[TowerTalk] Matchbox Info - Addendum

[Jim Reid]

Forgot to include a couple of points also from Russ,
NM6DX.

First,  about the modified Matchbox:

"You have two more variables than with a non-modified 
matchbox. They are the input coil tap switch and the input 
link variable capacitor. These can lead to ambiguous tuning 
of the system. Use of a computing power meter that
displays forward and reflected power simultaneously 
and VSWR is recommended for tuning ease. I used an 
Autek power meter and this works very well."

And,  also:

"If the tuning caps are close to a limit on any band then 
the easy way to correct this is to change the open wire 
feed line length."

One suggestion made for the low bands:  add 11 feet of
line.  Long enough to make a difference,  but not too much
to handle,  probably.

"It should be noted that the 275 watt matchbox uses plastic
coil supports. This tuner should not be used to drive an 
unbalanced load. It is very easy to get tuning that results in 
high circulating currents in the tuner. This heats the coil in 
the tuner. The plastic coil supports are then subject to
melting! This is not a problem with the KW matchbox because 
of the use of micalex for the coil supports."

Very complete set of info from you guys!!

73,  Jim,  KH7M






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