Andrea; I am a professional in this industry and I can tell you there is no need to "invent" this; there are literally dozens of these products out there. There are (as you figured out already) 2 parts to the product; the GPS "this is where I am" component and the reporting component. While GPS location "where am I" is the easy part; clearly defined, pretty much only one "source" of the data (put in a GPS receiver and listen to the NMEA string) but the reporting methods are based on YOUR end-result and defined by YOUR needs.
Both need a "carrier" to report the GPS data back and battery life is tied to two things; the power output on the transmission device (carrier transmitter) and the interval it reports. Remember the flight recorder from Flight 370 that got "lost" when the battery went dead? That issue is now your issue....and since they never found the plane you may not find your item either. If the battery is too big then the thief will SEE it and rip it off, leaving the GPS tracker in the yard and the item gone; so it can't be too big right? So if you MAKE it then you better be pretty good at engineering the end-result into microelectronics. The 40 MHz is unworkable as the antenna will be too long to radiate any distance (the higher the frequency the shorter the antenna) so stick to 450 MHz and UP but that isn't the only issue. If you buy the product like for example a PET TRACKER that is pre-built & ready to go they virtually all work on GSM type of cellular RENTED carriers so you pay a monthly data rate fee and in return get really GREAT coverage with very low transmitter power so the thief can take the item all the way to their home across town and you can track them on the Internet to their door 25 miles away. That is good but you pay for service...is that bad? You decide. If you buy and own it with NO rented carrier now the distance is tied to your transmitter power; if the unit puts out say 1/2 of a watt then you can track it for a short distance over a long period of time (recall the flight recorder at the bottom of the ocean problem here). If you want more power but small battery pack then you will get a longer distance but short battery life AND with both of these cases you have to be "on notice" as to WHEN the item was taken, then go start your search. If you put the tracker on the item, start it up PINGING and go to bed at say 9 PM and someone steals it at say 10 PM and you wake up at say 8 AM to discover it is gone; rush out to track it by either means then the clock started ticking for your battery when you turned it ON at 9 PM so you are burning battery for 11 hours now....see the issue? They don't call you up and let you know they are gone UNLESS you have an Internet based GPS/ Cellular tracker that is "FENCED" and when the GPS unit sees that it has gone outside of its FENCE (say 200 feet around your home for example) then it starts yelling at you, can probably be configured to send you a TEXT message to your phone, you are awakened by the DING sound and start following at 10 PM instead of 8 AM. Go look at http://www.pocketfinder.com/gps-locator/pet-locator/gps-dog-collars-worth-in vestment/ for example; there are lots of them; hunt for "pet tracker" as a search term and good luck. I suggest you don't try and build it but check back if you still want to create a new product someone else abandoned long ago... Each has their benefits; get the idea? Robert L. "Bob" Burchett Certified Communications Engineer Enterprise Electronics 22826 Mariposa Ave. Torrance CA 90502 Direct line: 310.534.4456 FAX: 310.534.1233 Website: www.EEonTheWeb.com -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of [email protected] Sent: Tuesday, May 27, 2014 9:00 AM To: [email protected] Subject: time-nuts Digest, Vol 118, Issue 58 Send time-nuts mailing list submissions to [email protected] To subscribe or unsubscribe via the World Wide Web, visit https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts or, via email, send a message with subject or body 'help' to [email protected] You can reach the person managing the list at [email protected] When replying, please edit your Subject line so it is more specific than "Re: Contents of time-nuts digest..." Today's Topics: 1. Toy radiolocation and LORAN envelope (Andrea Baldoni) 2. UK MSF off the air ... (David J Taylor) 3. Over optimistic PN measurements ([email protected]) 4. Re: Toy radiolocation and LORAN envelope (Graeme Zimmer) 5. Re: Beginner question - unexpected possible jitter in 1 PPS (Jason Rabel) ---------------------------------------------------------------------- Message: 1 Date: Tue, 27 May 2014 11:12:32 +0200 From: "Andrea Baldoni" <[email protected]> To: [email protected] Subject: [time-nuts] Toy radiolocation and LORAN envelope Message-ID: <[email protected]> Content-Type: text/plain; charset=us-ascii Hello! Years ago, I sometimes played the transmitter hunting game, probably known to most of the members of this list. A friend of mine recently suffered a theft so I thought about the opportunity to embed little marker transmitters in some object usually left in the yard (like bicycles for example), and have inside the house a system that constantly monitors them for unwanted movement, while at the same time be eventually able to recover them once "disappeared" using portable equipment. I think that the very simple RF power way to monitor movement is inadequate, but at the same time I would like to keep things very simple, little and really cheap, so no things like gps receivers on it: maybe just a 8 pin microcontroller and a crystal. Also, the battery life should be the maximum possible, so the RF power will be little and this also exclude to put a transponder inside the gadget, unless its on-time could be limited to short and precise slots, because a constantly-on RX will consume more power than a low duty cycle (say, 0.1pps) pulsed TX. Obviously, the goal is to reach the best positional accuracy possible within the constraints. The frequency is yet to choose, but I think it should stay in the ISM band around 40MHz. The angle could be found with a directional antenna or inerferometry, but about the distance? There is the need of a very good accuracy of the transmitter pulses. It's obtainable at least in the short term (the time needed to recover the object, for instance) for low power and low price? The long term inaccuracy could tracked and offset when the system is aware that the target is not moving. By the way, the LORAN envelope, was so shaped just to limit harmonics, push up energy efficiency, or there were other reasons not to transmit a square one? Best regards, Andrea Baldoni ------------------------------ Message: 2 Date: Tue, 27 May 2014 10:32:44 +0100 From: "David J Taylor" <[email protected]> To: "Time-nuts mailing list" <[email protected]> Subject: [time-nuts] UK MSF off the air ... Message-ID: <642642419E4840278740729A296B704C@Alta> Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=original From: http://www.npl.co.uk/science-technology/time-frequency/products-and-services /time/msf-outages "MSF signal off-air "Please note that the MSF signal has had to be taken off-air from Saturday evening, 24 May, until late Tuesday, 27 May, at the earliest, due to a technical fault. "Further updates will be posted here when received." Cheers, David -- SatSignal Software - Quality software written to your requirements Web: http://www.satsignal.eu Email: [email protected] ------------------------------ Message: 3 Date: Tue, 27 May 2014 06:31:52 -0400 (EDT) From: "[email protected]" <[email protected]> To: [email protected] Subject: [time-nuts] Over optimistic PN measurements Message-ID: <582894685.402.1401186712874.open-xcha...@oxuslxltgw10.lxa.perfora.net> Content-Type: text/plain; charset=UTF-8 There has been some controversy over the Phase noise of CMOS logic devices. Perhaps the apparently anomalously low PN measures are due to the use of cross correlation in the phase noise measurement equipment and the occurrence of phenomena detailed in the recent NIST papers: http://tf.boulder.nist.gov/general/pdf/2697.pdf http://tf.boulder.nist.gov/general/pdf/2698.pdf Such collapse of the cross-spectral function may also be present in the PN plots shown in the datasheets for some OCXOs. Bruce ------------------------------ Message: 4 Date: Tue, 27 May 2014 20:40:24 +1000 From: Graeme Zimmer <[email protected]> To: Discussion of precise time and frequency measurement <[email protected]> Subject: Re: [time-nuts] Toy radiolocation and LORAN envelope Message-ID: <[email protected]> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Hello Andrea, > The angle could be found with a directional antenna or inerferometry, but about > the distance? About the only reliable way to locate hidden transmitters is by field strength. The problem in built-up areas is reflections. At one time Doppler DF systems were popular, but anybody who has used one will tell you they are usually more trouble than they are worth. A simple beam or dipole is useful, but only when out in the open country By simply gridding the area, and drawing a field strength map, you will soon cut the location down to a small area. Then with a field strength meter you can walk right up to it. When doing professional DF work, I would use a scanner with an external S-meter and an effective attenuator in the antenna lead. Regards........... Zim ------------------------------ Message: 5 Date: Tue, 27 May 2014 08:04:50 -0500 From: "Jason Rabel" <[email protected]> To: <[email protected]> Subject: Re: [time-nuts] Beginner question - unexpected possible jitter in 1 PPS Message-ID: <[email protected]> Content-Type: text/plain; charset="us-ascii" > My question is this: Under what conditions can the > 1 PPS signal be relied on to meet its period uncertainty > spec? The UT+ emits 1 PPS regardless of whether > satellites are visible or not Look under the TRAIM settings. You should have several choices: 1PPS disabled 1PPS always on 1PPS when tracking at least 1 sat 1PPS when TRAIM conditions are met I would chose the last in the list as that would ensure your PPS is valid. ------------------------------ _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts End of time-nuts Digest, Vol 118, Issue 58 ****************************************** _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
