FlightAware Discussions

ADSB Antennas

I am intrested in these 2 antennas which would work best will be 9 metres high do have other adsb antennas…

Regards Lino…


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Second one is active, it has a LNB inside.
Overpriced both of them IMO.

Find an FightAware antenna (very good) and add your own filtered LNC:

1090 MHz ADS-B Antenna - 66 cm / 26 in

ADS-B LNA High Performance Triple Filter Low NF Amplifier by RTL-SDR Blog

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I am very happy with this one
Jetvision

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The only advantage of the Jetvision is that you can use it outdoor without using an additional weather case.

From the cabling i have no idea what is better:
antenna - LNA - long cable - receiver or
antenna - long cable - LNA - receiver

The active antenna is indeed overpriced.

The DPD antenna is probably one of the best antennas around.
Also overkill for most locations.

Have you checked the terrain that will limit you?
GitHub - wiedehopf/tar1090: Provides an improved webinterface for use with ADS-B decoders readsb / dump1090-fa

No antenna / reception system can overcome the terrain / curvature of earth.

If you go with a DPD antenna … you’d want to also get a good coax and a filtered LNA.
The whole system needs to make sense.

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First one is better for the noise chain. Always better to first amplify and then attenuate, than the other way around.

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I always filter first so that noise is not amplified. I’m in a very active signal area with lots of UHF traffic.

Antenna → Filter → LNA → Cable → Receiver

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Usually the LNA include filters, no need of an additional filter in front of it.

The filters in the RTL-SDR LNA did not do a very good job because the pass band was too wide. I use a Flight Aware dark blue filter with a very tight pass band (1080 MHz to 1100 MHz) that does a much better job. In addition I can use a much less expensive general purpose LNA without filtering.

You can use that after the LNA if you want.
Any loss in the signal before the LNA translates in lower signal/noise ratio at the receiver end.

If the interference overloads the LNA … then no you cant …

It doesn’t even have to be a complete overload … i’m not exactly familiar with how an increasing power level of interference will gradually influence the performance of the LNA in the band of interest.
So … it very likely depends on the magnitude of the interfering signal where you’d want to put the filter.

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Newer LNA chips are awesome in that regard. Unless you are like meters away from a celltower emitting antenna I doubt that the first stage gets overloaded, they are not that powerful.

FM and TV are a different issue, they have indeed higher powers, but still, they are not very often found in residential areas. My LNA has a FM trap in front of the first stage.

Relevant search terms are “third order intercept point” / “IP3” (for intermodulation-related interference) and “1dB compression point” (for outright “can’t produce that much output power” distortion)

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Thanks, learned something new…

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For reference, here is the datasheet of the above LNA chip:
https://datasheetspdf.com/pdf/855258/AvagoTechnologies/MGA-13116/1

x 0.51 dB Noise Figure
x 38 dB Gain
x 52 dB RFoutQ1 to RFinQ2 Isolation
x 41.4 dBm Output IP3
x 23.3 dBm Output Power at 1dB gain compression

Same problem over here, 3 independant mobile providers each of them spewing out about 80W with 17dBi antenna gain on the 900MHz band in my direction at a distance of less than 150m (500ft)!
I once tried to put my LNA (rtl-sdr with saw filters) in front of my cavity filter and my range immediately dropped by 50%.

Back of an envelope calculation puts the input power you’d see on 900Mhz somewhere around -3dBm - yikes.

(The LNA mentioned above would reach its 1dB compression point somewhere around -14dBm input power)

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… and I didn’t even mention the 4kW (ERP) DAB+ transmitter on 217MHz on the same structure :open_mouth:

The 217MHz is much easier to cut out than the 900MHz.

By trial and error I found that it’s best to amplify then attenuate.

I personally love the performance of the Uputronics filtered preamp and get great results putting it on the end of a 10m coax run - keeps everything indoors then.

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