433 MHz issue !


Senior Member
FYI: Publicity has -sigh- again arisen here in NZ when car remotes refused to operate in a shopping mall carpark. Management declared it an "electrical incident", but it's probably 433MHz band interference.


Here's an earlier incident => https://i.stuff.co.nz/national/106902631/dozens-locked-out-of-car-in-invercargill-cbd-because-radio-equipment-blocked-car-remotes

Radio amateurs ("Hams") have primary use of the frequency range 433.050 to 434.920MHz as part of their wider 430-440 (or 420-450) MHz "70 cm" band entitlement. Transmitter powers of 10s of Watts are permitted. Commercial services also may use this slot.

Many car door remotes operate under SRD (Short Range Device) rights giving secondary use of the same 433.050 to 434.920MHz frequency range. Only flea power transmitters are permitted -typically just 10s of milliWatts.

As parties are legally allowed to transmit on this band it's probably worth spectrum scanning for interference if your PICAXE wireless system misbehaves! Frequencies other than 433 MHz (900 MHz? ) may offer workarounds too. Stan.
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Senior Member
Several years ago, I was experimenting with sending serial data using inexpensive Chinese transmitters and receivers and discovered that the garage door opener had "stopped working". The serial transmitter (running on 5 volts) was maybe 40 feet from the garage door opener's receiver but it was totally blocking that receiver. The opener didn't respond when its remote was within ten feet, even though normal range was 100 feet plus.

Definitely a way to get even with someone - PICAXE reading a RTC chip and turning on the "interference" transmitter for the morning and evening to/from work hours. Small weatherproof box with rechargeable batteries and a solar panel - just put it in some inconspicuous place. The hapless target would call for service and the techs would find no problems, so the target would call another service company the next week - repeat... repeat...

The older I get, the more devious I become ;-)


Senior Member
I once left a cheap 433 MHz ASK module on in the lab overnight. The next morning I looked out the window to see the next door neighbor unable to disable his car's security system. Lots of horn honking and cursing ....

It took about 5 mins for me to realize what was going on.