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Author Topic: I finally put up a Beverage antenna  (Read 17141 times)

Offline Jari Finland

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Re: I finally put up a Beverage antenna
« Reply #30 on: November 08, 2014, 1933 UTC »
I'd say around 100 metres would be where beverage starts working (on MW). Before that it is a bit toy. :P
If it is possible, 200 metres is much better of course, and there is no limit...

Offline ChrisSmolinski

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Re: I finally put up a Beverage antenna
« Reply #31 on: November 08, 2014, 1946 UTC »
I'd say around 100 metres would be where beverage starts working (on MW). Before that it is a bit toy. :P
If it is possible, 200 metres is much better of course, and there is no limit...

My primary band of interest is 48 meters, not MW. So I am wondering if it is already long enough, and I've reached the point of diminishing returns.
Chris Smolinski
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Offline Rafman

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Re: I finally put up a Beverage antenna
« Reply #32 on: November 08, 2014, 2003 UTC »
Chris, is it 1 wavelength [~150']???

I would try adding resistance. I am using a 470 ohm & am about to add another 500 ohm pot to see if I can find a "sweet spot"...

Since you are targeting a region, adding another 150' [2 WL long], would narrow the lobe & increase forward gain...

My 1 WL exhibits good forward direction, on 49mb...  Try peaking your termination value... IMHO

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Offline ChrisSmolinski

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Re: I finally put up a Beverage antenna
« Reply #33 on: November 08, 2014, 2025 UTC »
It's about 1.3 wavelengths long now. So another 100 feet or so would take it to 2 wavelengths.  It will be a bit of a project cutting a path through the brush to do that, which is why I am asking around before I start :-)

I can try tweaking the termination resistance, maybe early this next week before the cold blast arrives.
Chris Smolinski
Westminster, MD
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Offline Jari Finland

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Re: I finally put up a Beverage antenna
« Reply #34 on: November 08, 2014, 2224 UTC »
For what it's worth...

Even in the case I modeled long wire wrong (hey, everything is possible) I'd seriously consider using termination resistor to avoid antenna working as a backbeam. Look the front/back ratio.

Chris might be interested in comparing 60 m and 100 m behaviour on 6.3 MHz. It looks like a real choice would be 110 m (360 feet).

Needless to say, but take this only as an approximation.

Long wire for 6.3 MHz on 3 m height

               Gain dBi F/B dB angle Z=R+jX

50 m perfect ground   8.71   -0.02   62   53-1021
50 m my real ground   10.46   0.52   57.6   53-1021
60 m perfect      2.26   0.08   33.7   15+250
60 m real         8.73   -4.96   31.0   15+250
70 m perfect      6.31   -0.01   47   2624+6214
70 m real         9.15   -0.34   44   2624+6214
80 m perfect      3.38   0.04   53.8   17-21
80 m real         8.07   -2.94   28   17-21
90 m perfect      7.6   0.07   37.7   36+982
90 m real         12.65   -1.71   32   36+982
100 m perfect      7.28   -0.07   45   23-414
100 m real         11.52   1.13   33.7   23-414
110 m perfect      3.03   0.06   29.9   24+447
110 m real         10.86   -2.89   26   24+447
150 m perfect      4.9   -0.15   38   18-130
150 m real         12.04   -0.72   22   18-130
200 m perfect      1.79   -0.38   35   19+65
200 m real         13.03   -1.31   19   19+65
300 m perfect      0.39   -0.1   37   43+431
300 m real         13.58   -1.09   17   43+431
400 m perfect      1.05   -0.02   34   271+1232
400 m real         13.32   --   14.5   271+1232
500 m perfect      0.62   -0.05   31   1079-1693
500 m real         14.09   1.09   13.5   1079-1693

(modeling and "perfect ground" as figured by MMANA-Gal Basic)

My hunch is that there is something wrong here in this table, but... maybe I ponder the case later.

I started playing with MMANA-Gal because I wanted to design a perfect multiband wire antenna for ham purposes, which are completely different thing than listening purposes, and I almost think I found a solution with the magical length of 84 metres. But I haven't tested that in real life yet...
« Last Edit: November 08, 2014, 2251 UTC by Jari Finland »

Offline RobRich

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Re: I finally put up a Beverage antenna
« Reply #35 on: November 09, 2014, 0039 UTC »
Adding another 100' is not likely to offer a dramatic return IMO. If you could add a few hundred more feet, then I would say go for it.

I am with Rafman. Optimize what you have. Tweak the termination resistance. How is the feedline isolation? Consider winding a 1:1 choke out of the feeline at the feed point transformer. Install multiple ferrite chokes at random interval along the feedline. Each dB you can drop in locally coupled noise is hopefully another dB you can add to the S/N ratio.
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Offline ChrisSmolinski

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Re: I finally put up a Beverage antenna
« Reply #36 on: November 10, 2014, 2037 UTC »
I tried to adjust the termination resistance today, without success.

I used SdrDx on a laptop outside, via WiFi, so I could sit next to the termination point while adjusting it. I used a 1K potentiometer, not multi turn, so I don't think it was inductive. I first tried using WWCR on 31 meters, as it was pretty much in the backend of my desired pattern. I don't think I was able to get a null, but it was difficult to tell, due to fading. I then tried a MW station, which had a constant signal, but I could not get any sort of a null. Perhaps because the antenna is too short to be directional down there. (930 kHz station, the antenna is 200 ft long)
Chris Smolinski
Westminster, MD
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netSDR / AFE822x / AirSpy HF+ / KiwiSDR / 670 ft horizontal loop / 500 ft northeast beverage / 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: I finally put up a Beverage antenna
« Reply #37 on: November 11, 2014, 2118 UTC »
Your 200' beverage will be practically almost omnidirectional at MW, and probably similar up through much of the tropical HF bands.

To tweak resistance tuning, instead try to find a decently stable station at a HF frequency where your antenna is multiples of the wavelength, thus allowing you to better assess the directivity and null(s).

BTW, did you ever determine if the transformer you are using is 4:1, 9:1, etc.? Balun or unun? A balun might have better isolation, but an unun is typically more appropriate for a traditional beverage. Try it both ways, though if going with an unun, you will probably want at least stacked/looped ferrites on the feedline to help with antenna RF isolation.
Tampa, FL USA | US Map Grid EL88
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