Just for fun, I modeled a 160m low inverted-V in NEC4.2, using 4NEC2 to
look at the patterns. The apex was 15m up. Each leg was 40.7m long
with the ends 7.5m up. It was fed with 300 Ohm open wire dropping
vertically to 1m above the ground. I fed it from a 300 Ohm source.
Directly under the antenna I created 36 radials 30m long in order to
compare 3 different configurations. I used Sommerfeld standard ground.
All wire was #14 bare copper.
1) the balanced, ungrounded, inverted-V.
2) The same antenna, but with a 1m wire connecting one side of the
feedline to the ground plane to simulate a real unbalance.
3) The same antenna but with both sides of the feedline fed against the
ground plane as a "T".
As expected, the results support vertical radiators, and balance in the
inverted-V
Vertical radiation off the ends
_Antenna of the inv-V at 30 degrees el Radiation
Efficiency Comments_
1) Balanced inv-V -8.8dBi 7.03% Total
radiation pattern (H + V) is omni but with vertical nulls off the sides.
2) Unbalanced inv-V -11dBi 3.95% Total
radiation pattern is omni, low angle vertical is also omni.
3) Inv-V used as "T" +1.4dBi 38.4% Peak
radiation at 30 degrees el, mostly vertical, -2.8dB nulls off the sides.
On 3/29/2018 10:11 AM, K4SAV wrote:
If you run a NEC analysis it will show that a 160 dipole at a half
wavelength height will blow away any vertical when the signal is
broadside to the dipole. The people that have tried this say it aint
so. At least some of the reasons are that NEC knows nothing about 160
propagation and it knows nothing about the effect of Earth's electron
gyrofrequency. That varies a lot depending on where you are located
on this earth. Analysis is nice and easy but you have to include
everything for it to simulate the real world, and the real world on
160 is very complicated.
Jerry, K4SAV
On 3/28/2018 9:50 PM, Mark K3MSB wrote:
I don't think so. In my Electromagnetic Fields and Waves class in EE
school (way back when dinosaurs just stopped roaming the earth and
Constellations still graced the skies...) the prof derived the
equation for
a received signal. The polarization terms disappeared after the first
ionospheric bounce.
73 Mark K3MSB
On Wed, Mar 28, 2018, 9:03 PM Steve Maki <lists@oakcom.org> wrote:
Interesting. Some say that on 160 vertical polarization rules, while on
80, horizontal polarization rules (or at least *often* rules). Of
course
polarization and angle of arrival are two different things...
-Steve K8LX
On 03/28/18 17:23 PM, Roger Kennedy wrote:
Well I've said it before and I'll doubtless say it again . . .
In my experience, most DX propagation on 160m ISN'T low angle (unlike
80m
when it nearly always IS.)
For the past 45 years, at several different QTHs I've always used a
horizontal co-ax fed halfwave dipole, only 50ft high . . . I'm sure
most
people would agree I put a respectable DX signal. I've regularly
worked
all
over the world on Top band, and I've never had trouble getting through
pile-ups to work Dx-peditions.
Plus a dipole at 40 feet will never really be an inverted vee !
(just a
horizontal antenna with drooping ends) - You'd have to have the
centre at
least 100ft high for it to be an inverted vee.
Roger G3YRO
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