Hi Ed,
The loss due to 90 degree off-alignment in free space (no reflections from nearby buildings, satellites, mountains or earth moving equipment) is potentially infinite. It’s tan(90 degrees) (infinity) converted to a decibel loss. In practice that is very hard to achieve. Using limits we can say it approaches infinite cancellation as the angle approaches 90 degrees and assuming there is only one signal path.
Calculating for an 85 degree twist gives you only about 20 db loss and the loss from 45 degree offset is 3db. Don’t know about you but I rarely use a spirit level to adjust my antenna polarity to precisely horizontal or vertical, not at that level of accuracy.
Like balancing a balanced modulator in an ssb exciter, it’s something that never can be perfect, due to drift in component values, dielectric changes and diode/transistor variations.
It can be compared to the difficulty of achieving a perfect balance in a “balanced line” transmission line.
Ideally we would use circularly polarisation and cop the 3db loss, but then we’d have to align our antennas towards each other and use the same sense rotation (clockwise or anti). Experiments with circular polarisation show that fading is much reduced compared with either horizontal or vertical. That must be due to polarisation changes over the path, due to refraction and reflection in a changing troposphere and mountainous paths. Instead of attenuation when the signal changes polarisation, the circularly polarised antenna just receives it equally well whether it’s 0, 45 or 90 degrees off horizontal.
Between our summits in vk1/vk2 numerous experiments have found that tilting even a HT so that its antenna is horizontal and broadside to the incoming signal produces better signal levels - even if the transmitting station is “vertical”. And if both ends go horizontal, the signals increase further. It doesn’t happen this way for clear line of sight S2S paths, it’s only when it’s a path that forces the signal to scrape over some hilltops, perhaps with multiple reflections off other peaks, etc, that the horizontal preference becomes apparent.
So my intention is to use horizontal all the time this year, either with a 3 el yagi or with a one element rectangular loop. I made a contact this morning that was about 300km using the loop, and my tx was the ft817 at 5 watts. The other station was a well equipped ssb dx station with multiple yagi and “ample” power. But he gave me a 5x3 signal report so my puny signal was able to reach him despite 5 watt output level.
HNY
73
Andrew VK1DA/VK2DA