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N0AKF
10-26-2012, 05:37 PM
Any thoughts on rotatable dipoles v Vertical Antennas for HF (10 / 20 / 40 meters)? I would be able to mount on a small tower approx 28' above the ground. Thanks for the input!

K0RGR
10-26-2012, 05:39 PM
On the higher bands, particularly 15, 12, and 10, the rotary dipole even at that low height would have at least a slight advantage.

WB2WIK
10-26-2012, 05:40 PM
Rotatable dipole is overall a better choice, provided it's well made, offers sufficient bandwidth, and you can rotate it!

N0AKF
10-26-2012, 05:44 PM
Thanks for the replies! I am still trying to decide what route to go. Since I am not going to be up too high I am not sure a beam would be worth it. The rotatable dipole looks interesting. Looks like a light duty rotor would turn it too. Any recommendations on brand/model?

WB2WIK
10-26-2012, 05:45 PM
Thanks for the replies! I am still trying to decide what route to go. Since I am not going to be up too high I am not sure a beam would be worth it. The rotatable dipole looks interesting. Looks like a light duty rotor would turn it too. Any recommendations on brand/model?

Cushcraft D4 and Yaesu G450 rotator (or Hy-Gain CD45-II rotator) would do it.

N0AKF
10-26-2012, 05:50 PM
THANKS! Will look into those :)

WB2WIK
10-26-2012, 05:51 PM
Make sure the tower has the rotator plate installed in it. If it doesn't, you'll need one.

AA8IA
10-26-2012, 06:02 PM
Make sure the tower has the rotator plate installed in it. If it doesn't, you'll need one.

The OP didn't say if he was wanting to work DX or not. I"m assuming he does. Are you not weighing in on the dipole vs vertical thing, or are you suggesting that he should go with a rotatable dipole and that it should do well @28 feet? If the latter, on 40m wouldn't a vertical perform better at nearly every useful DX angle than a 40m dipole @28 ft? I'd do a rotatable 10-20m dipole @28ft, but I'd think a 40m dipole would be a waste at that height unless stateside / closer DX is all one cares about.

Your thoughts?

Mike

N0AKF
10-26-2012, 06:07 PM
THANKS for the info! My concern is that I won't have much height so am trying to figure out if a beam/rotatable dipole for HF would be worth the cost. A vertical and a wire antenna are also possible. I am looking to dx mostly :)

KH2G
10-26-2012, 06:15 PM
A full sized dipole for 40M is about 63 feet depending on where in the band you want to operate. You might consider useing a rotatable dipole for the higher bands and a vertical for the lower. There would be tradeoffs either way but a full size 40M dipole is pretty big if your thinking small rotor.
Regards.
Dick

WB2WIK
10-26-2012, 06:16 PM
A very good 40m vertical over a great radial field probably is a better DX antenna than a dipole at 28 feet.

But the ground reflection gain enjoyed by horizontally polarized antennas is large and includes a big lobe that covers low and medium angles pretty well even at that height on 40m. It would be better at 65 feet elevation. The S/N advantage that can be often had with a rotatable antenna is pretty significant; can't work 'em if ya can't hear 'em.:o

WB3BEL
10-26-2012, 06:53 PM
Even at 28 feet a beam for the upper HF bands 14MHz + will likely be massively better for DXing. It will provide rejection of interference off the main beam which is very useful especially if you have local QRN.

Ground gain is also a major benefit of horizontal polarization if the antenna is high enough and your terrain is conducive. For almost everyone this is true with a few exceptions like those living on salt water or badly sloping terrain or super low antenna. This is another plus for rotary dipole or beam antenna.

At this height a vertical will likely be better for 7 MHz for DX.

I'd put up a small beam and shunt load the tower as vertical for the lower bands.

N0AKF
10-26-2012, 08:32 PM
My location is pretty good - one of the higher areas around (remember it's Iowa so not that high :) ) There is a cell phone tower next door to us as it is the high point of the area. Thank you for all the help! :)

WB2WIK
10-26-2012, 08:35 PM
My location is pretty good - one of the higher areas around (remember it's Iowa so not that high :) ) There is a cell phone tower next door to us as it is the high point of the area. Thank you for all the help! :)

Elevation above sea level doesn't mean much on HF. Soil conductivity below you is generally more important.

I'm envisioning running a wire antenna over to the top of the cell phone tower...:p

PA1ZP
10-26-2012, 08:42 PM
Hi N0NKF

I think that a rotatable dipole does the better job on 14-30 MHz.
On the bands 40 and 80 mtrs a vertical will do a better job on DX if the vertical is full size.
I had many verticals from 10 t/m 80 mtrs (all full size even a colineair 2 x 5/8 vert for 10mtrs)
Vertical or horizontal is very simple if you have half wave hight the dipole will be a better choise.
If you can not make the half wave hight for a dipole the vertical can do a better job.

For what brand and type , pse do not ask me I once bought a HF antenna and the disspointment was that great, since then I only use homebrew antennas.

73 Jos

N0AKF
10-26-2012, 08:42 PM
Now if I could run a wire to the top of the cell tower - that wold be a nice sloper! :)

WB2WIK
10-26-2012, 08:47 PM
Now if I could run a wire to the top of the cell tower - that wold be a nice sloper! :)

I'd be tempted.

Of course, next time they send anyone out to service their site, they'd probably remove it. But who knows? That might be a year from now.

N0AKF
10-26-2012, 08:56 PM
The cell tower looks like a big flag pole so would be hard to scale :) But I am thinking that the rotatable dipole might just be the best bang for my buck :) 10 - 20 meters will be my main stomping grounds. Just 10 for now until I upgrade ;)

WB2WIK
10-26-2012, 09:17 PM
I agree 10-15-20m can be your "DX" bands, leaving 40m as your "rag chew band," and where you can get in touch with more local hams (40's great daytime out to 500 miles or so, then stretches out after dark; the higher bands are rarely good for close work).

Get your feet wet a while and you can always change or add stuff later.

I find it almost amusing when a "new" ham says "I want to get on all the bands, 160m through..." -- it shows they've read about those bands but haven't experienced them yet. Almost nobody can do this without a lot of experience or a very big budget.

N0AKF
10-26-2012, 09:26 PM
So true! 10 is my only choice at the moment, but 20 is the other band I hear a lot of activity on. Those will be my main 2 bands ;) Thanks again for all the info!

AA8IA
10-27-2012, 01:33 AM
So true! 10 is my only choice at the moment, but 20 is the other band I hear a lot of activity on. Those will be my main 2 bands ;) Thanks again for all the info!

Now is definitely the time for 10m. I encourage you to upgrade, but with that said, this year and next year are probably going to be the best years for 10m. A rotatable dipole at one wavelength (28ft is close enough) is going to give you some really nice DX on 10m when the band is open. A 10-20m rotatable deal (any combo i guess from 20/17/15/12/10) will be great. Wait a few years until the high bands start going south, and then focus on DX for 40m+.

BTW, I'm in much the same situation with you as far as height. I'm constantly weighing my options. I do have a dipole up, in a Vee, with the apex higher, and I almost have DXCC on 40m. So you definitely can work DX with a low antenna on 40m. It's just harder than on the high bands.

Mike

N0AKF
10-27-2012, 01:56 AM
Thanks for the reply! Tower gets delivered Sunday so will know more then :)

KC8VWM
10-27-2012, 04:41 AM
Thanks for the reply! Tower gets delivered Sunday so will know more then :)


The only antenna that will beat a rotatable dipole is a Yagi antenna. Remember, the difference between a rotatable dipole and a Yagi array equates to the addition of just one single element.

The main advantage of using a vertical on 40,80 and the 160 m bands is in the fact that you can use/install them at lower heights to significantly reduce ground losses as opposed to the idea of installing a dipole on those bands at a frequency related lower height above ground level instead. On these bands, IR heat losses can be significant at these lower heights. In other words, that is to say, a horizontal dipole on 20 thru 10m meters will perform quite well at a height of 28 feet but not so much for the 40,80 and 160m bands by comparision. In fact, on the 20 thru 10m bands, regular DX should be a daily event and overall performance would be stellar using such a setup and 33 feet up would be just about perfect.

In addition, I think its a fair statement to suggest that a rotatable dipole works better than an inverted V by direct comparison. The main idea with any antenna installation is to install the entire antenna in the clear and above any ground clutter that would reduce your signal to the horizon. This doesn't mean the antenna has to be mounted at 200 feet above the ground in order to achieve this objective, especially when we are talking about HF bands. After all this is not VHF. This is because we are mostly dealing with take off angles (TOA) and not line of sight (LOS) communications on HF bands.

Additionally, another improvement you can make to a rotatable dipole is to add capacity hats to the ends of the antenna. This improves currents flowing on the antenna. Another suggestion is to install a choke at the feedpoint. Such methods serve to increase efficiency and radiation resistance. This combined with the idea of reducing ground losses is key to the success of any antenna installation.

Also if I might add, my own elmer of long ago, once told me any homebrew rotatable dipole exhibits at least an additional 3 dB gain over any commercially purchased antenna.... :) So, if you should need help in this area just ask.

My Best,

N0AKF
10-27-2012, 06:30 AM
Thanks for the info! Would you happen to have a link to plans for one? Am getting excited about this project! :)

N0SYA
10-27-2012, 07:38 PM
Something to consider if you're going the dipole or yagi route is to make the tower itself a vertical antenna. I would run a wire a ew feet from the tower up to just under the rotator to a yard arm and ground the wire to the tower. Feed the wire at the base, tie the outer shield of the coax to the tower ground and use a tuner with your new multiband vertical. Heat, serve, enjoy.

N0AKF
10-27-2012, 07:56 PM
Good idea! THANKS!

KC8VWM
10-28-2012, 06:22 AM
Something to consider if you're going the dipole or yagi route is to make the tower itself a vertical antenna. I would run a wire a ew feet from the tower up to just under the rotator to a yard arm and ground the wire to the tower. Feed the wire at the base, tie the outer shield of the coax to the tower ground and use a tuner with your new multiband vertical. Heat, serve, enjoy.

See this is where things get entirely redirected into something else on these forums. I would like to help but I am always facing this sort of thing....Sorry.

NH7RO
10-28-2012, 05:16 PM
I used to have a rotatable folded dipole fed with twin lead to a 4:1 current balun at ground level.
Worked a ton of DX on 20 meters with it and it was only about 30-32' high. I used a bamboo pole that I cut down nearby and mounted next to our kitchen door. I could run into the kitchen, reach out and Armstrong the dipole to the right "beam heading" easily.

I concur with what others said, especially about using a vertical for 40 but using the dipole for 10-20; except you might find a bit more bandwith with a folded version. Very quiet receive, too since it is essentially a closed loop.

73, Jeff

N0AKF
10-28-2012, 07:37 PM
ok tower was delivered today. It is a Rohn 25 and is 20 feet tall. So it should be perfect - by the time I plant it in cement the top should be about 5' above my roof. I will add a 5' or so mast so will be about 20-22' above ground. Might not be best for beams and such but will be perfect for v/uhf, scanner and as an anchor for longwires. I think I will put the 10m vertical (will replace down the road with a multiband vertical) on some chainlink fence post as mast about 2 or 3 feet above the roof line. I have quite an over hang on my roof so can only get 1 mount in. I plan on putting the fence post into the ground a few feet and ru the mast up an anchor it the eave. Looking forward to this antenna project! :)

N0SYA
10-28-2012, 09:40 PM
See this is where things get entirely redirected into something else on these forums. I would like to help but I am always facing this sort of thing....Sorry.


Oh no old man you helped fb! I reread mine after reading your wonderfull post and saw that I left out that he could just as easily feed the tower at the base against ground as run a "linear loading" wire up to a yard arm. The yard arm doesn't have to be conductive either, it could be wood or anything, you just have to couple the wire to the tower one way or another.

F8DRA
01-09-2013, 10:24 PM
Hi,

I use to have a 40m vertical array spaced 1/8 lambda, it works very well and gives me a very interesting F/B ratio.
On 15m with the same antenna, the gain is also interesting and the F/B is more interesting than on 40M.
I've just put up a 15m full size rotary dipole at 12 meter high, and the more effective antenna on this band is the 2 elements phased array 40M antenna by 2 s Unit ! so i think i'm going to work on a real phased array antenna for 15 meter ...

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