Is it possible to connect multiple antennas (amazon.com/gp/product/B009U7WZCA) to the same raspberry pi via the multiple USB ports or do I need multiple raspberry pi’s?
And in a similar vein, what about multiple pi’s on a single antenna feed?
There’s no fundamental reason you can’t run multiple dongles on one Pi, AFAIK, but you will probably find yourself running short on CPU and/or power - dump1090 is CPU-hungry and the dongles are power-hungry.
While you could take an antenna and with a Y type cable connected it to two different receivers the correct way to do this would be to use a 2-way power divider. You’d need one that works at the intended frequency (1.09 GHz) and correct impedance (which I thought was 50 ohms based on previous info but in another thread I learned that may be incorrect).
I’d guess you should be able to find such a power divider on eBay in the USD $30 range.
I’m running Piaware on a Pi B+ and dump1090 uses 25% of CPU consistently. I’m guessing I could add a second dongle. My question is, how would dump1090 handle the input from two receivers and what would the output look like on my ADS-B page. Would it appear as two stations?
Is anyone doing this now?
I think you’d need to run a second dump1090 with a command line switch to tell it to use the second dongle.
You’d also need switches so it presented data on only selected TCP ports
then you’d need to tell the first dump1090 to take data from the second to merge all the received data into one stream for uploading.
Multiple SDRs on a single antenna feed–
This is a good way to experiment with filters, amps, SDR settings, and the like.
One secret to success is to connect the antenna to a splitter (power divider) and connect the outputs of the splitter to the SDRs. Using a splitter provides some isolation between the two SDRs, and also keeps the impedance more or less equal.
Look on eBay – Mini Circuits ZAPD-21+ has BNC connectors, good for 500 MHz to 2 GHz. ZX10-2-20-S has SMA connectors and is smaller.
Look for something that covers 1GHz. You shouldn’t have to spend more than $20.
Keep feedlines short, and use quality cables. In many instances.