N4ZR wrote:
>Well then, I guess I share Tom's confusion. You did state that verticals
would be the antennas of choice in NA and EU, based on the amount of
insertion loss for a dipole. It seems reasonable to ask, "24 dB compared
to what?" Or asking the question the other way round, what would be the
insertion loss of a vertical at the same locations?
Compared to the dipole's normal pattern. This is why power
coupling loss must be considered as only one component of the total
pattern. To compare a vertical and horizontal antenna, you need
to do compute total system gains including pattern gain over
the actual ground conductivity and at actual takeoff angles, and then
superimpose the power coupling loss on the horizontal and vertical
antenna patterns. Bob did give coupling loss by TOA for vertical
polarizations here:
http://lists.contesting.com/pipermail/topband/2002May/014848.html
but I haven't seen the equivalent by TOA for horizontal polarizations.
I'm not going to do this but here's what you need to do to
compare antennas:
1. Model a vertical over actual ground conductivity (near and far fields).
2. Model a dipole over the same and at the actual height.
3. Choose a common takeoff angle (this is very important!)
4. Add the vertical coupling loss in the direction of interest (North)
to the vertical at the selected takeoff angle.
5. Add the horizontal coupling loss in the same direction and at the
same takeoff angle for the dipole.
6. Compare the two models.
Here's the problem as I see it. A low dipole has its TOA peak
at 90 degrees and a decent vertical has its TOA peak around 20 degrees,
so the antennas are VERY different in TOA patterns before you even take
power coupling into account. The main question in making any comparisons
is to choose the takeoff angle to W8 or VE3. I would guess 3040 degrees
but I really have no idea, and without choosing the correct takeoff
angle, any modeling comparisons are meaningless. If you could estimate
the correct angle, it should be possible to compute #6 above and do
some actual ontheair tests after Tom reorients his 300' dipole from
broadside E/W to broadside N/S! :)
73, Bill W4ZV
