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W1JJ coil dimensions/specs??




 
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Author Topic: W1JJ coil dimensions/specs??  (Read 3408 times)
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K6LMP
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« on: January 11, 2011, 03:18:18 PM »

I have been surfing the web looking for a good design for a balanced input tuner, having recently converted my 40-meter horizontal loop antenna to 450 ohm ladder line  input.  I like everything I see and read about the W1JJ design.

My question is simple:  what are the dimensions of the coil in the tuner? I've found numerous sources that say 5" diameter plastic pipe, and 40 turns. What I haven't found is the length across which those 40 turns are spaced. This obviously has a significant effect on the impedance of the coil.

So, two simple questions:
1. What is the specified length for the 40 turns of copper pipe?
2. What is the specified inductance of the coil?

Thanks!

Lew K6LMP
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KF1Z
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« Reply #1 on: January 11, 2011, 03:45:37 PM »

Generally I try to wind coils with the spacing between each turn equal to the diameter of the wire.

You're looking for around 40 to 45 uH

Example
for a 5" diam form:

1/4" od tubing, 2 TPI, 40 turns, would be coil length of +/- 20 inches  = 45uH

1/8" od wire ,4 TPI,  24 turns, 6" length = 44uH
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K1JJ
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"Let's go kayaking, Tommy!" - Yaz


« Reply #2 on: January 11, 2011, 03:47:55 PM »

Hi Lew -

Welcome to the forum with post #1 !

The dimensions of the coil are not critical as long as you have enough inductance to handle any impedance situation. Sometimes on 160M you will need the whole coil and sometimes not.  The 40 turns suggestion wound on a common 4" PVC pipe using 1/4" copper tubing is a good start. (or 5" diameter if available is better) The coil will naturally find its own spacing so it doesn't short out on itself. If you find you need more coil, you can add some, but that is a PIA. Be sure your main capacitor is big enuff too.  Guys have good luck using a commonly-found 500pf vacuum variable there.

The "ideal" coil on any given frequency will have a ~ 1:1 to 2:1 length to diameter ratio for best Q, but this cannot be done on a single, multi-band coil. But again, it's not critical.  Just be sure to wind a coil that is MORE than big enuff for the lowest band and start tapping away to find the best matches for each band - then premark them with copper tabs for quick bandswitching with large, flat-mouthed, alligator clips.

Bruce/KF1Z's suggestions above will get you zeroed in even closer.

Tom, K1JJ
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WA1GFZ
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« Reply #3 on: January 11, 2011, 03:53:19 PM »

my fugly is 2X 22uh inductors. I wish I had a bit more L tuning 250 foot center fed with 85 feet of 450 ohm OWL
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K6LMP
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« Reply #4 on: January 11, 2011, 07:04:44 PM »

Thanks. This gives me all the information that I need.

Lew K6LMP
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K1JJ
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« Reply #5 on: January 11, 2011, 08:38:08 PM »

BTW, here's a nice simple, low power version built by N2LK. His comments below:

Tom, K1JJ
----------


"I too have spent some time bread boarding different types of tuners and the
K1JJ design is my favorite. Pictures below show my final version, cant get any simpler than this!

Primary is 5 turns #14 solid copper wire, just solder to a PL259..
Secondary is some #8 solid copper wire I had in garage. I wrapped it around a piece of scrap 2" diam. pvc I had out there...

The cap is from a scrapped MFJ tuner. Thats it. Tunes my 52 ft. long attic dipole on 12-40 meters just fine. Run up to 100 watts into it and no RFI at all.
feeder is about 70 ft. of Radio Shack twinlead. I colored the different band taps with my daughters nail polish collection.

Downside: Have to change taps when you change bands. Buts was fun to build and nice to have some old technology in shack that works.

Have fun building!

N2LK
"






* K1JJ Tuner by N2LK.jpg (566.56 KB, 2591x1943 - viewed 489 times.)

* K1JJ Tuner by N2LK 2.jpg (970.02 KB, 2592x1944 - viewed 531 times.)
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Use an "AM Courtesy Filter" to limit transmit audio bandwidth  +-4.5 KHz, +-6.0 KHz or +-8.0 KHz when needed. 

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

And, nothing like an old dog.
K6LMP
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« Reply #6 on: January 11, 2011, 09:29:27 PM »

'Way cool.  Since I am running an Elecraft K3 at 10 watts, this more compact approach is just what I needed. I can build this from my junk box, total cost $0.00.  Thanks!

Lew K6LMP
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K3TKJ
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« Reply #7 on: January 12, 2011, 12:21:24 PM »

http://www.wz5q.net/index/shack_data/tuna.htm

This should help
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