if the motion sensor in my driveway transmits the signal to the alarm at 433mhz, why can't i pick up some sort of sound from that on my scanner when tuned to 433mhz?
picking up the driveway alarm
- Thread starter wildbilll
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n5ims
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Chances are you're not on the frequency it's actually transmitting on. When a device indicates it transmits on 433 MHz, chances are very good that it won't be on 433.000000 MHz, but simply that is uses the 433 MHz band. One common frequency used for key fobs is 433.92 MHz. I believe that this band is nearly 2 MHz wide so you may need to scan around to find it. Please note that they don't have to follow the common spacing used for 2 way radios since their devices only need to talk to eachother.
makes sense. if i use the close call option, is it also only scanning on the usual "stepped" frequencies and may therefore miss the signal?
The typical signal levels for these type devices may not be near enough to trip close call. Plus the modulation may not be your typical AM or FM type modulation that you are used to with a scanner. Usually these types of devices emit short bursts of data or pulses.
If you find the center freq, you should still be able to hear the signal. Play around with AM as well as FM.
I can hear key fobs using an R9000 in one of the SSB modes the best or even CW. I seem to recall barely being able to detect the signal in FM on some of these type devices.
Try searching the band in wide steps like 25 kHz and keep tripping the driveway alarm. It will not have a constant carrier, it will only transmit when something trips it. You should start hearing pulses or something similar when you are getting close.
You may need to open the squelch and advance a step or two at a tme while tripping the sensor. The squelch will quiet down when you get close but it should be pulses of data and not a constant carrier.
Another thing is look on the receiver for an FCC ID number. If you find that, visit the FCC and do a lookup on that number.
Some manufacturers will have test data that may list the actual frequency. They now allow the data to be hidden to protect trade secrets from others but usually you will find something that will show a more accurate frequency or like was stated, you may jusr find the range of frequencies that the device may fall within.
Here's a link for the FCC ID number lookup: https://fjallfoss.fcc.gov/oetcf/eas/reports/GenericSearch.cfm
It seems my link above is dead or the site is having problems. I've not used it for a few months and it was working so I posted it anyway in case it is just a temp site issue.
If you find the center freq, you should still be able to hear the signal. Play around with AM as well as FM.
I can hear key fobs using an R9000 in one of the SSB modes the best or even CW. I seem to recall barely being able to detect the signal in FM on some of these type devices.
Try searching the band in wide steps like 25 kHz and keep tripping the driveway alarm. It will not have a constant carrier, it will only transmit when something trips it. You should start hearing pulses or something similar when you are getting close.
You may need to open the squelch and advance a step or two at a tme while tripping the sensor. The squelch will quiet down when you get close but it should be pulses of data and not a constant carrier.
Another thing is look on the receiver for an FCC ID number. If you find that, visit the FCC and do a lookup on that number.
Some manufacturers will have test data that may list the actual frequency. They now allow the data to be hidden to protect trade secrets from others but usually you will find something that will show a more accurate frequency or like was stated, you may jusr find the range of frequencies that the device may fall within.
Here's a link for the FCC ID number lookup: https://fjallfoss.fcc.gov/oetcf/eas/reports/GenericSearch.cfm
It seems my link above is dead or the site is having problems. I've not used it for a few months and it was working so I posted it anyway in case it is just a temp site issue.
Last edited:
K9WG
Member
I have an outside thermometer that transmits on 433Mhz When I "listen" to it I have to have the squealch wide open because the data burst is very short. Sounds like a very short hiss.
neat! i'll have to give that a shot too. i have a davis vantagePRO weather station that xmits every 2.5 seconds. i never even thought of trying to listen to that.
well, that sure is a lot to think about! it all sounds good and i can't wait to give it a try and see what i find and HOW i find it. i'll let you know what happens; thanks for the help.
Is it a Vantage PRO II or just Vantage Pro?
I had the original Vantage Pro but I do not remember what frequencies they used for the radio signal.
The newer VP II stuff is all 900 MHz and uses frequency hopping in the 902 - 928 MHz ISM band.
It is hard to catch as it is always changing frequency and the data bursts are very short.
You can "see" the signals with a spectrum analyzer otherwise it is hard to catch with a scanner.
Even though a lot of things are hard to hear, it's still fun trying!
I had the original Vantage Pro but I do not remember what frequencies they used for the radio signal.
The newer VP II stuff is all 900 MHz and uses frequency hopping in the 902 - 928 MHz ISM band.
It is hard to catch as it is always changing frequency and the data bursts are very short.
You can "see" the signals with a spectrum analyzer otherwise it is hard to catch with a scanner.
Even though a lot of things are hard to hear, it's still fun trying!
i have the original vantage pro.
I think you can hear something with that model.
It appears they used a single frequency of 916.500 MHz for the US models.
It will still be very short bursts of RF with data but at least on a single frequency.
The power is low though at under 1 mW so the range will be limited when trying to tune it with a scanner. Try and monitor that signal and it may give you an idea of what your driveway sensor may sound like on a scanner when you try and find its signal.
I don't think I've ever seen anyone decode the data from the Davis radios before. I've seen some users dissect the wired stations and intercept the data on the wire or at the data logger connector in a wireless station (it's basically serial data at that point) but can't say I've seen anyone demodulate the data from the RF signal before.
That would have been a fun project if your neighbor had a station and you did not!
well, i'm happy to report that i finally heard my driveway alarm sensor on 433.75mhz, AM and the squelch turned to zero. it wasn't really that exciting, only a half dozen "dit, dit, dit" noises but i was really happy to have finally found it. thanks a bunch to those that helped me out!! now to go and find some other noises that nobody but you and i care about 
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