Post by thread:[EE:] 2km UHF transponder ideas

I'm building a unit that needs to head away from its point of origin until it gets to a preset distance. At the moment the distance calc is based on time elapsed. This doesn't work very well because speed varies. I like the idea of building a UHF transponder/beacon set. The unit sends a unique pulse train then listens for a reply. The beacon receives and decodes the pulse train, waits a preset time, then replys. The unit receives the reply and calculates distance from the signal's time of flight. Jittering the PRF and range gating would improve signal to noise. Max distance is around 1500m so a 2km range would be desireable. I'd like transmit status information in the pulse. Basically what I'm after is a low power UHF (~400MHz) version of the air traffic secondary surveilance radar. Trouble is I don't know where to start :( I'm comfortable making my own PCBs and programming PICs but don't know much at all about RF circuits. Would someone care to point me to a good starting point? A website or a readily available book would be nice. A similar project I could examine would be even nicer :) TIA Rob -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email spam_OUTlistservTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

Check out http://www.telelink.com.au/ http://www.radiomodules.net/ As advertised on the back page of Silicon Chip Magazine. We use selcom radio's at work - will need to find the address - Christchurch I think. ps I see u are in NZ ************************************************* Roy Hopkins .....rdhopkinsKILLspam@spam@ihug.co.nz ************************************************* {Quote hidden}> I like the idea of building a UHF transponder/beacon set. The unit sends > a unique pulse train then listens for a reply. The beacon receives and > decodes the pulse train, waits a preset time, then replys. The unit > receives the reply and calculates distance from the signal's time of > flight. Jittering the PRF and range gating would improve signal to > noise. > > Max distance is around 1500m so a 2km range would be desireable. I'd > like transmit status information in the pulse. Basically what I'm after > is a low power UHF (~400MHz) version of the air traffic secondary > surveilance radar. > --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.560 / Virus Database: 352 - Release Date: 8/01/2004 -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listservKILLspammitvma.mit.edu with SET PICList DIGEST in the body

On Mon, 2004-01-12 at 01:18, Hopkins wrote: > Check out > http://www.telelink.com.au/ > http://www.radiomodules.net/ > > As advertised on the back page of Silicon Chip Magazine. > > We use selcom radio's at work - will need to find the address - Christchurch > I think. > > ps I see u are in NZ The second link times out. The first link has some real possibilities although I imagine they are on the pricey side. I'll have to wait for their reply. I was actually more interested in learning about RF circuits and building my own. I have some old "Electronics Notebooks" by Colin Mitchell which have a bit about RF circuits, however, they are all based on tank circuits and I want more stability than that. Still if the Telelink modules are cheap enough I might not bother building. Rob -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email .....listservKILLspam.....mitvma.mit.edu with SET PICList DIGEST in the body

You may want to check with the New Zeland equivalent of the FCC. Here in the U.S., unlicensed 435 MHz operation is limited to very low power and very small antennas. Under those conditions, 2 km may be unrealistic. Since all nations coordinate their spectrum use, it is very likely that NZ rules are similar. 72/73 de WB8RCR http://www.qsl.net/wb8rcr didileydadidah QRP-L #1446 Code Warriors #35 ----- Original Message ----- From: "Rob Stockley" To: <EraseMEPICLISTspam_OUTTakeThisOuTMITVMA.MIT.EDU> Sent: Saturday, January 10, 2004 5:52 PM Subject: [EE:] 2km UHF transponder ideas -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listservspam_OUTmitvma.mit.edu with SET PICList DIGEST in the body

I don't know that much about making your own RF stuff. If you have the budget, I'd suggest using premade modules, unless you have a particular need for space or tight integration. In either case, a good book might be the ARRL handbook. I believe their website is http://www.arrl.org. It's a pretty good reference on many things RF. Hope that helps. Josh -- A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools. -Douglas Adams Rob Stockley wrote: > Trouble is I don't know where to start :( > > I'm comfortable making my own PCBs and programming PICs but don't know > much at all about RF circuits. Would someone care to point me to a good > starting point? A website or a readily available book would be nice. A > similar project I could examine would be even nicer :) -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email @spam@listservKILLspammitvma.mit.edu with SET PICList DIGEST in the body

----- Original Message ----- From: "Rob Stockley" > I was actually more interested in learning about RF circuits and > building my own. I have some old "Electronics Notebooks" by Colin > Mitchell which have a bit about RF circuits, however, they are all based > on tank circuits and I want more stability than that. 70 cm stuff isn't easy to build, but it's not impossible, either. This is a popular amateur radio band, so you can find a lot of construction information looking at amateur publications. There are plenty of DDS parts capable of generating stable 435 MHz and many include fsk capability on chip. Amplifier parts are quite widely available, as well as mixers. The challenge is that capacitances and inductances at this frequency are quite small, so construction techniques are a bigger deal than the actual circuits. 72/73 de WB8RCR http://www.qsl.net/wb8rcr didileydadidah QRP-L #1446 Code Warriors #35 -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email KILLspamlistservKILLspammitvma.mit.edu with SET PICList DIGEST in the body

On Sun, 2004-01-11 at 12:56, John J. McDonough wrote: > You may want to check with the New Zeland equivalent of the FCC. Here in > the U.S., unlicensed 435 MHz operation is limited to very low power and very > small antennas. Under those conditions, 2 km may be unrealistic. Since all > nations coordinate their spectrum use, it is very likely that NZ rules are > similar. Excellent advice. In NZ the information is available from http://www.med.govt.nz/rsm/. The amateur window at just over 400MHz is small. There are others at approx (read from chart) 30MHz, 51-54MHz and 144-148MHz. From comments and web reading so far it seems UHF may not be a beginner's best option. I'm still searching for the national regs on tx power, antenna length and sideband attenuation. Thanks for the steer on the ARRL. I remembered I have a copy (1997) tucked away and have just laid my hand back on it. Since the unit will always be heading away from the base the antennae could be highly directional perhaps mitigating the range vs power issue. I'll look into special function ic's once I am more familiar with the RF concepts. Rob -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email RemoveMElistservTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

The simple answer - unless you are very experienced in analog RF design - is BUY IT. It is one thing to build a small short-range transmitter-receiver for experimental work around your lab, but the approval process you would need to go through to be able to SELL the product would be prohibitive in the extreme. With spectrum space as scarce as it is these days the international governing bodies are very strict about what is allowed to broadcast. There are a few blocks in the microwave area which can be used by individuals (garage door/car door openers and the like) but even they must be type approved by the FCC. Anything which could work over a 2 km range would use more than the allowed output power and or have a very state-of-the-art receiver. Roy J. Gromlich (once WA2CMB, and an analog circuit designer) {Original Message removed}

Rob Stockley <spamBeGonerobstockleyspamBeGoneMOWGLI.NET.NZ> wrote: > I like the idea of building a UHF transponder/beacon set. The unit sends > a unique pulse train then listens for a reply. The beacon receives and > decodes the pulse train, waits a preset time, then replys. The unit > receives the reply and calculates distance from the signal's time of > flight. Jittering the PRF and range gating would improve signal to > noise. You've just described DME (distance-measuring equipment) as used on aircraft almost exactly. See http://www.acay.com.au/~willt/yssy/enthus/whatis/vordme.html You might be able to pick up some used equipment and modify its frequencies and power levels to suit your project. To address a point that another responder brought up, there are ways to achieve high precision in time while still using narrowband signals. For example, look up "chirp radar" on Google. -- Dave Tweed -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email TakeThisOuTlistservEraseMEspam_OUTmitvma.mit.edu with SET PICList DIGEST in the body

And a $80 GPS puck giving meter position accuracy is too expensive for him?? What is your time worth? Do you have the deep pockets needed to pay for certification of your system since it is unlikely they would work out to 2km in any license free band/power? FRS radios are probably close, but they are not licensed for use with any antenna other than the one they come with. But you are not prevented from strapping one to a tower to increase it's range. Some even have subaudible tones to open the squelch, and which might be usable for phase measurement to get distance if hacked up to a high, inaudible frequency (as suggested in an earlier post). See also 'radio altimeter' for ranging methods using frequency chirps. There are also a couple of patents on using existing radio stations to navigate by looking at multiple carrier phase relationships, and comparing them to a 'reference' station log (which you would send to your rover). Do let us know what you finally work out. Robert Dave Tweed wrote: {Quote hidden}> > Rob Stockley <RemoveMErobstockleyTakeThisOuTMOWGLI.NET.NZ> wrote: > > I like the idea of building a UHF transponder/beacon set. The unit sends > > a unique pulse train then listens for a reply. The beacon receives and > > decodes the pulse train, waits a preset time, then replys. The unit > > receives the reply and calculates distance from the signal's time of > > flight. Jittering the PRF and range gating would improve signal to > > noise. > > You've just described DME (distance-measuring equipment) as used on > aircraft almost exactly. See > http://www.acay.com.au/~willt/yssy/enthus/whatis/vordme.html > > You might be able to pick up some used equipment and modify its frequencies > and power levels to suit your project. > > To address a point that another responder brought up, there are ways to > achieve high precision in time while still using narrowband signals. > For example, look up "chirp radar" on Google. > > -- Dave Tweed -- http://www.piclist.com hint: To leave the PICList piclist-unsubscribe-requestEraseME.....mitvma.mit.edu

Where can you get this GPS puck - web address? ************************************************* Roy Hopkins EraseMErdhopkinsihug.co.nz ************************************************* > And a $80 GPS puck giving meter position accuracy is too expensive for him?? > --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.560 / Virus Database: 352 - Release Date: 8/01/2004 -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestEraseMEEraseMEmitvma.mit.edu

Another thought is passive such as a gyro system or electronic compass http://www.robot-electronics.com/ Are you using a model plane? Do you want to know its distance from you or are is the model? trying to do it's own calculation internally? ************************************************* Roy Hopkins RemoveMErdhopkinsspam_OUTKILLspamihug.co.nz ************************************************* > > And a $80 GPS puck giving meter position accuracy is too expensive for --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.560 / Virus Database: 352 - Release Date: 8/01/2004 -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestTakeThisOuTspammitvma.mit.edu

Yet another thought - how are you controlling this object? If you have a radio control system why can't you send data over the same link i.e. when the model senses there are no radio control commands been sent to it's receiver it can send data back to you - PWM etc. ************************************************* Roy Hopkins EraseMErdhopkinsspamspamBeGoneihug.co.nz ************************************************* --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.560 / Virus Database: 352 - Release Date: 8/01/2004 -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestKILLspammitvma.mit.edu

www.globalsat.com.tw/web/A3-1.php?serial=41 -----Original Message----- From: pic microcontroller discussion list [spamBeGonePICLISTSTOPspamEraseMEMITVMA.MIT.EDU]On Behalf Of Rob Stockley Sent: 11 January 2004 18:28 To: KILLspamPICLISTspamBeGoneMITVMA.MIT.EDU Subject: Re: [EE:] 2km UHF transponder ideas Importance: High On Sun, 2004-01-11 at 22:49, Robert Rolf wrote: > And a $80 GPS puck giving meter position accuracy is too expensive for him?? > No this is not too expensive. Where would I find one? What are they like to integrate? The vehicle is autonomous so this would be a great solution. Rob -- http://www.piclist.com hint: To leave the PICList EraseMEpiclist-unsubscribe-requestEraseMEmitvma.mit.edu -- http://www.piclist.com hint: To leave the PICList @spam@piclist-unsubscribe-request@spam@spam_OUTmitvma.mit.edu

Bear in mind you will also need the radio link between the unit to the base Which depending on terrain may be a lot harder than you think -----Original Message----- From: pic microcontroller discussion list [spamBeGonePICLISTKILLspamMITVMA.MIT.EDU] On Behalf Of Paul Tustin Sent: 11 January 2004 18:48 To: .....PICLISTspam_OUTMITVMA.MIT.EDU Subject: Re: [EE:] 2km UHF transponder ideas http://www.globalsat.com.tw/web/A3-1.php?serial=41 -- http://www.piclist.com hint: To leave the PICList TakeThisOuTpiclist-unsubscribe-request.....TakeThisOuTmitvma.mit.edu

> > And a $80 GPS puck giving meter position accuracy is too expensive ? > No this is not too expensive. Where would I find one? What are they like > to integrate? The vehicle is autonomous so this would be a great > solution. What is being referred to is the use of ANY GPS receiver to give you positional accuracy of from 1m to 10m without reference to the base station. (They access the GPS satellite constellation instead). GPS receivers are available in NZ form eg DSE from about $NZ300 up BUT almost any GPS module or receiver with an output would do. Many receivers have a 4800 baud serial output which is very easily read by a microcontroller to determine (amongst other things) speed, position in 3 dimensions and time of day. If you want to use a UHF link - you can buy a pair of UHF transceivers from eg DSE for about $NZ120. These will probably achieve a range of 2 to 3 km if placed on a pole with a clear line of sight. Range is much less if hand held and with obstructed sight lines. NZ max allowed power output is substantially greater than that allowed in some other countries. RM -- http://www.piclist.com hint: To leave the PICList TakeThisOuTpiclist-unsubscribe-requestKILLspamspammitvma.mit.edu

www.codereward.org/ > Where can you get this GPS puck - web address? > ************************************************* > > Roy Hopkins > > .....rdhopkinsRemoveMEihug.co.nz > > ************************************************* Mike DeMetz N9GEZ RemoveMEn9gezspamBeGoneqsl.net -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

Mike DeMetz wrote: > http://www.codereward.org/ > > >>Where can you get this GPS puck - web address? >>************************************************* >> >>Roy Hopkins >> >>spamBeGonerdhopkins@spam@spam_OUTihug.co.nz >> >>************************************************* > > > Mike DeMetz > N9GEZ > TakeThisOuTn9gezspamqsl.net Thanks mike, I was also looking for something like this :D -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads