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K5WLF
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« on: December 18, 2011, 04:15:52 PM » |
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I have a Hustler 5-BTV mounted on my metal roof. No radials, just using the roof as the ground plane. Great antenna, I love it and it talks fine. For DX. But it's pretty much deaf and mute inside of 200-300 miles.
Are there any tricks to change the take-off angle so it's a better local/regional antenna? I'd cheerfully give up the super DX ability to be able to get in on the local/regional nets and ragchews.
I'm getting ready to put up an inverted-V for the short stuff, but if there's a way to tweak the vertical I'd much rather do that, since the vertical is a much better antenna format for my tiny city lot.
TIA,
ldb
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Steve - K4HX
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« Reply #1 on: December 18, 2011, 06:18:39 PM » |
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I can't think of anything easy to change on the vertical. Your inverted-V will do the trick.
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K5WLF
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« Reply #2 on: December 18, 2011, 06:25:26 PM » |
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I couldn't think of anything either, Steve. Just hoping some of the gurus here know something I don't.
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Steve - K4HX
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« Reply #3 on: December 18, 2011, 06:27:02 PM » |
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I suppose you could connect a horizontal wire of the top of it. But I'm guessing that's no less effort than putting up the IV.
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W3RSW
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Rick & "Roosevelt"
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« Reply #4 on: December 18, 2011, 06:29:17 PM » |
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What is the circumference of your house? Place a 30 ft. pole (30 ft. above roof edge line) at each corner. String a loop connecting the four poles. Feed it as a horizontal loop with a 4:1 balun. String plastic lanterns from the loop at 10 ft. intervals. Call it a Chinese Pagoda if any nosey neighbors ask.  Seriously - there ought to be a way to get somewhat, straight up radiation.. -a cloud burner from that metal roof. Perhaps a wire around the periphery at six feet or so away from the roof. Are all the roof panels really electrically bonded? Another thought. Electrically Isolate the roof and assuming it's 20 or more feet above ground, then lay a good ground radial system away from the house, then feed the roof with the center conductor of coax and the ground system from the coax shield. Suitable matching, baluns, etc. to take care of the mismatch squirrels. |
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RICK *W3RSW*
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Jim, W5JO
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« Reply #5 on: December 18, 2011, 06:45:37 PM » |
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Turn it horizontal. Elevate it as much as possible above the roof.
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w4bfs
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more inpoot often yields more outpoot
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« Reply #6 on: December 18, 2011, 08:12:38 PM » |
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I remember a discussion/article a few years ago that discussed ground mounted vs elevated mounted verticals ...it seems that if you elevate the vertical mounting just a few feet and slope the radials downward that the sloping radials will yield a high angle component of radiation without decreasing the low angle portion.
I had a trapped multiband vertical up a few years ago with the feedpoint up about 15 feet and 4 sloping radials ....thing got out like a bomb ... good on local and dx .... seemed to be about an s unit down over a dipole for local stuff
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Beefus
O would some power the gift give us
to see ourselves as others see us.
It would from many blunders free us. Robert Burns
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K5WLF
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« Reply #7 on: December 18, 2011, 08:20:57 PM » |
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I remember a discussion/article a few years ago that discussed ground mounted vs elevated mounted verticals ...it seems that if you elevate the vertical mounting just a few feet and slope the radials downward that the sloping radials will yield a high angle component of radiation without decreasing the low angle portion.
I had a trapped multiband vertical up a few years ago with the feedpoint up about 15 feet and 4 sloping radials ....thing got out like a bomb ... good on local and dx .... seemed to be about an s unit down over a dipole for local stuff
That might just be worth a try. The antenna feedpoint's not but about 2' above the roof, but it's about 15' off the ground. If that worked, it'd sure cut down on the Cu & Al overcast in the back yard. |
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ke7trp
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« Reply #8 on: December 18, 2011, 08:26:58 PM » |
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There was an article in a recent QST that talked about verticals at various heights above the ground. If you want a higher angle, you must raise the antenna above ground. It mentioned that getting it up .25 wavelenghts or higher the lobe starts to angle up. I had a R6 at 70Ft once and it worked great for both local and DX. I really miss it.
In your case, A horizontal wire even at 15 to 20 ft will out talk the vertical. Dont you have any trees or supports to add a wire?
C
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The Slab Bacon
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« Reply #9 on: December 19, 2011, 01:05:13 PM » |
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This works for me and puts out a good high angle signal. You could probably shorten it further if you absolutely had to. I've been using it for many years now.
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"No is not an answer and failure is not an option!"
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k4kyv
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« Reply #10 on: December 19, 2011, 01:36:58 PM » |
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My quarter-wave vertical on 160 doesn't work very well for distances less than about 100 miles. I've been told my 80m dipole tuned as a shortened dipole on 160 puts 30 dB more signal into Nashville than does the vertical. But out beyond a couple of hundred miles the vertical is better. At more than 800 miles or so the vertical is far superior.
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Don, K4KYV AMI#5 Licensed since 1959 and not happy to be back on AM... Never got off AM in the first place.- - - This message was typed using the DVORAK keyboard layout. http://www.mwbrooks.com/dvorak |
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Steve - K4HX
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« Reply #11 on: December 19, 2011, 02:06:09 PM » |
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It's not clear to me how sloping radials would create any high angle radiation. If they are symmetric and one-quarter wavelength long, little or no radiation will be produced by them. Even if they did radiate, how effective would they be at only a few feet above the ground?
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W2VW
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« Reply #12 on: December 19, 2011, 02:48:19 PM » |
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Make the physical length of the vertical longer than .625 wavelength.
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KM1H
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« Reply #13 on: December 19, 2011, 05:01:36 PM » |
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It's not clear to me how sloping radials would create any high angle radiation. If they are symmetric and one-quarter wavelength long, little or no radiation will be produced by them. Even if they did radiate, how effective would they be at only a few feet above the ground? They dont unless they are actually radiating when in reality it is the radiating feedline. Use a choke balun to prevent that and use some low horizontal antenna for NVIS work. OTOH, verticals are good for close in groundwave work as well as DX. Carl |
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Steve - K4HX
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« Reply #14 on: December 19, 2011, 05:14:56 PM » |
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If he can do that, he could just put up an inverted-V with the center at 0.625 WL. That would strap! Make the physical length of the vertical longer than .625 wavelength.
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ke7trp
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« Reply #15 on: December 19, 2011, 05:58:25 PM » |
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What about running 3 or more Ground radials off the base but having them angle UP instead of down?
C
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W4AAB
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« Reply #16 on: December 19, 2011, 10:03:30 PM » |
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I would forget the elevated radials and go with a dipole or inverted -Vee at .625 wavelength.
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flintstone mop
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« Reply #17 on: December 20, 2011, 11:06:06 AM » |
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YUP Do the VEE.
Broadcasters can do this with their verticals coz they have some play room to eliminate uwanted sky wave.
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Fred KC4MOP
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K5WLF
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« Reply #18 on: December 20, 2011, 06:39:02 PM » |
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I was hoping there might be some proven mod to the 5-BTV, but it sounds like going ahead with the Inverted-V is the best and simplest idea. I'll be able to get the feedpoint about 32' or so off the ground.
Thanks y'all.
Merry Christmas.
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KM1H
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« Reply #19 on: December 21, 2011, 08:45:45 PM » |
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That will be good for local QSO's unless you got big enough tubes to be heard. At 1/8 wave high the signal goes mostly straight up.
The vertical will give you very close in ground wave and also again beyond a few hundred miles. At 65' up a horizontal starts to get effective for long haul and at 130' you own the frequency.
Carl
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