Meaning run the wires NE-SW? The article I read did mention the polarity being vertical in the direction of the wires, consistent with your model.
Would the same apply to the 80m portion? Thanks & 73, Dick -----Original Message----- From: Brian Pease <bpea...@myfairpoint.net> Sent: Sunday, April 1, 2018 7:41 PM To: topband@contesting.com Subject: Re: Topband: 160m inv vee questions I modeled an inverted-V last week. If the feed is balanced, the total radiation pattern (Hor + Ver) is omni-azimuthal with a lot of upward radiation. Directly broadside, the radiation is horizontal but off the ends it is entirely vertical. For 160 to EU I would orient NE-SW. On 4/1/2018 6:41 PM, Dick Green WC1M wrote: > Hi all, > > > > For many years I’ve had a trapped 80m/160m inverted vee with the apex > at about 94’ on a tower that’s loaded with various yagis. The vee is > oriented so that it’s 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 can’t 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. I’ve worked at least > 100 countries with it, and in a typical contest I can work EU and > SA/Caribbean if conditions are good. But I’m 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. They’re 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 there’s 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 it’s 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 I’m > 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 it’s not clear to me what advantage that might confer. > However, there’s 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 > _________________ Topband Reflector Archives - http://www.contesting.com/_topband