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My Recent Real World Beverage Receiving Antenna Comparisons




 
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Author Topic: My Recent Real World Beverage Receiving Antenna Comparisons  (Read 62 times)
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K1JJ
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"Let's go sailing, Tommy!" - Yaz


« on: February 18, 2020, 01:34:10 PM »

Background:

A Beverage antenna on the lower bands (160-75M and sometimes 40M) can help you dig down deeper to the next receiving level of weaker stations.  If you have the room and can string one away from obstructions like houses and other antennas, a receiving Beverage can compete with the best of bigger, elaborate antennas, like Yagis, vertical arrays, etc..

I've had a 600' Beverage at 6' high strung to the NE for years covering Europe. The feedpoint is 1000' from the shack away from all noise or antennas, metal, etc.   However over the last 10 years the mice have been chewing up my underground coaxial cable. I got tired of splicing in new coax so I just installed elevated open wire spaced 6" apart feeding the Beverage. This solved the mice problem. It required a 1:1 balanced to unbalanced toroidal transformer at the Beverage feedpoint and a 9:1 stepdown balanced to unbalanced at the coax shack feed. I have a flat match of 50 ohms at the shack receiver.  A full coax run is easier if openwire is not your thing. The Bev is terminated at the far end with a 450 ohm resistor to ground to suppress reflections and give it a ~ 20 DB f-b ratio.  There are plenty of Bev designs on the web.


Comparisons:

During prime nighttime condix into Europe I found the Beverage to have about 5-10 DB BETTER S/N ratio than a 75M dipole at 90' broadside to Eu. There were times I could not hear the Eu station on the dipole but clearly on the Bev. It was all about noise reduction and the front to back of the Bev.

I then tried the Bev compared against my main transmitting antenna, a pair of full size delta loops at 190' high on a 40' boom. This is the equivalent to a 3 el full size 75M Yagi at 140'. The loop array's average height and computer modeling shows the same pattern and take-off angle as the Yagi.

The Beverage had a slightly poorer S/N ratio when compared to the loops at about 12:00 midnight last night into Eu. However, later on when the Europeans were in full daylight (1-2 AM EST) the Beverage was actually 5 DB BETTER in S/N than the loops!  I've never seen this before since the loops were always better in the past. This tells me the Bev system is working well.

So now that I see the two antennas are near par for receiving in prime time, I combined them together in a dual diversity sync'd receiving system. The FT-1000D has a mod to control the two internal receivers in sync and have the Bev in one ear and the loops in the other. (using quality stereo headphones)  It actually sounds like a stereo FM station with the trippy phase noise drifting back and forth between ears. Stations get a stereo sound to them even though they are mono. It's all about the RF waves coming in at different times on the separate antennas. (phasing)  

I then tried A/B tests with the loops alone, the Bev alone and then the two combined in diversity.  There is no doubt I can hear the weak ones better in diversity!  Receiving resolution and word articulation is definitely improved. This is most of the time, not just a fluke fading event.  

The real integration happens in the brain, just like when combining two ears or two eyes to hear or see in 3D.  Research shows, just like using binoculars vs: a monocular, there is about a 41% gain in resolution. I feel it is similar in dual diversity receiving.

The real test is trying to pick out the words of a VERY weak station almost in the noise. Euro accents can make it even more difficult. But there is no doubt that when conditions are good and the two antennas are working and adding well together to complement, there is a receiving edge to be had over a single antenna/ receiver.  Just picking out 50% of the words can sometimes allow the brain to fill in the blanks enough to finish a QSO successfully.

I wanted to pass this info along since it works just as well for AM operation in case someone wants to do something like this himself. A standard dipole and Bev works FB. With the new SDR dual receivers it is a FB project.   I have used Bevs (and dual diversity) for west coast AM DXing for years and they work.


Tom, K1JJ
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