I have access to a couple of rather large antennas, but they are labeled as 900-935 MHz. Is there any chance that they might work at 2.4 GHz? Would modifications be required? I haven’t been able to get the antennas out of their boxes to see what they actually look like. If there’s a chance they could work, I might be able to get them out of the shipping cylinders.
@sej7278, according to the creator, he tested them to 1 km without any problems (outdoor, line of sight) and he says they should be able to go to 3 km. Definitely a good deal WITH a processor onboard, crypto and huge range!
So I was pretty sure based on the range, but it took me a long time to find where it says on their site that Flutter is 915MHz ISM band device. So legally that is a ITU region 2-only device, so sorry Kenneth. The ISM band rules are that you have to limit tx power and accept all interference, so the range is a bit of random variable. There are plusses and minuses to any frequency band these days, I guess.
You can get a $12 module at Sparkfun that transmits at +20dBm, which would likely get you 250meters. He must be using spread-spectrum or some other digital modulation technique to get to 1km. The max tx power in that band is spec’ed as an electric field a certain distance from the the antenna (EIRP), not a power level, so modulation matters. I see some folks have transmitters doing +36dBm tx in that band with digital modulation.