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Author Topic: 250 foot V Beam Antenna Aimed To Europe  (Read 371 times)

Offline ChrisSmolinski

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250 foot V Beam Antenna Aimed To Europe
« on: August 18, 2020, 1339 UTC »
Construction details for yet another antenna, this time a 250 ft V Beam. It's a pair of 250 ft long wires, about 50 degrees apart, feeding a transformer located up 52 ft. The wires are sloped down to the ground, and terminate into 400 ohm resistors to ground.
The transformer has 3 turns on the RG-6 input and 10 turns on the output, wound on the standard BN 202-73 binocular core.

The goal for this antenna is good directivity towards Europe (especially on the 48 meter and other pirate bands), which is at about a 50 degree azimuth from me, hence the orientation of the wires at 25 and 75 degrees. 

Construction was indeed a bit tricky, as I had to not only get the feedpoint high, but also run the two wires at the correct azimuth angles, and (relatively) equal slopes, dealing with numerous tree branches in the way on the two paths (although they also provided some support for the wires along the way). I ended up launching several temporary ropes over branches to pull the wires along the correct path, sort of weaving them into the trees. The Big Shot came in handy: https://www.hfunderground.com/board/index.php/topic,60415.0.html

So how does it work?  From early testing (it's not really DX season yet and there is a lot of storm static) quite well. I get noticeably better signal to noise when listening to stations from Europe vs my other antennas. Last night I had not only great reception from The Vault on 6985 (which often comes in well here anyway) but several other Europirates. I then took a spin down to the LW band, and was rewarded with audio from several LWBC stations which were just faint carriers on the 120 ft T2FD. I need to do some more one on one comparisons vs the 500 ft beverage and sky loop, at the time they were otherwise occupied. 

Right now I have this antenna connected to KiwiSDR #2: http://sdr.hfunderpants.com:8074/
The 120 ft T2FD, which is also an excellent performer, is on KiwiSDR #1, for comparison purposes: http://sdr.hfunderpants.com:8073/

I found a V Beam drawing online which I marked up with the details for my antenna:


SWR (as measured in the shack):


Resistance and Reactance (as measured in the shack):



MiniNEC calculations of the radiation pattern for the 48 meter band. Note for the azimuth pattern it's assumed the antenna is aimed north, for ease of calculations:





Not bad on 20 meters:





11 meters, interesting if true:






Even on 75 meters it is not bad:






Not spectacular (in theory anyway) on MW as expected, here is 1700 kHz, but on the air testing shows it really works well, even down to LW:


Chris Smolinski
Westminster, MD
eQSLs appreciated! csmolinski@blackcatsystems.com
netSDR / AFE822x / AirSpy HF+ / KiwiSDR / 900 ft Horz skyloop / 500 ft NE beverage / 250 ft V Beam / 58 ft T2FD / 120 ft T2FD / 300 ft south beverage / 43m, 20m, 10m  dipoles / Crossed Parallel Loop / Discone in a tree

Offline RobRich

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Re: 250 foot V Beam Antenna Aimed To Europe
« Reply #1 on: August 18, 2020, 2216 UTC »
Looking good. :) Definitely keep us updated.

Sadly, I do not have room for such a large antenna. I have been considering a N4GG array at ~6-7MHz for improved directivity into EU and maybe VK as a bonus, but I am not too thrilled about trying to layout and rig it for a residential lot.
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Offline pinto vortando

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Re: 250 foot V Beam Antenna Aimed To Europe
« Reply #2 on: August 18, 2020, 2311 UTC »
Sorta looks like half of a rhombic  ???
Which begs the question: would it be bi-directional (ZL, South Pacific) if left unterminated ?
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Online Ray Lalleu

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Re: 250 foot V Beam Antenna Aimed To Europe
« Reply #3 on: August 20, 2020, 1720 UTC »
Have you simulated your V beam with various values for the terminating resistors?
The idea would be to get the best F/B ratio.

D/E/F/G/It/Sp : Dutch/English/French/German/Italian/Spanish
+/- : about 0.02 offset, ++/-- 0.03/0.04 offset
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Offline ChrisSmolinski

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Re: 250 foot V Beam Antenna Aimed To Europe
« Reply #4 on: August 20, 2020, 1742 UTC »
Have you simulated your V beam with various values for the terminating resistors?
The idea would be to get the best F/B ratio.

Good question. Yes, I did experiment a bit with values in the models and that seemed to be the best compromise over the intended frequency range.
Chris Smolinski
Westminster, MD
eQSLs appreciated! csmolinski@blackcatsystems.com
netSDR / AFE822x / AirSpy HF+ / KiwiSDR / 900 ft Horz skyloop / 500 ft NE beverage / 250 ft V Beam / 58 ft T2FD / 120 ft T2FD / 300 ft south beverage / 43m, 20m, 10m  dipoles / Crossed Parallel Loop / Discone in a tree

Offline Charlie_Dont_Surf

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Re: 250 foot V Beam Antenna Aimed To Europe
« Reply #5 on: September 13, 2020, 0124 UTC »
How long is the coax feeding this antenna?
"Every minute Charlie squats in the bush, his signal gets stronger..."

Offline ChrisSmolinski

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Re: 250 foot V Beam Antenna Aimed To Europe
« Reply #6 on: September 13, 2020, 1147 UTC »
How long is the coax feeding this antenna?

Good question. My ball park guess is 75 to 100 ft from the feedpoint down to a grounding block where it enters an underground coax run through conduit. That is 70 feet, then another grounding block and another 25 ft or so to the patch board in the shack.  So probably something in the 175 to 200 ft range, give or take. Signal levels are still plenty strong. No doubt the long coax run is heavily influencing what impedance values I see here in the shack, as well.

I really only had one viable location for the feedpoint that would allow me to run two 250 ft wires in the correct directions, mostly dictated by the locations of trees (both to use for support, as well as staying away from other trees that would make installation difficult or impossible) as well as staying away from other antennas. That meant it's some distance from the house, as well as (unfortunately) aimed at the house. I think it's picking up some RFI from stuff in the house, I want try and try down some of the worst offenders and see if they can be dealt with.
Chris Smolinski
Westminster, MD
eQSLs appreciated! csmolinski@blackcatsystems.com
netSDR / AFE822x / AirSpy HF+ / KiwiSDR / 900 ft Horz skyloop / 500 ft NE beverage / 250 ft V Beam / 58 ft T2FD / 120 ft T2FD / 300 ft south beverage / 43m, 20m, 10m  dipoles / Crossed Parallel Loop / Discone in a tree

Offline Charlie_Dont_Surf

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Re: 250 foot V Beam Antenna Aimed To Europe
« Reply #7 on: September 13, 2020, 2002 UTC »
No doubt the long coax run is heavily influencing what impedance values I see here in the shack, as well.

Yeah, that's where I was going with that question. I don't have much experience (i.e., none) with terminated wire antennas so I was surprised by the relatively tame impedance variation across the wide bandwidth, so at first I was thinking that the long coax feed was reducing the return loss. However, thinking about this some more (and thinking out loud), that's the whole point of a terminated wire antenna: relatively tame impedance variation across frequency.

I really only had one viable location for the feedpoint that would allow me to run two 250 ft wires in the correct directions, mostly dictated by the locations of trees (both to use for support, as well as staying away from other trees that would make installation difficult or impossible) as well as staying away from other antennas. That meant it's some distance from the house, as well as (unfortunately) aimed at the house.

These are the trade-offs and compromises that have to be made. That's life.
"Every minute Charlie squats in the bush, his signal gets stronger..."