The primary refracting medium at night time for 160 meter signals on the
first and second hops within approximately 2500-3100 miles is the E region.
The night time ionization source for the E region is not our Sun. The source
is galactic (out of our solar system) electromagnetic radiation at 10 to 100
Angstroms (Soft X-rays), Cosmic Rays and to a lesser extent Earth bound
Lightning activity. Therefore you will not see a multipathing improvement of
a 160 meter RTTY signal between the high point and low point of a sunspot
cycle.
Medium frequency (300-3000 kc) radio waves possess elliptical polarization,
with the signal splitting into ordinary and extra-ordinary rays as it
refracts from the E region. These rays can propagate in or out of phase,
usually out of phase and create part of what we call multipathing
conditions. The out of phase extra-ordinary ray also represents a 50% power
loss on the receive end of a path.
Personally I've never had any real difficulty working 160 meter RTTY within
2500-3100 miles and multipathing should not be a factor in anyone's personal
decision as to whether one works 160 meter RTTY or not.
--... ...--,
Thomas F. Giella, KN4LF
Lakeland, FL, USA
Grid Square EL97AW
kn4lf@arrl.net
KN4LF Amateur & SWL Radio History: http://www.kn4lf.com
KN4LF 160 Meter Propagation Theory Notes: http://www.kn4lf.com/kn4lf8.htm
Man Induced Climate Change Refuted:
http://www.kn4lf.com/globalwarminglie.htm
Problem with RTTY operation on 160m has to do with multi-path
propagation causing inter-symbol interference. It's the same reason
why 300 baud packet works on 20m, but not on 80m.
Reducing the symbol rate decreases the inter-symbol interference.
This is why 31 baud PSK has less trouble than 45 baud RTTY.
Of course, now that we are at the bottom of the sunspot cycle, 160m
RTTY may be practical at 45 baud, since the less intense ionization
of the ionosphere would reduce the multi-path propagation.
Bill Coleman, AA4LR,
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