MFJ 986 Differential-T Tuner ???

[KG4CGC]

Anyone ever use one?
What are your opinions?
Pros, cons Etc.

http://www.universal-radio.com/catalog/hamtune/0706.html

Buddy has a used one so I'm not paying anywhere near that price but just asking of the Islander's experience.
Looking at a Johnson Matchbox too but it lacks WARC band tuning.

[WØTKX]

Well, the Matchbox might tune WARC, with a particular antenna.

I have a used MFJ-989C on the way, the old Dentron is getting goofy mechanically.

MFJ is OK, you may have to open it and do minor repairs. It's really a 1K+ tuner, as is mine.

[N9FE]

Diff t's are just a roller and one cap. I Think. Might be limited tuning. Try it. See what happens. As you know MFJ power rating is like a quarter of what they say. I Like this heath 2040A. You can tune a screen door. I mean anything, And tough as nails. 3000 watts. Giver Er

[KJ3N]

Diff t's are just a roller and one cap. I Think.

Not quite. Two counter rotating caps on a single shaft. This means that you will only find one tuning solution; the correct one. On most tuners with 2 cap controls and 1 inductor control, you can find multiple tuning solutions. Not every solution you find will be the most efficient one. Differential-T tuners will find the most efficient solution and it will be the only one.


Might be limited tuning. Try it. See what happens.

See above. The "limited tuning" is a misunderstanding of a Diff-T tuner. If the Diff-T won't load it, there's something wrong with the antenna system. This was pointed out to me when I had to add a bit of ladder line to my doublet to get it to tune 15m. It was fine everywhere else, but 15m. After adding about 7 feet, no more issue.


As you know MFJ power rating is like a quarter of what they say.

Actually, about half. ;) :lol:

[KG4CGC]

Thanks so far.
On the Match Box, it has the Viking logo and comes with the directional coupler. Not sure what direction it's going in.

[N9FE]

My matchbox would never tune ten. I played with the feed line lenght about five times. It helped. But ten would never quite go. Now with the 2060a no prob. 60 meters warc bands, ten.. Its all good

[N9FE]

I have the manual on PDF for the matchbox with the directional deal if you want it.

[KG4CGC]

I have the manual on PDF for the matchbox with the directional deal if you want it.
Sounds cool. I have no clue about Johnson Matchboxes but I'll try anything once.

[KB3LAZ]

Anyone ever use one?
What are your opinions?
Pros, cons Etc.

http://www.universal-radio.com/catalog/hamtune/0706.html

Buddy has a used one so I'm not paying anywhere near that price but just asking of the Islander's experience.
Looking at a Johnson Matchbox too but it lacks WARC band tuning.

I have one, it works. Though Im not fond of it..I got it after my 989 crapped out. In retrospect I I should have got a Palstar. I use the 986 for 40/80/20 with my amp but it seems to have a limited tuning range. Soooo I tweaked my antenna a bit and now dont use a tuner...well I use it on 20 still.

[KB3LAZ]

There was a matchbox at the hamfest today. Look to be in good order. It was 60$ I believe.

[N9FE]

Matchbox's are good efficient tuners. Cept the tuning range in limited. I could tune 17. But never 60. Yeah you want that manwell charles, We'll have tp pm or whatever. The damn BAMA charges for stuff now. I got some, Friends got others, for the older stuff.

[N9FE]

for 160

[N4VGB]

The damn BAMA charges for stuff now.

No problem here downloading anything I want free from BAMA. But I never used the main FTP website only the mirror site: http://bama.edebris.com/manuals/

[W1GUH]

2 months later...

Don't know if you've gotten something by now or not, but this is my favorite antenna topic. Assuming you need the power of the MFJ tuner you're asking about, you'd probably need the Kilowatt Matchbox, but maybe not. It's been guessed that the small matchbox will handle 1 kw of SSB; it's rated at (I think) 300 w of plate modulated AM making it good for 1200 watts peak. And yes, the small matchbox is pretty available at hamfests for 50-100 bucks. I got one last year, without the meter, for $50. Saw a couple other, too. One looked pretty minty for $75.

After using a matchbox with balanced feedline, I'll never consider a "not balanced" tuner again. A tuner with a balun on the output is only a pretender -- output baluns can be problematic. Besdes, with a link-coupled balanced tuner you KNOW that you've got the most efficient matching there is. And, BTW, balanced tuners are almost trivial to homebrew. Here's K1JJ's design. (http://amfone.net/ECSound/K1JJ13.htm)

[WØTKX]

Been looking at simple designs like that with an eye on making a remote tuner with a vacuum variable.

Currently Using "double beefy" tuners with baluns rated at about twice the power I'm running.
This causes me no grief at all, double check things with the analyzer to make sure, and optimize it.

I don't use tuners much as a rule above 10Mhz. Imagine that. ;)