I have an RF Explorer handheld spectrum analyzer. In my area there are few Ham radio repeaters in general, but almost nothing happening on the 70cm band.
I set up the RF Explorer to scan from 420 to 450 MHz. Every so often, I would see a large signal at 433.124 MHz (according to the peak detector). I was thinking that this might be close to the 3rd harmonic of the APRS frequency of 144.39 MHz (here in the US). I got out my Kenwood TH-D72 with APRS and kept it nearby when the Explorer was scanning the UHF band.
Sure enough every time I saw one of the peaks near 433 MHz, I could hear the APRS packets on the Kenwood. This was exactly coincident in time.
3 x 144.39 MHz is 433.17 MHz, which is close enough for me.
Recently I had re-purposed my Acurite 00381 wireless thermometer to keep track of the freezer temperature. (it works, amazingly)
The Acurite uses 433 MHz, as to many other consumer weather sensors as found on this forum. I also have a Meade thermometer that uses 433 MHz.
Musing on this a bit, I began to wonder if strong harmonic signals from APRS might "stomp" on these sensors data transmissions.
APRS.fi shows the location of APRS digipeaters, trackers and other devices.
I thought that I would share this tidbit. My transmitters are fairly close, with the antennas mounted on the roof of the house and garage. I do have the power set low at 5W and 1W respectively. One would need to be fairly close to a transmitter for this to be a problem, but in my case I believe that this is a potential issue. (my transmitters are standard commercial units that supposedly pass FCC regs.)
Greg H.
