K1TTT Technical Reference

 
Subj:   Summary of SWR Analyzer Comments
Date:   94-08-09 01:28:43 EDT
From:   KWIDELITZ@delphi.com
To:     N1MM
 
MFJ-247 has worked well on 2 dxpeditions and here at home.  Have not
tried the others.  73,
Glenn, W6OTC (mgvinson@crl.com)
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I have the MFJ-249. Haven't been convinced that the SWR is accurate
during much of antenna work here. Used MFJ to tune to lowest SWR, but
then used SWR on rig to really measure its value and bandwidth. Am
currently thinking of buying Autek unit -- mainly because I'm interested
in measuring impedance with something less expensive than a General
Radio Antenna Bridge.
73 de Bruce, WA7BNM   (bhorn@netcom.com)
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Hi Ken,  I have the AEA SWR analyzer and I think it is just fantastic.  I
take it on my DXpeditions and I can tune my antennas from the outside in a
fraction of the time that it used to take me to keep going in and out of
whereever I'm staying to take measurements at the rig.
 
Being that it is easier, I find that I tune it better as when using the old
method the words "close enough" used to surface quickly.
CUL, Dave, WJ2O
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I have the AEA.  N4RJ has the MFJ and I have used it of course.  The AEA has
75ohm capability.  The MFJ does not.  Other than that, the AEA is a very
professional looking piece.  The MFJ... Well, it looks like MFJ if you know
what I mean.
BUT!!!
The MFJ is easier to use in my opinion.  I like having a meter to dip rather
than punching in frequencies and waiting for the the computer to figure out
the SWR curve.  The AEA has this feature where is will beep at you and the
faster it beeps the lower the SWR.  That is kind of neat I guess?  I havn't
used it yet.
 
Considering the price difference, if I had to do it again, I would buy
the MFJ.
Bill Fisher, KM9P
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The MFJ is awesome............it will save your sanity and a lot of
time.  We build temporary phased array for 80 and 160 Meters at our
contest stattion in the Carribean V31DX.  I cant even begin to explain
how much easier it is to set it up.
 
Also very usefull for analyzing Veloctiy factor of Coax, good vs. bad
coax etc.  It really takes the guesswork out of a lot of the mysteries of
antennae and feedlines.
* Victor Burns - KI6IM / V31VB               *   CUBA LIBRE CONTEST CLUB
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I just ordered the autek unit,  It has more features for the money
than all of em.....Tried an MFJ and it measured to high an swr into
a bird 50 ohm dummy load.
 
It went wild above 21 mhz.  Ill let you know hw this one works
when I get it.....but for 129 bucks with all those features it s a
hands down winner, if it works as advertized
CU Jay WX0B
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I had the original MFJ HF one, then upgraded to the one which goes  through
170 MHz, though not the one with the internal frequency counter (instead  I
put  the difference in price toward one of the  Optoelectronics  counters),
though  the internal counter would certainly reduce the amount of  jugling.
If  I tuned antennas every weekend, I might be tempted to get the one  that
draws SWR curves, but it's a lot more expensive.  For typical tuning,  with
a  frequency counter in or near the analyzer, it takes only a  few  seconds
turning  the sweep knob to find the low point and edges for any  given  SWR
cutoff (in fact it takes little time to make an all-band survey of all  the
dips).
In terms of absolute SWR accuracy, I am not overly impressed, but where  it
says SWR is low, it has been low to the radio and everything else.
 
I certainly could not imagine ever going back to on-air transmitting to do
SWR tests for antenna tuneup (even when I had to use a Drake TR-7 as the
frequency counter!).
From:   IN%"palomino!darrel@uunet.uu.net"
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Between the MFJ and the AEA, the AEA wins hands down.
It is an extremely powerful diagnostic tool.
 
The computer interface is crude, but it is a good start.
Tom, K5RC
_____________________________________________________________________________K
I have the basic MFJ one. It works fine, but I should have bought the one
with the built in frequency counter as the analogue dial is not that accurate
and it is necessary to go back indoors and check the actual frequency by
listening for it on the station rx. We also had some problems with the unit
earlier this year, operating from the TV transmitter site on GJ. Because the
built-in SWR meter is looking for rf coming back down the co-ax, and there
was plenty of that from the TV tx!, it never did show a low SWR, hi.
 
My friend G3ZAY has the AEA meter with the spectrum display. It's everything
a ham could want, but of course you pay the price - it costs more than twice
as much as the one I have.
 
So it's the old story, you gets what you pays for.
73 Don G3XTT, field@btq2ec.igw.bt.co.uk
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K1VR:  KA1BQ has the MFJ with the Optoelectronics frequency
readout.  I believe that they are now combined in one MFJ
unit.  We use it for tuning the omega match on my gamma rod
to load the tower to EXACTLY 1832 KHz.  Used to accomplish
this task by hauling a table out to the tower, with AC line,
TS-820, SWR bridge, tarpaulin to protect from snow falling
from branches, etc.  Hauling, set up, tuning, etc. would
take 1 hour.  Now it takes six minutes.  When the temp is
minus 10 F, six minutes is a lot better than one hour.  We
love it.
Fred Hopengarten K1VR  internet:  k1vr@k1vr.jjm.com
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Thanks all for your input. I found the MFJ-259 in the HTYS for $135 and 
bought it. At that price, if I don't like it I can sell it for what I paid
for it and buy something else!
 
73, Ken, AB6FO KWIDELITZ@DELPHI.COM
 


MFJ 249/259 calibration procedure:
 
Rick's comment is surprising, since MFJ sent me the complete calibration
procedure a few months ago, but FWIW, here is the SWR and Impedence
procedure.
 
1. Set the unit to the 1.8-4 Mhz band.
 
2. Make a 100 ohm dummy load (100 or 2 50 ohm in series or whatever
installed in a PL-259 with leads as short as possible. 
 
3. Looking at the circuit board with the tune capacitor at BOTTOM RIGHT,
IC1 is about 20% down from the top on the right side of the board.
The pot to the left of IC1 is R-17, the SWR adjustment. The pot in the
middle of the 3 below IC1 is the resistance pot. 
 
OK, here we go...
 
4. Turn the unit on 
 
5. Use the 100 ohm dummy load and adjust R17 until a 2:1 SWR is
obtained.
 
6. Replace the 100 ohm dummy load with a 50 ohm dummy load.
 
7. Adjust R31 until 50 ohms resistance is read.
 
8. Repeat as necessary until SWR reads 1:1 and impedence meter reads
50. ( never could get mine exactly on 50, but close enough )
 
And that's it. Don't mess with R-32 ( left hand pot ) or R-18 ( right 
hand pot ( AGC ).
 
BTW, just in case anyone is interested, the pin numbers for IC1 are:
Pin 1. Bottom right. Pin 7 Bottom left. Pin 8 Top left. Pin 14, Top
right.
 
Hope this helps.
 
73
 
Ed