[TowerTalk] Folded dipole

[DF3KV]

Hi Dave,

You might use the forecast Software by W6EL to find out about the
propagation angles. There is advanced function which shows the number of
hops and the take off angle to your target area.

A 40m dipole higher then 3/8 lambda is already good for DX, for NVIS 15 ft
is not optimum, get it on 27ft.
You will gain 1db at 90° and 1,5db at 50°.
Your dipole at 65ft gets its maximum gain at 31° and at 10° your gain is
still 3dbi.

I suspended my 40m dipole on purpose at 100ft, to have high and low angle
radiation.
On 90° the gain is the same as a NVIS dipole and at 20° it is 8dbi, 5dbi at
10°.

73
Peter



-----Original Message-----
From: towertalk-bounces at contesting.com
[mailto:towertalk-bounces at contesting.com] On Behalf Of WA3GIN
Sent: Mittwoch, 26. August 2009 00:46
To: K4SAV; towertalk at contesting.com
Subject: Re: [TowerTalk] Folded dipole

OK,

I don't use EZNEC...I guess its too EZ.

I have installed a NVIS  40m dipole at 15ft above the sandy loam soil where 
I live.  I also have a 40m dipole aboutg 300ft away at 65ft and also a 1/4 
wave cage vertical on 40m.

Back in the old days when we had sun spots tand conditions that supported 
high angle radiation the NVIS would blow away the dipole at 65ft anywhere 
within 0-250 miles.  Out past 400 miles the dipole was the clear winner in 
comparison testing and held that lead out to about 1500-2000 miles when the 
ground mounted cage vertical on 40m then started to pull ahead of the dipole

at 65ft. As the sun spot cycle continued to decline the usefulness of the 
NVIS has become less and less.  I guess the signals just go straight up and 
not much signal gets reflected back.  Seems like if you till the take-off 
angle a bit more signal gets reflected.

I wonder if EZNEC has a parameter to simulate the conditions of the 
inonousphere?  Seems that might be a really useful element to the equation 
for folks that prefer to model antennas before the build them and play with 
them.

Just my subjective opinion and experience of one.

73,
dave
wa3gin
==========================================================

These days however the conditions do not favor an NVIS on 40m.... 

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