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Author Topic: Tuners... Who uses what and the best type to homebrew...  (Read 16025 times)
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W3MMR
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« on: September 03, 2019, 07:37:58 AM »

Okay, so I finally made the jump to 600 ohm ladder line, a 125' doublet, and its been great so far. I have a KW Matchbox but the "Matching" cap arched and now wont stop arching.(The tuner sat in my fathers barn for 20 years before I took it home with me, so it was kind of expected) I am currently using an MFJ-989C Versa Tuner V and its working pretty good. The 1:1 current balun isn't getting warm so there doesn't appear to be much loss. Anyway, I want to homebrew a tuner. I have been reading up on Balanced L-Network tuners and I think that's the route I am going to go. I don't want to have to mess with alligator clips and all that because I band cruise almost every band and It wouldn't be practical. So, who has homebrewed a balanced L-network tuner and what tuners are you guys using? Any info an constructive criticism is welcome!


Perry
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« Reply #1 on: September 03, 2019, 09:12:27 AM »

I have built a couple different balanced L-network tuners and they work well.  Don't scrimp on the input balun.  Keep the L and C mounted on standoffs well above any metal chassis so that you don't add any too much stray capacitance to ground.  This would tend to unbalance the output side that you have carefully maintained during construction of the antenna and transmission line.
I have tuners built for different bands to facilitate fairly quick band changes.  On my two element driven 80 meter array, there's even a CW tuner and a Phone tuner.  PA0FRI has an interesting design on his web page that I might try this winter. 
As for that Johnson Flashbox, you probably have a burr on a capacitor from that arc, which makes it "want" to arc there even more as the E field concentration provides a breakdown point.  Get in there with one of those sandpaper files that women use on their fingernails and clean it up.  You can never have too many tuners.
de Norm W1ITT
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W2NBC
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« Reply #2 on: September 03, 2019, 09:18:11 AM »

Hey Perry,

Look at the post from Bruce W2XR in this archived topic:

http://amfone.net/Amforum/index.php?topic=29563.0

Jeff W2NBC
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WA4WAX
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« Reply #3 on: September 03, 2019, 05:38:05 PM »

Let me help.....

1) You could prune that doublet to 105 or 110 feet.

2) Drop a 135 foot Zepp feeder from it.  Make the Zepp feeder out of insulated #14 save for the last 40 feet or so near the ground.

3) Make a balanced L, fed with a high performance 1:1 current balun.

4) Go from the tuner to the Zepp feeder with 600 ohm OWL made out of #1 insulated, stranded copper.

Depending on the band, the Impedance at feedpoint will be less than or greater than 600 ohms.

If less than, short the Zepp at 1/2 lambda or 1 lambda, and feed end to side with the 600 ohm OWL a few feed above the short.  Experiment with short position and feed position above short to get 600 ohms at the tuner output.

If greater, do the same at an odd multiple of 1/4 lambda.

Have fun!
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WA4WAX
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« Reply #4 on: September 03, 2019, 08:35:22 PM »

ER, I meant to say #16 stranded copper, insulated.

Sorry!

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« Reply #5 on: September 03, 2019, 09:52:31 PM »

In case you did not see it:

How to make FB current baluns.

I would use the 2.4 inch #31 toroids, two in series.  Pick the frequency response you want.

http://k9yc.com/2018Cookbook.pdf

Zepp feeders.....people should use them more often.
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WA4WAX
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« Reply #6 on: September 04, 2019, 06:34:22 PM »

The last 40 feet or so of the feeder is bare solid copper.  This allows you to attach the OWL end to side with copper gator clips, and, of course, put a short bar across it.

You need not hit 600 ohms spot on at the tuner.....just something within the tuner's transformation limit.

For each band, you will have a short bar location and a feeder location.  Pretty easy.

The only hassle is going outside to move the short bar and the 600 ohm OWL tap point when you change bands.

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W3MMR
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« Reply #7 on: September 05, 2019, 06:11:34 AM »

The last 40 feet or so of the feeder is bare solid copper.  This allows you to attach the OWL end to side with copper gator clips, and, of course, put a short bar across it.

You need not hit 600 ohms spot on at the tuner.....just something within the tuner's transformation limit.

For each band, you will have a short bar location and a feeder location.  Pretty easy.

The only hassle is going outside to move the short bar and the 600 ohm OWL tap point when you change bands.



Sorry it took me so long to reply. Unfortunately, thats not going to be practical or even feasable at my QTH. I had a hard enough time just being able to get the ladder line to the shack window. I live in the city, I have a small lot, the antenna stretches from one corner to another, and the OWL is draped across the roof, over the gutter, then into the front window of the shack.


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W3MMR
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« Reply #8 on: September 05, 2019, 06:12:52 AM »

In case you did not see it:

How to make FB current baluns.

I would use the 2.4 inch #31 toroids, two in series.  Pick the frequency response you want.

http://k9yc.com/2018Cookbook.pdf

Zepp feeders.....people should use them more often.
Awesome info. Thanks!
Hey Perry,

Look at the post from Bruce W2XR in this archived topic:

http://amfone.net/Amforum/index.php?topic=29563.0

Jeff W2NBC
I did not see that, thanks Jeff!

W3MMR
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Bob W8LXJ
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« Reply #9 on: September 05, 2019, 01:18:45 PM »

  330 ft center fed, home made 600 ohm  feed line , have seen 2,000 pep go thru it many times, no arcs, no sparks, no case on it. Several mods, the fixed stator plates on the bottom differential
cap, cut the grounding wire lose from chassis ground.   2nd mod , a 500 mmfd variable cap in
series with the ground side of  the input link of the main tank coil. It is mounted on a piece of wood mounted  above ground on top of the frame of  the main  capacitor. Stator plates to ground side of link, rotator plates and shaft to chassis ground. We are now matching the link input impedance to  the transmitter. From what I have read, experienced, and have heard, , perfect, matched balance feed line is a must, each side matches to the inch, no sharp 90 degree turns, , no touching of metal gutters, no duct taping to sides of towers so it won't blow in wind. I saw your pictures  and  I see problems.
      Last winter , rf in audio on certain frequencies  check all connections good, looked out the window and the rubber tension line had rotted and slack in the open wire and one side of it was in the snow, other side  wasn't. Corrected problem no rf audio. Touching snow and unbalancing feed line, was the problem.  Converted another matchbox to 160, replaced tank coil with 43mmh edge wound  coil,  padded 100 vac cap across main tuning cap, 500mdf cap in series with link, works wonderful.
      One test I tried, disconnect one side of the open wire from the matchbox, tuned to 40 watts out, perfect swr 40 watts out, disconnected other side on same teminal, same output and  swr.
  Bob  W8LXJ
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W3MMR
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« Reply #10 on: September 06, 2019, 08:08:56 PM »

  330 ft center fed, home made 600 ohm  feed line , have seen 2,000 pep go thru it many times, no arcs, no sparks, no case on it. Several mods, the fixed stator plates on the bottom differential
cap, cut the grounding wire lose from chassis ground.   2nd mod , a 500 mmfd variable cap in
series with the ground side of  the input link of the main tank coil. It is mounted on a piece of wood mounted  above ground on top of the frame of  the main  capacitor. Stator plates to ground side of link, rotator plates and shaft to chassis ground. We are now matching the link input impedance to  the transmitter. From what I have read, experienced, and have heard, , perfect, matched balance feed line is a must, each side matches to the inch, no sharp 90 degree turns, , no touching of metal gutters, no duct taping to sides of towers so it won't blow in wind. I saw your pictures  and  I see problems.
      Last winter , rf in audio on certain frequencies  check all connections good, looked out the window and the rubber tension line had rotted and slack in the open wire and one side of it was in the snow, other side  wasn't. Corrected problem no rf audio. Touching snow and unbalancing feed line, was the problem.  Converted another matchbox to 160, replaced tank coil with 43mmh edge wound  coil,  padded 100 vac cap across main tuning cap, 500mdf cap in series with link, works wonderful.
      One test I tried, disconnect one side of the open wire from the matchbox, tuned to 40 watts out, perfect swr 40 watts out, disconnected other side on same teminal, same output and  swr.
  Bob  W8LXJ


You say you see problems, what problems do you see? I cant do much else with the position of the feedline, with the exception of getting it up off the roof more or getting it away from the gutter more. I dont have any other options really. I dont really have any RF issues, with the exception of 20m, at 1kw, I get some RF into my computer to where I cant type while transmitting, but thats it. I get zero RF in my audio at all, zero RF into my PC speakers, which are the speakers for my Anan, And mind you, thats using an SDR. And any RF Im getting into the shack Is coming from the antenna itself and not the feedline radiating because the one leg of my antenna is only 15'-20' outside the shack. So how much better can I really make things?
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Bob W8LXJ
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« Reply #11 on: September 07, 2019, 04:38:49 PM »


 You said the matching cap is arcing and won't stop. I assume you mean the  the cap on the right side of the cabinet. It is either a completely unbalance feed line, or an internal short in the matchbox component. Do you have the cabinet off the match box? If so, check the 4 small
ceramic stand offs this cap  is mounted on . One might be destroyed. Also the band switch, blew one apart, the center ceramic coupler between the 2 sections of the band switch arced across
leaving a carbon trail between both ends of the tank coil. Ended up taking ceramic ring out a built
one from plastic.  You might try , disconnecting feed line from box, , attach a light bulb or 50 ohm dummy load  to the matchbox open wire feed throughs and see what happens.  Arcs, problems in the box, no arcs line problems

Bob
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« Reply #12 on: September 07, 2019, 07:12:10 PM »


 You said the matching cap is arcing and won't stop. I assume you mean the  the cap on the right side of the cabinet. It is either a completely unbalance feed line, or an internal short in the matchbox component. Do you have the cabinet off the match box? If so, check the 4 small
ceramic stand offs this cap  is mounted on . One might be destroyed. Also the band switch, blew one apart, the center ceramic coupler between the 2 sections of the band switch arced across
leaving a carbon trail between both ends of the tank coil. Ended up taking ceramic ring out a built
one from plastic.  You might try , disconnecting feed line from box, , attach a light bulb or 50 ohm dummy load  to the matchbox open wire feed throughs and see what happens.  Arcs, problems in the box, no arcs line problems

Bob

Oh, i thought you were seeing problems with my antenna and feed line setup. The feedline isnt unbalanced, well not much if any. I should have said that the arching happened with a coax fed dipole, not the doublet. But it also did it with the doublet when I tried it. Like I said, the tuner was in my fathers barn for 20 years and was taken out of service for a reason and I had issues with it immediately. Anyway, I am buying a Ten-Tec 238A off a friend for next to nothing so Ill try that out for a while until I build one.
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« Reply #13 on: September 08, 2019, 01:12:03 PM »

Here    https://pa0fri.home.xs4all.nl/ATU/Smatch/smatcheng.htm  is a very interesting balanced tuner that seems to work very nice. Heard good things about it. I like to build one, but can't get the cores here in Costa Rica and I don't have them in stock
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« Reply #14 on: September 08, 2019, 04:53:41 PM »

http://www.somis.org/bbat.html

http://amfone.net/Amforum/index.php?action=printpage;topic=12059.0

Good ideas for a simple tuna there.

And you can use Jim Browns ideas for a choke balun to make it force balance....

--Shane
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Steve - K4HX
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« Reply #15 on: September 10, 2019, 11:22:10 AM »

I came across this several years ago. Seems like a nice design. Can also be used as a tank circuit for push-pull tube final.



Here    https://pa0fri.home.xs4all.nl/ATU/Smatch/smatcheng.htm  is a very interesting balanced tuner that seems to work very nice. Heard good things about it. I like to build one, but can't get the cores here in Costa Rica and I don't have them in stock
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« Reply #16 on: September 11, 2019, 07:38:18 PM »

I've wanted to build a balanced L-network tuner for a while.  I went a different way as shown in my QRZ page.  Good luck.

Best regards,
Fox
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« Reply #17 on: September 11, 2019, 09:29:54 PM »

   I wanted an antenna that would give me multiband coverage and was easy to deploy and take down. I built a 130 foot dipole using 450 ohm window line as feedline and a WA1FFL dipole center. This antenna was used at both of my sisters homes in MA while visiting. I purchased a used Palstar BT-1500A tuner, this gave 80 to 15 band coverage and worked very well especially since at one location is was hung out a second floor window and only 25 feet above ground.

   I was so pleased with the antenna I built one for my DPRK QTH which is a bit more challenging, a 50 X 100 Bay Area urban lot. I have a 50 foot tree 10 feet in from the property line which is my antenna support. Construction was the same, 450 ohm window line, WA1FFL center support, height is at 45 feet. I had a tree climber clear some limbs and put a bracket with pulleys in the tree. I bought another used Palstar 1500A tuner and also got a lightening protector from Array Solutions that is made for window line. Because of my small yard the antenna is in a lopsided V, see picture.

   I have 80 to 15 meter band coverage, almost all of my operating is on 75 meter phone, either AM or SSB. Coverage is good North to South, the sides of the V are North South. This gives me good signal into LA and Southern California plus Arizona and Southern Nevada. I also get into Oregon/Washington and BC OK too. Coverage to the East of me is OK, one of the nets I check into is run out of Reno area and they hear me OK and I can also hear one station from Colorado that checks in on occasion. I don't think coverage to the West is very good.

   Considering my limitations of space I'm happy, my urban noise floor is S7 on a good day and S9 is often the case. This antenna works much better than the coax fed 80/40 fan dipole it replaced.


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« Reply #18 on: September 15, 2019, 11:17:29 AM »

Playing with the Bal-Bal Tuner. Had some Air-Dux coils and a 300pf cap. Resonates fine on 80m and 40M. Still have to play with 160M. Best I get is 7:1 with full mesh of the breadslicer. Going to pad it with 500pf and see what happens. I made this to test out. I will use my inductance meter to give me the best values then go shopping for a pair of rollers. Then will make it belt driven like the Measures design. I like this better than the big K1JJ tuna. Once I get it fine tuned, no clips.

I am using a DX Engineering 160M doublet with their 300 ohm ladder. Trying to decide if I should go with 600 open line. This 300 ohm stuff is easier to get into the shack downstairs and is more agreeable with the XYL HOA.

John


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K1JJ
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« Reply #19 on: September 15, 2019, 12:15:36 PM »

"I like this better than the big K1JJ tuna. Once I get it fine tuned, no clips. "

Hi John,

That tuner seems like a nice design and convenient to tune around the bands with the roller inductors and capacitor.

Though there are no free lunches.   The balun costs $174, the roller inductors will cost probably over $125 each if you get big ones that will handle the power... and the output cap will need to be a vacuum variable if you plan to handle the pair of plate modulated 813s at 3KV.

That's around $600 for parts if you do it right.   See below the kind of roller you will need. I doubt the MFJ roller will handle it.

In contrast, the JJ tuner requires one vacuum variable cap and a copper fixed coil, but that's it for virtually unlimited power. Made to be simple and cheap. It is good if you build several tuners to stay "pre-tuned" on various bands like I did. I had 5 tuners at one time - all from junk parts.

For your balun design tuner, look around for something rugged like the roller inductor linked below. To gang them together, they need to be identical.  Make sure there is enuff inductance to cover 160M. Notice the fat finger stock contacting the coil. Also, a very heavy-duty wheel works well too. Flat coil stock is the way to go. The currents and voltages on the various bands for a perfect match can be brutal - especially for a big plate modulated AM rig. Many marginal roller inductors develop "hot spots" between the coil stock and roller contact. It depends on ratings and actual power levels, but generally, never rotate the roller inductor with full power going thru it.

Sample roller inductor:

https://www.ebay.com/i/143246306942?rt=nc&_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D2%26asc%3D20160908110712%26meid%3Dc722ccb104954d49924505df4efc2786%26pid%3D100677%26rk%3D13%26rkt%3D30%26sd%3D283494476263%26itm%3D143246306942%26pmt%3D0%26noa%3D1%26pg%3D2385738

T
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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.  Easily done in DSP.

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« Reply #20 on: September 15, 2019, 02:22:35 PM »

Nice layout. I would advise against use AirDux or other coils designed for use in transmitter tanks. For use in tuners, where the circulating current can be far higher than in a transmitter tank, the size of the conductors is too small. The result is loss.



Playing with the Bal-Bal Tuner. Had some Air-Dux coils and a 300pf cap. Resonates fine on 80m and 40M. Still have to play with 160M. Best I get is 7:1 with full mesh of the breadslicer. Going to pad it with 500pf and see what happens. I made this to test out. I will use my inductance meter to give me the best values then go shopping for a pair of rollers. Then will make it belt driven like the Measures design. I like this better than the big K1JJ tuna. Once I get it fine tuned, no clips.

I am using a DX Engineering 160M doublet with their 300 ohm ladder. Trying to decide if I should go with 600 open line. This 300 ohm stuff is easier to get into the shack downstairs and is more agreeable with the XYL HOA.

John
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« Reply #21 on: September 15, 2019, 03:43:23 PM »

Well, this is a fun experiment. Easy to throw together with parts laying around the shack.

I hear what you both are saying. Big tunas matter with big power. JJ it is.

I mainly threw this together to play with the Drake. With only one 3-500Z this may work ok for now.

John
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« Reply #22 on: September 15, 2019, 05:05:23 PM »

I agree with Steve on AirDux.......if you are using a high Q tuna.

If you use a balanced L with a Zepp feeder, things will be "prematched" to about 600 ohms at the tuna. Thus, your tuna will never be asked to wrangle with a large transformation ratio.

A balance L with a current balun will be fine with AirDux or something similar, as the Q of the tuna will be around 3 or 4. Thus, currents in the inductors will not be excessive. 

If you are using modern gear, harmonic suppression by the tuna is not a concern, so a low Q L is fine.  If you are running a high powered class C beast, consider something else, like a low pass balanced Pi with #8 bare copper wire, or copper tubing.

Have fun!
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« Reply #23 on: September 15, 2019, 10:07:25 PM »

How so, across multiple bands? Where did the 600 Ohms come from?

Quote
If you use a balanced L with a Zepp feeder, things will be "prematched" to about 600 ohms at the tuna. Thus, your tuna will never be asked to wrangle with a large transformation ratio.
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« Reply #24 on: September 15, 2019, 11:10:29 PM »

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?

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