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Author Topic: Rotatable dipole or vertical for 40 meters  (Read 225 times)
NK8A
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« on: February 27, 2007, 01:19:34 PM »

I would like to know if I should buy  a rotatable dipole with 40 meters on it , or stick to my ground mounted vertical with 26 radials.I would only be able to mount the dipole about 25 feet above ground.I would like to have 10/15/20 meter capability that a rotatable dipole that i have in mind would offer. I could buy a dipole that also has 40 meters on it also.I thought it would be nice to have 2 antennas on 40 meters to compare.By the way ,my vertical covers only 40 and 80 meters. Thanks for any suggestions or advice....Dave..NK8A
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W9OY
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« Reply #1 on: February 27, 2007, 01:42:29 PM »

You can answer your own question by putting up a wire 40M dipole or inv-V at 25ft for very little money.  At 25ft on 40M the directivity will be minimal.  I use a 130ft dipole fed with open wire at a out 55ft and it is useful over my verticals especially on daytime close in contacts.  For DX it is typically not as good as the vert.

73  W9OY
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AA4PB
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« Reply #2 on: February 27, 2007, 03:25:05 PM »

The vertical will have primarily low angle radiation. Thats good for DX provided that it is not surrounded by ground clutter and noise sources.

The low dipole will radiate primarily high angle radiation. Thats good for closer in contacts out to a few hundred miles. There is no sense in rotating a low dipole since it will be mostly omni-directional at low heights. Since rotatable dipoles are generally short (loaded) they have more loss than a full sized wire antenna. You'd be better off with an inexpensive fixed 1/2 wavelength wire dipole.
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K0RFD
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« Reply #3 on: February 27, 2007, 03:58:47 PM »

Put up a wire dipole for close-in contacts on 40, keep using your vertical for DX, and you'll have the best of all worlds for about 20 bucks.
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K0RFD
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« Reply #4 on: February 27, 2007, 04:01:59 PM »

Oh, and you can use the 40 meter wire dipole on 15.  Even as low as 25 feet, it's 1/2 wave high and ought to work pretty well on that band.
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KE6VG
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« Reply #5 on: February 27, 2007, 04:12:19 PM »

I agree... go with the wire dipole for 40. You could add a second wire for 20m also. 25' is still a little low for 20m. 32' up, a half wave on 20m is a sweet spot for the 20m antenna. If you are only puting up a wire dipole... is there any reason you couldn't go a little higher?
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N6AJR
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« Reply #6 on: February 27, 2007, 04:48:12 PM »

the rotatable dipole will work ok but you need to get it up  at least 1/2 wave so 30 feet for minimum height and higher is better, any closer to the ground and it is almost  omnidirectional.  so if you get one  put it up high
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W9OY
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« Reply #7 on: February 27, 2007, 09:00:42 PM »

On 40M, 1/2 wave is closer to 65ft than 30

73  
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N6AJR
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« Reply #8 on: February 27, 2007, 09:13:13 PM »

your right I was thinking of one leg of a Fan Dipole.. about 66 feet is good on 40 m
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