| Index | Thread | Archive | May-2000 | Archive | Send |
 |
  |
 |
   |
|
  |
|
>Hi Ralph and gang, > I have to agree with you Ralph, and disagree with K2AW, as regards >"salt water enhancement." In the 1960's i lived in Key West for a couple >of years. I was active in chasing dx and had modest means, being a sailor >at Fleet Sonar School, so my station consisted of a Knight T-60 and >National NC-300. Antennas were low dipoles(20-30 ft. high) and a windom >20 ft. high at one end and 35 ft. high at the other. My output power was >about 15-30 watts on 10-20 meters. I worked piles of dx, on cw, including >Don Miller W9WNV/ZK1S at Suwaro Atol. Later, aboard destroyers in the >Pacific, North and South Atlantic , Indian , and Artic Oceans, i found >the propagation to be excellent, anywhere i went. My power output was 100 >watts and my antennas were either verticals or sloping dipoles. > I grew up on the east coast of N.C. ,within 300 yds. of salt water. I >enjoyed excellent propagation there too. In 1968, i lived in Jacksonville >Beach ,Fl. and had a homemade 2 element yagi on 10 meters with .25 wl >spacing between the elements(Ref., D.E.) and 30 ft. high, no more than >100 yds from the Atlantic. Europe, Africa and South America were >extremely easy to work on cw and ssb with my NC-200 transceiver(100 wts. >output).( The f/b on that antenna was 6 s units, yet nowadays i'm given >to understand that only 2 or 3 s units is possible. Makes one wonder!) > In 1932 Bell Labs conducted test to determine where to locate shore >stations for communicating with ships at sea. These tests were conducted >in the 66 and 33 meter bands, under both day and night conditions.They >reported" attenuation of 8 db to 12 db is observed at a distance of one >mile inland for both 33 and 66 meter transmissions." When i read it, it >reminded me that when i was a kid and broadcast band dx'ing, i logged >WAPE in Jacksonville ,Fl. while living in Morehead City, N.C. In the 60's >and 70's, whenever i went home to visit my parents, i'd frequently look >for WAPE on the car radio(680 khz. if i remember correctly).At and around >my parents house(300 yds. from a salt water sound, i could receive it. >But a mile further inland, it became unreadable. > Computer simulations of real world conditions cannot tell the whole >story. For that matter, humans don't know the whole story, in which to >write programs with. There remains much to be learned about propagation >and antennas, etc. We won't know it all till we know it all! And thats a >very long way off! > 73 Roy Lincoln WA4DOU FWIW: Bell Labs data cited above confirmed from British Post Office and Marconi Wireless Co experiments of 1920s and 1930s, also show ca 10db enchancement for coastal locations. In practice may be even better due to site enhancement from slope down to sea. My physics weak in this area, but think the conclusion about lack of difference between land and sea comes from Brewster angle effects. As sun reaches a critical angle to the sea, strong glare from the sea surface may be experienced. A similar effect may be observed on a smooth land surface e.g. a concrete road. Both rough seas and textured land remove most of the glare effect. Computer modelling programs typically show the land as a uniform surface, thereby giving higher Brewster reflection than most real earth surfaces. The above applies to HF radio waves within limits. Someone more learned than me may be inclined to comment. Even taking slope effects into account, my present QTH on top of slope 300ft above the beach is by informal observation worth at least 10dB over former city QTH only a mile or so in from the sea. 73 Barry ZL1DD end Barry (Baz) Kirkwood PhD ZL1DD ex ZL1BN, ZL4OK etc Signal Hill 66 Cory Road STOP AT SIGNAL HILL HOMESTAY B&B Palm Beach ON BEAUTIFUL WAIHEKE ISLAND Waiheke Island 1240 ONLY 35 MINUTES BY FERRY NEW ZEALAND FROM DOWNTOWN AUCKLAND Ph/Fax 64-9-372-5161 www.waiheke.co.nz/signal.htm -------------------------------------------- Force12Talk mailing list provided as a service by Force 12 Antennas, Inc. Force 12 Web site: http://www.qth.com/force12 Submissions: send to Force12Talk@qth.com To unsubscribe: send a blank e-mail to Force12Talk-leave@qth.com Force12Talk Message Archive: http://www.qth.com/force12/list/force12talk For problems with the list, contact force12@qth.com |
This Thread
|
This Author (May-2000)
|