[600MRG] Em Con with 630m - Mountain "propagation"

Edward R Cole kl7uw at acsalaska.net
Mon Jan 6 18:49:01 CST 2014 

At 12:16 PM 1/6/2014, Laurence KL7 L wrote:
>Ed/Ken = there is a radio station in Homer Alaska  KGTL at 5Kw on 
>620KHz which sits on the a piece of land fairly up but below a East 
>/West Ridge and further "down" and screened partly from us up here 
>North of Anchorage, but open to the Sea and bays to the South = 
>fringe coverage is shown as Seward,  South Anchorage and just South 
>of Kodiak over a Sea path but attenuation really increases on any 
>increase of mountain range that intervenes pretty quickly.
>
>  If I drive in Anchorage from 50 miles North in Wasilla (about 160 
> miles from the TX) I can listen to the oldies music (and Rush L in 
> the mornings, god help me) but driving South towards the TX  and 
> close in to the Chugach mountains the signal dissapears only to 
> reappear further  as we move away from the mountains again.
>
>  Ive not seen knife edge at MF but thats not to say it doesnt exist 
> -  For NDBs here in the Anchorage area there is a warning that 
> going into the mountains at low levels can produce false bearing 
> and of course weak signals. And looking at how XPQ behaves on 
> ground wave I lose it pretty quickly moving North into the 
> Talkeetnas again only to reappear when we have an wide open valley- 
> so we do get shadowing.
>
>Case in part is the NDB  FA up on 510kHz to the North of me - given 
>its a low power and particularly awful short top loaded Tee its ERP 
>is low but I would expect to see it nightly if I was say in Okie at 
>the same distance - but Ive not seen it at all this winter, 
>though  the Iono gods havent smiled much. There are a number of 
>(high)mountain ranges which Ed mentions nearby which means low angle 
>stuff is cut and ground waves are obliterated/broken up..

When I began monitoring in 2010, I saw FA most nights fairly 
strong.  But it is in the direction north up the long valley of the 
Susitna River for me.  Mt Mckinley is about az=5 for me whereas 
direct az to Fairbanks (BP64) is 19.7 degrees.  There is a well known 
VHF shot between Anchorage and Fairbanks by forward scatter off the 
mountain (about a 30-degree dogleg).  I have worked KL7EDK (BP64lv) 
on 2m FM with both of us using four yagi arrays and my running 150w 
over a 350mi path with the 18K Alaska Range in between.  Mckinley is 
visible from Anchorage (sits nearly 21K).  Wasilla is blocked to the 
north by the Talkeena Mountains so one must rely on knife-edge prop 
in addition.

>
>I know theres a lot more...Ed those volcanic eruptions played havoc 
>with my microwave links to the platforms in the Cook Inlet - :-)
>
>Laurence

Yeah, volcanic ash fertilizes my lawn and my sled dogs!  Mt. Redoubt 
is about 50 mi from me and Mt. Spurr about the same.  Two more active 
volcanoes are Mt. Illiamna and Mt. St. Augustine further south in the 
10K Alaska Range that runs along the western shore of Cook Inlet.  I 
live 2-miles from the eastern shore with average width of 30-50 mi.

Oh well so much for the geography lesson - sorry!

73, Ed

>
>
>
>
>
>
> > From: kgordon2006 at frontier.com
> > To: 600mrg at w7ekb.com
> > Date: Mon, 6 Jan 2014 10:14:44 -0800
> > Subject: Re: [600MRG] Em Con with 630m - Mountain "propagation"
> >
> > Gents: You might consider the phenomenon of what is sometimes called,
> > "knife edging" of propagation.
> >
> > I remember reading a study on this wherein the signal levels at certain
> > distances from the tops of mountains or ridges were very significantly
> > stronger than both closer-to and further-from those "edges", and 
> that there
> > were "zones" wherein this phenomenon was repeated.
> >
> > As I remember it, the signals were refracted downward at various angles
> > due to the edge of the obstruction, somewhat the way light is 
> refracted by a
> > sharp edge.
> >
> > This may explain otherwise difficult-to-explain results.
> >
> > Further testing is necessary.
> >
> > Ken W7EKB
> >
> >
> > On 6 Jan 2014 at 9:06, Edward R Cole wrote:
> >
> > > Mike,
> > >
> > > That is interesting to know.  The front range is very high reaching
> > > 14K peaks so would not expect good signal levels the other side.  The
> > > Kenai Peninsula is rolling hills and lakes similar to parts of
> > > Minnesota with about 15mi over water to Anchorage then a basin in the
> > > mountains so not too much obstruction on the path we tested.  About
> > > 12mi beyond Wasilla are the Talkeetna Mountains which are in the 4-6K
> > > range.  The Eastern half of the Kenai Peninsula is covered with 4K
> > > mountains which block VHF path to Seward where one hospital is
> > > located.  Homer hospital is on the south side of a 1.1K ridge so
> > > similarly has no VHF path though a 2m repeater is located on the ridge
> > > which is in range of me at 90mi.  South of Homer is a bay and then
> > > high mountains.  The Soldotna Hospital and KPB 911 call center are
> > > 22mi south of me, so closer to the other two sites.
> > >
> > > I would expect fair coverage for 600m to Homer but wonder how it would
> > > reach to Seward about 120mi thru mountains and valleys.  Occasionally
> > > we hear the Seward 2m repeater, but this is VHF prop which would be
> > > totally different.
> > >
> > > Normally I get night-time 80m coverage out 400 to 800 mi. which
> > > covers a lot of Alaska.  SE AK is hardest to reach at 800+ miles,
> > > though very easy on 6m meteor scatter.
> > >
> > > For emcomm the officials want comms on the Peninsula and then links to
> > > Anchorage 80mi north of the 911call center (which is co-location of
> > > the Kenai Bureau Emergency Response Center).  Our local ham club holds
> > > meetings and its annual hamfest in that building.  It would take a
> > > world-class earthquake to affect all of Alaska infrastructure.  But
> > > the communications industry now have mobile earth stations to support
> > > long-distance phone/internet.  250 villages in AK are provided routine
> > > phone/internet/TV via satellite link using local earth stations.  That
> > > makes the AK communications system much more endurable to what mother
> > > nature dishes out.  I believe two undersea phone lines connect us to
> > > lower-48 plus satellite links.  Those lines were disrupted in the 1964
> > > event.  The AK RR tracks out of Anchorage to Seward were destroyed and
> > > took months to restore train traffic.  Seward was nearly destroyed as
> > > a town since it was hit by Tsunami.  it is the southern RR terminus
> > > and ice-free port of much shipping.  Tracks go thru Anchorage which
> > > was created by the RR in 1915 to serve Fairbanks 750mi further north.
> > > This is the only RR in state with no connection out of state.  Most
> > > freight is brought by barge from Seattle.
> > >
> > > Major volcanic eruption, extreme wind storms, and wildfire are other
> > > potential disasters.  I have seen three eruptions since living up here
> > > 35 years and many earthquakes.  Fortunately no nearby fires as we are
> > > in the forest.  Have seen lots of wind over 65mph.  Anchorage hillside
> > > is subject to 50-100 mph winds several times per year.  So emcomm
> > > prepareness is important up here.
> > >
> > > OK enough of this, thanks for reading.
> > >
> > > 73, Ed - KL7UW
> > >
> > > At 04:39 AM 1/6/2014, Michael Mussler wrote:
> > > >My son and I did some 600m tests a few years ago running about 1 w
> > > >ERP using PSK31 and a mobile 600m receiver. We found that in very
> > > >rugged terrain (i.e. steep, narrow valleys and canyons here in the
> > > >Front Range foothills of Colorado) we got solid copy out to 10 miles
> > > >from the transmitter site. The receive set up consisted of a ferrite
> > > >rod loop antenna with preamp driving the 630m receiver and laptop
> > > >computer. We even copied the PSK31 signals with the loop antenna
> > > >resting on the dashboard inside the vehicle.
> > > >
> > > >Consider the utility of a one way communication system during an
> > > >emergency such as a forest fire or other natural disasters:
> > > >transmissions of low data rate information (localized WX info, road
> > > >closures, situation status) could be made to field teams that would
> > > >not be possible with VHF/UHF repeaters and cell sites that were down.
> > > >
> > > >Due to the improved S/N with the WSPR modes, even better coverage
> > > >should be possible for this application.
> > > >
> > > >-Mike Mussler
> > > >WD2XSH/12
> > > >AI8Z
> > > >
> > > >
> > > >
> > >
> > > 73, Ed - KL7UW
> > > http://www.kl7uw.com
> > >      "Kits made by KL7UW"
> > > Dubus Mag business:
> > >      dubususa at gmail.com
> > >
> > >
> > > _______________________________________________
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> > >
> >
> >
> >
> > Kenneth G. Gordon W7EKB
> >
> > "Courage is being scared to death but saddling up anyway."--- John
> > Wayne
> >
> >
> > _______________________________________________
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>
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73, Ed - KL7UW
http://www.kl7uw.com
     "Kits made by KL7UW"
Dubus Mag business:
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