Towertalk
[Top] [All Lists]

[TowerTalk] MFJ Antenna Tuner Design

To: <towertalk@contesting.com>
Subject: [TowerTalk] MFJ Antenna Tuner Design
From: w1vxv@mail.gwi.net (Robert C. Boyd)
Date: Fri, 05 Feb 1999 17:35:22 -0500
Re the inquiry about antenna tuners:

For about ten years I used with success a tuner manufactured by MFJ
called the MFJ-949E Versa Tuner II which uses a switched inductor and is
rated at 300 watts.  Since the inductor is switched and not rotary it is
not always possible to get SWR of 1:1, but it has always been at least
2:1 or better.  Due to it's small size, approximately the size of a
KENWOOD TS-440S, I have taken it on a series of semi-DXpeditions and
have had success matching a variety of antennas.  I should point out
that I have owned four of these at various times and in various places
and always with consistent results.  I still own one and will keep it.
At $150 list price it works.  I probably should have been happy with it
and not gone further.

Two years ago when I owned a linear I purchased a MFJ-989C Versa Tuner V
which reportedly handles 3 KW PEP.  This tuner features a roller
inductor and did allow me to achieve an SWR of 1:1.  I sold it about a
year ago about the same time I sold the linear; it worked as
advertised.  100 watts is sufficient for my needs now.  :>)

Now I was back to a 949E without the rotary inductor, and I longed for
being able to tune to 1:1 SWR.  So I bought a MFJ-969 Roller Inductor
Tuner rated for 300 watts priced at $190 list.  This did allow me to
tune to a 1:1 SWR, but the inductor slipped and resettability (a must
for contests) was near NIL.  (This was after I straightened out the
plates on a variable capacitor in the tuner which were shorted.  Yes, it
DID have a quality control sticker on it.)  I talked several times with
Richard Stubbs who is evidently Martin Jue's "right-hand man" for
solving problems.  He immediately said, "send it back for a
replacement".  Since I had already straightened the plates I at first
said no, but in mid-December since the inductor was slipping I told him
that I'd like to pay the differance and upgrade to a unit rated at a KW,
the MFJ-962D, at $270 list but much smaller in physical size than the
989C.  I did upgrade, it was shipped via UPS during the Christmas rush,
and it arrived damaged.  Part of the reason for the damage, in my
non-expert opinion, was that it was NOT packaged properly.  In addition,
the "quality" was once again missing, as there was a 1/2" piece of bare
wire as well as some other "crap" floating around inside the unit; I did
not relate this to Richard, but simply asked for a replacement which was
finally shipped in late January.  This unit works fine, appears not to
have the slipping problem, and certainly will NOT have any problem with
the power which I am pushing into it.  Yes, the SWR is 1:1 with five
differant antennas:  a Cushcraft A3S tribander, a Cushcraft R5 5-band
vertical, an 80-meter Gladiator vertical with 4 full-size elevated
radials (performs super on 40 meters), a 40 meter sloper, and a 80 meter
Carolina Windom.  Yes, I am happy, but as you can see it did have a
price.

Why did I not homebrew a tuner?  I have done so it the past, and I
probably should have done so here.  Poor eyesight is the primary
reason.  Or perhaps I should have investigated other commercial tuners. 
(Good results with other MFJ products probably swayed me in this
decision, and certainly will in the future!)  Does a rotary inductor
make a differance?  Yes, I think so, but let the experts relate how much
degradation would result from 2:1 instead of 1:1 SWR with 100 watts into
the tuner using mediocre antennas.  Replies, please; would the
differance on the receiving end even be noticed?

73, Bob - W1VXV


--
FAQ on WWW:               http://www.contesting.com/towertalkfaq.html
Submissions:              towertalk@contesting.com
Administrative requests:  towertalk-REQUEST@contesting.com
Problems:                 owner-towertalk@contesting.com
Search:                   http://www.contesting.com/km9p/search.htm


<Prev in Thread] Current Thread [Next in Thread>
  • [TowerTalk] MFJ Antenna Tuner Design, Robert C. Boyd <=