[TowerTalk] Tuners

[Jim Reid]

> Hi all....In your opinion, who CURRENTLY makes the 
> best hi-power antenna  tuner on the market??? 
> Thanks....Al/W8FAX

Or,  similarly,  which woman will be the best wife?

But anyway,  for "real"  QRO:  Palstar AT4K,
see,  http://www.palstarinc.com/palmain.htm

For 160 and 80 QRO,  have a look at the
"Classic Lowbander - XMatch"  by N4XM,
ads in QST usually.

"Least"  expensive of these,  but excellently engineered
tuner,  good to 3kW,  see the Ameritron ATR-30,
ads in many QST, CQ issues.  

Look for input/output variable C's with highest
pF ratings and wide plate spacing.  XMatch
has a fixed set of C's in parallel which can
be switched between the input or output
side of the T tuner.  Usually,  highest efficiency
obtains when either the in or our variable cap
is at the maximum setting.  

Palstar allows up to 700 pF,  6 kV capacitance
on the output;  high output C is needed when the
real part of Z is below around 25 or so ohms.
This can happen most often with vertical antennas,
which are "short" compared to the radiated wavelength.
Input variable of AT4K is 350 pF max, 7.5 kV unit.

XMatch switchable fixed bank of C's is a total of
575 pF,  5 kV rating.  Don't know the cap value
of the BIG,  dual section variable cap in this
unit,  but it is big,  and sufficient!  Note,  this unit
has no metering,  nor choice of antennas;  only
bypass and to a dummy load.
See: http://www.c-space.net/xmatch/

For the Ameritron ATR-30,  see:
http://www.ameritron.com/ameritron/products/accessories/atr30.html
note their spec shows "over 500 pF capacitance",  not sure
what that means exactly,  hi.  Their ads in QST many months
ago used to give the values of each capacitor;  I couldn't
lay my hands on an issue old enough,  look through 1999
issues for the Ameritron ads of the ATR-30.

If you know the R and X of your antenna system,  that is
at the end of the feedline in your shack (you do have
an MFJ-259B or similar antenna analyzer,  right?),
you can go to the tuner simulator site at the University
of Chicago,  and learn exactly what tuner component
values you will need for any band/frequency for which
you can input the R and X at the feedline terminal
which will be "screwed"  onto the tuner output
terminal.  Go to:
http://fermi.la.asu.edu/w9cf/tuner/tuner.html

This simulator was set up by Kevin, W9CF.  Read
the brief instructions and enter your R and X values,
along with the values of the tuner components,  if
you know them;  otherwise just accept the default
values provided.  You will know in an instant the
C and L values needed within the T tuner to
get a 1:1 match and highest transfer efficiency for
your particular antenna system conditions.

Have fun.

73,  Jim,  KH7M




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