[TransAtlantic] Fw: New participant - I think!

[Mark Casey]

From: "Bob Cooper" <skyking at clear.net.nz>

If on a high percentage, inside massive high pressure areas (over water) the
ducts are more elevated at the western end than the eastern, what does that
suggest? It could mean the KH6 end is not the 'end of the line' - the duct
might be extending well further west and it is only because of excessive
elevation in say KH6 that there is 'coupling' into the duct. On the other
hand, once you go 'past' the KH6 beacon/portable operation point, it is one
very long distance to the theoretical far western end of the duct (which
may - or may not - be back at surface level again). The problem with this
scenario is further west than say the KH6 functional point, or Monterey's
elevations for TV DX observations, we run into either 'nothing' or we bump
into much higher elevations (further west than our Monterey observer the
elevations rapidly rise and logically they would be the end of the duct).
The Monterey observer, Fernando Garcia, was especially astute with enough
knowledge to concentrate primarily on (then analog) UHF-TV and FM. From his
1,400' elevation home base, on numerous band openings he was clever enough
to drive higher into the mountains, and then down hill, to determine where
on his car's FM radio the ducting signals simply disappeared (i.e.. he drove
'out of the duct'). There is good value here for all of us (the answer to
your question varied from opening to opening but on average the ducts
appeared to be around 300 feet in thickness; above or below and the signals
were gone).

When I lived in VP5 and (May 9-10, 1989) worked from North Carolina to Maine
on 2 and 432, numerous folks would later report to me their frustration that
a fellow ham "two miles away made contact and I never heard you!" What they
would later work out was the guy I worked was 100 feet higher (or lower)
than they were. Ducts are invisible-to-the-eye frequency selective
'waveguides' with well defined boundaries. There is good value here as well.

No two 'openings' will be 'the same' as Fernando Garcia documented over many
years of careful records. Here are the basics. Every (NA) spring, high
pressure with ducting potential forms over the middle and western Gulf of
Mexico (GOM). Going back to 1950, adventurous folks in Mexico down the
coastline south of Harlingen/Matamaros invested in huge fringe area TV
antenna arrays and the latest 4-IF low-noise TV sets. And as far south as
Belize and Merida, these 'TV DXers' knew when spring arrived because
suddenly one evening KGUL-11 from Galveston would snuff out the snow and be
on their screens rock solid; for six hours, six days.

By mid to late March, every year, folks along the Gulf Coast were
experiencing the same kind of distant reception; Florida to Texas, northern
Louisiana to South Texas. By mid-April this day-after-day high pressure
ducting moved slowly eastward and slightly north; now it was Cuban TV into
South Carolina, mid-Florida coast to North Carolina. For the 11 years I was
VP5D I could count on 500-900 mile reception morning after morning, day
after day, from anyplace from North Carolina down to Cuba. On occasions, the
end of the GOM season would lap over with the now off the east coast period
and Texas VHF and UHF stations (out to 1,700 miles) would be logged in VP5.
By early to mid-May the GOM stuff pretty much disappears but the 'ducting
bubble' does not; it moves slightly north and eastward. It would be this
particular bubble that provided me with the now legendary 'opening' of May
9-10, 1989.

By mid-May the 'Gulf Coast High' has become the start of 'The Atlantic High'
or 'Bermuda High' which is by late May a characteristic of the Atlantic
Ocean region from say Cape Hatteras east to - well, sometimes as far as the
Azores and even rarer occasions the coast of Portugal.

Living in VP5 with the appropriate equipment and skills, I during mid-April
to late May often experienced bone crushing signals from Puerto Rico, west
to Cuba and south Florida, south even to the coastal areas of Venezuela and
Colombia. The 'ducting high' was alive and well although I lived, literally,
at sea level.

It is as this annual 'high' drifts slowly northward that we build our
expectations for a trans-atlantic crossing on 144 (or even 432) MHz. Now, if
my 'theory' about 'elevated-west end, near-sea-level east end' is correct,
what does that say about where to be to take advantage of this annual
natural occurrence?

Cape Hatteras (to Cork, Ireland - 3,423 miles; Honolulu to LA is 2,563)) is
the wrong place to be; on the west end. On the other hand, if height equals
getting into the duct' there are locations inside of Puerto Rico (San Juan
is 2,296m to Terceira in the Azores) or The Dominican Republic (Santo
Domingo which you would not select is 1,991 miles to Terceira) where
mountainous locations at heights from sea level to 4357 feet are available
(10,417 in the DR). Remember: The Brendan Trophy requires a 144 (+) 2-way
contact between North America and Europe (PR and DR qualify as NA; Azores
apparently do as Europe).

So now consider what happens to 'The Atlantic High' as May turns into June
and then July. It does not keep moving north (dragging the duct potential
with it); it stagnates sometime in mid to late June and then shuts down, or,
settles as a north by south high sitting between southern UK and the Canary
Islands. When I visited CU3/Terceira in Azores for nearly a month in (June)
1992 (yes - there was a purpose!), and met and spent many hours with the
'official meteorologist' at the US AFB (Lajes Field) there, we went through
a twenty year collection of June-July archived weather maps covering the
region from the east coast of the US to Portugal, going right over the top
of Terceira. He was a quick study and with his assistance we pinned down
days (not many but some) most years when a 'duct coupled' transmitter along
the eastern seaboard of the United States would be 'on the deck - at sea
level' - at Lajes Field. This was 'Basic Tropo Ducting 101A' and far from
difficult to interpret. Remember - it was late in the 50s (or so) when a W6
licensed ham living on Lajes Field found two days of high quality FM band
reception from the northeastern USA on his table top radio.

What is suspected but not verified. #1 - the further north in latitude one
is or goes to attempt to cross the Atlantic, the smaller the odds. Not only
does the 'Atlantic High' not extend very far north but even in the
summertime the disruption to ducting (squall lines, unsettled weather,
however localized) is present much of the time. It takes very little to
tear-a-duct asunder - just an updraft below originating from crossing over a
land mass area and bingo - the duct is broken. #2 - at some point between
early June and early July, the ducting capabilities swing from east-west to
north by south. It is my theory there is a transition period here, during
which a properly situated station at a duct-accessible location in Puerto
Rico or the DR would have access to a similar station in the Azores (Santa
Maria may actually be a better choice than Terceira and it is closer by a
couple of hundred miles to PR/DR).

Getting even to the Azores, the most likely spot for Europe, from any part
of North America is problematic - setting aside the FM band reception at
Lajes Field from Boston (2296m). Returning to Fernando's pioneering work in
Monterey, when he was intercepting UHF TV from stations in North and South
Carolina and Virginia, relatively low power stations using 600 foot towers
were loud and clear while full 5 megawatt stations almost adjacent to the
600 footers on 1,000 foot + towers were simply not there. Which only
substantiates if you are 'in the duct' it is clear sailing; if you are
outside - well, even K6MYC at-elevation above Fresno has his annual problems
with KH6 and as we all know nobody but nobody has more two meter ERP than
Mick.

The answer to the conundrum is 'find the duct and be there.' There is no
gray area here. And it applies to both ends although if we buy my
'high-west/low east' suggestion, it becomes less complex. Ideally, the
distance should be as short as possible - elevated west and lower east. At
the same time, if the ducting is 'high' one might need to be 'up east' as
well (Terceira has many elevations easily reached to 2044 feet msl). The
west end - well, yes KH6 has been worked from sea level at both ends but it
is rare and hard to build a plan around. Fernando with his TV and FM DXing
skills never (NEVER) found a long haul duct opening where he could descend
to near sea-level and still hold ducting signals. This of course is not very
encouraging to seashore located two meter serious operators hoping to be
'first to cross.' A kilowatt into no duct is -60 dB no matter how you
measure it on Terceira (or Cork or wherever). Miami to Terceira is 3877
miles; Habana 4065 (although there are some 'very attractive' mountain sides
in Cuba). The further back you are from the coast, even with elevation (such
as in New Hampshire), the more likely the last ten-50 miles to you will have
enough disturbed air patterns to shut down a duct. I say that knowing full
well I did work New Hampshire from VP5D on May 9, 1989; but - this was an
essentially north-south path, not east-west.

In conclusion, the west end is well populated while the eastern end is not.
If the Azores is the best place to be (2467 miles from NYC; compare to
LA-Honolulu 2563m), and there is no difficulty with the Brenden Trophy's
interpretation of 'The Continental Shelf' description of where Europe
'ends,' that is where I would be; actually on the island of Flores, the
western most of the Azores (2078m from Boston). All of which is best left to
another time. (K6EDX/ZL4AAA)




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