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Author Topic: K1JJ Antenna Tuner Coil Taps??  (Read 12433 times)
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W9GT
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« on: July 02, 2007, 09:16:54 AM »

Hello!

I recently built-up the K1JJ designed link coupled tuner, but I am having some problems coming up with good settings for the coil taps.  I am using an MFJ antenna analyzer for set-up, but getting some wierd results....at least not a definitive read out for a good match  As a sanity check....I get good readout results when using a 275W Johnson Matchbox with the same antenna on 75M - up, but not able to find a good combination with the 'JJ box.


Just wondering about some starting points for coil taps.  I would like to set-up the tuner for all bands, but I'm specifically interested in 40, 75, and 160M.  I'm using 450 ohm open wire to feed a 75 M dipole antenna for 75 M (and higher freq bands) and a loaded 160 M dipole fed with open wire for 160.

Anyway, wondering about taps for the variable capacitor and for the output to the open wire feeders.  I also could add a variable in series with the input link to get a better match.  Could those of you who have built this tuner give me some ideas about where your tap settings are for the various bands to give me a starting point?

Thanks much!!

73,  Jack, W9GT


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73, Jack, W9GT
KF1Z
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« Reply #1 on: July 02, 2007, 09:35:59 AM »

I was in the same boat.....

I found I HAD to add the variable cap to the input link to get anything reasonable.

Have since gone to a more "standard" link coupled tuner, with the split-stator cap, input cap and grounded the center of the secondary, and the cap.
Much more reliable (in my situation...)

And have found I can "tune" anywhere from 1.8mhz to 30mhz.... with my 75 meter ant.

I know others have used the K1JJ style, with better results.....
But I wasn't able to......

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Steve - WB3HUZ
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« Reply #2 on: July 02, 2007, 10:04:04 AM »

Always work from the outside in on the coil taps. This will ensure you get the lowest Q setting. You should be able to calculate the amount of L needed for each band to get you close. But it usually boils down to trial and error. I'd recommend the series cap on the transmitter side too.
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W9GT
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« Reply #3 on: July 02, 2007, 10:52:54 AM »

I was in the same boat.....

I found I HAD to add the variable cap to the input link to get anything reasonable.

Have since gone to a more "standard" link coupled tuner, with the split-stator cap, input cap and grounded the center of the secondary, and the cap.
Much more reliable (in my situation...)

And have found I can "tune" anywhere from 1.8mhz to 30mhz.... with my 75 meter ant.

I know others have used the K1JJ style, with better results.....
But I wasn't able to......

Yes, I have a couple of big split stator (230 pf total for both sections) caps.  Maybe, I could gang them and parallel them, but I still might need more cap for 160M.  Might be worth trying.

But it usually boils down to trial and error. I'd recommend the series cap on the transmitter side too.

Yes, but I guess my trials have been more errors.  Anyway I appreciate the suggestions.  I think that series cap might help, but have not seen anything looking like a good match, even when I used the amount of L that I thought was correct...or in the ballpark.  I'm a persistent cuss, so I'm sure I'll get it going, but it helps to hear from others who have tried something, and get some pointers.

Thanx!!

73,  Jack, W9GT
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73, Jack, W9GT
kf6pqt
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« Reply #4 on: July 02, 2007, 11:09:31 AM »

I have yet to finish (for lack of a need, and space)  my monster version, but I did successfully slap together a smaller, lower power version that I'm now using.

My interesting observation is that the MFJ analyzer will get you close, and you'll be saying to yourself, MAN, is this thing ever touchy!

Then, as you actually run RF through it and adjust with your swr meter, you'll find it doesnt adjust so sharp after all, and will be able to adjust for a perfect ( as limited by your meter) match.

Definitely put the variable cap in the input link.

-Jason kf6pqt
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flintstone mop
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« Reply #5 on: July 02, 2007, 04:14:12 PM »

To make taps for the tuner, I used copper ground strap material and formed into the shape of a "U" and soldered it to the tubing. Trying to be sure that there was the same number of turns from each end to the center for all of the possibilities for a match. I included my pics of my K1JJ tuner and found no need for a series cap on the input coil.
There was 40 turns of the 1/4 inch copper tubing and the input coil was 6 turns of # 10 wire on a ceramic form.
Finding the magic match, using my  MFJ analyzer, took about 30 minutes for 160M, 80, and 40M.
The vacuum variable, which might be gay, (10-500pf) is also tapped along the coil with the ladder line. You are really tapping the vac variable and the ladder line. You will get a "feel" for the direction of your match. The picture shows it all. Do not pay attention to the beads for the 50 ohm side of the tuner. I removed them. It didn't affect performance at all. It was to de-couple the transmitter from the tuner. After you have obtained the match, color code the taps for the ladder line and the capacitor. Make a log so that changing bands is a breeze. My cap seems to be on the inside of the taps for the ladder line.
Doesn't get warm with an old buzzard using legal limit.
Fred


* TUNA.jpg (17.76 KB, 320x240 - viewed 1275 times.)

* TUNA Input coil.jpg (13.51 KB, 320x240 - viewed 820 times.)
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Fred KC4MOP
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« Reply #6 on: July 02, 2007, 04:15:43 PM »

Sorry it looks like the the ladder line is on the outside taps and the cap is on the inside taps.
Fred
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Fred KC4MOP
N3DRB The Derb
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« Reply #7 on: July 06, 2007, 11:40:47 PM »

bah humbug. put a rf ammeter in ur ladder line and tune for maximum blowsmoke on 1/2 plate voltage or a lightbulb in series with ur ac line to ur plate supply.

--->The vacuum variable, which might be gay,

Phred, ROTFL. Cheesy
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W1IA
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« Reply #8 on: July 06, 2007, 11:59:57 PM »

Check out my design...tunes anything!
http://home.comcast.net/~w1ia/
Simple and happy to help with any question.

Brent W1IA
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« Reply #9 on: July 07, 2007, 10:01:55 AM »

I have a Phased Bed Spring at 80 feet fed with 32 pills will that tune on the "other band"
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« Reply #10 on: July 07, 2007, 04:15:17 PM »

Nice job, Brent. It gets the RF out there. AND it's simple
Fred
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Fred KC4MOP
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« Reply #11 on: July 09, 2007, 09:30:59 AM »

When I want to find taps on a tuner I put a 6 dB pad on the RX and tune for maximum background noise. The pad forces the RX input to 50 ohms so you can get very close using this method. gfz
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