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Author Topic: Which is a better 40m limited space DX antenna?  (Read 6356 times)
STAYVERTICAL
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Posts: 854




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« Reply #30 on: November 08, 2012, 03:40:28 PM »

Without trying to start a flame war on the merits of end fed half wave antenna's, you might try this for your particular situation.
BYU is correct with the coax feed problems with centre fed vertical dipoles, so perhaps you may wish to investigate the end fed option.
You WILL need a counterpoise, but from stuff I have seen on the net it seems it only has to be 0.05 wavelengths long (2 metres on 40m).

It seems the method you use to tune up one of these beasties is to use a link coupled parallel tuned circuit.
Then replace the antenna with a 4700 ohm carbon resistor, and adjust the tuned circuit/link until you get a 1:1 swr.
Then replace the 4700 ohm resistor with the antenna and 0.05 wavelength counterpoise.
Leave the tuned circuit alone, and adjust the length of the half wave antenna until you get 1:1 SWR - that's it!
You will find free programs on the net to give you values of coils, link windings and capacitance for whatever frequency you wish.

Again, I have not tried this in practice, but will when my other 5000 projects are complete.
I include it to give you a distilled down version of one method which is proposed, and give you somewhere to start.
I understand the need for stealth - same situation here, but no big tree unfortunately.

Good luck, 73 - Rob
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AJ8MH
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Posts: 120


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« Reply #31 on: November 08, 2012, 05:01:09 PM »

I've been playing with an antenna about half the size of a 40 meter vertical dipole, and have been pleased with its performance.  It's much better than a 44 foot inverted V at 32 feet.  However, it does NOT have a small footprint when you have to deal with guys and "T" loading sections.  More info at ( http://webpages.charter.net/aj8mh-radio/notebookind7.html ).

In the past year and a half, I've managed 67 LoTW countries confirmed on 40 with different variations of this antenna, and hope to finish 40 meter DXCC this winter.  64 of these countries were snagged with 100 watts.
« Last Edit: November 08, 2012, 05:03:46 PM by AJ8MH » Logged
NK7Z
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« Reply #32 on: November 08, 2012, 08:09:11 PM »

Hi,

I use a Gap Challenger, ground mounted.  Works wonderfully on 40 and 20, not so hot on 80, 15, and 10.  Requires three radials, actually they are a capacity hat.  The antenna is really a vertical dipole.  it works very well, and only has one set of guy wires at mid point.

73's
Dave
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Thanks,
Dave
For reviews and setups see: http://www.nk7z.net
W8GP
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Posts: 196




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« Reply #33 on: November 12, 2012, 11:41:45 AM »

The following are only my observations, theory aside. I have available 3 antennas for 40m:
         1/4 wave vertical ground mounted over 100 70' radials
         1/2 wave fixed dipole at 60'
         1/2 wave rotatable dipole at 125'
   While listening to Europeans last night I recorded the following signal strengths (typical) using a K3 with attenuator on:
         vertical-S3
         60' dipole- S4
         125' dipole- S7
   These results were consistent over several hours. I have used these antennas for several years and notice similar results about 80% of the time.
   Other observations:
   Occasionally the vertical will beat the low dipole, both DX and stateside.
   Occasionally the low dipole will beat the high dipole on stateside but NEVER on DX.
   The high dipole is much noiser that either of the other antennas.I have to rely on beverages for recieve to get the most of this antenna.
   Now, to answer your question.For your situation, I think you will be happy with the vertical, either ground mounted over 30-60 radials, or elevated with at least a dozen radials.I would not recommend the dipole for DX unless you can get it up 60' or so. On second thought, why not put up BOTH and see for yourself? I'm never happy with just one antenna anyway! Good luck!
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W4RS
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Posts: 64




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« Reply #34 on: November 14, 2012, 04:41:55 PM »

a vertical with elevated radials,it sure wked a lot of folks from kh5!
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WA4053SWL
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Posts: 169


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« Reply #35 on: November 15, 2012, 01:52:44 PM »

Hello, if I had to choose between one antenna, a rotating 40m dipole or a 40m vertical, which one would be more consistent for 40m DX? I am in a small lot limited space situation. Also maximum height will be about 25Ft.

Also, any suggestions for a more directional rotatable 40m DX antenna, that doesn't take up as much room as a full size 40m 2 element beam? I heard Optibeam makes some but aren't they pretty expensive?

Thanks for any feedback. 73.
Todd - KT0DD
A good directional antenna and cheaper to build is a mono band Quad.
I made a one element Quad only to listen DX in 40m with very good result, the antenna also work on the others high bands.
Some #12 copper wire, 4 fiberglass pole, balun 1:1 and you are already in business.
My antenna is somewhat low, only 8 meters above the ground, has a small RS rotor to move and give directionality.
73 george Grin
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WA2TPU
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Posts: 208




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« Reply #36 on: November 15, 2012, 02:50:09 PM »

Hi to all,
Many very nice postings on this topic. I'll add my 2 cents-worth now.

I use single and multi-element vertically polarized Delta loops on 40 and with great results...even at the Qrp level(5 watts).

Best regards and many72/73.
Don sr. --WA2TPU--
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