Topband: 160m inv vee questions

Sun Apr 1 21:32:21 EDT 2018

Yes run the wires NE-SW for 160.  This might not help (or hurt) 80m.
Even a flat (low) dipole has vertical radiation off the ends.  I have a 
full-size NE-SW 630m dipole only 2m off the ground that has been heard 
in EU many times on WSPR.

On 4/1/2018 8:19 PM, Dick Green WC1M wrote:
> 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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