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Author Topic: Has anyone modified their Johnson kilowatt tuner for 160 meters  (Read 1732 times)
N4MQ
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Posts: 138




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« on: September 15, 2017, 09:21:57 PM »

Got a horizontal loop for 160 meters, and the tuner works great for 80m, want to extend that for 160 meters and I can not find solid info on the modifications.  Looked at qst and others without real description and wanted to ask this group, enjoy. Woody N4MQ
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KD8IIC
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Posts: 648




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« Reply #1 on: September 15, 2017, 11:28:54 PM »

   Try W8JI web site.  I know the plans exist.  Added inductance outboard the tuner if memory serves.
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KD8IIC
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« Reply #2 on: September 15, 2017, 11:41:14 PM »

 Find here; www.qsl.net/w2xs/new life for the johnson matchbox.pdf
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N4MQ
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Posts: 138




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« Reply #3 on: September 16, 2017, 05:14:58 AM »

I get a 404 fault code when I pull up the swl page, is there a better way to get the info, KD8IIC ?  Thanks Woody
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KD8IIC
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« Reply #4 on: September 16, 2017, 08:28:21 AM »

I just searched 'Johnson KW Matchbox 160m'.
The qsl.net web page works this morning. Maybe get on QSL.com and do a search there.
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KD8IIC
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« Reply #5 on: September 16, 2017, 08:36:09 AM »

getting same here when click on this link.
google "new life for the Johnson matchbox" perhaps as that is the article's name.
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KM1H
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« Reply #6 on: September 16, 2017, 05:28:03 PM »

That tuner needs more C also if you want reasonable efficiency, and then you wind up with a real kluge that "may" work on some 160 loads.

It would be easier to sell it and buy a big Dentron MT-3000A, or other tuners with 160 for less money than the Matchbox sells for these days.
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WA3SKN
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« Reply #7 on: September 19, 2017, 02:47:23 PM »

The old johnson was rated for 1kwatt INPUT transmitters... so you might want to up the variable caps plate spacing for 1500 watt output amps.  But as long as the match is not too far of a range it will probably work.
73s.

-Mike.
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WB6BYU
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Posts: 17049




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« Reply #8 on: September 19, 2017, 03:55:08 PM »

Quote from: WA3SKN

The old johnson was rated for 1kwatt INPUT transmitters...



Though that was 1 kW INPUT for 100% modulated AM, which is actually exceeds the current
1.5 kW PEP output limit.
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KC4ZGP
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Posts: 1637




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« Reply #9 on: September 20, 2017, 05:27:10 AM »


Woody,

Add capacitance and inductance to tune down the amplifier. By formula, if it works fine at 80 meters,
double the values for 160 meters.

You're a ham. Experiment. It's what we do.

Who's up for 160 meters CW? Getting dark early. The band is coming alive.

Kraus





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