Topband: Modeling the proverbial "vertical on a beach"

[Mark Connelly via Topband]

I'll just stick in a few responses to others' comments about what I 
wrote on the 'beach' thread and then I'll get out of the way.

<<
It is tricky to use receiving tests to gauge the
effectiveness of proposed transmitting antennas
for two reasons.  You are probably listening on
receiving type antennas rather than transmitting
antennas.  In that case, you have only shown that
receiving antennas work better over salt water.
>>

Definitely, as I'd mentioned, less site-to-site variability would be 
shown with a full-size efficient transmitting type antenna, whether a 
vertical over a good ground system or a high (>150 ft. elevation) 
horizontal dipole / yagi.

Smaller receiving loops and active whips exhibit the greatest influence 
due to surrounding ground conductivity and elevation profiles.  This is 
particularly the case on groundwave or very low angle skip.  High angle 
skip is largely unaffected by the nature of the surrounding landscape; 
certainly by the time you get to Near Vertical Incidence, that can work 
even if you are surrounded by tall buildings or mountains.

As some of the propagation paths we desire do involve things such as 
the ability to "open" the band pre-sunset on the US/Canada East Coast 
to incoming Europeans, skip propagation at very low angles is a matter 
of interest.  If sunset is at 4 p.m. EST (2100 UTC) in December in 
MA/ME, for instance, the ability to work Europeans as much as three 
hours earlier than that is going to be more likely at a shore site for 
a given transmitter/receiver/antenna configuration.  For such early 
QSO's inland I think a mountain top (and a heck of a lot of buried 
copper) would be needed.  By an hour or so after sunset, the shore 
versus inland differences would reduce to barely perceptible as the 
optimum take-off angle would be considerably higher above the horizon.

Still, having potentially two or more hours of useful communication at 
the start of an opening going east or the end of an opening going west 
is still not a trivial matter, especially in a contest scenario when 
every added QSO point matters.

Extrapolating groundwave results from a proper-size broadcast vertical 
with radials exhibits that coverage even from a professional-grade 
antenna is affected greatly by surrounding ground conductivity.

Keeping in mind that the following map for WOND 1400 (near Atlantic 
City, NJ) shows a pattern from a single-tower non-directional antenna, 
it's quite obvious that sea gain is for real:
http://www.radio-locator.com/cgi-bin/pat?call=WOND&service=AM&status=L&hours=U

This station is easy daytime copy here on Cape Cod at over 250 miles.  
Going inland to the northwest of the tower, WOND has less strength at a 
mere 30 miles.

Reciprocity would mean that the same tower used as a receiving antenna 
would have a similar pick-up pattern: far better sensitivity going east 
than west.  This jibes quite well with what is observed routinely at 
seashore broadcast-band DXpeditions even when talking about afternoon 
low-angle skip from Europe, the Middle East, Africa, and Brazil.

<<
Second, are these comparisons based on S meter readings
or signal to noise ratio?  If the latter, then it
could just as well be that it is very quiet on the
shore because nothing is out there.  Especially if
you use directional antennas to listen.
>>

S-meter readings.  Northeastern Brazil stations (Fortaleza / Natal / 
Recife areas) and "deep" Africans (e.g. the former BBC Lesotho on 1197 
kHz) that could routinely hit S-9 on the Drake R8A or Perseus with car 
roof loop at shore sites in Rockport, MA and Orleans, MA were, at best, 
in the S-2 category (or more likely just non-existent) with the same 
mobile set-up at my former location in Billerica, MA (15 miles 
northwest of Boston; 15-25 miles inland on bearings of interest).  
Differences on western Europe (e.g. Absolute Radio UK 1215), especially 
after sunset, were a good deal less as the skip was at a high enough 
angle to be less "groundwave-like."

I believe that Nick Hall-Patch and others have done simultaneous inland 
versus coastal signal observations of Asian and Down Under signals 
received around dawn in BC, WA, and OR on a fairly regular basis.  I 
think that, for them, coastal beats inland most of the time on both 
actual signal strength as well as signal-to-noise / 
signal-to-interfering stations metrics.

Once in a while greyline does give you one of those "high angle is 
best" tilted-layer paths and the best location winds up being the one 
under the spotlight.  In that case, coastal versus inland becomes 
largely irrelevant.

<<
BTW, what are the best California BC stations to look for? Its been 
decades
since Ive heard one but I havent tried hard at all.

Carl
KM1H
>>

KNX on 1070 is about the only California station that has a ghost of a 
chance to make it to New England now that the former clear channels are 
plugged up with so many domestic and Cuban stations.  Try just before 
dawn.  A properly-aimed Beverage will help.  640 KFI and 680 KNBR used 
to make the trip east in the '60s/'70s when many US stations went off 
the air after midnight.  Those days are gone.  The 1070 situation 
actually improved when CBA New Brunswick went silent about 10 years ago.

West Coast AM broadcast stations are actually heard more often in 
Scandinavia (over the pole) than on the US East Coast.

<<
ENOUGH of the "...modeling the proverbial 'vertical on the beach'" 
already...!

My "delete" button is beginning to wear out.
>>

<<
I swear I am going to start a self serving thread called ? vertical 
near by to a
beach.??
>>

<<
Yeah!!  -This one's been "done to death'!
>>

I receive the postings in digest form so I guess that means I have to 
hit delete less often if at all.

I suppose I was under the mistaken notion that antenna and propagation 
discussions were a legitimate topic here.

Mark Connelly, WA1ION
South Yarmouth, MA