Guys, read what he wrote, not what you think he wrote.
He had a question about the operation of the metering in the KAT500, he wasn't
looking for advice on antenna design or on the use of ladder line.
If he wants that he can read my paper here:
http://k6mhe.com/n7ws/Ladder_Line.pdf
11/4/2015 3:37 PM, Fred Jensen wrote:
On 11/4/2015 12:59 PM, Phil Hystad wrote:
I use the KAT500 with my 80-meter dipole fed by ladder line and a 4:1
Balun to Coax for last 20 feet. This antenna works excellently in
concert with the KAT500 for 80, 40, and 30 meter bands. I don’t use
it with other bands.
Feed point Z's:
1.9: 5.6-j1149
3.9: 78+j2
7.2: 2703+j2201
Your ladder line will transform these impedances to something else ... unless
it happens to be a multiple of a half-wave at one of those frequencies. Tell
me how long it is and we can calculate what it looks like on the high side of
your 4:1 transformer. I don't recommend holding your breath that it will be
good on all three bands though.
This weekend, I was curious as to how close (or far) the KAT500 could
bring the antenna in for the 160 meter band. I knew that it would
not work though I was wondering how bad it would be.
The radiation resistance on 160 will be very low and the 4:1 transformer will
divide it by 4, meaning just a tad above 1 ohm. It is also very reactive.
If you really want to use it on 160, try shorting the ladder line at the feed
end, remove the transformer, and connect the shorted end to the coax through a
variable cap. Run 1 or 2 wires on the ground from the coax shield and see if
you can feed it as a Marconi-T.
If your ladder line is 60 ft long, feed Z at the shorted end of the ladder
line will be about 110+j1400 and an Xc of 1400 ohms will probably work fine
for the KAT500.
So, as I expected, the tuning never closed in on a descent SWR, the
best I saw on one test only was SWR about 49:1 as reported by the
KAT500 utility. But, the BYPASS SWR reported was about 11:1.
SWR meters, which usually measure VSWR are fairly unreliable at high values of
mismatch.
73,
Fred K6DGW
- Northern California Contest Club
- CU in the Cal QSO Party 1-2 Oct 2016
- www.cqp.org
Message delivered to w...@triconet.org
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