It's not necessary to place a vertical antenna at waters edge to gain the low angle efficiency advantages of an oceanfront site. There are two zones of interest: the area immediately adjacent to the antenna which primarily affects efficiency (very important for transmitting and very unimportant for top band receiving) and the Fresnel Zone which is very important for the very low angles that difficult to achieve at most land sites. Salt marshes (e.g., W1KM) are practical for long term installation but antennas over ocean water are rarely practical except on ships. The most practical ocean front permanent transmitting antenna is a land based vertical over an extensive radial system sited so that most of its Fresnel Zone is over salt water.
73 Frank W3LPL ----- Original Message ----- From: Guy Olinger K2AV <k2av....@gmail.com> To: Tom W8JI <w...@w8ji.com> Cc: Mark Connelly <markwa1...@aol.com>, TopBand List <topband@contesting.com> Sent: Tue, 19 Aug 2014 21:21:03 -0400 (EDT) Subject: Re: Topband: Modeling the proverbial "vertical on a beach" On Tue, Aug 19, 2014 at 11:24 AM, Tom W8JI <w...@w8ji.com> wrote: > Why would it matter? > > The receiving antenna does not matter, provided it responds to the wave > angle at the receive site. It doesn't matter if it is loop, a 10 foot > vertical, or a 200 foot vertical so long as the antenna does not null the > primary wave angle for the incoming signal. It does not matter if it is a > large receiving array or a whip, provided each are not nulling the primary > signal arrival. Or giving advantage to one or the other incoming angle in effect setting the primary signal arrival Not using a small omni RX antenna for this experiment introduces some serious calculation issues. E.g. if the RX setup has pattern and gain, we first have to know what incoming angle and direction a signal is arriving at and then divide the pattern out BEFORE any comparisons are made. So how do we know that? VOACAP has that built in where you are supposed to supply the RX pattern, which otherwise defaults to omni. No pattern is required to eliminate direction and elevation arrival adjustments to reported readings if the antenna is truly omni. If the RX antenna is "omni" and low enough then any enhancements are due to the propagation or environment or the TX station's antennas, which is what you WANT to see. FURTHER, since nearly all ham TX antennas are NOT at water's edge, then any tests looking for water's edge enhancement must do so by placing RX at water's edge and placing another identical RX/antenna back on the beach a few hundred feet off and another identical RX/antenna at typical shore site antenna-distance-from-actual-water's edge as in 1500 feet for W2GD and K3ZM. Putting up and maintaining TX antennas right at water's edge and feedline back to safe location for transceivers, etc, is something that likely unworkable or will not be tolerated by those controlling public beach fronts, would be a maintenance nightmare to begin with. These include such things as guy anchors under water on the beach, that will not come loose under typical random sand rearrangement underwater. Or continuous corrosive/shorting salt spray on metal and insulators. Or exposure to vandalism. RX skimmers with a short antenna can be made very small, battery charged by solar power, completely enclosed in smallish sealed box and communicating with the internet via wifi back off the beach. They can be put on top of pier poles, etc, and completely controlled remotely. 73, Guy _________________ Topband Reflector Archives - http://www.contesting.com/_topband _________________ Topband Reflector Archives - http://www.contesting.com/_topband