So currently I have 3 antennas dedicated to pilot aware, an 868 colinear for Pilotaware, an 868 colinear for Flarm and a multiband colinear being used for ADSB.
I need to free up the Multiband colinear for other purposes, so am going to try splitting the Flarm aerial between the adsb and Flarm dongles.
The 3db loss from the split I can make up with an LNA. The worse 1090 reception due to a shorter and 868 tuned antenna i will have to live with - but adsb is the least of my worries given the higher power transmissions.
Any thoughts? I will have to wait till we get some gliders back in the air to really tell the difference of course!
Cheers
Kev
Hi Kev
I used 50 ohm splitters to share the Flarm and PAW antennas. It works well.
You lost 3 dB on each of the antennas - but the range is fine for the Flarm, and in the PAW case it's easily made up by the 9dBi antennas I was using. But you will I think lose that much by using a 75 ohm splitter anyway.
In your case you could do that, or you could try sharing the Flarm and ADSB antennas. Generally there's enough power in the ADSB signal for the mismatch not to be a problem (I use an 868 co-linear as my ADSB antenna because I have a spare, and it works fine).
I had a batch of ~12 splitters donated to me which I used, but I've used a few of these
https://www.instockwireless.com/power_divider_pd1020.htm I think that's what Orwell has (plus a GSM filter).
I've also just tried this
https://www.m2.wifi-antennas.co.uk/2-way-wifi-gsm-splitter-unit which you can source from the UK.
I'm not sure it's worth using an LNA for the ADSB to make up for the splitter gain. You've probably already got plenty of signal, and the issue seems often to be signal / external noise rather than signal / receiver noise. In that case, your LNA merely amplifies both the signal and the external noise. The exception is when you can put a narrowband filter in, which can help (which is why I've got a GSM filter at Orwell - a cell tower was installed 100m away). But no harm trying.
You're not really trying for extreme range - what you want is good signals from more local aircraft. It may amount to the same thing though.
Paul