Antenna too long??
 

I am trying to put up a dipole for 40 m. The formula calls for about 65
feet.

Between my tress I easily have space for twice that.

That would still resonate, would it not.

Tell me that longer is better, at least when it comes in multiples.






73 Uwe

66 feet 4 inches drops you in the middle of 40 metre band.

33 feet 2 inch a leg.

Between trees is better than through them.
Re check everything, when the leaves are on the trees.

QRP HomeBuilder web site is at

http://qrp.pops.net/qrp/default.htm

They have dipole antenna software for free.

Best of luck

Uwe,
'Bigger/longer' isn't necessarily 'better'! A longer
dipole -may- resonante on the desired frequency, but the
65 feet (approximate) is really all you need. Twice that
length would probably work for you, but feeding it in the
center would also be a very bad impedance match for 50 ohm
coax. Not to mention will produce a radiation pattern
different from what you might expect. A full wave, instead
of a 1/2 wave, dipole can be made to work, but all things
considered, why bother?
'Doc

On Thu, 15 Apr 2004 06:31:41 -0500, 'Doc wrote:

Not to mention will produce a radiation pattern
different from what you might expect.

Oh, and just how different would the pattern be?

Danny, K6MHE

Uwe wrote:
I am trying to put up a dipole for 40 m. The formula calls for about 65
feet.

Between my tress I easily have space for twice that.

That would still resonate, would it not.

If you say a 6000 ohm feedpoint is resonant. I personally call that
the (anti)resonant point.

Tell me that longer is better, at least when it comes in multiples.

You will be able to use the longer dipole on 75m. It will be about
one-wavelength long on 40m which gives some broadside gain over a
1/2WL dipole. But the feedpoint impedance on 40m will be so high
you will need to avoid coax and feed it with some variation of
ladder-line.
--
73, Cecil http://www.qsl.net/w5dxp



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Dan Richardson wrote:

On Thu, 15 Apr 2004 06:31:41 -0500, 'Doc wrote:
Not to mention will produce a radiation pattern
different from what you might expect.

Oh, and just how different would the pattern be?

A one-wavelength dipole has about 2 dB gain over a 1/2WL
dipole at the expense of other directions assuming a
height of 1/2WL+.
--
73, Cecil http://www.qsl.net/w5dxp



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Dan,
It's green instead of the 'normal' blue...
'Doc

On Thu, 15 Apr 2004 17:39:32 -0500, 'Doc wrote:



Dan,
It's green instead of the 'normal' blue...
'Doc

I fail to see that answers my question. Which was and is just how is
the pattern of a ½-wave dipole different than a full-wave dipole?

I know the answer, base upon you response to the original question I
wonder if you do.

However, because of you refusal to include the portion of the previous
message that you responding too in your postings (normal N/G
etiquette) it is difficult to be sure what you are talking about.

Danny

"'Doc" wrote in message ...


Uwe,
'Bigger/longer' isn't necessarily 'better'! A longer
dipole -may- resonante on the desired frequency, but the
65 feet (approximate) is really all you need. Twice that
length would probably work for you, but feeding it in the
center would also be a very bad impedance match for 50 ohm
coax.

The impedance will still be 50-to-70 ohms if you add the extra
half-wavelength to just one end of the antenna.
i.e. The wire on one side of the antenna feed point (coax connection) is
still 32.5 feet, and the wire on the other side would be 65' + 32.5' plus
another 3.3', since there is no end-effect on the extra half-wavelength of
wire you are adding. So actually, one side is 32.5 feet and the other side
is 100.8 feet. You should get almost 2 db of gain in four directions (a
"cloverleaf") by doing that. You will also get a significant reduction in
signal strength (a "null") broadside to the antenna and off the ends. I used
a dipole like that for years in Florida where one of the gain lobes was NE
and the nulls cut out a lot of the stateside QRM for me during European
contests. The full-wave dipole was up about a half-wavelength (65 feet), so
I used RG59 (75 ohm) coax instead of RG58 (50 ohm) coax, and had a good
match. No balun was needed.

Andy

"Dan Richardson @mendolink.com" ChangeThisToCallSign wrote in message
...
On Thu, 15 Apr 2004 17:39:32 -0500, 'Doc wrote:

However, because of you refusal to include the portion of the previous
message that you responding too in your postings (normal N/G
etiquette) it is difficult to be sure what you are talking about.

He claims he doesn't know how to quote. I plonked him some time ago. Got
tired of trying to figure out what he was responding to. Would rather have
not done that as he does have useful information but his posting method is
just to cryptic.