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instructions to build the k1jj tuner




 
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Author Topic: instructions to build the k1jj tuner  (Read 33651 times)
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kc1gtk
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« Reply #50 on: April 24, 2021, 11:59:14 PM »

Ok She's about finished and works well!

BE interested in info about how to put 2 bulbs on the feed wires to see if any noticeable imbalance?

I have taps now on the link, before the taps I could tune 160 to 20m, 80 to 20 works with the big cap parallel. never tried above 20 yet.

Works well with the amp too.

That's about a compact as i could make it.

There are 2 high resistance resistors shunting to a ground rod behind the wall where the feed comes in.

Any comments or suggestions welcome!
thanks
KC1GTK
Paul
73



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K1JJ
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« Reply #51 on: April 25, 2021, 12:22:14 PM »

OK Paul -

For the light bulb feedline indicators:  You can use  most any flashlight bulb, 1.5 to 6V with two wires soldered on each bulb.  Start with one feeder leg and attach a bulb  a few inches spaced onto ONE leg. This will pick up a voltage drop. Tune the rig up to say, 1/4 power output and adjust the two wires spacing until the bulb JUST starts to light. The eye is most sensitive to light intensity changes when the bulb is barely lit. Do the same for the other side, making it the same spacing as the first bulb. Compare the bulbs for brightness.

Just to be sure, you are not going across the feeder line but each bulb goes onto one feeder leg.   When dimly lit you will see the difference in RF voltage drop quite easily. If the bulbs are too bright, the eye cannot see the difference as easily.    Also, a more expensive but effective way is to find a pair of RF current meters to put in series with each leg.


As for the center tap using high value resistors to ground, let's get some more opinions on that. Maybe it would be better to make a hard DC connection to the coil CT then run to it the station ground as well as the copper rod outside.   I also received an email from someone who showed a variable cap from CT to ground with a balance "0" meter used.

T

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W1NJC
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« Reply #52 on: May 04, 2023, 05:20:49 PM »

Hey guys, long time lurker around these parts.

Two things:

1) I've been using this method to check balance with good results.  Take a FT240 core (any kind) and wind a couple turns of small wire around it.  Connect the ends of this wire to a scope probe/gnd clip.  Then pass both balanced lines through the core.  Using low RF drive, tweak your taps for the lowest displayed signal on your scope.

2) I've built this tuner and I've been modifying and playing with it for over a year now.  My main changes have been varying degrees of coupling by winding the primary on a section of cardboard tube which is slid over the secondary, and changing that diameter by adding foam and/or the number of turns.  Of course this also changes the L of the primary. 
I can get it to work quite well on 160-80-40.  That is to say, good match and good balance.  What I would like to do is get it to be able to work well on 20-17-15-10.  There are a lot of variables going on when trying to find the sweet spot(s): Co tuning, Co taps, Ci tuning, Feedline taps.  When in "discovery mode" after a change, I hook up a VNA and watch the Smith chart.  To try to do it any other way would result in lots of profanity and possibly lost tools!  In the cases where I have gotten a match on the higher bands, the taps are very close to the middle, and I get poor balance (and thus RFI in the shack, speakers buzzing, etc.). 
So I could use a little guidance on what to try next.  I realize I might not be able to get a one-size-fits-all 160-10 configuration.  That's ok, but I'd like to better understand the variables that need to change and I could rig something up to try it.  Have any of you guys gotten a design like this to play well on the upper bands?

I should mention that my antenna is a 700+ft loop, so in general the impedances presented in the shack are not low.  This is from a while ago, but should still be close (attached file).


Thanks in advance,
Nick W1NJC


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Tom WA3KLR
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« Reply #53 on: May 05, 2023, 05:25:07 PM »

Hi Nick,

I would think that the 800-foot loop is not a good antenna for the higher bands, pattern-wise and I do wonder about the ac resistance of the 800 foot loop of wire. I recommend a trap vertical for 20 meters and higher with a good ground plane or trap yagis. I have my 20-15-10 trap vertical on the ridge of my pole barn and the roof is sheet steel, works well.

I do like your home-brew antenna tuner I saw in your QRZ photos. So you have a good set-up for the lower bands and I think you should draw the line there on that system. I have a friend with a 75 meter dipole that works well up to 10 meters. You could have a separate dipole that is a 20 meter half-wave dipole and I found on simulations in the past if the dipole is not all horizontal but the ends come straight down on the outer 1/3 of total length, that the nulls of the lobing are reduced on 17, 15 and 10. And a separate tuner for these bands.

My 2 cents worth.
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73 de Tom WA3KLR  AMI # 77   Amplitude Modulation - a force Now and for the Future!
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« Reply #54 on: May 05, 2023, 06:12:00 PM »

Tom, I had fantastic results with my 510' 160M loop on 10M when I was at the other QTH and that was during a sunspot null.
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Mike(y)/W3SLK
Invisible airwaves crackle with life, bright antenna bristle with the energy. Emotional feedback, on timeless wavelength, bearing a gift beyond lights, almost free.... Spirit of Radio/Rush
Tom WA3KLR
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« Reply #55 on: May 05, 2023, 06:48:41 PM »

Hi Mike,

What kind of wire were you using in your loop? As Vortex Joe would say, inquiring minds want to know.
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73 de Tom WA3KLR  AMI # 77   Amplitude Modulation - a force Now and for the Future!
W1NJC
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« Reply #56 on: May 05, 2023, 07:57:54 PM »

Yes, I have excellent results on the higher bands with this loop.  It's a real pileup buster on 40 and above, sometimes with just 100W on SSB.  On the upper bands it has lots of low-angle gain (9-12dB at 10-25).  Sure it's not 100% coverage in the azimuth (nulls) but so what? 

The wire is 13AWG Davis WM516 which now seems to be unobtanium.  It's good wire.  Feedline is 4-inch spaced open wire.

Honestly I've been fairly satisfied using this LCT for 40 and below (maybe 20) and just using a MFJ T-match on the upper bands...but it's like unfinished business in my mind.  I took off some turns on my primary and it makes 20m possible while still being able to use 160, though the Q seems to be even higher on 160 so I'm guessing there's going to be a point where 160 will be tough to match - but I'm not sure, which is why I'm asking the brain trust here!

Nick


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W3SLK
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« Reply #57 on: May 05, 2023, 10:41:52 PM »

WA3KLR said:
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Tom WA3KLR
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Hi Mike,

What kind of wire were you using in your loop? As Vortex Joe would say, inquiring minds want to know.
Tom it was nothing more than a pseudo parallelogram with about 512 feet of #14 gauge. Maybe up 30' at the highest. Nothing fancy really.
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Mike(y)/W3SLK
Invisible airwaves crackle with life, bright antenna bristle with the energy. Emotional feedback, on timeless wavelength, bearing a gift beyond lights, almost free.... Spirit of Radio/Rush
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