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Author Topic: Ideas for antenna / station improvement  (Read 1558 times)
KB2FCV
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« on: March 01, 2013, 08:42:25 AM »

I'm always looking for ways to improve my station on HF. Let me first start out with what I have. I have a 102' dipole antenna from trueladderline.com which has 600 ohm feed that comes straight into my Johnson KW matchbox. I am running ungrounded (no ground rods, etc). My antenna is up probably about 60-70 feet on the ends, I have one big tree in the front and a few in the back. The antenna wires are pointed North-South. It's a very tight fit as some of the antenna wire ends / insulator does go into the trees.

The antenna performance is pretty good. When the propagation is right I've worked into places like India, Bangladesh, and some parts of South East Asia (Laos, Singapore, etc). I think it tends to hear the best on 40-20m. 15 is ok, 12 and 10 can be a little tougher. 80m it seems to work well also.

There are times I'm wondering what I can do better to make improvements. Sure, I'd love a tower and a beam.. but finacially that's out of the picture for the time being. Just seeing what some ideas for improving what I have or perhaps other better performing wire antennas to work in the space I have.
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W1JKA
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« Reply #1 on: March 01, 2013, 08:55:44 AM »

  Have you considered and have room for a small homebrew 20m one element hex beam for some directability? Inexpensive to build.Sounds as though you already have what a lot of hams desire,a satisfactory antenna with height.
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N6AJR
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« Reply #2 on: March 01, 2013, 09:23:46 AM »

check out the MA5B, it will actually do fine on a 30 foot oush up mast with guys. and a medium rotor.
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WB2WIK
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« Reply #3 on: March 01, 2013, 10:56:58 AM »

A 102' dipole should be about a dB below an 80m 1/2-wave dipole on 80m, and very good on 60m, 30m, and 20m if you can achieve good matches on those bands.

It would normally be a difficult antenna on 10/12m because it's so long it will be directional off the ends of the antenna, with some long, narrow (skinny) lobes that have gain, and there will be substantial "negative gain" (loss, or nulls) in lots of directions that might be more useful for you.

I'd expect a N-S oriented long dipole like that to mostly work north and south on 10/12m, while it would mostly work east and west on the lower bands.

I like a good coax-fed parallel dipole better, for covering multiple bands.  Can provide real, predictable 1/2-wave performance on several bands using a single transmission line, and provide a good match to that line on all of them.
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W5WSS
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« Reply #4 on: March 01, 2013, 12:05:38 PM »

A rotatable trap horizontal multiple band dipole installed on a 40ft Rohn brand push up pole with good rope and anchors.
and a rotator sufficient for the job is a very good antenna system capable of working long distance dx 20m and higher.

A trap multiple band  sloper intentionally oriented with as much vertical orientation as you can provide for the lower bands will work very nice long distance dx on the low bands.

Two antennas and really good return for the money.

 The horizontal trap dipole will work the nearby sky wave on the low bands and the long distance from 20m and up.
The trap sloper will work the long distance on the low bands and upwards.

73
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KB2FCV
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« Reply #5 on: April 09, 2013, 01:02:07 PM »

Thanks guys for some of the suggestions.

I think I definitely want to focus on the higher frequencies. As WB2WIK predicted, my dipole works well on 80, 30 and 20m (as well as 40m). 10m/12m performance is pretty poor and I'd love to try adding some kind of antenna that would improve performance on those bands.

Any sort of tower would have to be self supporting or attached to the house as any guys would most likely extend into my neighbor's property. The few open areas that I can fit a tower are rather close to the property line... which opens up another concern of a potential beam or rotatable dipole antenna hanging over the neighbors property. I do have a M2 3el 6m yagi that replaced the old TV and TV rotator that was on the chimney (chimney is in center of house/roof) but I don't think I would want to put on any more / anything bigger than that on the chimney as a chimney is really not designed to support anything (the 6m yagi and rotator was about the same size and weighs a little less/has less wind load than the old TV antenna/rotator)

I've thought about a wire vertical for 10 or 12m... or perhaps a coax fed wire dipole for 10 or 12. Would it be better to try to get a wire vertical up in the trees somehow for some height or am I better off on the ground? I might add on the ground at the end of my property is a body of water, a freshwater river. I doubt that makes any difference. I recall having a wire vertical at my parents house as a teenager.. LOL it had a mount hot-glued to the peak of the roof  Shocked Shocked Shocked Shocked (and and expensive roof repair bill to show for it) I guess if I had a coax fed wire dipole for 10 or 12 I'd want to get it at a good height / orientation to aim towards Asia / South Pacific.

The trap dipole and trap slopers also sound like good ideas worth trying. I just helped my friend put up a 10-20-40 trap end-fed sloper so I'll be curious to see how he makes out with it.

I'm just brainstorming right now as springtime is here and the wx is getting nice to play around with some antennas.
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WB6BYU
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« Reply #6 on: April 09, 2013, 03:04:40 PM »

While you could try a vertical, if you have that much height available then
a horizontal antenna high in the trees will likely do much better.

Let's start by defining an objective:  we can look at an Azimuth map based
on New Jersey using NS6T's website here: 
http://ns6t.net/azimuth/azimuth.html

India spans from 15 to 40 degrees; Vietnam and parts of Indonesia are due
North;  Australia spans about 250 to 330 degrees, and New Zealand is
around 245 degrees.  And, of course, roughly the opposite directions for
long path.  It sounds as though your current antenna is working well for
more North/South paths, while an antenna that fires East/West will give
you better coverage of the East coast of Australia and New Zealand.

One simple approach is to make a half-sized version of your current
antenna and string it up between two trees about North/South:  maximum
radiation will be broadside on 20 and 15m, and a multi-lobe pattern on
10m.  Actually you can shorten it somewhat:  40' or so will give you a
broadside main lobe on 10m and all lower bands.  As long as it is at least
a half wave on the lowest main band of interest (say 17m or 15m in this case)
then it will work well on the higher bands and can be pressed into service
somewhat lower in frequency if desired.

Another option is a vertical loop.  Probably the easiest would be a delta loop
with the point down, fed at the bottom using open wire line.  A full wave
loop for 15m will also give broadside radiation on 12m and 10m, and can be
pressed into service on 17m and 20m.  That requires less than 20' of horizontal
space between supports, which may give you more options of how to place it.

You have enough height that there may be an advantage in using a broadside
array:  two straight wire radiators spaced perhaps 20' to 25' apart vertically
(one under the other) and fed in phase with ladder line:  that gives you some
gain at low elevation angles.  The wire lengths would be as discussed above.
Otherwise there are various types of colinear, arrays, etc. that can be hung
between the trees with more gain, but you do need to be careful because more
gain in one direction comes at the cost of less gain in another, where you may
also want to make contacts.
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