The AM Forum

I currently have an old MFJ 969 tuner. It is the older 3KW ( ;) ) roller tuner for 160-10m. It has the ceramic roller. I have a chance to swap it for a Johnson Matchbox, the 275 watt one. I think it would be a good move, since I run open wire feed. Any thoughts from the esteemed gallery?
Norm K7NCR

In a heartbeat!
He who hesitates is lost!
Don't look back!
In the wink of an eye!

or as we said in Cleveland; snatch n' run!

If you ever plan to run much power I would take pause.  But with  lower power the matchbox beats the hell out of any tuner with a balun to get to balanced feedline.

Fast as your li'l feet can fly!
Damn the naysayers. Full speed ahead!
Don't let the sun go down.

it depends on how much powah you plan to run, and whether or not you're using a resonant antenna or not.

The Viking matchbox is a better, more robust tuna (especially the KW model), but the rollie duck will have more "range" matching up a bad load. (nonresonant antenner)

I am currently using a homebrew tuna that is a supersized copy of the mfj tuna. It is a "T" type with the roller inductor out of a broadcast transmitter and 2 large wide spaced breadslicers. The Balun is wound on 10 t-120 cores and never even gets warm, even with a bad load and very high power levels. it fills a cabinet the size of an R-390. I had no space at the operating position for it, so i cut a hole in the wall and racked it into the wall, henceforth its name: "the hole in the wall tuner". It will load a bedspring dead flat on 160!
Chris, W2JBL, calls it "the world's largest MFJ tuner"

A tough choice, you'll have to pick the one that best fitz your situation  ???  ???

                                                               The Slab Bacon

Since you are running open wire, it is a no brainer. A junkston KW matchbox should handle almost anything u could throw at it. It has the fast make/slow break antenna relay. Stock it doesn't do 160 very well or handle a wide tuning range.

Homebrew a big beast for 160 and QSYing up n' down the bands.

Craig,

If you want to operate on 160, not a good move. It doesn't cover it.
If you plan to operate high power, this baby version won't do it.  I tried using this low power version with a Valiant several years ago, and on modulation peaks, I could arc this thing.  Finally gave it away to someone using a DX-40.
Although I don't have high regards for many of MFJ's antenna tuners, the one you have has the baby Matchbox beat. If you do the trade, you would be getting the lesser deal.

My antenna is the nearly folded slab bacon special, only with 120' per leg folded with 12" spacing. Some photos of the antenna are posted in my gallery, along with my tuner setup. I plan on a home brew tuner at some point, but right now with the Apache I worry about the MFJ balun.
Norm K7NCR

The others have laid it out for you.. But I agree:

Better tuner for open wire line, its balanced.

The little 250 wont take a ton of AM power. I ran a Valiant on mine with out issue. 150 watts AM.

Limited Tuning range. The matchbox is a band switched box.  Not an issue for me. If it would not tune, I hacked the feedline until it tuned all bands. 

I have three  250s and two KW versions.  I wont look back.  I have owned palstars, MFJ, Heath, and even that mega buck Bliss tuner.  I would rather have the band switched KW any day.  Simple to operate and they are balanced.

There are a few versions..  One has the built in SWR meter and requires the almost always missing  Coupler.  The other has no SWR meter.

If you get it, Open it up.  Lots of people modify these because in stock form they had an antenna Changover relay built in. They bypass this in lots of crappy ways.  The last one I opened had Electrical tape jammed into the relay.. LOL.  If you want to bypass it, Do it correctly, read the manual.

If a Guy Hotswitched it even one time, The bandswitch might be damaged. You can find new switches and used switches around.


C

You missed:  "Make hay while the sun shines"    ;D

Hi Norm,

I would sell that MFJ tuner on e-Bay for top dollar.  Take the cash and take your girlfriend/wife out to dinner at the best joint in town.

Then wind up some copper tubing and mount a vacuum capacitor to build up a K1JJ Super Tuner... ;D
It will take 10KW easily and can be configured quickly to tune both series or parallel feeds. 160-10M

You'll be real proud of your own homebrew tuner and learn a lot about matching antennas. I know of at least ten tuners that have been built on this BB.

Here's a few threads with descriptions and pictures:



http://amfone.net/Amforum/index.php?topic=18054.0

http://amfone.net/Amforum/index.php?topic=10989.0
http://amfone.net/ECSound/K1JJ13.htm

For additional info do a search on this BB for " K1JJ Tuner"

Good luck -

Tom, K1JJ


** Build one and get your very own  JJ/Fabio QSL card!  (good towards WAF - "Worked all Fabios" award.)

Strike while the iron is hot.
A stitch in time saves nine
Here today, gone tomorrow.
Order before midnight.

Hows this,,,
I have an old navy tuning unit I made into my first tuner, a T with switchable output capacitance. But it never worked well on 80 due to low ind. value rollers. BUT I have 2 of the rollers and all the other assorted junk from 2 of them navy tuners,,
Maybe the 2 rollers in syc ballanced on the lines would be enough. All this in old buzzard style mil-spec parts. Mesa thinkin,,,
Norm K7NCR

.....and they are mild.


klc

um,

"Solder whilst the hammer is cold."

      ****  Carpe diem ****

I have 275 watt matchboxes at two of my stations, and they both easily handle a 300 watt carrier and 150% positive peaks on AM with no problem. note however that this is into good antennas, miniumum 130 feet center fed on 80 meters, 50-60 feet up in the clear fed with open wire line. if you try this with a blister packed G5RV six feet from the aluminum siding of your house 20 feet off the ground you may have issues.

operators are standing by.

use these coil clips instead of JS clip leads. Clip leads R NG for tunas.

http://www.bwantennas.com/coils/coilclip.htm

This brings up a philosophical(?) point about tuners.   Sure you can build up the mother of all tuners that will match a coat hanger but do you want to?  Only if you want a coat hanger for an antenna.  There's a reasonable tuner range beyond which, if the tuner doesn't solve the problem, maybe something else is the problem.  It's hard to know the difference without experience but for example, someone trying to use one of those 88 foot center fed ("Cebik") dipoles on 80 meters, if the tuner can't give a match, it might be better to make the antenna longer instead of finding huge L and C values that hide the real problem.

So far its a GREAT discussion!
I'm inclined to do the swap for now.
However, I thought I had read on this site about a balun input balanced tuner design that may be something I can use my mil-spec parts on. I can use the Matchbox for now, and brew a heavier tuna to use if I increase my power or need broader matching range.
Norm K7NCR

Rob,
      Sometimes ya just gotta do what ya gotta do. Its ALWAYS better to build with overkill so you dont have to worry about it later. If you are gonna run 500w, design and build everything to handle 1000w. This way you incorprate a large reliability factor, and that good "cant hurt it, its bulletproof" feeling. Not to mention minimise losses.

I am running a 60' flat top for the lower bands (160. 80. & 40) Not because I want to, but because I have no other choice. Many of the people here have been to my house and seen my dilema. I run a lot of power and a short antenna - the ticket for RF disaster!! I have melted and smoked commercial tunas, had burning and exploding baluns etc.

I finally got tired of playing around with stuff I knew would fail, and designed the whole system to be "bullet proof". Everything is designed to take the abuse of running a lot of power into a short antenna. with only a 60' antenna, I put out a signal that is right up there with many or most of the "tall ships" on 75m. I figgered out how to make it work for my specific application. NOTHING EVEN GETS SLIGHTLY WARM ! ! ! ! Nothing getting warm means minimal losses and most, if not all of the rf energy is going to the antenna instead of being dissapated heating things

Sometimes you just gotta do what you gotta do. The real deal is to pick what application works for YOUR particular situation.


                                                        the Slab Bacon

Slab, I agree but if ya got the room....full sized ant. when possible.  I used to use one of those 88' dipoles on 80, what eventually came to be called a Cebik dipole, with my tuner and 600 ohm feed & thought it was great.   Didn't think I could fit a full sized 80 m. dipole.  Never thought about putting one up and letting the ends dangle down until K1JJ and HUZ recommended it.  So my point was don't use a tuner to limit yourself any more than necessary, but of course every situation is different.

73
Rob

Good points Rob. Every situation is different. In general you should put up the best (longest, highest) antenna you can fit (this may mean zig-zag or ends hanging down, etc) into your space, then build an appropriate tuner to suit,

That is one kewl tuner!  It would look so sharp on the shack wall.  Maybe I will build one up and ditch the JV KW matchbox.

Rich

T,
How did you get such a nice even wind on the coil?  I'm reworking my tank coil on the 813 rig but cannot get what appears to be a almost factory look on the coil.  Just wondering what technique you used to get such a nice wind.
B

B,

That first tuner was made by KA2J. The second shot is one made by Fred/MOP.

Maybe KA2J will let us know how he wound that coil so perfectly.

I generally use something like a paint can as a form to wind it. Though, he obviously threaded it thru some Plexiglas to give it some good support.

 T

I must say that is a heck of a link coupled tuner in that photo.   I also wondered about the construction technique for getting the coil in the plexiglass holder strip (or is it Teflon?) and guessed he either sliced it in two lengthwise cutting through the holes then seating the coil and gluing the top half down, or drilled out the strip and cork screwed the coil through the strip working from one end using a hot glue gun to cement it in place (making the holes a tad bigger than the o.d. of the copper).

Just as good is the link coil and getting that wound and held in place.  Not sure what the link is made of.

Rob

You take a piece of plexi,  and drill all the holes, spaced properly...
The rows are staggered...

You wind the coil on a form...

Remove it from the form, and then screw it into the holes in the plexi.
The hole pattern in the plexi is like a tapped hole, the coil is the screw.

it really is THAT simple to make a nice coil..
Makes it real neat and easy to mount, and the coil won't move.


I see he used 2 strips... I usually just use one wide piece...

But obviously works both ways!

This is the typical AM forum discussion; full of information and civil!  To paraphrase George H.W. Bush this site represents a "kinder, gentler internet".

I agree with the philosophy of putting up the best antenna you can but I also subscribe to the "overkill tuner" because you never know in the dead of winter when you might need to operate on a less than optimal antenna after your desired antenna bites the dust. 

The original poster's MFJ tuner is one of the better ones they have sold but isn't a great choice for a balanced feed line with a mismatched antenna.  I would much prefer a true balanced tuner for this situation and they are easy to homebrew.  If you don't need 160 (or are willing to modify the KW matchbox) it would serve you well.

I have set up a swap with the other ham, and will get a hopefully decent matchbox. I think it is a good choice for my antenna.
I can get use of an MFJ antenna analyzer for testing. Do I need a balun to connect it to my open wire feed for a sweep?
In one of the archived posts, I read about a dual roller balanced tuner, with rollers driven in sync with belts. Anyone know who this might be? I'd like to get a photo of that setup, or at least a diagram. I may be able to use some of my junk box parts for one like that.
I wish I had access to antenna modeling software, I'd like to model the SLAB BACON SPECIAL X2 that I built to see how it looks.
Thanks everyone for your posts! Some great info! Keep it coming!!
Norm K7NCR

Norm,

The balanced, balanced tuner info is at Rich Measures, AG6Ks' website:

HTTP://WWW.SOMIS.ORG/bbat.html

Was published someplace, I can't recall at the moment but the full information
is there...

Thanks!! I have enough parts in my stash for one of these! (without the motors) I'll start gathering up stuff and keep you posted.
Norm K7NCR

No balun with Matchbox.  Hook up wire,  Plug in MFJ 259,  Make a chart for  1.0 50 ohms for each band/Freq. Post it on wall.  :) 

Some hints about matchbox.  You should need very little change on the dials for the bands if the Open wire line is the correct length.  If you cant tune a band or you need lots of dial changes to tune in,  Remove 6 inches of line at a time and check again.  Or add line.. 

Once correct, Mine needs only a 10 degree change from 80 to 40 on the AM Freqs. 

C

Er. There is nothing wrong with use of a BalUn if it is used properly. Don't write off systems which use one until you understand what's happening.

The little matchbox isn't worth as much as the trade tuner in question.

Build your own tuner and sell the MFJ to someone who can't read.

Matchbox doesn't work on 160 and has limited impedance range where it does work. This can be a problem or not. depends on your luck or research.

One guy sez 275 watt matchbox handles 100,000 watts other guy can't get his to work with 200 watts. Maybe the guy with the 200 watt zorch is at a voltage node and can't find a good text.

Antenna couplers bring out the very worst in hammy folklore.

Umm,
I was thinking I would sweep the current antenna setup without the tuner in line to see what I might be up against. That's why I asked if I would need a balun to hook it up to my open line. Am I off track?  ???
Norm K7NCR

IN one station the Matchbox will take 1500. In another it might take 500 or less.   Also.. They are old.  You might get one that is zorched with carbon marks on the plate. Then it will be more likely to Zorch again.

If you where asking about using the MFJ to sweep the antenna without the tuner, I think its a waste of time. There is no real point. It does not have to be resonant with a balanced tuner and open wire line.  However, You can do this if you want with the correct matching balun. 

C

Also don't let anyone know that a Jaw-N-Son (Pittsburgh pronunciation) Matchbox hooked up for 50 ohms in and balanced out IS a Balun.

Put a good balun on the output of the MFJ tuner and don't use the one in the tuner.   You will have a much better combination.   You will have better balance and will have the advantage of being able to receive on all the bands better, with the tuner on bypass.    I use a DX Engineering balun.    Following this you will hear from the balun haters, but it works well for me.    Better yet build a real balanced tuner as others have said.

If yu'uns are gonna do the pronunciation thing, it's Picksburgh.

In theory it's not a waste of time for analyzing the feed/antenna over a sweep of frequencies can yield useful information for getting a tuner to work i.e. choosing a range of L and C values for success.  The problem is that ham swr analyzers are normalized for 50 ohms unbalanced so you have a problem there with a 600 ohm balanced line.   You might be better off using a modeling program, maybe TLW (Transmission Line for Windows) along with an antenna modeling program.  The antenna modeling software can give you the feedpoint Z for a given balanced antenna of N wavelength on F frequency and with that you can use TLW to give you the line resistive and reactive values for 600 ohms ladder line on a line of so many feet in length, at the tuner end.   The Matchbox spec's give the Z matching range so then you'll know if it can do the job or not.    TLW comes packaged on a CD ROM that accompanies the ARRL antenna handbook.   You can try modeling different lengths of line for some load Z to find out what the line transforms to at the tuner end and thereby see if lengthing or shortening it X no. of feet will help or hurt.

73

Rob
K5UJ

 I was thinking about building my own Balun in a 4 ft tall Bud case.  I would use Huge Cores. The 2 ft diameter ones with some 00 cable. My only downfall right now is I cant find Gold plated 00 gauge Terminals to connect to the Solid gold Buss bar.   

Anyone know where I can find some solid gold Coax connectors?  I can only find Silver plated, pot metal and thin gold plated ones.  I really want to Get some solid Gold ones. Maybe I will contact a Jeweler to see if they can make some for us.

How many do you guys want?

C

Now you are just bein' sthilly!
Normie-poo

Yeah... LOL... I am bored..     I think you will like the Matchbox. Small, simple to use and great performance.

I guess I will go wash Toby the dog..

Cya

Clark

OK, here's the plan,,,
I only paid $25 for the 989, so I don't feel too bad about a swap. I think the Junkston will be a good match for my current bands and power (no 160, PW, or nearly so).
I'm going to build a balanced tuner ala AG6K, without the motors, but with switchable C on the input in case of low resistance antennas. (antenni? antenna?) He suggested this in the article.
I don't have access to any antenna or feeder modeling software right now. Maybe Santa can bring some?

Better watch the oxygen content of that 00 cable, or the tessitura of the sidebands might overcompensate for the sound stage presented by the carrier...... 

A Ham once told me " I would not walk across the room for a DB in gain".   

I told him "I will walk across the room 10 times"


Clark

Santa doesn't need to bring it. You can get it free.


Antenna Modeling

http://mmhamsoft.amateur-radio.ca/

http://home.ict.nl/~arivoors/


Transmission Line Calculations, etc

http://www.ac6la.com/tldetails.html

http://fermi.la.asu.edu/w9cf/tran/index.html

One way is to cornfigure the thing so any combination can be switched like this:

http://w2dtc.com/2009-0818-kc2ifr-photos/W2A28.jpg

This thing can put the C across the output or the juncture of the BalUn and coils or keep it out of the circus altogether. Same with the roller inductor at the top.

Less copper than a linky tooner and it isn't bandpass so you can hear stuff when cruising the bands without retuning.

The tuner was originally whipped up for K3L 2005 where we were stuck with a 60 foot center fed radiator. We did a lot of operating on 75. The Johnson KW matchbox would not load on 20 with our combination of feedline and flattop but this thing would. It can be difficult to setup initially however.

At W2A the antenna feedline combination was exactly resonant on 75 so the tuner didn't have much to do except for the input BalUn. On 40 we were almost exactly at the voltage maximum at the tuner's output. This required moving KG2IR's vehicle away from the tuner and feedline in order to get a measurement! It still manages to deliver power without any problems even with the 30S-1 at legal limit. Try that with a flashbox or a T nutwork with an output BalUn.

Thank you Santa!!!
My, what a long brown nose you have,,,
 ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D

You may be right. I was using the narrow filder. I replaced it with a capaster.

I designed the fugly balanced -balanced tuner in 1983 a few years before Measures invented it.

That circus was probably designed by someone in the 19 teens. Measures popularized it for hams again.

It is no big deal just two L networks fed out of phase