It’s not that, I’ve used the same adapters as I mentioned. I’ve also tested resistance to the antenna and ground and found no loss.
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Sorry - cant see it. What adapters are you using?
It’s the plugs on each end of the short cable @astrodeveloper was referring to.
What antenna are you using and what reading do you get?
With the RP-SMA connectors, the center pin of the male connector is a socket instead of a pin. You need to measure the resistance of center pin at the SDR dongle to the center pin of the antenna connection. This needs a low resistance, (not 50 ohms, as that is the impedance of the coax and not DC resistance). RP-SMA connectors do not provide the connectivity on the center pins, thus no signal arrives at the SDR dongle. No idea why anyone ever designed the RP-SMA connectors, as they mess up many installations. If this is your situation, you can do a fairly easy patch by using a 1/2 inch (10-12 mm) wire inside the RP-SMA connector. Cheap and easy, though the real connector is a better thing to use. Hope you get your system up and running well soon. Best wishes. I am an old ham radio / USAF retired electronics guy, just pushing electrons around in interesting projects.
I do know what RP connectors are and I’m not using any. Let me try to illustrate what’s happening since you all seem very confused.
RP-RTLSDR-XXAntenna - I get 5-10 messages per second / 1-2 aircraft
RP-RTLSDR-6m cable-XXAntenna - I get 250+ messages per second / 50+ aircraft
Same device, same power supply, same RTLSDR, same antenna. Putting a long cable between them has astronomical improvement in performance.
It doesn’t make sense. And yet there is is.
Even though you say you are using the same connectors adapters for both, if you could provide pics of the cables/adapters you are using for at least 1, both ends, that might help.
Other possibility already mentioned is you are getting some massive noise when the short connection is used so close to your pi.
You could run a freq scan for both setups and post those pics too.
Yes I can do that.
By frequency scan do you mean hook it up to like airpspy or some other radio software on a computer?
I was trying to make another pi with sdr software and was using a generic rtlsdr but haven’t really gotten it working well yet. So I’d probably have to use a laptop to do that.
I did try using the flightaware pro plus with the 1090mhz filter as mentioned and that didn’t make a difference with no cable or a short cable. I’m not sure how effective that filter is. It did boost performance slightly with the long cable.
Does anyone know where to get a 978mhz filter that doesn’t cost more than the whole usb setup?
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At this point, I believe you on your connectors. I have had bad cables not working and with poor connectivity for some reason. In the end, I cut the cable in two pieces and threw both away. I made a new cable and things worked well then. I suspect some non-visible flaw in the cable or connectors is messing you up. Perhaps using an ohm meter measure connectivity of the center pins and then shields. Both should be near zero as this is a DC resistance. Should be open between center pin and shield. Hope you can get it worked out. Might want to flex the cable as you make the measurements, as that will help find mechanical flaws. Good luck.
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Spectrum scan
At the risk of stating the obvious, there is something wrong with your cable.
If you can’t find the problem, follow this recommendation and replace it.
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