link tuner...I'll sweep its R&X tonight with an analyzer and post here.

Hopefully soon I will be increasing the length of that antenna to 84 feet so that it's an EDZ on 20, I hear there's AM action on 14330 these days but I can't hear it on the 67 footer.

I have these two coils, a 1:1 un/bal to feed them, and a 50-500pf 15kv vacuum variable.

[w9jsw]

Do it. 30min of work and then test it. I am using alligator clips for part of it.

[KC2ZFA]

I'm in the process of breadboarding it...meanwhile, here's a sweep of the 67 foot doublet. The window line goes through a 1:1 bal/un to the antenna analyzer and to the laptop on battery. The setup is floating.

[Steve - K4HX]

Running a sim and transmission line calculator for 67 foot center fed with 40 feet (it's probably more) 450 Ohm ladder line, your tuner will see something like 290 -j600 impedance on 7.290 MHz.

14.3 MHz: 61 -j400
21.3 MHz: 133 -j250
29 MHz: 56 +j82

Of course, 75 meters, the antenna is quite short, so the numbers get really ugly. But maybe you don't even use the antenna in the band.

3.885 MHz: 4 -j14.


I'll run the numbers for your 84 foot system tomorrow. Also, what is the exact length of your feed line?

What antenna system will you be "tuning" with it?

right now I have a 67 foot doublet up at 40 ft fed with window line and tuned with the smaller Johnson link tuner...I'll sweep its R&X tonight with an analyzer and post here.

Hopefully soon I will be increasing the length of that antenna to 84 feet so that it's an EDZ on 20, I hear there's AM action on 14330 these days but I can't hear it on the 67 footer.

I have these two coils, a 1:1 un/bal to feed them, and a 50-500pf 15kv vacuum variable.

[KC2ZFA]

Thanks 'HX ! the present feed line is 42.5 feet of the supposedly 450 window line. I'm looking at it now and there's a lot of sag...looks like the tree branch on one end broke and the rope landed on a branch below bringing the wire about 4 feet above the attic roof...

the unsimulated house below the ant (late 1800's brick and stucco cement) probably explains the big difference between what I measure and what you simulate.

[Steve - K4HX]

There are some difference in our numbers but the trends across the bands are pretty similar, except for 40 meters. I used a generic 450 ladder line in my sim. If you know the Wireman part number, I can probably go a better sim.

Why are you moving away from the Johnson tuner?

Running a sim and transmission line calculator for 67 foot center fed with 40 feet (it's probably more) 450 Ohm ladder line, your tuner will see something like 290 -j600 impedance on 7.290 MHz.

14.3 MHz: 61 -j400
21.3 MHz: 133 -j250
29 MHz: 56 +j82

Of course, 75 meters, the antenna is quite short, so the numbers get really ugly. But maybe you don't even use the antenna in the band.

3.885 MHz: 4 -j14.


I'll run the numbers for your 84 foot system tomorrow. Also, what is the exact length of your feed line?

What antenna system will you be "tuning" with it?

right now I have a 67 foot doublet up at 40 ft fed with window line and tuned with the smaller Johnson link tuner...I'll sweep its R&X tonight with an analyzer and post here.

Hopefully soon I will be increasing the length of that antenna to 84 feet so that it's an EDZ on 20, I hear there's AM action on 14330 these days but I can't hear it on the 67 footer.

I have these two coils, a 1:1 un/bal to feed them, and a 50-500pf 15kv vacuum variable.

[KC2ZFA]

just playing with parts on hand...

I breadboarded it and the results are kinda
funny...40 meters tunes with just one and a
quarter turn of coil    see the pic...the cap
is at about 50pf.

[WA4WAX]

What is the load?

How about checking the RF voltage on each feeder lead, using a reference.  If cap is dual section, use the rotor.  Other wise, use the common on the input connector.  VTVM or scope probe ought to do.  Use low power, such as a signal generator.

[K4RT]

I have enjoyed this thread and the photos.  In answer to the first question, I use a Heathkit SA-2060 with my Apache and DX-100B transmitters from 160m up, which has worked well for six years.

I'm about to put my Globe King 500B back on air, but don't know if the SA-2060 would be sufficiently robust for longer transmissions with the 500B. Anyone here using a 2040 or 2060 with a 250W AM transmitter?

N7ZDR's set up is very interesting.  Any more pics?

[N7ZDR]

If you do search on  "k1jj link coupled tuner" you will get tons if information.

In today's plug and play world the days of seeing this type of thing are long gone.

If you need anything let us know----73

[KK4YY]

If you do search on  "k1jj link coupled tuner" you will get tons if information.

In today's plug and play world the days of seeing this type of thing are long gone.

If you need anything let us know----73

Check out the Google image results too. More copper tubing than a backwoods distillery.

[w9jsw]

If only we could distill Whisky at the same time we would be in heaven...

John

ps. look at my tag line...

[K4RT]

If you do search on  "k1jj link coupled tuner" you will get tons if information.

Thanks. One of the photos on your QRZ page is what I was looking for. Nice work.

[WA4WAX]

I showed someone the rough layout of a link coupled tuner built around some BC-610 coils.  The miscreant said it looked like a moonshine still.  Uggh!


https://www.youtube.com/watch?v=WE5pM1HXxlI