Johnson 275 Watt Matchbox Improvements ? 160 mod?

[KA9UVY]

    I have seen and read much material on the Matchbox here in the archives and elsewhere and I have to say it certainly is not clear to me what is the best way to put a 275 Watt Matchbox on 160 meters.
  There was also some discussion about the dual differential capacitor changing the impedance of the lines when trying to tune (monkey chasing it's tail)  but there was no mention of how to bypass that part of the cap or fix the issue.
  I am trying to get a recently  acquired 275 watt MB back into service and make some improvements if possible along the way.
  Can anyone post some detailed info with internal pics if possible of their 275 MB with or without mods? ( I am trying to see what might be missing in mine :-)

Thanks!
73, Bob
KA9UVY

[K5UJ]

What kind of antenna do you want to use it with on 160?  What height?

Rob

[KA9UVY]

Rob, I guess I can't give a specific on that.  My antenna plans are ever changing so whatever I do must be flexible.
  Right now I have a coax fed full size 160 dipole at 100 feet but plan to maybe use a double extended zep for 75M on 160 with tuned feeders.
  Maybe even a loop, so you see what I mean (Flexible Mods)

   I like to see what others have done and then maybe decide on my best option for a given situation.

73, Bob
KA9UVY

[K5UJ]

Bob,

getting back to your original question, I was unable to find any photos of the interior of the 275 w. model.  There might be photos of the interior of the KW MB in images.google.com.  I know I have seen interior photos of the KW MB as a part of eBay auctions.   I'll see if I have one and if I do, I'll try to upload it here.

Okay found one.  Hope this helps.  I would think there would be enough similarity between the models (in terms of wiring) to make the KW interior useful.

In my opinion, if might be better to build a link coupled balanced tuner from scratch for 160, rather than try to modify a Matchbox.  In any event, if you are going to use tuned feeders, you won't need any kind of matching network anyway.  For more information on them, look in the older radio texts, for example the 1939 ARRL Handbook at the end of Chapter 4 and on p. 300 of the Antenna chapter.

73

Rob

[W3GMS]

Bob,
For my particular antenna, which is a 260' center fed with about 125' of open wire line I made my Johnson KW matchbox work quite nicely on 160 by adding about 216pf of capacity across the coil.  I used a vacuum variable to get the 216pf and then a vacuum relay to switch it in for 160 operation.  With a fixed setting on the vacuum cap, I was able to get about 100Khz of tuning out of the matchbox.  The "Q" was very high, but with the size of the coil in the KW model it handled full legal limit just fine.  I was able to mount the vacuum cap inside on standoff's right about the edge wound coil.  The mod was easily reversable and did not deface the tuner at all.  I brought the voltage to key the vacuum relay out the back where the barrier strip is located.  I used that for many years until I lengthen the feedline and could no longer match the reflected impedance.  My next turner was a link coupled traditional balanced deal which worked very well but ultimately went to the Rich Measures type tuner which has performed very well. 
Regards,
Joe, W3GMS 

[WA1GFZ]

I like the Measures style tuner the best. I built mine about 10 yesrs before Rick invented it. 2 knobs vs 3.
Another cool design was the N1KW. He grounded the center tap of the main coil and picked off a tap near CT to feed 50 ohms. So he eliminated the need for the link and tuning it. 

[KA9UVY]

Rob, Joe Thanks for the replies pics and advice. However  I would like to keep this thread specific to the 275 watt matchbox and not let it become a Oh, I like this tuner or that type thread.
  I am looking for specific info and pics on the 275 matchbox. Improvements and 160 or WARC band mods.
  I suppose I should have specified that in the tittle but I am new to using internet forums and didn't think before I typed.
  I had considered building my own link coupled tuner but the 275 watt MB came along and needs me.
  I will see if I can edit the tittle of this thread and ask my question differently.

Thanks, 73
Bob

[Pete, WA2CWA]

It's always good to check our archives. Just do a Search on "matchbox".

Here's just two but there are many others:

Johnson Matchbox 160 Meter Mods - Experiences/Suggestions? http://amfone.net/Amforum/index.php?topic=16984.0

Lots of good Matchbox info in this thread: Examining the Johnson Matchbox ATU http://amfone.net/Amforum/index.php?topic=24088.0

E.R. had two articles on the Matchbox (mods and restoration) March 2001 and Jan. 2005
73 Mag Modernizing the Johnson Matchbox June 1978
Ham Radio Mag. Matchbox Improvements July 1979
QST Extending Matchbox Range Dec. 1963

[w3jn]

Rob, Joe Thanks for the replies pics and advice. However  I would like to keep this thread specific to the 275 watt matchbox and not let it become a Oh, I like this tuner or that type thread.
  I am looking for specific info and pics on the 275 matchbox. Improvements and 160 or WARC band mods.
  I suppose I should have specified that in the tittle but I am new to using internet forums and didn't think before I typed.
  I had considered building my own link coupled tuner but the 275 watt MB came along and needs me.
  I will see if I can edit the tittle of this thread and ask my question differently.

Thanks, 73
Bob

Bob, welcome to AMFone.net!  Since you're new to internet forums, you'll soon discover it'll be difficult to steer the conversation.  In any event you can heed the advice given, or not - your choice - but rest assured the advice you'll receive here by guys that have been there/done that is universally good 

[KA9UVY]

Thanks Pete and Johnny, I had already looked into the archives and those posts raised even more questions to me so I will try and look for a few of the mentioned articles and do some more reading.
  I know that the topic of the Matchbox has been kicked about many times over here and elsewhere but I still would like some specifics if possible. 
 So if your reading this and need something to do on these cold nights when there's nobody on 75M but slop buckets take a handful of screws out of ye old  (275 Watt) matchbox and grab some close up pics of how yours is put together to post here so I or We can look it over.
Thanks!
73, Bob
KA9UVY

[The Slab Bacon]

Another cool design was the N1KW. He grounded the center tap of the main coil and picked off a tap near CT to feed 50 ohms. So he eliminated the need for the link and tuning it. 

Frank,
         I have several large edgewound inductors laying around. All are single layer design. I have pondered doing that for a long time but never found that elusive little piece called
a "round tuit".

I figgered it would still work the same way. Instead of being a full transformer, it becomes an autotransformer, but should work OK-Fine. I guess I'll have to build one and sweep it and see...................

[W2VW]

I have yet to see anyone who has built a Measures tuner go back to link coupled couplers.

There are quite a number of hams who like to write off the Measures design due to it's use of a BalUn. There's also a vertically challenged ham following Measures around the internet trying to settle some score. Too bad anyone would ruin their credibility over a little nichrome. Funny part is to watch how stubby behaves when someone gives it back over a loading coil!

A Johnson Matchbox and most link coupled tuners are BalUns themselves fellows!

A 1:1 BalUn used at 50 ohms j0 like in the Measures design works very well.

 

I like the Measures style tuner the best. I built mine about 10 yesrs before Rick invented it. 2 knobs vs 3.
Another cool design was the N1KW. He grounded the center tap of the main coil and picked off a tap near CT to feed 50 ohms. So he eliminated the need for the link and tuning it. 

[KB2WIG]

" I have pondered doing that for a long time but never found that elusive little piece called
a "round tuit". "


Guggle is yer friend.

http://www.roundtuitenterprises.com/

klc

[K5UJ]

I have yet to see anyone who has built a Measures tuner go back to link coupled couplers.

I used a Measures design tuner and went to a KW MB.

There are quite a number of hams who like to write off the Measures design due to it's use of a BalUn.

The 1:1 balun is usually either a coax solenoid or a ferrite bead choke.  The problems may have to do with the way the choke is constructed.   I used a small bead choke and smoked it due to my own incompetence.  After that I used a much more robust bead choke and didn't have any more problems with the choke itself.  I have also used a large solenoid coax choke.  My problem had to do with weird behavior of the tuner due to a signal path of direct connectivity between the coils and the unbalanced feed which I'm pretty sure was brought on by all my antennas in close prox. to each other on my 50 x 100 foot lot.   In my particular case, the matchbox (or probably any bal. tuner with a link coupling) did not give me the same difficulty--things like false SWR analyzer readings. 

A Johnson Matchbox and most link coupled tuners are BalUns themselves fellows!

True.  I often think of them as variable baluns, or RF isolation transformers.  The link in mine provided the isolation I needed here.   If I had all my antennas spaced far apart and not near any other metal structures I'd probably be happily using a Measures design balanced tuner.

A 1:1 BalUn used at 50 ohms j0 like in the Measures design works very well.

Indeed; no argument there however my experience was that the MB worked better for me.

[W2VW]

Interesing experiences. I live on an 80' X 100' lot so things are real easy here 

I've used homebrew link, 275 and KW Matchboxes, tuned feeders with just a balun and the Measures gizmo. Every one has given me good results on bands when the antenna was at last a half wave long. 

Used sleeve BalUns, choke BalUns and ferrite with teflon coax BalUn. Each one works OK but the choke BalUn isn't too good across all H.F. so i put a tweeter BalUn in series with it.

I've had antenna at 30' to 95' at this location and have been able to make them all work without R.F. every place. Even ran the feeders into the shack behind the audio gear a few years back.
A small lot can work.

[WA1GFZ]

I agree. I got exactly the same feeder current with the KW MB as the fugly.
The fugly covers 160. I've used a 1:1 BB transformer and coax balun with the same good results. My coax balun is 30 feet of RG393 on 4 inch PVC pipe.
Frank I bought a couple big inductors from Gary and want to try the CT method at GFZ south so I don need to cut the strap. I would go to link if it doesn't work but knowing N1KW it should be fine. You could series tune it if required. I like a tuner with a lot of range and not many knobs. 2 is plenty for me

[The Slab Bacon]

I like a tuner with a lot of range and not many knobs. 2 is plenty for me

Yea, sometimes 2 tuning capz and a roller inductor can just give you too many possible choices   

[W2VW]

Things get interesting when the limbo bar gets moved down a few rungs.

Short antenna. Johnson Matchbox = out

Any other coupler made without components able to handle high voltage AND current = out

Roller inductors = bye bye

[The Slab Bacon]

Things get interesting when the limbo bar gets moved down a few rungs.
Any other coupler made without components able to handle high voltage AND current = out
Roller inductors = bye bye

Bet me! ! ! !   Been doin it for years!! Big power + short ant = recipe for zorch out.
High feedline current is NOT your friend!! It makes for INTERESTING challenges. Been using 60' flat top for years now due to small lot size and layout. but noone has any trouble hearing me. I have even used this lashup on 160 with fairly good results.

Build a home brew tuna, design it for 3 to 5 times your outpoot level, and you'll be OK-FINE!! Overkill is your best friend!

Dave,
        Roller inductorz are fine, as long as they are BEEFY enough to handle the load.
No MFJ junk, this is a true case where BIGER is BETTER     

[W2VW]

Huge roller inductors might work for you but I'll take that bet. All my testing has been done in search of max R.F. amperes at the feeder with a given amount of power.

I've tried the typical surplus rollers from KW and 5KW AMBC stuff.
Roller inductors will not equal coils of optimum shape unless they are dialed near that shape.

An oversized roller inductor might have the contact resistance problem resolved but how much oversizing can one tolerate when already using very large inductors? Where do we use large inductors? When the radiation resistance is a low number.

I still use roller inductors. I don't use them when the antenna is short though. They make a nice easy way to find the match. After that I replace with fixed values.

Things get interesting when the limbo bar gets moved down a few rungs.
Any other coupler made without components able to handle high voltage AND current = out
Roller inductors = bye bye

Bet me! ! ! !   Been doin it for years!! Big power + short ant = recipe for zorch out.
High feedline current is NOT your friend!! It makes for INTERESTING challenges. Been using 60' flat top for years now due to small lot size and layout. but noone has any trouble hearing me. I have even used this lashup on 160 with fairly good results.

Build a home brew tuna, design it for 3 to 5 times your outpoot level, and you'll be OK-FINE!! Overkill is your best friend!

Dave,
        Roller inductorz are fine, as long as they are BEEFY enough to handle the load.
No MFJ junk, this is a true case where BIGER is BETTER     

[The Slab Bacon]

Dave,
        methinks you might be reading my last post wrong?? When I posted that "high feedline current is not your friend" I didnt mean that you dont want it. You want to get the most feedline current you can for a given application. Dealing with it is the issue. Most commercially made junk tunas usually cant take it and go the way of the buffalo.

Had I known what bands I would have been running, I would prolly have used fixed inductance, but I got a fairly good deal on a rather large rollie duck and the res is as they say ....history. I have never had a problem with the roller inductor and the high currents, it's a large edge wound one with ribbon that is prolly 7/16" wide x 3/32" thick and a large solid brass contact wheel. It takes it in it's stride and never even gets luke warm running high power.

[W2VW]

Here's a novel idea. Let's talk about it on the radio.

Dave,
        methinks you might be reading my last post wrong?? When I posted that "high feedline current is not your friend" I didnt mean that you dont want it. You want to get the most feedline current you can for a given application. Dealing with it is the issue. Most commercially made junk tunas usually cant take it and go the way of the buffalo.

Had I known what bands I would have been running, I would prolly have used fixed inductance, but I got a fairly good deal on a rather large rollie duck and the res is as they say ....history. I have never had a problem with the roller inductor and the high currents, it's a large edge wound one with ribbon that is prolly 7/16" wide x 3/32" thick and a large solid brass contact wheel. It takes it in it's stride and never even gets luke warm running high power.

[The Slab Bacon]

Here's a novel idea. Let's talk about it on the radio.
[

Werkz 4 Me!! It has been a looonnnnngggg time!

[KD3CN]

from WA1GFZ:

I like the Measures style tuner the best. I built mine about 10 yesrs before Rick invented it. 2 knobs vs 3.

Couldn't agree more Frank, for the same reason.  Too many controls to adjust on the link-coupled tuner. It is a fine tuner, but for convenience of use I prefer the Measures tuner, which I've used here for a couple years.  Two controls just make finding a match MUCH easier.
73, Karl

[KA9UVY]

  OK, I am glad that someone read this and decided to help me out instead of go on and on about what tuner they like or use.
  I want to thank Steve WØGSQ for sending me some very nice detailed pictures of a bare naked 275 watt matchbox.
  They helped me to verify that my MB is indeed pretty much stock and wired properly.  Now if anyone would care to share photos of their modified unit, either a 160 or any performance mod I would again be very grateful.
  If not then I will consider this subject closed.  The intent of this thread was only to explore the 275 Matchbox tuner, nothing more.

Thanks everyone and especially to you Steve!
73, Bob
KA9UVY