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instructions to build the k1jj tuner




 
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Author Topic: instructions to build the k1jj tuner  (Read 18870 times)
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kk6noh
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« on: February 22, 2016, 10:05:11 PM »

Hello
I created an account here specifically for this subject. I have been researching the k1jj style tuner for several days now. I have been on countless forums, spent hours reading posts on the subject. What I cannot find is either step by step instructions on how to build this tuner, or any videos of any kind. I have tried to figure out how to build it from pictures, but not a single one of them has the detail I need. I have run into this problem before with other projects I have wanted to do. Some vague text and nothing else. I am pretty good at following clear and concise instructions, not at just winging it.

I understand what materials I need, however I cannot seem to figure out what is connected to what.
Here is the link to the project. http://amfone.net/ECSound/K1JJ13.htm

what exactly does the capacitor connect to? What taps and where do they come from/where do they go? What does floating above ground mean? are there 2 sets of taps one set from the cap and another from the output? What is the optional input cap for and how can it connect to a ground that is floating?HuhHuh

I am trying to keep this cheap, because it doesn't make much sense to pay 1000 dollars to tune a 400 dollar radio. I will likely never use more than 100 watts. If I do buy an amp it will absolutely never reach past 500 watts much less 1.5kw. The antenna is a loop skywire designed for 160 on up.

Thanks
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K7LYF
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« Reply #1 on: February 22, 2016, 10:55:21 PM »

Follow this link. Hand drawing is down the page aways.

http://amfone.net/Amforum/index.php?topic=5931.0
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kk6noh
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« Reply #2 on: February 23, 2016, 12:02:55 AM »

I had already found that picture in my search. I cannot read half the handwriting because of pixelation. As I look at that picture several questions come to mind

1. I see an input on the left. One is connected to the center pin of the so239. according to the drawing the other half is ground. Where is the ground? it certainly isnt the wood or plastic box that most people use to make these things. What exactly do I connect this to or does it matter.

2. I have no desire to put an swr meter in the tuner itself, but ill have one inbetween the radio and tuner. I see one side of the smaller coil is connected there, but in other diagrams, that side of the small coil goes to ground. Is that correct? If so, read 1..... what and where is the ground.

3. On the right side of the drawing is the bannana plugs for the output and the variable capacitor. It appears that the variable capacitor is connected to both ends of the bigger coil. it also appears that the output plugs bypass over the capacitor and go straight to the large coil. if the outputs bypasses the capacitor, then what is its purpose? How does the capacitor affect the tune if its not in line with the output? does adjusting the capacitor have some form of electrical interaction to the large coil thus affecting it?

4. those connections coming from the variable capacitor to the large coil.... are they permanent on the very ends or are they alligator clips meant to be moved?

on to materials
seeing as how I have no intention of using more than 500-600 watts and thats a stretch.... what materials should I use for the coils? Any suggestions on variable capacitors? How about the connecting wires(teflon coated of what gauge)?

On the coils
the instructions say 40 turns on a 5 inch form... does it matter what the spacing is between the coils? Do I have to worry about arching? Does the spacing affect the tune?

On some designs I see the small coil on the outside of the large coil and sometimes its inside. Which is the correct way? what distance should I have between the small coil and the large coil?



thanks
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Todd, KA1KAQ
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« Reply #3 on: February 23, 2016, 10:00:44 AM »

Well, you're in luck - Tom/K1JJ is a regular here. Pull up a chair and relax, he's bound to wander in at some point. He's good at deciphering hieroglyphics, especially his own. He's pretty sharp technically as well.  Grin
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K1JJ
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« Reply #4 on: February 23, 2016, 01:29:46 PM »

Hi Tom,

Greetings to you in New Mexico and welcome to the AM forum!

There has never been formal instructions or a computer schematic done up on the tuner.  The enclosed handwritten schematic is all there is for now. I will try to answer your questions below...  BTW, this is a simple tuner and was designed so that a single vacuum variable (or ONE single section air variable) could be used as the main capacitor. The more complicated tuner designs with dual split capacitors will have better harmonic suppression, but most transmitters do not need the additional suppression and this design is usually adequate and very simple to build and use.



I had already found that picture in my search. I cannot read half the handwriting because of pixelation. As I look at that picture several questions come to mind

1. I see an input on the left. One is connected to the center pin of the so239. according to the drawing the other half is ground. Where is the ground? it certainly isnt the wood or plastic box that most people use to make these things. What exactly do I connect this to or does it matter.

ANS:  The ground is your coax shield that is used to connect the transmitter to the tuner. There is no other ground connection within the tuner.  The tuner input is unbalanced, thus a connection to ground. The rest of the tuner is floating above ground, thus no ground connection.   This picture should be clear enough to use. If not, then something needs to be adjusted in your picture reader software.  BTW, the input cap is not always needed. It simply adds more tuning range to the tuner. Some guys just ground the other end of the input coil to the coax shield  and eliminate the input cap. They then need to use the alligator clips more aggressively to increase the range lost by the missing input cap. Experiment and you will see.   Remember that the main capacitor will be floating and hot to RF, so you need a big knob and/ or insulated shaft/ coupling to tune this cap. Otherwise you will get an RF burn.  Again, this simple design allows you to use a single section vacuum variable where you otherwise could not.



2. I have no desire to put an swr meter in the tuner itself, but will have one inbetween the radio and tuner. I see one side of the smaller coil is connected there, but in other diagrams, that side of the small coil goes to ground. Is that correct? If so, read 1..... what and where is the ground.

ANS:

As before, the coax ground connects to the transmitter / swr meter and the other end goes tot he tuner. The inner connector connects to the input coil and the coax shield connects to the bottom of the input cap (ground) that we call "ground." This point can also be connected to your station ground. It should already be connected anyway via your transmitter chassis and  coax connector.


3. On the right side of the drawing is the bannana plugs for the output and the variable capacitor. It appears that the variable capacitor is connected to both ends of the bigger coil. it also appears that the output plugs bypass over the capacitor and go straight to the large coil. if the outputs bypasses the capacitor, then what is its purpose? How does the capacitor affect the tune if its not in line with the output? does adjusting the capacitor have some form of electrical interaction to the large coil thus affecting it?

ANS:

The main capacitor  or vacuum variable has two connections. They are connected across the coil. These connections are routinely moved to find the best 1:1 match as shown on the swr meter.  The main cap is also tuned to change its capacitance.  In addition, the antenna feeders are moved along the coil to find the best swr. These three changes are what's need to find a good match.  The tabs on the main big coil are used with alligator clips for easy movement. See the pictures and write ups of the various threads to better understand the adjustments.  Once the proper match is found for a band or frequency, they can be pre-marked on the coil using a marker of whatever for fast band changes. The large cap resonates with the coil and is always connected to the coil using the alligator clips.


4. those connections coming from the variable capacitor to the large coil.... are they permanent on the very ends or are they alligator clips meant to be moved?

Ans:  

Alligator clips get moved to help find a 1:1 swr match..

on to materials
seeing as how I have no intention of using more than 500-600 watts and thats a stretch.... what materials should I use for the coils? Any suggestions on variable capacitors? How about the connecting wires(teflon coated of what gauge)?

Ans:

"Floating above ground"  means there is no connection to the station ground or coax shield.  The input is unbalanced, connected to ground -- and the output has no ground connection and is connected to the balanced antenna feeders. (floated above ground)
 
The coil needs to be mounted on ceramic insulators, PVC blocks or whatever is a good RF insulator.  The main cap is hot and floating with the coil so also needs insulators. The input cap does not float above ground, so can get mounted on aluminum or whatever, as long as the coax shield is connected to the stator or frame of the input cap.

The coil can be whatever is convenient for the alligator clips to get a hold of and not short the adjacent coil turn.  Many guys use 1/4" copper tubing as found at Home Depot, etc. Some use larger  3/8" tubing. Many wind it on PVC pipe or simply support it any way they can. Remember that there is RF HV there and it needs to be mounted above ground with no arcing.   #10  to #14 Teflon wire is fine. You can use regular wire if it is insulated from the main coil well. You can use mylar or any kind of plastic sheet to wrap first and then wind the 5 turns on. Not critical. Use your imagination and whatever you have available for parts.

The input cap should be a standard 2000pf  or whatever variable commonly found. The output cap should be a wide spaced unit of 300 to 500 pf. If you can find a vacuum variable cap, that is best for power and ease using a turns counter.  160M demands 500 pf sometimes. If 75M or higher, then 300 pf may work fie. Much depends on your open wire feedline length and dipole length. That's why everything is adjustable. You can match anything.



On the coils
the instructions say 40 turns on a 5 inch form... does it matter what the spacing is between the coils? Do I have to worry about arching? Does the spacing affect the tune?

ANS:
The coil winding and spacing is not critical. That's what the alligator clips are for. Just make the coil so it is easy to clip to without shorting turns. Look at some of the pics of past projects. They are all different and work well.  As long as you have enough coil for the job, you can clip in what you need for a given match. The rest goes along for the ride and is not used towards the outer ends of the alligator clip positions.

On some designs I see the small coil on the outside of the large coil and sometimes its inside. Which is the correct way? what distance should I have between the small coil and the large coil?

Ans:   Insulated wire can be wound on the outside of the main coil or mounted inside. It does not matter. As long as it does not arc through it should work OK.  Both methods will give you plenty of coupling.

Build it, and experiment with the taps and you will get good 1:1 matches on all bands.


thanks


Hope this helps!

Tom, K1JJ


* JJTuner2.jpg (40.63 KB, 550x425 - viewed 1280 times.)
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kk6noh
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« Reply #5 on: February 23, 2016, 01:46:32 PM »

Hello

Thanks that actually clarifies a lot. However one thing is still unclear. Is the input cap absolutely necessary? According to your original design I thought it could be optional if you are not getting the match you need. The antenna I am tuning is resonate, and only has around 600 ohms impedance. Could it be possible to skip the input cap and connect one end of the small coil to the center pin and the other to the shield?


EDIT EDIT EDIT
Derp
It would help if I would stop confusicating myself and read it again Cheesy . I see the answer in the top of your reply.


Thanks for all your help. When I get to building it I will post another topic with extensive pictures.
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K1JJ
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« Reply #6 on: February 23, 2016, 01:51:22 PM »

Hello

Thanks that actually clarifies a lot. However one thing is still unclear. Is the input cap absolutely necessary? According to your original design I thought it could be optional if you are not getting the match you need. The antenna I am tuning is resonate, and only has around 600 ohms impedance. Could it be possible to skip the input cap and connect one end of the small coil to the center pin and the other to the shield?

Hi Tom,

Yes, you can skip the input cap. You may or may not need it. You can always add it later. It simply adds more range if needed for weird antennas, bands and matches.   

Reread my post above since I added some things about this subject as well as others in edit.

T
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KA2DZT
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« Reply #7 on: February 23, 2016, 02:08:18 PM »

Hello

Thanks that actually clarifies a lot. However one thing is still unclear. Is the input cap absolutely necessary? According to your original design I thought it could be optional if you are not getting the match you need. The antenna I am tuning is resonate, and only has around 600 ohms impedance. Could it be possible to skip the input cap and connect one end of the small coil to the center pin and the other to the shield?


EDIT EDIT EDIT
Derp
It would help if I would stop confusicating myself and read it again Cheesy . I see the answer in the top of your reply.


Thanks for all your help. When I get to building it I will post another topic with extensive pictures.

OK FB,  I didn't read all of Tom's comments, but that input cap may be needed to help match your xmtr to the input coil of the tuner.  The fact that your antenna is resonant isn't a factor in that, other antennas may not be.  You can put the input cap in series with the coax center to the coil, or you can put in it from the cold end (ground end) of the coil to the coax shield.  Either way should work.  You don't need a high voltage type tuning cap for the input cap because it is a low impedance (50 ohm output from your xmtr) high current part of the tuner's circuit.

Start building, post pictures and if something doesn't look correct the folks here will see it


Add another comment,  the ground that is shown in the drawing is your coax shield from the xmtr, the coax shield is grounded at the xmtr.  So, if you build on a wooden frame there is no real ground connection on the wood.  But, you can add a extra ground wire from the coax shield (at the tuner) if you want but it's not needed.

Fred

PS, I'm glad that Tom took the time to answer all your questions instead of me.
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kk6noh
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« Reply #8 on: February 23, 2016, 02:28:24 PM »



OK FB,  I didn't read all of Tom's comments, but that input cap may be needed to help match your xmtr to the input coil of the tuner.  The fact that your antenna is resonant isn't a factor in that, other antennas may not be.  You can put the input cap in series with the coax center to the coil, or you can put in it from the cold end (ground end) of the coil to the coax shield.  Either way should work.  You don't need a high voltage type tuning cap for the input cap because it is a low impedance (50 ohm output from your xmtr) high current part of the tuner's circuit.

Start building, post pictures and if something doesn't look correct the folks here will see it.

Fred

PS, I'm glad that Tom took the time to answer all your questions instead of me.

Do you  have any recommendations for an input capacitor? If it turns out to be cheap enough I might just go ahead and put it in from the get go. As it is the output cap costs a ton of money and I am trying to keep costs down. After all this is for an icom 735.... not the new fangled top of the line radio of today. Tom recommended a 2000pf..... what voltage rating should I be looking at?
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KA2DZT
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« Reply #9 on: February 23, 2016, 02:40:28 PM »



OK FB,  I didn't read all of Tom's comments, but that input cap may be needed to help match your xmtr to the input coil of the tuner.  The fact that your antenna is resonant isn't a factor in that, other antennas may not be.  You can put the input cap in series with the coax center to the coil, or you can put in it from the cold end (ground end) of the coil to the coax shield.  Either way should work.  You don't need a high voltage type tuning cap for the input cap because it is a low impedance (50 ohm output from your xmtr) high current part of the tuner's circuit.

Start building, post pictures and if something doesn't look correct the folks here will see it.

Fred

PS, I'm glad that Tom took the time to answer all your questions instead of me.

Do you  have any recommendations for an input capacitor? If it turns out to be cheap enough I might just go ahead and put it in from the get go. As it is the output cap costs a ton of money and I am trying to keep costs down. After all this is for an icom 735.... not the new fangled top of the line radio of today. Tom recommended a 2000pf..... what voltage rating should I be looking at?


Tom is correct about the 2000pf but you can use less if that's all you have.  You can use a broadcast type cap, close spacing.  Next question, what's a broadcast cap?  Ans, the kind you would find in an old AM radio.  You should be able to find someone that has one you can have for little or no cost.

Fred
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« Reply #10 on: February 23, 2016, 03:00:42 PM »

Do you  have any recommendations for an input capacitor? If it turns out to be cheap enough I might just go ahead and put it in from the get go. As it is the output cap costs a ton of money and I am trying to keep costs down. After all this is for an icom 735.... not the new fangled top of the line radio of today. Tom recommended a 2000pf..... what voltage rating should I be looking at?





http://www.ebay.com/itm/Pioneer-QX-9900-Quad-Receiver-TUNING-CAPACITOR-/291691305027?hash=item43ea281843:g:JoMAAOSwUuFWy3F4


Tom,

A common receiver tuning capacitor is what you want.  Look on eBay and I know flea markets and some of the guys here have them. Ask around.

Here's a sample from eBay, but look for 4-5 sections for 1500 to 2000 pF minimum if possible. Under $25 is a good price. I think Fair Radio used to have them, but too expensive there. You can always pad a smaller cap (<1500 pF)  with a 500 pF fixed cap if need be for 160M.

Glad to help!   This tuner project activity runs in cycles and I'll bet some others see the thread and build up a few too.

T
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Nothing like a new homebrew rig. Come into the shack, flip on the switches and everything works perfectly.

And, nothing like an old dog.
kk6noh
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« Reply #11 on: February 23, 2016, 03:17:57 PM »

OH
Now I Understand!

I was looking all over for a capacitor in that range... little did I know that they rate those things by section. So all those 3 to 4 or 5 section capacitors I kept finding are actually much better suited that I had thought.

Thanks for clearing that up.
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kk6noh
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« Reply #12 on: February 23, 2016, 09:41:32 PM »

another question... approx how many feet of tubing/wire will I need for the large coil... and how much teflon wire for the small coil?
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Steve - K4HX
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« Reply #13 on: February 23, 2016, 09:59:19 PM »

Circumference = pi x diameter

You do the rest.
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flintstone mop
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« Reply #14 on: February 24, 2016, 05:59:23 PM »

The tuner was a nice build just using the pictures. Ya buy a 25??? .... foot roll of 1/8 copper tubing for the big coil and wrap it on something round about 6 inches diameter. I wound 40 turns for the big coil.....The inner coil could be a few feet of 1/8 tubing about 6 or 8 turns..it is wound to fit inside the big coil. I picked a 40M freq and diddled with the tuning, experimenting with the taps,  and then I moved the little coil, inside the big coil for the lowest SWR, using the MFJ 259..I hope you have some sort of analyzer....this project will turn ugly if you do not have the MFJ or similar type of antenna analyzer...
I connected coax from the transmitter to this coil that sits inside the big coil and soldered taps on the big coil for connecting the antenna/ladder line. On the ends of the big coil is a huge vacuum variable cap. I forget the value. I know it was a Russian type rated for 25KV. No cheating here with a bread slicer...vacuum variable cap. I did not use a tuner cap for the input.
Antenna system is 240 feet of dipole about 65 feet in the air fed by 150 feet of ladder line, 600 ohms.
Antenna system is good from 160 M - 20M. Using a dipole this long on the upper bands would probably be a lot of pattern distortion. It would work, but I have other antennas that are better suited for the upper bands.
If you are researching this project in the Forum, you will see many nice pictures from others, and me on the construction.

Here's an old link when the tuner was first introduced here....further down the page I posted pictures of my tuner

http://amfone.net/Amforum/index.php?topic=11466.0


Fred
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« Reply #15 on: February 24, 2016, 08:41:44 PM »

This tuner project activity runs in cycles and I'll bet some others see the thread and build up a few too.

Glad to oblige!  Wink

I have a number of commercial tuners, varying in size from tiny to ginormous, and I've always wondered why their designs vary so much. Ergo, some questions, es TIA.

  • Carl Smith taught me that two capacitors and two inductors could match any load to any source, but also that either side might have to have the capacitor and inductor in series. Your design makes me wonder if all common antenna loads can be matched with a parallel-resonant circuit. Does that always work?
  • Does having the tuner "ground" supplied through the coax shield connection back to the source risk punching through the coax when there is an unusually high load impedance?
  • If the load is fed via coax, is it advisable to ground one side of the parallel-resonant output circuit?
  • Some tuner manufacturers use rolling inductors instead of variable caps. Does this change the output circuit's Q enough to be a factor?
  • Speaking of rolling inductors, I have a Heathkit tuner which uses one, along with a mechanical counter. It seems to take forever to change bands, but do I get some added functionality in return?
  • What are the advantages and disadvantages of clip leads? Are they unimportant at Amateur power levels?
  • Is there any electrical benefit to putting the tuner in an enclosure, or would that be only for cosmetic reasons?
  • I've heard some hams who say that an open wire line "must" terminate in a 4-1 or 6-1 balun. What do you think?

Bill, W4EWH
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« Reply #16 on: February 24, 2016, 09:38:50 PM »

    Hi Bill-

    See answers below:




Glad to oblige!  Wink

I have a number of commercial tuners, varying in size from tiny to ginormous, and I've always wondered why their designs vary so much. Ergo, some questions, es TIA.

  • Carl Smith taught me that two capacitors and two inductors could match any load to any source, but also that either side might have to have the capacitor and inductor in series. Your design makes me wonder if all common antenna loads can be matched with a parallel-resonant circuit. Does that always work?

ANS: Low impedance antennas may need a series configuration. It is easy to change this tuner to series with clip leads.  Does anyone have the series / parallel circuit diagram that K4HX drew up?   It's on this site somewhere..


  • Does having the tuner "ground" supplied through the coax shield connection back to the source risk punching through the coax when there is an unusually high load impedance?


ANS:   The coax to the tuner is low impedance at 50 ohms and no danger of arcing internally. The input is isolated from the high voltage output due to the input coil that is isolated.



  • If the load is fed via coax, is it advisable to ground one side of the parallel-resonant output circuit?

ANS:    I suppose that would work. Though for 50 0hms to 50 ohms I would recommend an unbalanced  T or Pi tuner that works best for low impedance.


  • Some tuner manufacturers use rolling inductors instead of variable caps. Does this change the output circuit's Q enough to be a factor?

ANS:   It would depend your preference and on the particular design.    Compared to a roller,  a fixed coil can be tapped or switched easily. It will need to change inductance to match loads on different bands. A roller inductor is nice for ease of use and finer tuning, but a fixed coil should work just as well..


  • Speaking of rolling inductors, I have a Heathkit tuner which uses one, along with a mechanical counter. It seems to take forever to change bands, but do I get some added functionality in return?

ANS:    Again, depends compared to switching or clip leads.  Changing inductance is changing inductance.



  • What are the advantages and disadvantages of clip leads? Are they unimportant at Amateur power levels?

 ANS:   Over 1KW may cause hot spots using clip leads. It is best to get clips that make fat contact to the coil.  12V battery clip leads of solid copper work well... the  2" size or so.


  • Is there any electrical benefit to putting the tuner in an enclosure, or would that be only for cosmetic reasons?

ANS:   Only if your shack is prone to RF getting into things like audio, etc.  I see many guys mount them on the wall where the OWL comes in and leave them open for ease of changing bands.


  • I've heard some hams who say that an open wire line "must" terminate in a 4-1 or 6-1 balun. What do you think?

 ANS:   No.  Open wire directly to the balanced tuner is the most effiecent way.   Who's to say what the OWL impedance at the balun input will be on different bands? It could be 100 ohms on one band and 800 ohms on another band with Xc and Xl all over the place. Why put a fixed impedance balan in line to muck things up?  No reason I can see IF the tuner is balanced and the OWL is balanced.


[/list]

Bill, W4EWH


73,

T
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Nothing like a new homebrew rig. Come into the shack, flip on the switches and everything works perfectly.

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« Reply #17 on: February 28, 2016, 10:23:26 PM »

Hi everyone.

Here is the link to the K1JJ Link Antenna Tuner schematics.

http://www.amwindow.org/tech/htm/160smallants.htm

73,

Chuck
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« Reply #18 on: March 03, 2016, 04:14:30 PM »

I thought I would post a picture of the one I use all the time.
The primary coil is 5 turns of copper tubing-- This is suspended on the inside of the secondary. You can see the coax coming from the radio with the center clipped to one side of the primary. The shield side of the coax connects to one side of the broadcast cap, then from the cap back to the other side of the primary.
I have added 3 500 Pf single caps if needed to the broadcast ( Most of the time I am sitting about 2000 PF).
The big variable is clipped on the secondary at equal spots. You can see the open line clipped out a couple turns from the Cap.

Hope this helps.

Cheers
Larry

* Tuner.pdf (31.78 KB - downloaded 307 times.)
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« Reply #19 on: March 03, 2016, 09:34:53 PM »

Questuon:  If one used dual indicators,  would you not be able to also use a clip lead style tuna to force balance in an unbalanced antenna?

I'm not thinking OCF style (maybe it would),  but more akin to having a vertical.   I've OWL my vertical.   Works great,  as long as the radials are resonant.   Could you not tap this style tuna (I only have the pair of Johnson boxes)  to give equal currents in a case like mine (using a 40 me ground plane on 20, for instance)?

U could see this becoming an autotransformer quickly.

--Shane
KD6VXI
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flintstone mop
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« Reply #20 on: March 04, 2016, 09:02:07 AM »

I hope the OP returns with some good news...It was a couple of days of getting ideas and supplies and actually mounting the tuner on a nice plywood platform... Waiting for the Russian vac variable was a while.

Fred
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Fred KC4MOP
kk6noh
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« Reply #21 on: March 07, 2016, 12:10:07 AM »

I hope the OP returns with some good news...It was a couple of days of getting ideas and supplies and actually mounting the tuner on a nice plywood platform... Waiting for the Russian vac variable was a while.

Fred

Its likely going to be a long time before I save up enough money for the vacuum variable capacitor. That is a LOT of money.
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KD6VXI
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Making AM GREAT Again!


« Reply #22 on: March 07, 2016, 03:23:32 AM »

Ebay and the fall of communism.   Hundred to two hundred bucks.

Or,  an air variable for lower power.

--Shane
KD6VXI
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flintstone mop
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« Reply #23 on: March 07, 2016, 10:48:51 AM »

Ebay and the fall of communism.   Hundred to two hundred bucks.

Or,  an air variable for lower power.

--Shane
KD6VXI

SAVE the money for a vac variable!!!! You'll be disappointed with and air variable. Low power is no fun!!! It's worth the money and don't worry about communism. The Russian caps are way overrated and you'll love it!!
Don't rush into this with less than QRO power...Always have that as a necessary option when the bands are messy.

Fred
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Fred KC4MOP
N7ZDR
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« Reply #24 on: March 07, 2016, 10:51:15 AM »

I actually like the large air variable better for my cardboard toner. I find myself never happy with anything I do in the shack, this being said-- a nice big vacuum capacitor works great but for me it takes too long to rotate it where I need it to be. On the other hand, one quick look at the big air variable and I can rotate it where it needs to be positioned in less than a seconded (Wham Bam done)

Flea- Bay is your friend for this stuff.

Cheers
Larry
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