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Author Topic: rotatable dipole below fence  (Read 564 times)

WB0UQD

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rotatable dipole below fence
« on: January 17, 2020, 09:34:00 PM »

I'm not sure if anyone has asked this before...

If I have a 6 foot privacy fence, could I put a rotatable dipole in my back yard, at a height of 5 feet, 10 inches?

Thanks!!!
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K0UA

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Re: rotatable dipole below fence
« Reply #1 on: January 17, 2020, 10:24:49 PM »

I'm not sure if anyone has asked this before...

If I have a 6 foot privacy fence, could I put a rotatable dipole in my back yard, at a height of 5 feet, 10 inches?

Thanks!!!

Can you do it sure, but the real question to ask is how well will it work? some of that depends on what band ro bands this rotatable dipole is on. But even best case scenario it is on 2 meters or 70 cm. it isn't going to be great, but is this on 20 meters?  You are going to have quite a lot of ground losses. It probably will work after a fashion. you may need a tuner to get an acceptable  SWR match. That is pretty low.  People put 80 meter NVIS antennas that low and they do work for NVIS short range (3 to 300 miles) comms.  It might be surprising what you can work with a low antenna on the upper HF bands. but the old axiom of "everything works" holds sway here. I am sure if you can provide us with some more information, someone on here can give you a bit better idea of how well it will work for you. Again, everything works, it is just a matter of how well. I don't think this will work all that well, but hey it doesn't cost much to try if you already have it in hand.
So tell us the band, or bands, tell us the mode you intend  to employ (Hope you say digital and not phone) and tell us the power level you intend to run, and we will go from there. Have you considered camouflage paint?
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73  James K0UA

KH6AQ

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Re: rotatable dipole below fence
« Reply #2 on: January 17, 2020, 10:53:23 PM »

Taking the 20 meter band as an example, EZNEC shows the low dipole to be almost omni-directional at low take-off-angles. Its gain at a take-off-angles below 20 degrees is down approximately -12 dB (~2 S-units) compared to a dipole at 30 ft. It will work and you will make contacts.

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W4FID

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Re: rotatable dipole below fence
« Reply #3 on: January 18, 2020, 06:44:28 AM »

people use hamsticks on a trailer hitch or bumper mount on their cars. They work QSOs on 20. Even on 40. I have one on a 3 magnet mount on the roof of my Honda and can even work a few on 75. But you will be weak and in or below the noise level much of the time -- especially busy times like Field Day and contest weekends. In your situation it may not be worth the effort - or cost if you're talking rotor -- to have it rotatable. Just put it up and work whomever you work and enjoy whatever you can enjoy. ANOTHER WAY TO GO. A 16 or 18 foot painter's pole  from Home Depot. Comes down to about 6 feet and "hides" in half a minute. Goes up in half a minute and you'll do better with the dipole at 3 times the height. Also that height is approaching 1/4 wave on 20M so that's nicer too. Get really slick and have quick disconnects on the hamstick dipole center and a collection of hamsticks and you can easily change from 20 to 30 to 40 meters.
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K0UA

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Re: rotatable dipole below fence
« Reply #4 on: January 18, 2020, 07:21:52 AM »

people use hamsticks on a trailer hitch or bumper mount on their cars. They work QSOs on 20. Even on 40. I have one on a 3 magnet mount on the roof of my Honda and can even work a few on 75. But you will be weak and in or below the noise level much of the time -- especially busy times like Field Day and contest weekends. In your situation it may not be worth the effort - or cost if you're talking rotor -- to have it rotatable. Just put it up and work whomever you work and enjoy whatever you can enjoy. ANOTHER WAY TO GO. A 16 or 18 foot painter's pole  from Home Depot. Comes down to about 6 feet and "hides" in half a minute. Goes up in half a minute and you'll do better with the dipole at 3 times the height. Also that height is approaching 1/4 wave on 20M so that's nicer too. Get really slick and have quick disconnects on the hamstick dipole center and a collection of hamsticks and you can easily change from 20 to 30 to 40 meters.

There you go, that "quick hide" painters pole is not a bad idea.  A quick way to get some gain over the very low dipole  and still be stealthy.

Another idea for an all band antenna is a Little Tarheel II vertical mobile screwdriver antenna mounted behind that wooden fence with just the whip sticking up.  No one would notice a black whip.  Replace the stock 32 inch whip with a 4 foot Larson black thin whip. I have one on my truck. Of course you will need to run some radials on the ground, but that shouldn't be a problem for you.  I bet that will work better than the dipole with lower take off angles and will work from 80 thru 6 meters.  Only downside is the initial cost of around $400. I have worked many DX stations from my truck with this antenna on SSB.  I would imagine you could do the same or better from your house with a good radial field especially if you worked FT8. Of course 80 meter performance isn't great but can be enhanced if you can stand making the whip longer (can be horizontal or sloping too)
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73  James K0UA

W8LV

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Re: rotatable dipole below fence
« Reply #5 on: February 12, 2020, 07:38:00 PM »

It might work, but it will have very limited directionality.

A big loop around that fence might actually work a LOT better: And it won't have moving parts to mess with. And will be cheaper. And less noticed. HOA Jackboots and Gladys Cravitz Busybody Types may be about. Certain HOA Goons are now using Selfie Sticks to infringe on homeowners privacy rights where they raise the selfie stick RIGHT OVER YOUR FENCE, I kid you not, you can find them (and a LOT of really pissed off homeowners) on youtube when it comes to HOAs, despite the few Disgusting HOA Apologist Lap Dog Types who lurk here on eham.net and talk crap. Don't be a Victim- Forewarned is Forearmed!

For a vertical, consider a small one... even a mobile, and put lots of radials under it. This is where YOU have a fantastic advantage! No one has ever fallen to their Death from radials being laid on the ground, either... Nor do they come down in bad weather. Though  I've tripped over a few... ;-) The radials do NOT have to be in a fan arrangement directly under the driven element. On a corner, just lay them out, the more the merrier, but even ONE will work. (Which is how the "Paliepole" Vertical works...)
SURE more radials work better, and SURE they work best fanned out in a circle, and SURE your signal is going to somewhat be "bent" with corner radials. But they'll WORK. Better than you think!

 If you have an "edge" on say the side of your house, run a vertical element up there. You can even bend the last part of it to up the side of the roof. Or "caulk one in" on a nonmetallic edge. Much like the radials, the vertical radiating element does NOT have to be perfectly straight!!!
 But I'd try the loop first, if I was in your shoes. It may be electrically QUIETER than the vertical anyway. With a good s/n ratio, you can HEAR THEM better.
You might even put up BOTH types of antennas and have fun with an "AB" comparison!

I wouldn't worry about the measurement of the loop, either. Just a big loop around the whole fence, feedline (not coax if you can, or just a short one if you must) feed it at the corner with an autotuner (preferably weatherproof grade and stick it in a box/shed or hey you could even bury it (again!) if you are dealing with SS Grade HOA Antenna Nazis, even one of those fake plastic rocks (in the city you can hide one in a Telco box... they're easy to obtain or just take a plastic grey box and put a logo on it or something.)
An autotuner can also go into a plastic trash barrel and the feedline can run into the dwelling through an already existing access. (They always drill them out too much so there's almost always space there and then there's also dryer ducts that aren't really dryer ducts... ;-))

If you go the vertical route: Don't attract a bunch of attention to yourself! And don't try to do this at night, because if you think that this is the best time to pull of an antenna installation, then you've watched too many Hogan's Heroes reruns. A couple of your buddies, a van, and a couple of hard hats can easily do this for you. THEY WON'T LOOK OUT OF PLACE PRECISELY BECAUSE THEY ARE UNFAMILIAR! They just show up, in daylight, best time is just after the HOA office has closed say on a Friday, or even on a lunch hour. Trust me on this, and read my other posts.
And you'll be in a position someday to be a "construction worker" at THEIR respective QTH's. No Ham tags, just get in and get out: You can gloat like 'mutas over beers later. And you will! If you thought Antenna Raising Parties were fun, well COVERT Antenna Raising Parties are a blast!

Look at my logbook. You can work everywhere QRP. Despite the sunspots. Despite the glossy ads for "Steped on an Infrared" and "Hi Flashover" Antennas , and Shooting Star Antennas, and The Hustle Antenna. (No doubt someday they will be monthly centerfolds... Have you laid eyes on the "Miss February" Antenna yet?)  It's not a boast: EVERY QRP Op knows it and does it!

Good Luck and
73! Let us know how it worked! You can see my very modest vertical mobile on a tripod home setup by looking me up on QRZ.
OR let me know by direct email w8lv (at sign you know what to do)arrl dot goes here net.

Caveat Emptor. NoTrademark was infringed upon in the writing of this message.

DE W8LV BILL
« Last Edit: February 12, 2020, 07:53:31 PM by W8LV »
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KL7CW

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Re: rotatable dipole below fence
« Reply #6 on: February 13, 2020, 11:32:18 AM »

Perhaps a decade or so ago, when propagation was much better, I operated from my daughters house in a typical suburban subdivision in California.  Tried a few antennas close to her house, too noisy.  Laid a 40 meter dipole along the back wooden fence top rail which was not too close to her or other houses.  Was acceptably quiet on RX and made some nice CW QSO's running about 1 watt on 40 meters out to perhaps 200 ? miles during the day.  I was sitting right at the center point and my rig had a built in antenna tuner, and I believe at least one leg of the dipole was shorter than 34 feet.  If I lived there, I think this would be an OK RX antenna, and hopefully I could use a better antenna near the house for TX.  Back then even 40 meters supported NVIS or near (NVIS) sometimes during the daytime, but not likely now.  If you have a wooden fence, you could try a 40, or probably better idea an 80 meter dipole, even with short legs on the fence with an automatic tuner at the feed point, even with our poor propagation, 75 and 80 meters should work OK during the day out to at least 100 miles, and may occasionally be OK at dusk, or into the early evening hours.  I think my antenna was about 5 feet high and just laid on the top rail a few inches below the top of the fence.  All bets are off if you have a concrete block, or chain link fence.  Just something to think about, not saying it will work.  Your biggest challenge may be RX noise and not how to TX a signal.  So try a few simple experiments on RX first, before you spend money on an ATU, or other expensive devices. We travel around the USA and overseas and mostly I only operate portable from parks, trails, etc. not from houses in subdivisions, and yes it is possible even from Alaska and northern Norway in the winter, although this is not everyone's cup of tea.    Cheers,   Rick KL7CW
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