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Horizontal vs. Vertical Stacking Test

stacked antenna 023.jpg (57681 bytes) vertical stacking 001.jpg (60718 bytes)

Description:

I used two Blake JBX21WB antennas. To confirm that the antennas were working properly and matched in performance I tested each antenna separately first. I used a Spectrum Analyzer to check the waveform for each station. The antennas were very closely matched. 

 

For horizontally stacking I mounted the antennas to my ATF-V100 Vertical Tilter using a custom made boom assembly. This boom assembly uses a fiberglass tube to prevent the boom from becoming a active element in the antenna system. Each antenna mount clamps to the boom and allows for easy adjustments to the spacing between antennas. I had already determined in previous tests that 36-44" spacing worked best, so I used 40". 

 

For vertically stacking I simply mounted both antennas to a common mast. I tested a 32" and 17" spacing.

See below for results and my comments following the tests.

 

Results Definition:

  • XX-XX = Measured signal strength level

  • 0-XX-XX = Signal locks on briefly but keeps dropping out

  • 0-50 = Signal was detected but not able to lock

  • 0 = No signal detected

  • - = Not tested

Note: Signal level refers to the Dish 6000 indicator which measures the signal quality based on percentage of errors. As long as the indicator stays above 48-50%, the signal will lock. I assume that if you have over 50% errors, the Dish 6000 does not have enough good signal to decode properly. A reading of 100% would indicate no errors in signal. I have found that at 47% I will see pixelation in the picture and below 46% the picture will drop out completely.

 

**For easier printing, click on image to bring up a separate page containing just results.

Test#1, Date: 03/03/02

 

Spectrum Analyzer Waveforms:

(click on image to enlarge)

Mt. Wilson Stations (15 mile distance)

Antenna A

Antenna B

Horizontal Stacked

36" spacing

Vertical Stacked 

32" spacing

Vertical Stacked 

17" spacing

WB-31A.jpg (56419 bytes)

Channel 31

WB-31B.jpg (53016 bytes)

Channel 31

WB-31AB-36.jpg (63150 bytes)

Channel 31

vert01-ch31.jpg (59348 bytes)

Channel 31

vert02-ch31.jpg (59291 bytes)

Channel 31

WB-36A.jpg (55873 bytes)

Channel 36

WB-36B.jpg (54867 bytes)

Channel 36

WB-36AB-36.jpg (61864 bytes)

Channel 36

vert01-ch36.jpg (57764 bytes)

Channel 36

vert02-ch36.jpg (57793 bytes)

Channel 36

WB-43A.jpg (53943 bytes)

Channel 42

WB-43B.jpg (52784 bytes)

Channel 42

WB-42AB-36.jpg (59323 bytes)

Channel 42

vert01-ch42.jpg (60193 bytes)

Channel 42

vert02-ch42.jpg (60615 bytes)

Channel 42

WB-53A.jpg (55285 bytes)

Channel 53

WB-53B.jpg (52374 bytes)

Channel 53

WB-53AB-36.jpg (61714 bytes)

Channel 53

vert01-ch53.jpg (61214 bytes)

Channel 53

vert02-ch53.jpg (60732 bytes)

Channel 53

WB-59A.jpg (56498 bytes)

Channel 59

WB-59B.jpg (54620 bytes)

Channel 59

WB-59AB-36.jpg (59648 bytes)

Channel 59

N/A

N/A

WB-60A.jpg (54801 bytes)

Channel 60

WB-60B.jpg (54724 bytes)

Channel 60

WB-60AB-36.jpg (60696 bytes)

Channel 60

vert01-ch60.jpg (59747 bytes)

Channel 60

vert02-ch60.jpg (61441 bytes)

Channel 60

WB-61A.jpg (55001 bytes)

Channel 61

WB-61B.jpg (54130 bytes)

Channel 61

WB-61AB-36.jpg (62399 bytes)

Channel 61

vert01-ch61.jpg (59641 bytes)

Channel 61

vert02-ch61.jpg (59750 bytes)

Channel 61

WB-65A.jpg (53190 bytes)

Channel 65

WB-65B.jpg (53850 bytes)

Channel 65

WB-65AB-36.jpg (60045 bytes)

Channel 65

vert01-ch65.jpg (59669 bytes)

Channel 65

vert02-ch65.jpg (60984 bytes)

Channel 65

WB-66A.jpg (54400 bytes)

Channel 66

WB-66B.jpg (54897 bytes)

Channel 66

WB-66AB-36.jpg (60486 bytes)

Channel 66

vert01-ch66.jpg (61892 bytes)

Channel 66

vert02-ch66.jpg (60448 bytes)

Channel 66

Conclusion:

  • The level of multipath can be seen in the waveform pictures. A clean signal should have a square top with a straight or sloping line. The bumps in this line drastically reduces the signal levels on the Dish6000'. I have found that the flatter this line gets, the higher the signal numbers get and the better the channel stays locked in.
  • Channels 31 and 36 are my strongest stations. most every type of antenna can pick these up. The real test is whether the difficult channels can be tuned in and locked.
  • Horizontal stacking resulted in a flatter signal waveform on all channels. Horizontal stacking also makes the antenna much more directional. Turning the horizontal rotator just 2-3 degrees in either direction makes a big difference on the signal numbers and the shape of the waveform.
  • Vertical stacking only seemed to increase the gain on some channels. The waveform remained about the same shape as when using just one antenna. On some channels, the multipath got even worse than a single antenna. The beamwidth was similar to that of a single antenna based on wider rotator tuning angles.
  • If multipath is a problem, horizontal stacking is the only way to go.
  • If multipath is not a problem, vertical stacking can increase your gain on weak channels.

 

 

  


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