First installment,
Disclaimer, I did this in my basement not an RF chamber but I did see some interesting results. When you look at this, the higher up the scale the signal is, the stronger it is.
First I turned off my phone and got a background measurement, the center is 457KHz the peaks you see are random in position
across the full spectrum. I'm looking at 250KHz on each side of center.
To get an idea of what the noise peaks to, I did a max hold measurement, this displays what all the random peaks look like over time
and sets the base line for what I want to look for.
Next I just turn on the phone and see if it does anything, and it does, there's a burst just under 457KHz. The right edge of it is close
to the boarder of where the Avy receiver should be sensitive.
I let things sit for a bit and captured this burst.
I now turned on my phones data and play Bohemian Rhapsody with youtube. I do this with the phone about 6 inches from the analyzers antenna.
I'm using max hold. There is something going on.
To get perspective on how distance matters, I do the same measurement with the phone about a meter away. You can see the level is greatly reduced.
So, there are some interesting things going on. The peaks I saw were pretty random, but there. There was never a constant signal at 457KHz
but they do show up. So when I think about what I saw, I don't think it's the cell frequency that is the issue. In the phone there are probably voltage
regulators that are likely switching regulators ( turn an electrical switch on and off really fast to make a voltage ). These can run in the KHz to MHz range.
There is also the speed of the various clocks and data buses in the phones, high MHZ to GHZ. Given the levels of the noise I saw and the way the peaks
looked, I'm thinking it's the data that is moving in the phone along with other lower frequency events. It is not the cell RF, BT RF... thats in the GHz range.
So, If you are using a beacon trying to find someone, your personal devices might interfere, phone, BT wearable devices.... You are not likely to interfere
with someone a ways away from you.
To tie this to a PLB without trying mine yet, you have some of the same things going on to a lesser extent, probably have a voltage regulator along
with a CPU. You might have some but not the same type of data transfers going on. I'm going to try and see if I can sneak into the RF chamber where I work
and do some PLB measurements there. If not, I'll see if I can find a way to do it at home. At the very least, I can get an idle measurement.
all of the signal levels I measured were pretty low. So the next experiment is with the Avy receiver when I get it and see if I can determine it's sensitivity
and rejection.
So, based on what I see so far, at least if you are involved with a search, turn other stuff off. If you know a search is going on, maybe turn stuff off anyway for good mojo.