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Before I address the horizontal/vertical enhancement over water, I would like to offer a few other things to consider when you compare your station to your friends... >I live on a peninsula, about 220' ASL, with salt > water about 2 miles to my west and 3 miles to my east. My buddy lives 20 > miles away, 50' ASL on the east side of a small island, with his tower > about 100' from the shore line, and nothing but salt water for 20 miles > from 330 degrees to 150 degrees azimuth. If he is 100' from the shore, and the ground is at 50' ASL (ie on a cliff or small incline), he is likely getting a lowering of the take off angle. If you are on flat ground, that difference in performance could be significant and easily account for all the difference on the high bands. If your QTH at 220' is on a hill that is sloping down (and the antenna can see the sloping terrain), your antenna could be TOO HIGH, ie the antenna lobe could be split into many lobes, with nulls in useful take off angles. On hill top locations, often the best height for a 10m antenna is around 30'. BTW, What happens in the other directions? Does he beat you there? If so, then there are issues at play that have nothing to do with salt water. >We have identical 50' towers and > modest (nameless) trapped tribanders, Not all trapped tribanders are created equally. It is VERY possible there is a significant difference in the antenna performance. A few S-units could easily be involved. >He's been active at this location for a year, If your friends antenna and coax are new, and yours has been installed for a while (and at 2-3 miles from the ocean you are still getting a lot of salt corrosion) the difference in the newness of the antenna/coax could easily add a few dB. Though from the sounds of it, you are hoping to change that equation by installing a F12 antenna :) At the same time you install your F12 antenna, if you haven't replaced the coax in a few years, this would be a good time to do it, and of course, install the best coax you can - its worth every penny. Coax (RG-8, RG-213 etc) slowly degrades over time, and replacing it every 5-10 years is worth it if you want to maintain efficiency (especially in a harsh environment). At N6RO's contest station, we recently replaced the coax jumpers which had been there for 20 years (he uses hardline for the main feeders), and the coax jumpers were brittle, the outer jacket was gone in many areas, and in a few places you could even see the center conductor! (the foam had cracked and fallen away too). > similar wire antennas for 160 - 40 meters. What is the orientation of the antennas? There could be a directivity issue here, with a few S-units of difference if he's pointed at the DX, and your antenna tips are towards the DX (ie pointed away from the DX). Dipoles are fairly directive antennas (specifically a there is a large null off the ends of the antenna). If you are using inverted-V antennas on 40-160, there is a large vertical radiation component to that antenna. Being 100' away from the ocean would likely give your buddy a significant edge using an inverted-V due to the enhancement of the vertical polarized component. >On HF, I'm using an FT-990 > and he's using an FT-1000D, both barefoot. I have used both, and the 990 does seem to have a high background hiss. Also, there seems to be noticeable filter loss on the 990 (I dont remember about the 1000D). Many times I have used the 990 at N6RO's contest station and could run tons of weak JA's on CW using the SSB filters (IE wide open) when I couldn't hear a single one when using the 500hz CW filters. Though in all fairness, the difference in radios is probably not adding much to your friends performance. > I hope my new soon-to-be-erected Force 12 antenna will recover a db or so. You will likely improve much more than the "nameless manufacturers specifications" indicate. Let us know what happens. Without going into complicated math, horizontal polarized signals do not gain any enhancement over salt water... though to be specific for all the propagation gurus out there, there is about 1 dB of enhancement at extremely high take off angles 80-90 degrees, but NO ENHANCEMENT at typical angles used for skywave (DX) propagation. If you play with any antenna modeling program, and you can verify that horizontal polarization DOES NOT gain any enhancement from salt water. The salt water is a non-issue for the horizontal high band antennas. Though it may not seem like it, I didn't mean to beat you up with this Email :) But unfortunately there could be a number of variables which you have not considered that could easily account for the difference in performance. 73, Kenny K2KW PS dont forget to account for any installation issues, like antenna proximity that interferes with antenna patterns etc. -------------------------------------------- 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 |
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