Recently i’ve published Etherify – bringing the ether back to ethernet, please read this article first, before reading this one.
Script source is on: https://github.com/sq5bpf/etherify , see etherify3.sh
That article uses primarily raspberry PI 4 for transmission, which give an exceptionally strong signal, and fast link-up time.
So i wanted to investigate if maybe there is something unique to this device. And when i accidentally disconnected the ethernet cable it turned out there is 🙂
The Raspberry PI 4 ethernet hardware can send a very strong signal even when it is unconnected. To test i’ve connected it to a powerbank (so there is less wires to act as an antenna). The result is here (sorry for the upside-down video):
So i’ve set up an elaborate transmit position at 5m height using a balcony and 3 strategically placed chairs:
This was tested at various harmonics of 125MHz using and rtl-sdr and a simple dual-band 145/435MHz antenna mounted on a car. This antenna is not tuned to these frequencies, but is much easier to use outside. The mistuning probably isn’t a problem, because the signal/noise is affected by interference from local ethernet networks, not by the receiver noise factor.
Tests at various harmonics at 12m:
And a test at 50m:
The test at 50m is incredible, because the device doesn’t have any big conductors to radiate it. A 1/4 wave monopole is 19.2cm long at 375MHz, there are no conductors comparable in size on the Raspberry PI 4. Probably a similar result could be achieved with rpitx without an antenna at higher frequencies.
The board says: Raspberry PI 4 Model B, FCC ID: 2ABCB-RPI4B, IC: 20953-RPI4B.
I will test other Raspberry pi 4s in the future, because maybe i have a bad specimen. If this is true, then the 100m reception results shown in the Etherify article are not that spectacular. Actually i hope i have a bad specimen. Maybe others could test their hardware and send me a note?
But don’t fear, Etherify 4 will soon be published, with no RPIs, just good old laptops 🙂
If you cite this, please include the webpage address and attribute Jacek Lipkowski (SQ5BPF). Email can be sent to my_callsign @ this_domain.