The venerable Johnson Matchbox

[W1GUH]

I discussed them briefly on a thread on the 'zed where I posted a roadmap to an ARRL Product Review of 4 balanced balanced tuners, 3 contemporary, available now tuners, and the Johnson matchbox for comparison. The data in the charts showed that, in the matching range where the Matchbox can tune balanced line, the loss figures were roughly equivalent amongst the group, while outside the Matchbox's range, the loss went up, particularly in the MFJ tuner. Been thinking about that. One way I found to explain this in the Matcbox is that Johnson knew what he was doing by keeping it's tuning capabilities in the realm where losses are low, or, if you match sucks and the tuner would go inefficient, the Matchbox refuses to match the line because adjusting the feedline length won't result in inefficiency.

In this way, you KNOW your system is efficient. In, say, the MFJ tuner, you can match a wider range and you'll never know that it's gone very inefficient.

Johnson brilliance or coincidence? I'm so pre-disposed to the Matchbox that I say it's Johnson brilliance especially adding in the factor of the awesome quality of components used in the matching network.

AND, a little hamfest patience will yield a 275w Matchbox for only $50.00. 1/3 the price of the MFJ.

But, I have to acknowledge that the convenience factor could be a plus for the others. And there could be situations where you just can't tune the feedline, which would render the Matchbox useless.

And this is not to be viewed as knocking the MFJ. In the charts, it scored well against the Matchbox. And I've got one (I'm a sucker for balanced tuners). It tunes nicely and has a built-in lighted cross-meter SWR Power meter. Also looks good and you can get a brandy-new one. Kudos for MFJ for selling that, really.


The roadmap to the article (Ya gotta be a member to get there) is:

QST-> Product Review Archive -> Reviews Listed by Manufacturer -> M -> MFJ MFJ-974(H) Antenna Tuner (September 2004 [634 kB]).

BTW...was good to see some familiar calls over there!

[WØTKX]

I have a great desire to get a balanced tuner. Have an MFJ-989 that's OK, but using a balun is just wrong.

But it works pretty damn well, especially on the lower bands. By using an antenna analyzer, I know the (upper) bands that have higher impedances that might get the balun cooking with the amp on... rarely use an amp below 10mhz anyway, so it's really a non-issue.
Building a balanced tuner is an interesting idea, but I keep looking at the Palstar BT1500. $700 tho...

[W1GUH]

Don't overlook the Matchboxes. The low power one is dirt cheap ($50 - 75) at hamfests, and even the KW matchboxes aren't anywhere near $700!

I agree that baluns can suck, but they do work if it's all ya got!

[n2ize]

Baluns are ok depending on duty cycle. For continuous AM key-down (i.e old buzzard transmissions) they suck... I have burned out a couple on long winded transmissions. Enter the balanced link-coupled tuner (aka matchbox) works like a charm. Nice thing is they are not hard to build. a friend of mine bought a home-brew "Matchbox" built on a wooden block and it was the best damned tuner he ever owned.

[n2ize]

Don't overlook the Matchboxes. The low power one is dirt cheap ($50 - 75) at hamfests, and even the KW matchboxes aren't anywhere near $700!

I agree that baluns can suck, but they do work if it's all ya got!

And the low power matchbox will tolerate considerably more power than its rated.

[W1GUH]

Very true.

[WØTKX]

But I'm skeered I might blow it up.

[W1GUH]

275w of plate modulated AM = 1100w pep

[n2ize]

But I'm skeered I might blow it up.

Only a CB'er can blow up a Matchbox.