what about this shop? https://www.rfshop.com.au
and found a second shop that maybe is helpful: https://ozhack.com/collections/software-defined-radio
The RPi isn’t sensitive. The radio is sensitive and passes digital data to the Pi.
Several people have demonstrated the Zero has enough CPU using the FA image, and your RTL is ok on a Pi3. Have you swapped out your USB cable? It still sounds like a power problem to me. Can you measure the voltage downstream of the Pi?
Ant739h
Out of curiosity, have you run any tests without amps and unfiltered?
yes of course - because this is the most important scan! e.g. my scans above - the 24 hour and the one on top of the three scans in one picture - both are without amp or filters. open both pictures in a new browser window then you see the descriptions in the lower left corner.
That was my point. If the solution was to upgrade everything between the dongle and the antenna, then the problem would have to be at the pi end. Which I don’t think it is, just to be clear.
Exactly.
I have been the running the zero off the official raspberry pi power supply. I have also tried the USB and phone charger that my RPi3 has been happily running off.
The only real difference between my setup and everyone else’s really is only the dongle. I’m hoping that it is just a case that this dongle doesn’t play well with the zero and a different one will work.
I meant the USB cable between the Zero and the dongle - it seems to be the only thing you haven’t changed.
Oh that USB cable! Actually I haven’t. It is a new cable I ordered with the zero and seems reasonable quality so I have presumed it is not the cause. I’ll try and pick up another and test it.
If you see my posts further up, you’ll see that I have exactly this same issue and I have changed the cable between the Pi Zero W and the Pro Stick Plus. It made absolutely no difference whatsoever. I still get about a third of the number of aircraft received on the Zero W compared to the Pi3.
Damn! That doesn’t sound good for me. I have ordered the pro stick (orange). 
Have you tried piaware with stretch? I’m wondering whether I should give that go, I’ve tried raspbian manual setup + the SD image.
I agree it’s a long shot and it’s a configuration most people won’t have a spare, but it’s worth a try.
I tried running an extension lead between a Pi3 and RTL and had the same symptoms - it worked, but poor reception.
I just popped the case from one of my ‘no brand’ RTL sticks. The R820T (and probably the RTL2832) needs 3.3V. Interestingly, the PCB has provision to mount either an SMPS or linear regulator (to provide 3.3V from the USB 5V). Mine has the linear AMS1117-3.3 fitted which will work with as little as 1.1~1.3V over the output voltage. This means that it ‘should’ continue to work with as little as 4.6V on its USB connector, but empirical observations suggest poor performance can be expected.
Take a USB PSU, connect the PiZero, plug in an adapter cable and then hang an RTL dongle off that. Until you measure the voltage at the dongle, you don’t know where you are.
I had that issue too with the RPi3 and it appeared to be a good quality shielded extension too. It was originally for a WiFi dongle.
You mean like this? I presume you mean into the micro port then the cable + dongle but unfortunately I have no way of doing that at the moment.
Instead of microUSB to USB cable, why not use adapter. This will totally eliminate the cable. These are pretty cheap.
The only snag with those is that the USB ports for power and data are so close together. I’m not sure both will fit.
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Some of the sellers have given dimensions also. This may help to determine if this can fit in the space available in pi zero.
Yep, that’s the easiest way to measure the voltage, but be aware they are not particularly accurate. I’ve got two and they typically read about 5% different. Putting them both in series shows a voltage drop from 0.1 to 0.2V across the first, so leaving it in circuit will exaggerate any power problem you have.
A multi-meter would be more accurate, but less convenient.
Electrically that may be a good idea, but that puts a lot of leverage on the USB socket. A bump on the dongle will rip the socket off the board.
.
I do have a basic multimeter, should I pin it out on 1 + 4 on the dongle?
Edit
4.91V on the RPi3
5.1V on the zero.
A few tense moments when, like a complete numpty, I shorted 5V to ground and the dongle stopped receiving. A boot fixed it. Phew!
That’s certainly not what I expected given the problems you’re having.
Guess you can rule out a power problem.
Ooops!
HOORAY!
I shouldn’t speak too soon, but I think I have fixed it.
I was beginning to think that the el-cheapo dongle wasn’t playing nicely with the zero and I think that is partly the case. I thought I was getting interference through the USB OTG cable, and it also looks like that is partly the case. (well, there is interference)
I had been so concerned about reducing the OTG cable length (even soldering a micro USB connector directly to a type-A USB) that I forgot the obvious. Try moving it further away!
I had tried an extender cable with the RPi3 a few weeks ago without success (reduced my range). But, I found my other USB extender cable today and tried it on the RPi3 and the range was the same so, used it to move the dongle further from the zero and now my range and message rate appear to be the same as the RPi3!!!
Geez! What a palaver that was!
I’ve had to shut down PF (because it was using 45% cpu so cpu was over 100%) so I won’t get a nice polar plot to compare unfortunately.
Great work in tracking down the problem.
I guess the USB cable you are using is unshielded? This would isolate the problem to just the USB cable.
If the USB cable is shielded than some other part is causing the interference. Maybe a component on the RPi zero W board is causing interference to the RTL dongle?
For reference. USB is creates a lot of noise but is not effect by noise since it works on the same idea of twisted pair as in ethernet cables. For USB 1 and 2 they thought that the voltage and frequency was low enough to not cause any problems and this is mostly true. For USB 3 unshielded cables would cause so much interference that Wifi to stop working. USB 3 cables are almost always shielded but USB 2 cables are usually not.
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I now remember that last year when I plugged in a mini WiFi adapter directly to my RPi Model 2, it was touching the ProStick which was also plugged in directly to Pi. The USB slots on Pi are very close to each other. I faced poor performance. Then I used a USB extender cable to take the WiFi module away from ProStick, and it solved the problem
