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Got the Room? Try a PAIR of phased Beverages for receiving - side by side.




 
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Author Topic: Got the Room? Try a PAIR of phased Beverages for receiving - side by side.  (Read 11289 times)
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K1JJ
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« on: January 28, 2006, 11:28:19 AM »

Probably the best antenna for receving is a Beverage. Usually 1-2 wavelengths long is a good number, 6'-7' off the ground for 75M.  About 580' long on 75M is right.

If you have the room, consider running a second one alongside, but spaced about 200' apart. [3/4 wavelength spaced] Feed them in-phase with a "T" connector splitting the two feedpoints with equal coax lenghs.

This configuration USUALLY adds almost 3db in S/N by narrowing down the horizontal forward lobe and also giving superior side rejection over a single wire.

As you will see in this article, if a Beverage gets longer than 2 wavelengths, [600' or so] the pattern starts developing side lobes, the f-b deteriorates and the real world phase relationship of the incoming signal gets distorted. ie, it is hard for a wavefront to remain in phase if the physical wire structure is separated by more than a coupla of wavelengths in real life.  A LONGER than 2 -3 wavelength Beverage usually has this problem, depending upon conditions.  The wave at the front is not in phase with the one arriving at the rear, thus potential cancellation of varying degrees in random, etc.
This problem is solved by running shorter Beverages in phase.

I've decided to try another Beverage in-phase here. I was so impressed with this info, I wanted to pass it along.  Check out the relative performance between various receiving antennas including the difference over a single Beverage vs: two in phase.

http://www.w8ji.com/receiving.htm

http://www.kkn.net/~n2nc/bev_arrays/

http://www.eham.net/articles/503


73,
T

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Steve - K4HX
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« Reply #1 on: November 22, 2012, 01:35:11 PM »

Good stuff.

Here's something to think about. The boys at the Bell System knew this in the 1920s. From the Bell System Technical Journal from April 1929:

Quote
In the lateral array, the initial end of the wave-antennas are spaced in the direction perpendicular to the axes of the antennas. Since it extends over space in the lateral direction, unless there be undue sacrifice in the the desired signal, the lateral array can only reduce the width of the directional diagram.

The lateral array is what we would call a broadside array. The wave antenna in the Bell article was a Beverage. The system they ultimately set up used four Beverages. Two pairs were set up as lateral (broadside) arrays. Those two were then combined as a longitudinal (end-fire) array. In the end-fire phasing arrangement they could adjust the phase to place a null at a specific angle on the back side of the pattern.

You can read the entire article at the link below.

http://www.alcatel-lucent.com/bstj/vol08-1929/articles/bstj8-2-309.pdf


Pretty amazing stuff they did almost 90 years ago!
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Pete, WA2CWA
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« Reply #2 on: November 22, 2012, 01:54:36 PM »

We weren't dummies  Grin  and we liked to party too.
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