Absolutely, Ed! This really should be understood clearly by 6m newbies with
only HF experience. Sporadic-E is different than F2 in two important ways:
1) Sporadic-E is localized and dynamic. The sporadic-E "clouds", as they are
called, are sometimes quite small and localized. And they move, sometimes very
quickly. Consequently, you can't hear most of the people who are operating on
the band at any one instant in time. Due to shifting sporadic-E conditions,
signals can pop in or out very fast -- within minutes or seconds from "not
there" to "S9+40" or vice-versa.
2) Sporadic-E is extremely efficient. Sporadic-E clouds are formed by
high-energy horizontal wind shear at the E-layer boundary, and for this reason
they are very planar and can be intensely ionized, not unlike a mirror. It is
not uncommon for stations 1200 miles away to be 60 dB over S9 during extremely
intense openings -- (and you may be surprised to learn that that guy is
running 100W to a 3-element yagi at 20 feet).
People tend to self-channelize on 5 kHz spacing most of the time, but when an
S9+60 signal pops up 5 kHz away, you had BETTER have a good tight roofing
filter in your 1st IF. During the two annual summer VHF contests (ARRL, June,
and CQ, July), extremely strong signals are literally choking a wide-open 6m
band from 50125 up through 50200 and above, and as for the usual 5 kHz
spacing... Fuhgeddaboudit! :-)
Bill W5WVO
Ed Gray W0SD wrote:
Mentioned is a sixth reason to my recent post of additional reasons
besides contesting for a 1.8 filter for SSB. Six Meter sporadic E
signals can be very, very loud and band conditions often change
rapidly so two stations very close to each can appear very suddenly
through no fault of their own. This is even more true during the VHF
Contests if the band opens.
The questions I will answer direct.
73, Ed W0SD
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