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Author Topic: Rotatable Dipole Antenna  (Read 2888 times)
N2WSO
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Posts: 7




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« on: May 15, 2001, 10:47:53 PM »

Does anyone know where I could purchase a full size rotatable dipole that is tunable from about 14 MHz to 30 MHz.  I know Cushcraft has a tribander for 10M, 15M, & 20M but I'm really looking for a monobander that is tunable over that frequency range.  I considered homebrewing something, but by the time I added up all the aluminum tubing and the hardware, I was almost up to the price of commercially made antennas.  I'm sure someone out there manufactures these.

73, Bob (N2WSO)
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WB2WIK
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Posts: 20666




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« Reply #1 on: May 16, 2001, 03:13:01 PM »

Not so sure anyone really does manufacture what you're looking for.  However, it would be pretty easy to homebrew: Start out with fixed aluminum tubing for the 30 MHz dipole (15.6' overall length, 7.8' each side of center insulator), the make the rest of the dipole out of telescoping small-diameter mast.  To hit 14 MHz, the overall length will need to be 33.4', or 16.7' for each side of the dipole; thus, each side would need to "telescope" or extend for tuning by 8.9'.  You could use a few sections of aluminum tubing of gradually smaller diameter, with the mating ends slit to accommodate compression clamps, and use a permanent marker to mark each element half at appropriate places to tune it for frequency easily; or possibly use a pair of long telescoping AM antenna masts from an automotive radio shop -- all kinds of possibilities.

In 35+ years of hamming and following magazine ads for amateur antennas, I cannot recall seeing something like this commercially made, although surely something might have been.  There is an article in the May 2001 issue of QST on a "Catfish Rotary Dipole" or something, where the author used some inexpensive plastic, modular fishing rods as forms to make a 20m rotary dipole, using copper wire loosely wrapped around the fishing poles; it was a very low-cost idea that makes a lot of sense, but would not be that easy to tune to different frequencies.  Maybe take a look at that article and see if you can come up with a simple modification that would make tuning a bit easier.

73 de Steve WB2WIK/6
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KL7IPV
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Posts: 984




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« Reply #2 on: May 16, 2001, 05:18:26 PM »

Hy-Gain has a Discover series rotatable dipole for 30 or 40 meters. Cushcraft makes rotatable dipoles for single band or multi band use. Look for the D40, D3, D4 or D3W on the Cushcraft site.  Go to : www.Hy-gain.com or www.Cushcraft.com. You'll need to have an Acrobat reader for the Cushcraft site to download their catalogue. You can also check the ARRL antenna or handbook on ways to make your own. have fun.
73,
Frank
KL7IPV
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KD5KFL
Member

Posts: 55




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« Reply #3 on: May 16, 2001, 07:41:53 PM »

I've thought of making a cheap rotatable dipole this way:

Get two fiberglass dipoles. Firesticks, perhaps.

Make a mount with two metal blocks, insulated from each other & tapped 3/8-24, back to back. Feed one from the center conductor and one from the shield.

When not in use at the fixed QTH they would be available for use on the van and the motorhome.

Never actually tried this.
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KL7IPV
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Posts: 984




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« Reply #4 on: May 16, 2001, 10:58:24 PM »

That is another idea. Use two hamsticks. They do make an adapter to join them together for use as a rotatable dipole, I've never used them but hear they work okay. Good luck.
73,
Frank
KL7IPV
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WB2WIK
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Posts: 20666




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« Reply #5 on: May 17, 2001, 03:10:14 PM »

Everyone here ignored the original request, which was something "tunable from 14 through 30 MHz."

The author of the post acknowledged he had already researched triband dipoles using traps, and monoband dipoles that could not be adjusted for other bands.

WB2WIK/6
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KL7IPV
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Posts: 984




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« Reply #6 on: May 17, 2001, 06:17:19 PM »

The D3W is a 3 band rotatable dipole from 14Mhz to 30Mhz.  It fits the qestion.
73,
Frnk
KL7IPV
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KE4SKY
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Posts: 1045


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« Reply #7 on: February 15, 2002, 01:26:19 PM »

Virginia RACES has a short fact sheet on hamstick dipoles in Word format which I can email to anyone who wants one who would like to contact me.  They work really well on 20 meters and higher frequencies, but as you would expect their efficiency goes down dramatically on 40 and 75.  They DO beat not getting on the air at all and they outperform typical mobile whips for short path EmCom within 300 miles because they are horizontally polarized and have a high radiation angle.  They also have the advantage of being very easy to put up, especially if you need to set up in an open area where there are no trees or if you need to erect an antenna alone and in the dark, as happens with EmCom.

The setup in the handout describes a dual band version which uses two pairs of hamsticks on the same feed, so that you don't have to change from 40 to 75 meters in the middle of operations when an activation continues from daytime into the evening.

73 de KE4SKY
Virginia RACES State Training Officer

 
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KA5TAG
Member

Posts: 2




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« Reply #8 on: May 25, 2004, 01:11:39 AM »

has anybody ever experimented with 2 hustlers in a dipole formation with multiple coils.  I know that multiple coils work as a vertical on their mobile antennas so logic would tell you that they should work as a dipole as long as the coils are tuned close together on both ends???
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