[IRCA] "Bermuda Effect" and sech diabolical rubbage!

[Charles A Taylor <MWDXer@xxxxxxx>]

At 07:50 PM 6/17/2007 -0700, you wrote:
>Charles,
>
>
> > * This may be a manifestation of what I call the
> > "Bermuda Effect."
> > Noted in Bermuda 1978 - 1981, this consisted of such
> > far in-land
> > US stations as WLW-700 and WJR-760 going into the
> > usual dawn
> > induced fade-out of skywave; HOWEVER, to begin
> > FADING BACK IN
> > and at fair level at high noon, Bermuda time! I
> > conclude this is due to
> > some sort of sea/land refraction that bends
> > low-angle spacewave
> > (not skywave) back toward the ocean to be propagated
> > long distance.
> > (CAT*NC)
>
>
>By observation only, it appears to me that WJR in
>particular is feeding more of their nighttime
>transmissions into skywave than groundwave. For years,
>I can drive two hours out of town in any direction and
>their signal becomes quite unusable. Yet driving back
>from my father-in-law's funeral in Denver, we had a
>nice WJR signal to hear halfway across Nebraska.

Joe,

What you're observing there is high-angle takeoff
radiation from WJR's tower. It returns to the earth
inside the outer-most useful groundwave contour and
causes alternate strengthening and cancellation
(along with distortion) of the groundwave. This
skywave, of course, is unstable because it is always
changing; and since it is "close-in" skywave, it
changes rapidly.

This is not a problem with a 0.5-wavelength tower,
but a 0.625-wavelength tower has a significant high-
angle lobe that causes this annular area of mixing
of groundwave and skywave too close to the tower.

KDKA-1020 uses a "Franklin" antenna which has an
insulated section inserted about half-way up the
tower. The lower and upper halves of the tower are
phased to eliminated this spurious lobe.

>So I'm thinking if the conditions are right, their
>first skip lands in the Atlantic Ocean, then the salt
>water propagation takes over, I can see it being done.

NO SKYWAVE is the point I was making! This is after
skywave has been attenuated by the D layer. I surmise
that mid-angle takeoff signal from these stations
reaches the coast and meets a temperature-induced
defraction zone that bends the SPACEWAVE (same mode
of propagation that TV and FM use!) downward toward
the ocean where it becomes usefully intense.

SPACEWAVE versus SKYWAVE. The spacewave would still
be as intense as skywave at, say, 100 miles up!

>Funny back in the 1960's, WJR used to read letters
>received from out of state listeners (Texas was very
>common), but never recall them reading letters from
>Bermuda.

Aren't that many people out in Bermuda who are going
to be DXing on AM! Aren't that many people out in
Bermuda. End of sentence. Full stop. period. Dot.

>Thank you for the info.
>
>P.S. If this isn't what you meant, I apologize. This
>is the first time I've heard this idea.

Stick around and I'll come up with some more ideas!
Gotta keep then secret from DU1MOM/4, or she may
decide my ideas are going to come out of her cosmetic
(make-up/warpaint) fund!


>P.P.S. 15 meter band was open yesterday afternoon.
>Venezuela and 4 southern states...

Maybe you can QSO with Hugo Chávez. Advise him of a
different source of nutrition and where it is found
and how to kiss.

73,

Jollie Chollie

   Charles A Taylor, WD4INP
  Greenville, North Carolina 



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