I ordered a set of professionally tested phased feedlines from Comtek for my
80M 4SQR. They SIGNIFICANTLY improved the array's bandwidth and now allow me
to operate well within tolerance of both DX windows using a top loaded 1/4
wave vertical design.
I did not expect this big of an improvement. While the array's resonant
point remained the same, a lot else has changed.
First, Jim's phased lines were about 2 1/2 feet longer than mine. He tuned
them for around 3.650MHz. I thought mine were originally tuned from
3.800MHz, but had to cut them recently back due to water damage. They must
of been up near around 4MHz- But who knows as they each probably varied a bit
after being sliced and diced a few times-
The new lines reduced my power dumped at 3.500MHz from 23% down to 14% and I
was just slightly higher at 4.00MHz with old feedlines dumping 10% and the
new feedlines dumping 14%. At last I can be back in the CW window with a
decent F/B.
My 10% bandwidth of the array (as measured by power dumped into the dummy
load from the hybrid coupler) with the old lines was 3.600MHz to 4.000MHz has
changed with the new lines to 3.550MHz-3.900MHz. Slightly less with the new
feedlines but much less skewed towards the bottom end of the band making it
usable.
Also, while being able to push legal limit with either feedlines in the phone
window, I can now get the amp to push legal limit in the CW window vs only 1
KW with the old feedlines. If you are using a compromised 4SQR set up, and
you are looking for every way possible to keep your power dump at a minimum
due to shortened verticals etc..............you should have Jim make you up a
set. He has some terrific equipment to insure their accuracy which is
certainly reflected in my array's improvements.
I also got his vertical feedline feeders that will eliminate the problems of
water damage. These worked out very nicely and will make servicing the array
a lot easier. Now I can just unscrew a PL259 plug from the vertical feedline
vs having to scrape all the water proof crud off when disconnecting the old
style way of hooking up the center conductor directly to tha antenna.
Comtek is awesome and had a nice write up recently in The Low Band Monitor-
73 Paul N0AH
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