Re: Topband: Verticals by the sea
This is purely anecdotal. I visited San Andres Providencia Islands twenty times between 1970 and 1990. I always operated 160 during those visits. On three occasions, at three different locations, I set up a 43 foot Minooka Special within 30 feet of the waters edge and had some radials running out into the sea. On the rest of the trips I operated from the QTH of HK0BKX, HK0DMA, HK0COP or one of the other resident Hams. They were all 2000-3000 feet inland from the sea. You can't get much further from the water because San Andres is 7.5 miles long and 1.5 miles wide. The difference in success between waters edge and a half mile inland was like night and day using the same antenna system. The seaside locations usually brought us twenty over nine reports from the US as well as Europe using 100 watts on 160. We even ran phone patches on 160, There was no satellite phone service in the earlier years. On Providencia we used a 130 foot wire from our second story room at the Aury Hotel. It ran over a salt marsh/lagoon to the second story window of a house. We warned the owner to stay away from the end of that wire. We fed it against the hotel plumbing system. It worked surprisingly well. BTW, as an aside, the telephone system between San Andres and Providencia in those days was a couple 100 watt RCA SSB rigs on 5.3 mHz feeding dipoles about 30 feet high. The islands are 50 miles apart. Carrier pidgeons would have worked better. 73, Barry _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: verticals by the sea
NEC modeling to determine the effects on the fields radiated by a vertical monopole when siting it near a salt-water coastline can be highly misleading if the surface wave field is not considered. For example, the plots linked below show that for average earth conductivity the E-field at 5 degrees elevation is about 2.44 times greater in the surface wave plot than in the far-field plot, at the same horizontal distance from the radiator. Their difference is infinite in the horizontal plane. But if this radiator was sited 1 km from the ocean, then the fields at 1 km shown in the surface wave plot would decay at nearly a 1/r rate as they propagated further on that bearing, along and over the ocean surface. This is a much different conclusion than reached when considering only the NEC far-field analysis. Comment/discussion is invited. R. Fry http://s24.postimg.org/6nchfpt1h/NEC_FF_vs_NF_Calcs.jpg _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: verticals by the sea
Is there any advantage to using an inverted VEE by the sea? Didn't I read inverted VEEs had a lot of vertical polarization? Reason I ask is I plan to do the IOTA contest on an Island in NB or NS and have not yet decided on an antenna. Thanks, Mike VE9AA Mike, Coreen Corey Keswick Ridge, NB _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: verticals by the sea
Hi Mike, There's some vertical polarization off the ends of an inverted-V, but is significantly down from the horizontally polarized radiation broadside to the antenna. The advantages of a seaside location for horizontal polarization are an unobstructed horizon and very efficient ground gain from an extremely flat Fresnel zone. Many carefully selected land locations can provide the same benefits. Unless you can install your inverted-V sufficiently high to produce significant low angle radiation, you would would do much better with a vertical very close to the sea shore or a salt marsh. Installing your inverted-V near the edge of a bluff overlooking the sea would also be excellent if its sufficiently close to the edge so that the inverted-V illuminates most of the near edge of the Fresnel zone. Of course, many land locations can provide the same benefits. The benefits of a flat Fresnel zone are discussed in detail in: https://archive.org/download/sitingcriteriafo139utla/sitingcriteriafo139utla.pdf 73 Frank W3LPL From: Mike Smith VE9AA ve...@nbnet.nb.ca To: topband@contesting.com Sent: Friday, April 3, 2015 3:17:48 PM Subject: Re: Topband: verticals by the sea Is there any advantage to using an inverted VEE by the sea? Didn't I read inverted VEEs had a lot of vertical polarization? Reason I ask is I plan to do the IOTA contest on an Island in NB or NS and have not yet decided on an antenna. Thanks, Mike VE9AA Mike, Coreen Corey Keswick Ridge, NB _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: verticals by the sea
Mike An Inverted V does have the same lobe horizontal and vertical but they are 90 degree apart, If you run EZENEC and change description option to Ver. Hor. and Total field, you will see that at 0 degree Horizontal is maximum and Vertical is zero, at 45 degree both fields are the same, and at 90 degree Horizontal is zero and Vertical is max. However close to good ground the horizontal signals is attenuated so in practice the inverted V near the see will radiate only vertical in the direction of the wire. Better solution is a vertical with the radial inside the salt water., just toss few feet of wire inside the water, more is always better, the electrical contact with the salt water is the key point here. The wire will break , keep adding some more every day. You can check the TX3A antenna document from AA7JV, it has an elegant using a T vertical vertical. http://www.tx3a.com/equipment.html 73's JC N4IS -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Mike Smith VE9AA Sent: Friday, April 03, 2015 11:18 AM To: topband@contesting.com Subject: Re: Topband: verticals by the sea Is there any advantage to using an inverted VEE by the sea? Didn't I read inverted VEEs had a lot of vertical polarization? Reason I ask is I plan to do the IOTA contest on an Island in NB or NS and have not yet decided on an antenna. Thanks, Mike VE9AA Mike, Coreen Corey Keswick Ridge, NB _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
