I was searching old threads a couple of weeks ago because I saw one of these ADS-B antennas, cheap chinese PCBs and the others - #26 by abcd567 on eBay.
I couldn’t see whether anyone had actually tried one so I got one to try it out.
I didn’t really believe the specification or expect it to be that good but it doesn’t seem to work at all.
I tried it in place of a working Uputronics LNA and spider both direct on the RTL stick using a gender bender and in the loft using a known good cable.
If I look at the service, I can see that bias-t is active but because there’s no LED on the PCB, I can’t tell whether the voltage that bias-t is supplying is reaching the onboard LNA or whether the thing is faulty.
I have one in the drawer with other spare parts. Once got it with the buy of a FA dongle second hand.
It works but it’s range is limited and the numbers aren’t great.
So either you have a DOA (Death On Arrival) issue or it’s just poor.
I wouldn’t recommend it to anyone to be honest.
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based on my experience so far, nor would I
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I left this running for an hour or so and it did pick up a few planes that came very close.
So it works although not in any useful way and being as it was inexpensive and came direct from China, I took the RFI shield off to see what was on the board.
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I found this data sheet for the chip on here: https://www.qorvo.com/products/p/TQP3M9008
so presumably, their claim of 20db gain is based on that. But it say on that web site that the device is not recommended for new designs.
The centre frequency of the SAW filter is 1090Mhz.
One thing I noticed about this device is that the legs of the tuning forks are only 60mm long. Is that why it is so terrible?
Could also be a knockoff chip.
Well, anything is possible.
Is there a difference in the way that radio waves propagate through a PCB antenna compared to a bit of copper wire that would explain the discrepancy in length?
It is such a shame that the device RTL-SDR used in their triple filtered LNA is no longer available as the one that is still working properly beats the uputronics one I got hands down.
I’m also rather disappointed with the jetvision active diapason that I got as the message rate, number of planes and distance is very similar in results to the jetvision A3 with the uputonics LNA.
You can’t get more than good signal.
Either you hit terrain limits or just the noise floor at 1090 MHz.
Both are not unlikely in many locations.
But if you’re spending $$ like that, i’d go with a longer colinear antenna (vinnant or DPD), a cavity filter, probably stay with the uputronics LNA or try an unfiltered PGA103 based LNA.
And of course an airspy mini.
The same as said earlier applies even with the most expensive gear: At some points you hit a limit and better gear can’t improve things further.
Though at least in Europe, airspy mini will be a significant step up in message rate over an rtl-sdr.
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Don’t get me wrong, the jetvision active diapason is quite a bit better than my spiders with RTL-SDR triple filtered LNAs were, it just isn’t quite as good as the jetvision A3 with a uputronics LNA (a pairing which costs half the price) and it certainly isn’t as good as the A3 with the RTL-SDR triple filtered LNA.
Overall, I am happy with the improvement I have and will live with what I bought.
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WRT the Chinese active PCB antenna, I cut it in half and soldered an SMA connector to where the antenna half would have been. I connected it to an antenna in the loft and didn’t get a single airplane so I connected the antenna direct to the stick and got quite a few. So, it looks like the LNA is no good, but I don’t know about the antenna part and can’t be bothered to find out.
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