Johnson Matchbox 160 Meter Mods - Experiences/Suggestions?

[W1UJR]

Wonder if anyone has used the 160 meter Matchbox mods suggested by Bowie Bill in Electric Radio?
With winter approaching, and the beginning of the 160 meter "season", I'd like to get strapping signal out on 160, so I'd be interested in your experiences.

I tried the lash up on my KW Matchbox last night and it seems to work well, very little inductor heating even at 1KW of RF input.
Bill had suggested the use of series of fixed doorknob caps across the stators of the tuning air variable cap.
No having an set of fixed caps on hand, I used an old Johnson air variable for the task, clip leaded into the circuit.

What I am looking for is an elegant way to switch this in and out, either with a direct toggle, or vacuum relay.
There is no simple way to add an additional position on the band switch like the 275 watt version.

What are you thoughts about using a toggle switch for this, is the lead inductance going to be a problem?
Is there a potential flashpoint on voltage peaks, between the switch on the chassis it would be mounted too?
Will disconnecting only one lead on the cap be ok, or should it be disconnected on both ends when not operating on 160?

Aside from the power handling advantages of the KW vs the 275 watt version, Kurt Sterba in his series "Reflections", mentions that the KW unit is more efficient, and will enhance receiver sensitivity. Something to the effect that the larger box will allow you to hear things the smaller box won't, I'll have to search for the exact quote. Now I like Kurt's work, always right on point, but wonder if this is really accuruate.
Thoughts on this?


Tnx!

Bruce W1UJR
http://www.w1ujr.net/bruces_bench.htm

[w4bfs]

There was an unpublished mod done by EFJ for this purpose ... switch in two, one each of the inductor ends of C1 a 400pF 3kV 5Amp transmitting mica to ground ... recommended to use a heavy duty relay and route control outside to avoid hammy hambone type mod, unless thats what you want .. oh yes, use the 80mtr Flashbox setting ... just one of several ways to do ....hope this helps, Bruce ... 73 ...John

p.s. The efficiency thing about 275W vs KW boxes was first noted in a 60's QST article (3 parts) about station design for DX ... sure sings praises on 75A4 ... still goood stuff

[Mike/W8BAC]

Bruce,

I'm collecting parts to build a modern match box based on the link coupled Johnson/Annecke designs. It will cover BCB to 30 MHz and able to handle very high current and voltages.

I missed the ER article with the 160 meter matchbox mod's. Can you post the year and month please.

Mike

[W1UJR]

Hi John,
Good note, thanks, guess that confirms what Sterba wrote.
Now I will have to hunt up my old QSTs to review that.
I've been delighted with my 275 watt Matchbox, handles the 30K and 1KW Icom no problem, but perhaps I'm missing out.
Was not aware that article, so tnx for the tip OM.

As for control, I'd prefer to have the caps switched in and out via a manual switch, rather that running
power and control lines inside the box, just another route to couple RF in/out. Thanks for taking the time to respond.


Mike,

I have don't have the exact date in front of me.
But I do the article at home in digital form, email ok, or I can mail if that is easier?

Also you may want to take a look at W2XS interesting notes on the Matchbox -->> http://www.qsl.net/w2xs/New%20Life%20for%20the%20Johnson%20Matchbox.pdf

72 ES BTU DE W1UJR

[Mike/W8BAC]

Email is fine. Thanks

w8bac at comcast dot net

Mike

[WA1GFZ]

There is a lot of high voltage at the ends of the coil. How about trying the cap across the output terminals. you might get lucky.
You would need at least a 7000 volt switch or relay since that is the rating of the caps. 

[W3SLK]

Hmmmm, it seems to me that the ER mod utilized the internal antenna relay to switch what I remember a 100 µµf cap across the the coil. I used that pretty successfully with the 275 matchbox.

[WA1GFZ]

You know I bet that would work if the relay coil can stay on and not overheat. 

[Pete, WA2CWA]

The Electric Radio Magazine Index has been mentioned frequently here on the board.
It's updated monthly. Bookmark it.

http://home.wi.rr.com/n9oo/ersearch.html

[Pete, WA2CWA]

From FBTO INDEX:

Extending Johnson Matchbox Range - QST, Dec. 1963, page 67
Matchbox Improvements, Ham Radio Mag., July 1979, page 45, and Sept. 1979, page 92
Modernizing Johnson Viking Matchbox, 73 Mag., June 1978, page 84

[W1UJR]

Pete, you're the man, thanks for posting that!
I wish it would work with a Mac, Safari (the Mac browser), cuts off the end of the form, so I am unable to search it.

Mike, I think that Bill had installed some additional inductance on the 275 Matchbox, along with an extra position on the band switch.
He mentioned that he needed to remove one of the insulators for spacing reasons, as he was switching the inductors off the end of the center inductor.
I don't use the internal T/R relay, so that certainly would be a simple answer, if it can handle the voltage peaks Frank mentioned.
My concern is that I want to use this on 160 - 10, so sure that I'm going to encounter some crazy voltages.

I've always liked the Matchbox design with no balun, it is really quite elegant.
Just wish that old E.F. had thought about 160, but then again that was not popular band at the time.

Another thing I thought of was just removing all the componets from the metal Matchbox cabinet and mounted on a nice wood, cherry is ideal, breadboard.
Would have that classic 1930s look, and the extra space would also allow me to install the additional air variable cap right into the circuit, could easily jumper the cap in and out of circuit. I could mount the unit right on the wall next to the balance feed.

[WA1GFZ]

I found the fugly balanced / balanced tuner and kW match box produced the same feeder current at 1 KW. I would not trash the tuner I would build a homebrew get it working and save the box as a spare or set up a second antenna..   

[W1UJR]

I found the fugly balanced / balanced tuner and kW match box produced the same feeder current at 1 KW. I would not trash the tuner I would build a homebrew get it working and save the box as a spare or set up a second antenna..   

I would agree Frank, only this unit has been "Collinsnized" by the previous owner.
The cover was repainted, and Collins "meatball" logo attached with double sided tape.
I should post a photo, its a hoot!
I was thinking of having it powder coated in black wrinkle, but I like the open air look of things.

I've got all the parts and pieces right there, and it would be an easy matter to put it back together.

[N3DRB The Derb]

I would agree Frank, only this unit has been "Collinsnized" by the previous owner.
The cover was repainted, and Collins "meatball" logo attached with double sided tape.
I should post a photo, its a hoot!

please do! double sided tape is real classy and sceams "Art Collins wuz here" desingnin yur matchbox.

[N3DRB The Derb]

bruce, there is enough space on he back end of the factory bandswitch to mount a good stout ceramic wafer switch and a careful mounting hole in back to latch the back end shaft  onto. switch yer C or yer L or both using the factory bandswitch. was going to do his to mine but I'm sick of working on stuff and just want to get on the air now.

just use your 40 meter taps for 80 on the factory coil after extending the straps to the coil ends use the 80 meter straps to switch in yr 160 meter stuff.

[Steve - WB3HUZ]

Aside from the power handling advantages of the KW vs the 275 watt version, Kurt Sterba in his series "Reflections", mentions that the KW unit is more efficient, and will enhance receiver sensitivity. Something to the effect that the larger box will allow you to hear things the smaller box won't, I'll have to search for the exact quote. Now I like Kurt's work, always right on point, but wonder if this is really accuruate.
Thoughts on this?

I'd say Kurt is way off on this. Most often, on HF, whether you can hear someone is determined by the incoming SNR. If the Matchbox is more efficient, it will be more efficient for both the signal and the noise and the SNR will be unchanged.

[WA1GFZ]

Steve,
True unless the KW box has a lot higher Q. 

[W1UJR]

I need to look at the QST articles and see what they have to say.
Or ask our resident expert here, Walt W2DU.

I'll see if I can look up and post a summary here.
I'm interested myself.

BTW, that Matchbox with the added C is working well on 160, think I may just leave it like that, and add a nice knife switch to kick the C out of circuit when its not wanted.

As for the info Pete mentioned earlier:
Well the 1967 QST was about adding B&W coil stock to the output of the rear the Matchbox, not really a mod for 160.
I don't have Ham Radio or 73 magazine on the computer, so can't comment there.

[Steve - WB3HUZ]

Even then it doesn't matter. The SNR is the SNR. Unless you mean the Q would be so high as to make the bandwidth less than that of the receiver. But with a Q that high, the loss on transmit would be horrendous.

Steve,
True unless the KW box has a lot higher Q. 

[WA1GFZ]

true.

[Ralph W3GL]

Pete...

I checked your reference to the "Ham Radio" , Sept. '79, PP92 and
it is not the Johnson Match Box!  It is, however, the Drake Matching
network. No relation to "Johnson"...

The June, '79, PP45 is about adding a switch to apparently extend
the matching range but not the frequency range of the box.

I use a piece of B&W coil stock as an autotransformer when I run into
balanced feeders that are way beyond the internal range of the box.

I clip lead the coil externally as either step-up or step-down depending
on output frequency and feed line length.

My 275 watt match box has seen action in contest  operations, pushing
the envelope on power output and still keeps ticking!

Have yet to attempt putting 160 on it as I want to keep the box intact.
Perhaps something external using feed throughs out the back?

[Pete, WA2CWA]

Pete...

I checked your reference to the "Ham Radio" , Sept. '79, PP92 and
it is not the Johnson Match Box!  It is, however, the Drake Matching
network. No relation to "Johnson"...

The June, '79, PP45 is about adding a switch to apparently extend
the matching range but not the frequency range of the box.

Ham Radio Magazine July 1979, page 45
The Sept 1979, page 92, is Feedback on the original July article.

Of course, if you're an ARRL member, you can go here to also review the QST, QEX, and Ham Radio Indexes:
http://www.arrl.org/members-only/qqnsearch.html
My index includes CQ but doesn't include QEX.

[Ralph W3GL]

Pete...

I'm a 54 year member (Life member as of 1970) of ARRL !

I checked the index you mentioned and see that Demaw item
you mentioned but my QST collection is unavailable at this time
and I'm too cheap to request a photo copy from CT...

Oh well...

Later,

Ralph.

[ka3zlr]

Ralph you been a member longer than I've been walking on this planet...That's Dedication.....Wow....54 years....Wholly Smokes....

[Pete, WA2CWA]

Pete...

I'm a 54 year member (Life as well) of ARRL !

I checked the index you mentioned and see that Demaw item
you mentioned but my QST collection is unavailable at this time
and I'm too cheap to request a photo copy from CT...

Oh well...

Later,

Ralph.

Demaw didn't have any articles about the Matchbox.

Of couse, you can always Google "Johnson Matchbox" and review some of the 578 hits  including one that's called "Extending the Johnson Matchbox Range".