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adsb and height of antenna make a difference


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I watched the last show where they used a drone to raise the antenna 400' higher, kinda cool but will that really make a big difference when most aircraft will be above you and thus line of sight should not be an issue, For example where I am at in the Southern part of Denver, I see planes ranging from 7-8000 ft to 33000 ft elevation and I never see aircraft at DIA so they are either landing or taking off and to low, but I would think if I drove up Lookout mountain to receive, altitude wouldn't make a difference as long as I could see the airport and could then get the signals of the aircraft landing. Also from my experience it seems that the range airplanes broadcast seems to be limited to around 50 to 100 miles although I am using the antenna that came with the RTL usb Tuner and it sits on a metal base of a lamp and I would guess a well tuned antenna would do better. Interestingly I get better reception to the West over the mountains(80-90 Miles) then to the east (60 miles)

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Someone else used a drone a while back. They had the same results. In that situation, they figured it was the electric noise of the motors that was causing the issue. I would tend to agree with that. Also it appeared that when they were in front of the van, they were getting signals. I suspect that the van was acting as a reflector.

They dropped off when they hit 300 + feet, but if you looked at the screen, they were really dead before that. After a fixed amount of time with no new packets, the entries drop off the Dump1090 list. If you notice the message counts had long stopped on the assent.

One thing you can do to tune your stock antenna is cut it down to a 1/4 for 1090 mhz. (68 mm) . That should improve things some.

I've experimented with a lot of different designs for ADS-B antennas. The coax - co-linear has shown to be the best, However, pretty much anything mounted high, in the ball park, does well. The biggest factor is the loss from long coax runs.

Edited by PiDAR
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What surprised me about the show is that:

1. They didn't first just hover the drone at 10ft initially and check the signal - both wifi and collinear. Almost every time they first went up-up-up and then started looking only to end up being stumped.

2. They didn't try with the original antenna. Yeah it's a puny thing but there's not a lot that you can break on it, it's light and didn't you want to compare apples and apples to see which is better a few eps past?

Also, but this might just be me, the parts of the video showing the computer screen didn't look well on my screen. It's like the image didn't refresh or something.

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  • 2 weeks later...

"Maybe it was multi-path interference off the blades. :D" Maybe it was the several MWatts of RF floatting around on the tower behind them, plus the one at the other end of the parking lot! On that tower behind them you will find everything from VHF to 22GHZ , and at ERP levels exceeding safe exposure limits !!! Move closer to that tower and warm up your lunch! :ohmy:

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