Side by side antenna testing

ab cd

Senior Member
Great! Are the two amplifiers same make & model, with same gain, or different?
 
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ab cd

Senior Member
This shows that although identical, the amplifiers (at least PerfectVision ones) do no perform equally: a sign of poor design and/or poor quality control during manufacture. How much % difference in number of aircrafts/max range between two amplifiers?

Is not 30 dB gain of PerfectVision amplifier too high? Generally other makes of satellite amplifiers are rated between 15 to 20 dB.
 

TomW

Member
Test #4 Run #1 confirms that the difference is not caused by the power transformer and power supply wire. Next test will involve swapping the wires from spider to amplifier. Then will evaluate the power inserters. After that, I think I'll have to get a third amp to test....

ab cd - sorry for the delayed response.. I just realized the screen shot omitted the row labels. The one attached herein allows comparison of the numbers. As for the advertized dB gain... I have no idea..

7-14-2015 9-06-34 AM-blur.jpg 7-13-2015 2-19-05 PM.jpg
 

ab cd

Senior Member
Great! Resolving affect of each piece of the system bit by bit. You are gifted with a very analytical & logical brain.
 

TomW

Member
Confirmed....it's not the F cable from amp to antenna... Next test, I'll swap the power inserters. Assuming that doesn't make East better, it'll focus the spotlight on the amp...


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TomW

Member
The plot thickens... Back in April dibbyb posted about his results with alphaline SEA-100, I bought one and put it in the drawer. As my testing indicated a bad amp, I decided to slap it in and see how it would do... AND IT OUTPERFORMS the competition....

I have another alphaline on order (ebay) and will replace the other (now underperforming) amp/inserter next. Hopefully will get back to testing antennas soon....
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TomW

Member
The saga continues... May be onto something... Test #6 Run #1 complete. I replaced the second amplifier/power inserter with another alphaline. West is now better, but not as good as east, Swapping the amplifiers for next run. Hopefully that will allow continued testing of antenna combos.
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TomW

Member
More progress... with swapped amplifiers, East continues to perform better. East is the spider-8 with 69mm legs below the copper disk. Next I will swap antennas with this amplifier set up. Looks like I'm finally making some progress...

8-22-2015 8-06-59 AM_small.jpg 8-22-2015 8-10-27 AM_blur.jpg
 

ab cd

Senior Member
Hi Tom, your experiments expose the hidden aspects of the system & components, and help us to understand these. Thanks.
 

TomW

Member
Hi Tom, your experiments expose the hidden aspects of the system & components, and help us to understand these. Thanks.
Better understanding.....is the goal. Thanks!

Sneak peak at Test #7 Run#2 indicates Spider #4 performs better in the West position too (but there are still 2.5 days left in the test).
 

TomW

Member
Finally some results...!

The spider with the 69mm legs below the copper disk outperforms on both systems...

The next thing I'm going to do is swap the whips between the two spiders..... stand by!
Tom

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TomW

Member
Results, and some conclusions. After swapping whips between antennas, West (the spider with 69mm below the ring) continues to out perform East (69mm spider legs from the center line of the whip), but ONLY SLIGHTLY, and depending on your reference test. I think the coverage map overlay tells the story pretty well (west is blue, east is green).
Some conclusions:
1) Spider leg length matters, but not significantly (based solely on these two instances)
2) The N based whip outperforms the SO-239 whip
3) AMPLIFIERS are IMPORTANT, and they can vary in performance even within a single make/model (and possibly change performance with time) (personal note: I now plan to put my amplifier for my permanent installation in an accessible location)
4) Perhaps most importantly, side by side testing is far superior than trying to tweak a single installation. With all the variances and dependencies, it is virtually impossible to discern performance differences when the tests are performed at different times.

I'm going to leave my test set up operational, but plan to move the winning spider to a permanent mount about on my roof soon. I want to try some more antennas/ideas. PLEASE comment on this, and let me know if there is something you think should be tested.

Thanks for bearing with me on this.
Tom


9-4-2015 8-15-01 AM_small.jpg 9-4-2015 8-18-19 AM_blur.jpg
 

ab cd

Senior Member
Results, and some conclusions. After swapping whips between antennas, West (the spider with 69mm below the ring) continues to out perform East (69mm spider legs from the center line of the whip), but ONLY SLIGHTLY, and depending on your reference test. I think the coverage map overlay tells the story pretty well (west is blue, east is green).
Some conclusions:
1) Spider leg length matters, but not significantly (based solely on these two instances)
2) The N based whip outperforms the SO-239 whip
3) AMPLIFIERS are IMPORTANT, and they can vary in performance even within a single make/model (and possibly change performance with time) (personal note: I now plan to put my amplifier for my permanent installation in an accessible location)
4) Perhaps most importantly, side by side testing is far superior than trying to tweak a single installation. With all the variances and dependencies, it is virtually impossible to discern performance differences when the tests are performed at different times.

I'm going to leave my test set up operational, but plan to move the winning spider to a permanent mount about on my roof soon. I want to try some more antennas/ideas. PLEASE comment on this, and let me know if there is something you think should be tested.

Thanks for bearing with me on this.
Tom


View attachment 2332 View attachment 2333
GREAT EXPERIMENT!
Congratulations & thanks for sharing.

Now you have to make one more antenna (the design you want to use as your benchmark/refrence), and install and leave it in the side-by-side test rig.

You are right about amplifier. That is why I use following setup for my side-by-side testing:

System 1:No Amplifier Benchmark Antenna (Cantenna) > 15 ft / 5m RG6 Coax > F to MCX pigtail > dvb-t dongle #1 > RPi #1

System 2:No Amplifier Antenna Under test > 15 ft / 5m RG6 Coax > F to MCX pigtail > dvb-t dongle #2 > RPi #2

Both antennas are placed inside my apartment, near a large window, at same location, same height, at a horizontal distance of about 1 meter from each other. The height of both antennas above road/ground level is 60 ft / 20 m.

Image 1 of 2 (system 1 - benchmark antenna

system 1 (benchmark).png



Image 2 of 2 (system 2 - antenna under test)

system 2 (antenna under test).png
 
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