KAT100 80 Meter Problem

[Lowell-8]

My antenna is 137 ft CF with about 50 ft of 450 ohm ladderline terminating into a 9 to 1 balun with about 20 ft of coax to the K2/100/KAT100.  It works great---1 to 1 VSWR 160 through 10 meters.  However to get a decent VSWR at the low end of 80 Meters, it is necessary to hit the tune button at approximately 3600 Khz then tune down about 6 Khz at a time, hitting the tune button, step by step to get to the low end of the band.  Once there I can go to other bands, then come back to the same 80 Meter frequency and still get the 1 to 1 VSWR.  If I would hit the tune button say at 3570 Khz, then go back to the low end I would end up with about a 3 to 1 VSWR.  It would be necessary to creep it down again.  A 4 to 1 balun exhibits the same condition.  Adding 20 ft of ladderline made no appreciable difference.    Adding 3 ft of coax eliminated the problem,  but messed up other bands. I feed the coax to the center coil of the trifilar winding with the ladderline tied to the outer ends of the other windings.

This problem was not experienced when I had the balun in the shack, but put it outside to get rid of RF in the shack.

So, the tuner is capable of tuning whatever the impedance is at the low end of 80, but for some reason it needs help to get there.  Would appreciatel any comments.  73, Lowell, W5FH
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[Dan Barker]

Does it do the same thing (require weird procedures) when you use the ALT
mode instead of Auto? It's supposed to be more aggressive.

Dan / WG4S / K2 #2456 (KAT2; hopefully the  KAT100 has a similar menu
function)

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]]On Behalf Of Lowell
Sent: Thursday, March 29, 2007 2:23 PM
To: [hidden email]
Subject: [Elecraft] KAT100 80 Meter Problem


My antenna is 137 ft CF with about 50 ft of 450 ohm ladderline terminating
into a 9 to 1 balun with about 20 ft of coax to the K2/100/KAT100.  It works
great---1 to 1 VSWR 160 through 10 meters.  However to get a decent VSWR at
the low end of 80 Meters, it is necessary to hit the tune button at
approximately 3600 Khz then tune down about 6 Khz at a time, hitting the
tune button, step by step to get to the low end of the band.  Once there I
can go to other bands, then come back to the same 80 Meter frequency and
still get the 1 to 1 VSWR.  If I would hit the tune button say at 3570 Khz,
then go back to the low end I would end up with about a 3 to 1 VSWR.  It
would be necessary to creep it down again.  A 4 to 1 balun exhibits the same
condition.  Adding 20 ft of ladderline made no appreciable difference.
Adding 3 ft of coax eliminated the problem,  but messed up other bands. I
feed the coax to the center coil of the trifilar winding with the ladderline
tied to the outer ends of the other windings.

This problem was not experienced when I had the balun in the shack, but put
it outside to get rid of RF in the shack.

So, the tuner is capable of tuning whatever the impedance is at the low end
of 80, but for some reason it needs help to get there.  Would appreciatel
any comments.  73, Lowell, W5FH
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