[TowerTalk] Inverted Vee vs. Dipole QRN

[Michael Tope]

----- Original Message ----- 
From: "K4SAV" <RadioIR at charter.net>

> 
> 80 meter inverted vee with apex at 100ft, 90 degree included angle, 
> azimuth response at 10 deg el. Numbers are: Az angle in degrees, 
> Horizontal component in dBi, Vertical component in dBi, signal to noise 
> ratio in dB. 90 degrees is perpendicular the plane of the antenna.
> AZ  Horz  Vert   S/N
> 90  -2.7  -100   97.3
> 45  -6.2  -9.3   3.1
> 25  -10.9 -7.4  -4.5
> 10  -18.7 -6.8  -11.9
> 0   -45   -6.4  -38.6
> 
> 80 meter horizontal dipole at 100ft, azimuth response at 10 degrees 
> elevation:
> AZ  Horz  Vert   S/N
> 90  -1.1  -100   98.9
> 45  -4.9  -16.1  11.2
> 25  -10   -14.5  4.5
> 10  -18   -14    -4
> 0   -100  -13.9  -86.1
> 

These results suggest to me that in an urban environment 
where the noise is fairly isotropic (lots of small sources 
coming from all directions adding up non-coherently) that 
the dipole in general will be better than the inverted-vee 
for receiving (unless the desired signal is in the null off 
then end of the dipole). I've seen this in practice 
comparing a 160 meter horizontal dipole at 90ft to a 80 
meter inverted-vee at 90ft in an urban location (very high 
man-made local noise floor). On 80 meters, 9 times out 
of 10, the 160 meter dipole produces a significantly better 
SNR on receive than the 80 meter inverted-vee. It could 
be that the noise at this location isn't as isotropic as I 
assume, but I am betting its the polarization characteristics 
rather than the directivity of the two antennas that makes 
the difference. 

In a rural location where all the noise arrives via skywave, 
I don't think it matters too much. 

73, Mike W4EF........................