Topband: 160m inv vee questions

[Dick Green WC1M]

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 <bpease2 at myfairpoint.net> 
Sent: Sunday, April 1, 2018 7:41 PM
To: topband at 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
>
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