To: <topband@contesting.com>
>Date: Thu, 02 Jan 1997 10:40:33
>To: Morel Grunberg <morel.grunberg@telrad.co.il>, "'Ham-ant'"
<ham-ant@ucsd.edu>
>From: "Paul D. Schrader" <n4xm@iglou.com>
>Subject: Re: MFJ-989 antenna tuner comments review - more
>Cc: "'Ahron Slonim'" <aron@jupiter1.tau.ac.il>, "'Ham-equip'"
<ham-equip@ucsd.edu>, "'Marv W6FR'" <w6frmarv@juno.com>, "'Moni'"
<xzk@shani.net>, "'Paul BRZ'" <aip@oradea.banat.vsat.ro>,
"'Radu HW'" <yo4hw@next.adcon.ro>
>
>I am the inventor of the XMatch (a registered trademark) Antenna Tuner.
>
>I am also a registered professional electrical engineer and a ham since 1953.
>
>The XMatch antenna tuner is NOT a T network tuner. It uses a patented
>circuit. And it really "does the job", including 160 meters.
>
>I do not agree with many statements made in the attached comments, but do
>not intend to debate them on the internet.
>
> 73 and DX, Paul N4XM
>
>
>
>At 11:38 1/1/97 +0200, Morel Grunberg wrote:
>>
>>Happy New Year, folks
>>
>>>From more than 100 answers I've got for my posting regarding
>>MFJ-989 antenna tuner, I'm feeling that is one more from a
>>professional one, I want to share with all of you.
>>
>>73 de Morel, 4X1AD
>>
>>>Subject: Re: MFJ-989 antenna tuner comments review
>>>
>>>I'm an independent RF designer. I started going through the MFJ
>>>tuners about a year or two ago. I feel insight into engineering facts
>>>is important. People should understand a few things about tuners
>>>in general, and the 989 in particular.
>>>
>>>I've yet to find any tuner (except the ATR-15 as advertised by
>>>Ameritron in the 80's, and the old EF Johnson KW Matchbox) that
>>>alway met power specifications as advertised. The ATR 15 was
>>>rated at the RF output power over a specific load impedance and
>>>frequency range, and the KW Johnson Matchbox was rated for a
>>>1 kW AM transmitter (about 750 watts continuous carrier and
>>>3 kW PEP modulation peaks, so it easily handles 1500 watts CW
>>>or PEP output).
>>>
>>>Power ratings are an offshoot of when PA's were measured by
>>>plate input power. For example, the SB-220 (I am a former RF
>>>consultant for Heath-Zenith) was advertised as a 2 kW PEP
>>>Input Power PA, but the SB-220 was really a ~1kW SSB PEP
>>>and 600 watt CW output PA.
>>>
>>>Matching tuners were called 2 kW tuners, because they went
>>>with 2 kW PEP INPUT POWER PA's (that really only put out
>>>600 watts or so CW, and 1 kW or so SSB peaks).
>>>
>>>Enter Dentron. They made PA's that were called 3 kW PA's, and
>>>only put out the same reliable power as the 220. Dentron called
>>>their matching 600 watt CW output tuners 3 kW tuners. The
>>>name 3 kW became "attached" to any tuner of the same basic
>>>quality components as Dentron's, and it seems to have stuck.
>>>
>>>A typical 3 kW tuner is actually a 600-700 watt CW (1200 watt
>>>PEP SSB) tuner by today's OUTPUT power standards.
>>>
>>>The MFJ 989 used a roller produced by Oren Elliot Products. It is
>>>an industry standard roller, and is similar or the same as rollers
>>>used in high dollar tuners. Unfortunately, the Oren Elliot roller has
>>>a delron form, it is the overall roller design that seriously lowers
>>>the power rating. Roller Q is absolutely NOT a problem of cabinet
>>>size or anything external to the roller, it is a problem of materials
>>>used in the roller and the basic roller design. Even the expensive
>>>ceramic form roller from Cardwell barely offers an improvement. It
>>>has almost the same loss, but the ceramic form does stand heat
>>>much better. The new design air coil roller used in the MFJ 989
>>>does help solve Q and heating problems, and the manual was
>>>also re-written to correct misinformation on how to adjust the
>>>tuner.
>>>
>>>As for power ratings, it is NOT correct to specify a power rating
>>>without specifying a load impedance and frequency. ANY
>>>manufacturer who says "this is a 3 KW tuner" without being band
>>>and load specific is just howling out a number that may not and
>>>probably will not mean anything to you. The only way to know for
>>>sure a certain tuner will work is to try it with your own antennas.
>>>
>>>T network tuners (like the 989, Xmatch, Vectronics, Tucker,
>>>Murch, etc) handle the least power on 160 and with capacitive
>>>reactance low resistance loads. T network tuners handle MORE
>>>power into higher resistance loads or loads with some amount
>>>of inductive reactance.
>>>
>>>L network tuners (like the Ten-Tec, Nye Viking, etc) handle more
>>>power into impedances near 50 ohms, but often do a poor job
>>>matching reactive or very low impedance loads on low frequencies. (Sometimes
>>>these tuners are called Pi-networks, even though
>>>they do not really function as a pi except perhaps on 15 or ten
>>>meters)
>>>
>>>In a T network tuner, maximum efficiency and power handling
>>>generally occurs when maximum and equal amounts of
>>>capacitance are used in the capacitors, and the least amount of
>>>inductance is used. This is true even though many other settings
>>>will produce a low SWR.
>>>
>>>I hope this dispells some of the hyperbole about tuners.
>>>
>>>73 Tom
>>W8JI
>>>
>>>.
>>>
>>
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>
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