Hi all,
For many years Ive had a trapped 80m/160m inverted vee with the apex at about 94 on a tower thats loaded with various yagis. The vee is oriented so that its broadside to the NE and SW (wires running SE to NW). The tower is on a steep hill, so the wire that runs to the uphill side is only about 17 feet off the ground, while the wire on the downhill side is about 27 feet off the ground (maybe more). The traps are Rayco KW-80C, which is cut for 3.625 MHz, setup for two-band operation. On each side, the 80m portion above the trap is cut to 68 feet and the portion below the trap is cut to ~47, for an overall length of ~115 feet per leg. As you would expect, the bandwidth on both bands is narrow. Since I operate almost exclusively on CW, and have an 80m delta loop with better radiation angle and bandwidth, I only use the 80m portion of the trapped vee for an SDR that monitors the band (due to switching limitations, the SDR cant use the delta loop). The lower wires have been trimmed to center the antenna at 1.830 MHz on 160m. The 2:1 bandwidth is about 40 KHz, and around 70 KHz between the 3:1 marks. So the antenna is useful on most of the CW portion of the band. It hears OK when the atmosphere is quiet, but normally I use a 520 dual-direction NE-SW beverage for listening. As expected, the effectiveness of the transmit portion is limited. Ive worked at least 100 countries with it, and in a typical contest I can work EU and SA/Caribbean if conditions are good. But Im usually well behind the top stations in multipliers maybe a little better than half what they have. Again, no surprise. Recently I started thinking that maybe I should ditch the traps and convert the antenna to a full-size 160m inverted vee. The overall length and height of the ends above ground will be comparable. But when I compared the 160m inverted vee to the 80m/160m trapped inverted vee in EZNEC+, there was only marginal difference. Theyre both cloud warmers at DX angles, and the SWR bandwidths were the same. I found this somewhat surprising, given trap losses and such. I would have expected a more noticeable difference in gain, angle and especially bandwidth. So, my first question is, am I reading the EZNEC+ results right, and theres no real advantage to converting the antenna, especially in light of losing it for SDR use on 80m? Second question came up while I was reading some articles about 160m antennas and came across one that said more radiation comes off the wires of an inverted vee than broadside. I was under the impression that inverted vees are omnidirectional, and if there was any directivity it would be broadside, like a dipole. I happened to orient my trapped inv vee so its broadside to EU (NE/SW) on the tiny chance there could be some directivity in that direction. But if the article is right, or if the radiation is truly omnidirectional, then Im better off orienting the legs NE/SW (broadside NW/SE) because the slope of the land would allow for the uphill leg to be considerably higher off the ground (it would run mostly over flat ground), though its not clear to me what advantage that might confer. However, theres a more definite advantage because the legs of the inverted vee would be much farther away from my beverage. Right now, one leg comes within about 20 feet of it. If I reorient the antenna it would be over 100 feet away. Comments? Finally, another option would be to ditch the traps and one leg, and slope the other leg towards EU as a ¼-wave vertical on 160m (with lots of ground-mounted radials, of course.) Unfortunately, that would have to be the uphill leg, so the vertical would be somewhat flatter than if I could point it SW. Would such a vertical be superior to what I have now or the dedicated inverted vee? 73, Dick WC1M _________________ Topband Reflector Archives - http://www.contesting.com/_topband