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| Reviews Summary for Johnson KW Matchbox |
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Reviews: 12
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Average rating: 4.2/5
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MSRP: $ $150-$350 USed DOC
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write your own review of the Johnson KW Matchbox.
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K6JHD
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Rating: 5/5
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Dec 25, 2006 20:29
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Matchbox missing the High Z single wire input.
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Time owned: more than 12 months
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I have owned a KW Matchbox since the 1950's. I could never get it to load a single wire High Z antenna. My V-Beam was designed for 20-15 & 10 meters and the Matchbox worked on these bands as expected. I tried to load the V-Beam on 40 and 80 meters with no success with the ladder lead in shorted together on the single wire input. So I wondered why this was happening. I removed the tuner from the case and compared the tuner with the schematic and the instruction sheet. My tuner has two ceramic feed-throughs for a balanced line input and a coax connector for a coax antenna feed line. The back panel does not have a connector for a High Z single wire connection. To use the coax connector for a coax feed line, the left feed post, the one under the ground strap, has to be grounded! The two connectors for the balanced line input work normally. The schematic, and the instructions indicated there should be a High Z input connector matching the two for the balanced line. My Matchbox did not have one! I believe there was an engineering snafu that led to the omission of the high Z input connector on my model of the Matchbox! I installed a glass feed through next to the coax connector and connected it to the end of the loading coil near the back panel. This is the High Z point of the coil. Now the two wires of the ladder line of the V-Beam can be connected to the High Z output connector and the left most connector is grounded. Using this method with the Matchbox, my KWS-1 was loaded up on the V-Beam conected as a single wire antenna and I made my first contact on 80 meters with this xmtr and antenna! The SWR was 1.04:1 with 700 watts.
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KC8HXO
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Rating: 5/5
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Jan 21, 2006 09:41
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Just the facts
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Time owned: 0 to 3 months
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Of course, you may have different results, but here are mine:
1)Able to match by EDZ on all bands 80-10M, INCLUDING WARC.
2)My Palstar BT-1500A was not able to do that.
3)No sweat running legal limit through it.
4)Quality, USA made, from back when we did it right.
5)Will stay in the shack with my Ten Tec 238A, until I am SK.
Good luck with yours!
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DD3LY
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Rating: 1/5
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Oct 14, 2002 06:30
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Poor for today
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Time owned: 3 to 6 months
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As WA8KJP mentioned the Johnson tuner has really limited tunig range (there is a review about tuners in an old QST of the 90s). I built a balanced L-network out of two roller inductors and one vacuum variable, as WA8KJP did, but simplified it: a 50:12.5 Ohm transmission line broadband BalUn instead of the cap between BalUn and the coils. The effect: Just two points to tune and tuning range again starts at low-Z.
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K0ZN
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Rating: 5/5
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Mar 26, 2002 00:41
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Still an Excellent tuner.
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Time owned: more than 12 months
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I can't believe you guys are giving away our "secret" about the Matchboxes. What are you trying to do? Drive up the prices at hamfests?
Seriously, I am a diagnosed "Tuner-aholic" and I have yet to see anything better than a Matchbox for balanced line. Actually, they do pretty well unbalanced too with in a reasonable range of Z.
There is an EASY fix to Matchboxes not handling low impedances well. A 2:1 or 3:1 UN-UN at the imput. I use a "12.4 Mhz Zepp" (because that is the distance from the house top to the nearest tree!) on 30M thru 10M fed with 450 ladderline with excellent results. This antenna/line length yields a low Z on 30 M. I simply put the UN-UN (as opposed to a BAL-un) at the input to the Matchbox. e.g. a 2 to 1 step up transformer between the tuner output and the 50 ohm coax. This greatly extends the range of the Matchbox.
In a very low-Z situation, you could use a 3:1 Un-Un. You can also turn it around and step the Matchbox output DOWN to 50 ohms, thus extending the Hi-Z range too. I use the W2FMI UN-UN from Amidon Associates. Works like a CHARM! My KW Matchbox sits between a legal limit Linear and the Zepp and has NEVER given any problems.
I have two KW Matchboxes and would pick up a clean small one if I saw it at a hamfest. These things are quality pieces of gear: they DON'T make 'em like this anymore.
73.
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K8KAS
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Rating: 5/5
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Mar 12, 2002 14:29
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Good Low loss Balanced Tuner-The best..
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Time owned: more than 12 months
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Great tuner for balanced fed antennas. When you look for current balance and low tuner loss this tuner is tops. It is possiable to loose up to 6db with Tee Type tuners and baluns feeding a balanced line, thats 3/4 of your power wasted in tuner and balun loss..now thats poor, as for short/lo-z to me that means lossy and improvised. If this tuner is not prone to matching those loads in no way says its a "poor tuner".To call this "a poor tuner" makes my fur stand...I own two KW Matchbox, I would never part with them.
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Anonymous
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Rating: 1/5
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Mar 12, 2002 12:45
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Poor for today's use
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Time owned: more than 12 months
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I wouldn't give this tuner the high marks others have for use today. This tuner uses a differential cap instead of taps on the coil. Tuner also does not have a cap in series with the link. What this means is that this tuner is great for hi-z loads like loops and 2 wave length antennas that were common in the 50's and 60's. Now, alot of antennas are short and are lo-z and very reactive. The Johnson tuner is a poor choice for lo-z work. The only solution for lo-z balanced work is to make your own tuner using 2 separate reverseable L networks connected with the use of an unbalanced to balanced balun at the input end. This is probably beyond alot of hams today and that is why there is continuous discussion for the ultimate antenna tuner, it doesn't exist on any vendor shelf. I built one using 2 roller inductors connected by gears with a 1000pf 2kv cap connected across to the lo-z ends of the 2 rollers, and a 250pf 4.5kv cap connected to the hi-z ends of the rollers. I can match around 1 ohm to 5k on 80 - 10 meters with it. Only problem is, you want one, you have to make it. Sorry
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W1DB
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Rating: 5/5
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Mar 12, 2002 08:36
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It's a keeper
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Time owned: more than 12 months
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I also own both Matchboxes and will never part with them. Our local recycling center, upon several occasions has had large spools of telephone hardline aparently dumped by Verizon. This wire is called RDW or rural distribution wire and is copper covered steel wire with a black polyethylene jacket. I naturally stocked up on several thousand feet of the "treasure" and with a precision micrometer, measured the diameter and spacing to calculate its characteristic impediance. It works out to aound 65 ohms....nice.
I started out feeding simple dipoles with this wire as both radiator and feedline, and using the Matchbox. The wire is incredibily strong btw. I am always pleased with the results of balanced feed over coax.
Several years ago I was having trouble with the balun at the center feed of my Gem quad, as it was arcing and starting to break down. I temporarily replaced the coax feed with RDW and tuned with the Matchbox and it was slick! On 15 and 10 usually only one tune is required, as it is broad enough to cover the entire band. I can also tune the WARC bands on the quad with ease. I never went back to coax.
I love my Matchboxes.
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KC2IFR
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Rating: 5/5
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Mar 12, 2002 05:46
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Simply the best.........
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Time owned: 3 to 6 months
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After trying many different matchboxes, this is THE BEST tuner for tuning any antenna using balanced feed line. This tuner was made for balanced line. Its a link coupled tuner and has no lossy balun. It will handle full power...even AM......without any problem. Don't waste your money on the other stuff. I compared this tuner side by side with the Palstar AT4K and the Johnson won hands down for ease of tuning and had less loss on both transmit and receive. The only problem is that it will not cover 160 but I understand there are mods for this.
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W6EZ
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Rating: 5/5
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Apr 30, 2001 15:56
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Great equipment
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Time owned: 6 to 12 months
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Well the BIG Matchbox will handle more than the little matchbox. Pretty Simple. But it will also tune a bit wider than the little one, but it has a tad bit more loss. Fair enough.
Word seems to be getting out about the matchboxes. Prices are going up everyday. They are going for around 350 to 400 dollars on the online auctions. In a copy of the 1962 ARRL antenna handbook, the 1 KW matchbox, with SWR meter sold for $149.50, so it wasn't cheap then either. I can load my 80 meter ladder line fed dipole anywhere ( WARC too! ). Well, 30 meters is really touchy. A couple of big caps across the outputs will even get you onto 160. ( The loss is pretty hight there however. )
Matchboxes have a LOT less loss than the regular T network with a balun that most manufacturs sell today. There is a noticeable difference in signal reports.
I own both big and little versions and have no intention of EVER parting with either of them.
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KB0LSG
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Rating: 5/5
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Sep 12, 2000 18:31
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This is not your average tuner
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Time owned: more than 12 months
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I have been using Johnson for several years now with no problems. I have owned both the 275 watt and 1 kW versions of this well made link coupled tuner. Many hams will turn up their nose at the fact it does not tune 160. With a couple of 200 to 250pf 3+ KV doorknob capacitors placed in parallel with both stages of the output capacitor, you can gain the range needed to tune most balanced fed 160 antenna's. I added in a Jennings vacuum switch and a placed a small power jack in the back to switch in or out the doorknobs to allow tuning on 80 or 160.
Before you pass by another one of these "bullet proof gems" at the next swap meet take a good look at the quality. I have never arced my KW tuner even on 160 using 1000W +. An added bonus...If you are also experiencing RFI and TVI problems consider a link coupled tuner such as the Johnson. It has helped at my QTH.
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