[opendtv] Re: 200 Mile 8VSB Reception
- From: Richard Hollandsworth <holl_ands@xxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Wed, 17 Jan 2007 16:58:14 -0800 (PST)
Ccccoooollldddd.....it's SNOWING in Malibu Canyon....
For the record, San Diego Airport temperature was about
"average" on 1 Jan with high of 61F and low of 50F.
I couldn't pull up the Tropo Duct prediction for that day, but this is
what it looks like when it's "cold":
http://www.dxinfocentre.com/tropo_enp.html
Not hopeless, but looking better on Saturday....
Compare to "hot spot" tropo duct preditions for southern climates:
http://www.dxinfocentre.com/tropo_oce.html
In the summer SOCAL frequently gets orange-red along the coast..
BTW: Although HEAT creates the evaporation ducts, WIND will
rough up the ocean surface and create turbulence in the overlaying
duct, negating the duct effect.
holl_ands
========================================
John Willkie <johnwillkie@xxxxxxxxxxxxx> wrote: v\:*
{behavior:url(#default#VML);} o\:* {behavior:url(#default#VML);} w\:*
{behavior:url(#default#VML);} .shape {behavior:url(#default#VML);}
st1\:*{behavior:url(#default#ieooui) } It should also be noted that
the effect is generally more pronounced in summer than winter, and that this is
a particularly cold winter, and last weekend was very cold. For Southern
California.
John Willkie
---------------------------------
From: opendtv-bounce@xxxxxxxxxxxxx [mailto:opendtv-bounce@xxxxxxxxxxxxx] On
Behalf Of Richard Hollandsworth
Sent: Wednesday, January 17, 2007 3:19 PM
To: opendtv@xxxxxxxxxxxxx
Subject: [opendtv] Re: 200 Mile 8VSB Reception
A couple comments re. "Ducting".
The San Diego to Santa Barbara path is almost all over water and
hence relies on the SURFACE Ducting effect, wherein the signal
is trapped in a fairly low loss "waveguide" formed by the ocean's
surface and a low lying reflective layer.
This also explains many extremely long DX events, such as report
of 2500 miles FM from Tijuana to Hawaii, found in the Wiki article...
Things get more "interesting" when TX or RX sites are at or above the
reflective layer.....such as attenuating coupling into the "waveguide"....or
forming a less efficient secondary duct above the surface duct...such as the Mt
top to Mt top links...
Another, oftentimes overlooked, aspect of long distance DX is the
need for an on-channel noise floor close to the receiver's thermal
noise floor.....which can be very difficult to achieve if there are high
power transmitters generating intermod noise in your front end.
Hence, these long distance DX reports are almost always from
extremely rural locations....and rarely from the outer suburbs...
holl_ands
====================================
John Willkie <johnwillkie@xxxxxxxxxxxxx> wrote:
The ducting effect along the Southern
California/Northern Baja coast is well known. There?s a mountaintop just north
of Ensenada (90 miles south of the border) where people with analog cell phones
can get native LA analog cellular (no roaming.)
John Willkie
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