[time-nuts] Toy radiolocation and LORAN envelope
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 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Toy radiolocation and LORAN envelope
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 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Toy radiolocation and LORAN envelope
Hi Andrea: There are a number of object location schemes. I got interested after seeing the blue dot in the movie The Da Vinci Code. It is a totally fictional device. A lot of new products like a blue dot are coming on the market based on Bluetooth and the use of smart phones. But there are many other methods used for things like pets, see: http://www.prc68.com/I/ObjectLocationTags.html Note the various modes of operation. The bandwidth of low frequency antennas is very narrow (high Q) since there is a direct tradeoff between bandwidth and antenna size. See the Wiki page for Chu–Harrington limit: http://en.wikipedia.org/wiki/Chu%E2%80%93Harrington_limit At 100 kHz a wavelength is 3,000 meters. So the waveform needs to have minimal bandwidth. Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html http://www.prc68.com/I/DietNutrition.html Andrea Baldoni wrote: 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 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Toy radiolocation and LORAN envelope
You don't need much power because the device in the toy only needs to transmit for a few milliseconds then shut off. Some transmuter you have pings the device in the toy that acts like a transponder. It only transmits in response to a ping. So limey it can be powered by a button battery. How to power the receiver? RFID tags are devices that are powered by rectifying the RF energy from the antenna . Crystal sets work this way also. as for logic, the TI MSP430 can run on nano amps of current. and sleep modes use pico amps. So it could be powered by a capacitor that is charge from some powerful AM broadcast station. It turns out that energy harvesting (getting power from the environment) is a hot tops right now. The simplest method would be the solar powered calculator. That tiny little cell runs a uP and an LCD screen. The old mechanical self winding watch was another example of harvesting energy. You could run the receiver and logic on harvested energy and then use the coid cell battery for a transmitter. Your locator device would measure time of flight to the toy and its own location via GPS. As you move the locator it gathers data used for a solution. All the smarts is on the hand held locator that has a high power transmitter, sensitive receive, GPS and a computer. The device in the toy is a simple transponder. In monitor mode the locator would request a micro-power ping (not using the coin battery, just the capacitor. from the toy and use a large non-mobile antenna and would alarm if the time of flight changed. You'd want some frequency that would go through walls and trees and in some band that is legal for such stuff. ... 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, -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Toy radiolocation and LORAN envelope
Hi Chris: The trouble with a transponder is the receiver is a power hog. One way to mitigate that is to have the receiver operate on a low duty cycle and use a transmit signal that's longer than the receive period. The military PRC-68 squad radio used this method and the squelch opened so fast you would not know it worked that way. http://www.prc68.com/I/PRC68.shtml PS that radio is the basis of my web page URL. In Leash mode the location tag transmits a pulse (has no receive function) with a low duty cycle and the smart phone looks for some number of missing pulses in order to sound an alarm. This is one way the Bluetooth tags work. The smart phone stores it's location every time it receives a ping from the tag, not all of them just the last known location, so that when the tag goes missing you know it's last location. Some proprietary smart phone software allows other smart phones to report hearing a tag that's been reported as stolen. Another mode is Find or Locate, i.e. where are my keys? This requires the tag to act as a Bluetooth receiver and beep when queried. This may be the most popular Bluetooth tag mode. http://www.prc68.com/I/ObjectLocationTags.html Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html http://www.prc68.com/I/DietNutrition.html Chris Albertson wrote: You don't need much power because the device in the toy only needs to transmit for a few milliseconds then shut off. Some transmuter you have pings the device in the toy that acts like a transponder. It only transmits in response to a ping. So limey it can be powered by a button battery. How to power the receiver? RFID tags are devices that are powered by rectifying the RF energy from the antenna . Crystal sets work this way also. as for logic, the TI MSP430 can run on nano amps of current. and sleep modes use pico amps. So it could be powered by a capacitor that is charge from some powerful AM broadcast station. It turns out that energy harvesting (getting power from the environment) is a hot tops right now. The simplest method would be the solar powered calculator. That tiny little cell runs a uP and an LCD screen. The old mechanical self winding watch was another example of harvesting energy. You could run the receiver and logic on harvested energy and then use the coid cell battery for a transmitter. Your locator device would measure time of flight to the toy and its own location via GPS. As you move the locator it gathers data used for a solution. All the smarts is on the hand held locator that has a high power transmitter, sensitive receive, GPS and a computer. The device in the toy is a simple transponder. In monitor mode the locator would request a micro-power ping (not using the coin battery, just the capacitor. from the toy and use a large non-mobile antenna and would alarm if the time of flight changed. You'd want some frequency that would go through walls and trees and in some band that is legal for such stuff. ... 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, ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Toy radiolocation and LORAN envelope
I should mention that the circuit that I attached in the previous post does not output at 49.152 MHz The output is the third (or fifth?) harmonic of the crystal frequency... ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Toy radiolocation and LORAN envelope
At 06:40 AM 5/27/2014, Graeme Zimmer wrote: A simple beam or dipole is useful, but only when out in the open country I have seen some of the equipment used by FCC field agents when DFing deliberate interference to aircraft communications. They used three transportable fixed mountaintop installations ringing the area of interest that measured field strength and also recorded transmitter spectra for later identification of the suspect transmitter, and three mobile equipment sets employing directional antennas used in a small-city urban area. Dale H. Cook, GR / HP Collector, Roanoke/Lynchburg, VA http://plymouthcolony.net/starcity/radios/index.html ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Toy radiolocation and LORAN envelope
On Tuesday, May 27, 2014, Mark Sims hol...@hotmail.com wrote: I should mention that the circuit that I attached in the previous post does not output at 49.152 MHz The output is the third (or fifth?) harmonic of the crystal frequency... I have had very good luck with these 433 MHz TX modules. Easily received with a ham 70cm SSB RX. http://www.dx.com/p/433mhz-wireless-transmitter-module-superregeneration-for-arduino-green-149254?tc=USDgclid=CM3Opqf4zL4CFVQFMgodPHEAlw#.U4T1YNq9KK1 Great because there is no need to tweak to make them operate and you can easily do OOK to tx telemetry using a PIC or other uP. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Toy radiolocation and LORAN envelope
I built some RF beacons for my friend's high power (TRIPOLI) rocketry projects. We use a TELEVILT UHF wildlife tracking receiver from Sweden (pricey) that operates in the 434 MHz ISM band. The transmitters are LINX TXM-LR series transmitter chips with an 8 pin PICAXE processor. The modulation is OOK (pulsed CW) for best signal to noise using the TELEVILT narrow band receiver and its BFO.I will share some code examples if interested. It was pretty simple. The FCC part 15 rules unfortunately are restrictive on duty cycle so you need a ham license to operate them. If I had gotten fancy and made them transpond upon interrogation, it could probably be type accepted. The battery is a 3.2V CR-123 type and could run weeks most likely at the duty cycle of 1 pps. A smaller battery is certainly possible. If I had to do it again, I would leverage one of the very tiny GPS receivers that are for cellphones and simply packetize (APRS) the location data and use an FM ISM transmitter. But I would cycle to a CW mode periodically for the high sensitivity mode. This because, in rocketry, the antenna is often obscured when the rocket body lands on earth. It is quite noticeable when landing since the signal drops suddenly. -- Joe Leikhim Leikhim and Associates Communications Consultants Oviedo, Florida jleik...@leikhim.com 407-982-0446 WWW.LEIKHIM.COM ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Toy radiolocation and LORAN envelope
On Tue, May 27, 2014 at 11:32 AM, Brooke Clarke bro...@pacific.net wrote: Hi Chris: The trouble with a transponder is the receiver is a power hog. Why does a receiver have to be a power hog? I remember building a receiver once that did not use any power other then the energy coming in from the antenna. RFID chips work like that, with no power. I think you could build a receiver that uses almost no power. -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
