4905	2010-08-16 09:11:04	aa7hq	those signals on 433.92 MHZ
Message	Date	From	Subject
if i tune my receiver to 433.92 MHZ, CW, i hear little bursts, repeating every few seconds. an example: my oregon scientific outdoor thermometer. Audacity lets me look at these bursts. does anyone else find this interesting?
4906	2010-08-16 09:39:48	w4zcb	Re: those signals on 433.92 MHZ
if i tune my receiver to 433.92 MHZ, CW, i hear little bursts, repeating every few seconds. an example: my oregon scientific outdoor thermometer. Audacity lets me look at these bursts. does anyone else find this interesting? Actually, not here. In the event you wish to work some real DX though, you might want to listen for someone unlocking their car door. I'm not aware of any certificates available though, so if you can figure out a way to get a QSL, you could perhaps, start a new business selling certificates. Maybe a WAKC for Worked All Key Chains? W4ZCB Watching the grass grow.
4908	2010-08-16 11:17:46	aa7hq@comcast.net	Re: those signals on 433.92 MHZ
thanks for your thoughtful reply. 73, ed ----- Original Message -----
4909	2010-08-16 11:48:13	Tim	Re: those signals on 433.92 MHZ

4910	2010-08-16 12:45:56	aa7hq@comcast.net	Re: those signals on 433.92 MHZ
thank you for your response to my question about 433.92MHZ (and other frequencies as well). there is plenty of stuff i have found on the internet about such systems, old and new. (new, such as tire pressure monitors on newer cars!) however, decoding even the simplest schemes, so far is beyond me. the techniques must be proprietary. when i examine a burst with Audacity, i assume it comes from a very simple system using ASK modulation, and i am trying to reconstruct the digital signal from the expanded (timewise) signal. i recognize that this is a difficult puzzle to solve, and that i am not likely to get very far into decoding even those signals over which i have some control. i would like to hear from one who has looked at the receiver output of the signals sent and received from an OSC thermometer, and has some inkling of what they looked like at the sensor output and transmitter input. i have already had a response from someone who derided me for doing dumb things that no real ham would do. i have been lectured by a myriad of fools. nevertheless, i find this stuff interesting, and i will be happy if those who do not decide to go their own way. thanks, tim, e ed ----- Original Message -----
4911	2010-08-16 12:46:10	Lasse	Re: those signals on 433.92 MHZ
Most of those simpler key fobs are using a variant of the venerable Motorola chips And yes uses ASK, but some may go for FM. http://www.freescale.com/files/rf_if/doc/data_sheet/MC145026.pdf Newer ones are a bit smater using rolling codes, making it harder to "steal" the code and then play it back... Lasse SM5GLC Tim skrev 2010-08-16 20:47: >
4912	2010-08-16 12:56:49	Tim	Re: those signals on 433.92 MHZ

4913	2010-08-16 13:08:16	aa7hq@comcast.net	Re: those signals on 433.92 MHZ
hey! svenska! thank you, Lasse! i did not know the term "rolling codes" before. my car was long ago forced out of the garage by others among my toys, hi! maybe i should record my OSI transmitter, to interrogate the outdoor transmitter wthout a wait! thank you. de ed ----- Original Message -----
4914	2010-08-16 13:43:09	Chris Howard	Re: those signals on 433.92 MHZ
I for one would like to see the Audacity you are seeing Ed. I don't expect I will make any more sense of it than you have but it would be educational. Chris w0ep
4915	2010-08-16 14:06:15	aa7hq@comcast.net	Re: those signals on 433.92 MHZ
Audacity is a free download from source forge. a cord with 1/8th plugs connects rx output and sound card input.. move the mouse around the tool bar to learn how to start and stop recording, how to expand the time frame and select a burst, and thus view the signal. using Audacity is very intuitive, and there are many potential uses for this fine program. Audacity will show you a lot about the signal as received. i am hoping to find out about the signal as seen at the temperature sensor. chris, good luck de ed ----- Original Message -----
4935	2010-08-28 07:18:55	TwoEngineers	Re: those signals on 433.92 MHZ
GNURadio is a powerful tool for this kind of investigation. You might be interested in this paper about decoding the TPMS signals: ftp.cse.sc.edu/reports/drafts/2010-002-tpms.pdf
4943	2010-08-29 12:47:59	aa7hq@comcast.net	Re: those signals on 433.92 MHZ
thank you very much for the reference to the TPM measurements. that is a very interesting discussion, better than the other TPM references i have found. i also thank you for the reference to GNU radio. i have been enjoying the softrock series, but have not used it at uhf. i will think some more about how i might use such an approach. at the moment, a kindle and a barcode reader are distractions. regards, ed ----- Original Message -----