Some long-time observations from about 55 years of AM broadcast band
DXing MAY have some relevance to this discussion.
That hobby has had a lot of simultaneous inland-versus-coastal signal
strength comparison studies over the years, largely from the US and
Canadian Atlantic and Pacific coasts but also from a variety of other
sites around the globe.
Nick Hall-Patch (VE7DXR) and Chuck Hutton (WD4ELO) who comment
periodically on this list are both active in both amateur radio and
broadcast DXing. They, along with Bruce Portzer, Guy Atkins, Gary
DeBock, Pat Martin, Walter Salmaniw, Dallas Lankford, and others have
done a lot of DXing at prime sites along the Oregon, Washington, and
British Columbia coast.
Here on the East Coast, many observations have been done by enthusiasts
such as Bruce Conti, Neil Kazaross, Ben Dangerfield, Jean Burnell, Marc
DeLorenzo, and myself. Both simultaneous listening at various sites
and long-term observations from somewhat-inland and "beach DXpedition"
sites have given rise to a number of findings. There could be at least
a certain amount of crossover relevance to 160m and perhaps even 80/75m.
Here are a few conclusions:
* The advantages of being at the shore are substantial in the
pre-sunset period along east-facing shorelines and post-sunrise along
west-facing shorelines. Saudi Arabia 1521 (2 megawatts) can be heard
up to 4 hours pre-sunset in autumn / winter right at the shore in New
England and Atlantic Canada, even with modest antennas. At sites even
just 10 miles (16 km) inland, two hours pre-sunset is about as good as
you get on similar "compromise" antennas. Here's a typical
Massachusetts coast recording of the 1521 flamethrower:
"
http://www.qsl.net/wa1ion/audio1/dx_saudi_arabia-1521_20060503_2300z.mp3
". A small car roof mounted loop was all that was necessary.
* The differences between shore and inland are less when efficient
full-sized antennas (vertical at least 1/8 wave over a good radial
system, or halfwave dipole mounted a quarter wave or higher above the
ground directly below it) as contrasted with lower-efficiency / smaller
antennas often used for receive (figure-of-8 or cardioid-pickup loops,
active whips), especially if those antennas are near the ground. No
surprise there.
* The differences between shore and inland are less when the route is
shorter, the path is all dark, and solar activity is low. New England
to UK or Norway in autumn or winter might only show about a 6 dB
advantage to a coastal site to a similarly-equipped station inland
(meaning, roughly, more than 20 miles of average soil to the nearest
salt water on the bearing of interest). Deep Africans and South
Americans heard during auroral conditions, or anything from the Middle
East and beyond (> 5000 miles) at any time, will show a strong
enhancement, at least on smaller antennas, near the shore. For many
years I have been noting what medium wave stations from places such as
South Africa, Lesotho, Brazil, and Argentina can do at various sites in
Massachusetts. Up to 2012 I lived in west-suburban locations near
Boston. These are more than 30 miles from the ocean on the
southeasterly bearings towards Brazil. In thousands of hours of
listening over more than 50 years I think that four or five Brazilians
would be the maximum logged in the 530-1710 kHz range. Where I am now
in South Yarmouth, MA on Cape Cod - about two miles from West Dennis
Beach on the range of Brazil-ward bearings - I've logged close to 10
Brazilians in about two years. My parents' house in West Yarmouth
(1974-2001) and my brother-in-law's in East Harwich (1994-2004), also
about two miles inland on Brazil bearings, performed similarly to my
present QTH. But the big winner is listening from the car directly
sited at beaches with open water to the southeast. I had more than a
dozen Brazilian stations in a single two-hour session at Orleans, MA
and, cumulatively, over 20 stations from Brazil in the logbook as a
result of various MA beach DXpeditions over the years just using small
loop or active whip antennas mounted on the car roof - antennas far
inferior to what could be run at various house-based sites. The
station from Fortaleza, Brazil on 760 kHz barely ever registers a peep
in the suburbs west of Boston but it's often loud around sunset (after
semi-local WVNE power-down) at shore locations such as Tonset Rd. -
Orleans, MA (Cape Cod) and Granite Pier - Rockport, MA (Cape Ann). The
shore-vs.-inland difference on that one is easily 25 dB. This is why,
on both coasts of North America, year after year, broadcast-band
DXpeditions produce loggings in a single night that the same DXers have
not heard from home in a lifetime of listening, sometimes even if using
better receivers and antennas. So many years of different DXers noting
the same results take a lot of the statistical uncertainty out of the
equation - it just can't be that every time someone went out to the
shore the propagation magically went crazy and then went back to dull /
normal as soon the DXer was back in his own driveway. Anyway, that
significant shore-versus-inland conditions can exist is borne out by
the fact that, on at least some occasions, several DXers were listening
at the same time from various sites and noting big differences in
strengths and quantity of long-haul loggings. It used to be difficult
to prove things when you had to be on the exact same frequency at the
exact same time. Nowadays DXers are saving the entire spectrum to disk
from SDR receivers such as Perseus and Excalibur. A top-of-hour (prime
ID time) +/- 2 minutes band capture from Location A can now very
accurately be compared to one made during the same time interval from
Location B.
* There are times that, contrary to common intuition, a very long haul
route is best covered by antenna that works for high take-off angles.
This is typically during greyline transitions and results from
reflective-layer tilting / chordal-mode propagation. During such a
condition, my "gut feel" is that there should be very little difference
between coastal and inland sites.
* To muddy things up further, inland sites can vary quite a bit too.
Some of the advantage of shore sites may be owing to minimal
obstructions as well as to good conductivity. Obstructions degrade
lower-angle signals as well as poor ground conductivity. An inland
"wide open farm" (or grassy marsh area) with a long view to the horizon
in the direction of interest is going to outperform a "typical
suburban" site with buildings, power lines, and tall trees towards the
DX. An elevated site would outperform normal suburbia for the same
reason. Just as with a shore site, the unobstructed-view inland site
is also apt to have less man-made RF / local electrical noise coming in
from the desired direction than "average" sites in developed areas.
* If you don't have a coastal site, altitude would be the next-best
magic bullet. This means both in terms of the antenna height above the
ground directly below it and the actual surface level relative to
surrounding terrain. A house site that I used in East Harwich, MA was
about a mile and a half inland over lossy sandy soil. Sunset-period
transatlantic reception on a small homebrew broadband loop of similar
performance to a Wellbrook ALA1530 was evaluated at a nearby shore site
(Town Landing near Tar Kiln Road - S. Orleans, MA) and at the house.
Predictably, big stations such as Algeria 549 and Saudi Arabia 1521
came in an hour earlier right at the seashore. Some of the inland
deficiency was removed by relocating the small loop from
near-ground-level to about 70 ft. height (via rope over the top of a
pitch pine tree). I'd say that the treetop loop performance came in
about halfway between the near-the-ground loop operated at the house
and operated at the shore.
The latest crazy aspect of medium-wave DXpeditioning is exploiting TWO
magic bullets - seaside PLUS altitude - at the same time. Gary DeBock
(N7EKX) has led the charge on this at the "Rockwork 4" site on the
Oregon coast. See "
http://www.antenadx.com.br/?wpdmact=process&did=MjcxLmhvdGxpbms= " for
one write-up. From 2013 we have a DXpedition article starting with
"Concurrent with a separate DXpedition in Yachats (OR), from July 21-27
another wild ocean cliff DXpedition was conducted from "Rockwork 4," a
400' high sheer cliff located on Highway 101 in Tillamook County,
Oregon."
See "
http://www.hard-core-dx.com/article.php?story=20130731111543372&mode=print
".
Sample reception of 603 kHz Radio Waatea in Auckland, New Zealand, 5 kW:
"
http://www.mediafire.com/listen/u25glqbzfr7e2h3/603-R.Waatea-1253z072213PL380.MP3
". No one in the USA has heard a signal like that from this station at
inland home sites.
Acadia National Park in Maine has similar sites with both salt water
proximity and high altitude. Strong Brazilians on 1100, 1220, 1280,
etc. are pretty common stuff at the top of Cadillac Mountain there.
As others have mentioned, you can undo a lot of the "inland
disadvantage" by the use of highly-efficient tall verticals over a
copious radial field or a horizontal antenna at heights in the
half-wavelength or greater range, e.g. 250 ft. at Topband. Site
altitude (mountaintop) or, barring that, wide open level or downsloping
farmland free of obstructions will help too.
Sometimes it's all up to the ionosphere. Of US regions, New England
often has the best punch to Europe if only because of shortest distance
- coastal vs. inland notwithstanding. But if the auroral "doughnut"
(torus) is too much in the way, Florida will outperform by using open
paths south of the auroral zone. Northern Lakes and Plains states
(e.g. Minnesota) might also outdo W1-land by getting through the
"doughnut hole." Certainly going US to northern Norway and Sweden this
is often the case: the route from MN, ND, etc. over Hudson Bay can
frequently beat what's coming from MA, NY, etc. along the Atlantic but
heading straight into the jaws of the aurora.
Now that we've analyzed the heck out of shore versus inland, I guess
mountaintop versus lowland would be the next thing to discuss.
Mark Connelly, WA1ION
South Yarmouth, MA
<<
Hi Guys
K3ZM is my brother - and his 160m antenna is located in a salt marsh
just to the
West of Chesapeake Bay in Matthews, Va as I recall. Indeed he is
located inland
a bit (eg: not directly at water's edge) - perhaps 1000 feet distant
(although
this is only a guess on my part from photos I have seen). But the
intervening
land is also primarily salt marsh. At certain times of the year this
land
floods with salt water and it is necessary to wear very tall boots in
order to
walk out to the base of the towers Peter owns. I am sure Peter could
add more
specifics.
From conversations I have had with Peter over the years - and from
listening to
his signal over at 7O6T, I can tell you that he is very competitive
when
compared to his peers. Additionally, his ability to hear for a
location so far
South (eg - not in New England) - especially in winter is quite
remarkable His
contest results in 160M contests speak for themselves.
Other observations - perhaps relevant, perhaps not.
W1WEF and I often get together for lunch in Orleans on Cape Cod. Jack
works the
HF bands from his mobile CW rig in his car - and when he drives out to
the
peninsula where I live (just off Pleasant bay which is salt water) -
dead 15m
and 20M bands magically go from NO European signals to a full band of
signals as
he comes up the road that runs along the Bay. He describes it as going
from a
DEAD BAND to a wide open band as he nears my home. This is in the
daytime in
summer as I recall.
Personally here at VY2ZM - I am sure by co-locating my vertical systems
at or
near the water's edge has helped me - to what degree I am not sure -
but it is
rare to be outheard looking NE or East on the lowbands.
During this thread I am pretty sure I read a post that co-location near
Salt
water is additive also for horizontal yagis. I do not believe this to
be
correct. My good friend Don Toman has several times told me the effect
we are
seeing here is primarily limited to verticals - and not to horizontal
yagis -
which according to Don, rely principally on their height above ground
as the key
variable impacting their performance.
On the other hand, shooting out over open ocean from a slightly
elevated
position with HF yagis is a pretty good takeoff to be sure. Especially
when
compared to looking uphill over land in other directions - which I find
causes
performance to suffer by comparison.
FWIW
Salt water is good stuff. Especially for verticals placed at or near
the ocean
- with additional ocean out in front of the antenna for hundreds of
miles. I
too have never fully understood the phenomena but I know it is magical
in terms
of lowband DX'ing performance.
73 JEFF K1ZM/VY2ZM
_________________
Topband Reflector Archives - http://www.contesting.com/_topband
|