Thanks to everyone that has written to me on the reflector and via email.
I've read everything you've written and hopefully your efforts have helped
me or guided me towards getting this antenna working better.
I've made some changes, bought some equipment/parts and built some stuff
per all of your advise. So I have some new observations and data and a few
more questions. I'd really just like to get this playing better for the
160m CW contest in a couple of weeks.
First, so I could use my antenna analyzer (by knocking down the 27.5KW AM
station just down the road) I bought a DLW Associates BCB brickwall filter
customized to have a strong dip at 1210kHz. It works great all across the
BC band and my transciever is happier and I can use it out at the antenna
to help the Comet CAA-500 analyzer actually make measurements.
I also ordered the 2.4" #31 toroids and some RG400 as suggested at the
often referenced K9YC website. I will build the choke as directed but for
now I am using a DX Engineering Maxi-Core feedline choke that is supposedy
effective to 160m but they provide no data sheet. I'll get the parts for
the K9YC designed choke this week and will substitute that right away.
The antenna (freshly measured and rehung) has a near-ground mounted feed
point. The insulated 14g THHN wire is a total of 135' in length. It goes
straight vertical for 90', makes a 90 degree bend and runs horizontally for
45'. It is well insulated at the end and it does not touch any trees at any
point.
I have attached 30 insulated wire radials each 42' in length (as suggested
in a K9YC presentation referencing a K3LC study in the NCJ) laying on the
ground roughly evenly distributed. The paper said that 12 radials would be
"adequate" but I had room and materials for 30 so that's what I laid out.
Here are some measurements I made and I can take others you may wish to
see. My analyzer does not sign the reactance value.
R=50 X=27 SWR=1.7 @ 1813 MHz
then also
R=50 and X=21 SWR=1.5 @ 1890 MHz
The lowest X value I could obtain is X=5 with R=35 SWR=1.4 @ 1845 MHz
This is with a 15' piece of coax from the feedpoint to the choke then a
very short jumper to the BCB filter then a short jumper to the analyzer.
I'll be able to put the choke right at the feedpoint (if that will make a
difference) when the toroid/RG400 arrives.
I measured the SWR curve and it starts at 2.0 @ 1800 and bottoms around
1.4 @ 1840 but it doesn't rise above 2.0 again until 1940. That is far too
broad, right? Lots of loss somewhere still?
So, that's where I am. It has worked US coast to coast, easily to Alaska
and Hawaii and to N. Cook. It is being heard in VK and I worked half a
dozen JAs all with 100 watts but I still think it has many problems. This
is definitely an improvement thanks to all of your tips and advise but what
can I reasonably do to make it better or am I at diminishing returns?
I'm willing to put some more time and energy into it and also take more
measurements if that would help. Any ideas?
73,
Todd - NR7RR
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