Topband: low inv-vee

[Brian Pease]

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 at 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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