wendt@arizona.edu (Alan Lee Wendt) (06/01/89)
I'd like to build a direction finder that my wife (who's blind) can use to find the house. Something with a range of 2 miles or so, that could be left on all the time at the house and a small battery-operated hand buzzer that would stop buzzing when lined up with the direction of the house. Help me get my wife her instrument license. What frequencies are available for this kind of use? Anybody have any designs for bits of this? Alan Wendt
prem@crackle.amd.com (Prem Sobel) (06/01/89)
In article <11269@megaron.arizona.edu> wendt@arizona.edu (Alan Lee Wendt) writes: >I'd like to build a direction finder that my wife (who's blind) >can use to find the house. Something with a range of 2 miles or >so, that could be left on all the time at the house and a small >battery-operated hand buzzer that would stop buzzing when lined >up with the direction of the house. > >Help me get my wife her instrument license. What frequencies >are available for this kind of use? Anybody have any designs >for bits of this? Since city blocks are not radial, it might be useful for there to also be an audible distance measurement, but that is VERY expensive. For direction a system similar to the aircraft VOR system might be useful (again unfortunately very expensive), which sends an omnidirectional radio pulse out at the same time it uses a phased array to sweep a beam around at a known rate. The receiver measure the time between the omnnidirectional and swept beam to give angle to transmitter. If power levels are below a certain level (100 milliwatts I believe) or the signal is on on certain allowable experimental frequencies (above VHF) then no license is needed.
tomb@hplsla.HP.COM (Tom Bruhns) (06/02/89)
prem@crackle.amd.com (Prem Sobel) writes: >In article <11269@megaron.arizona.edu> wendt@arizona.edu (Alan Lee Wendt) writes: >>I'd like to build a direction finder that my wife (who's blind) >>can use to find the house. Something with a range of 2 miles or >>so, that could be left on all the time at the house and a small >>battery-operated hand buzzer that would stop buzzing when lined >>up with the direction of the house. >> >>Help me get my wife her instrument license. What frequencies >>are available for this kind of use? Anybody have any designs >>for bits of this? > >Since city blocks are not radial, it might be useful for there to also >be an audible distance measurement, but that is VERY expensive. For >direction a system similar to the aircraft VOR system might be useful >(again unfortunately very expensive), which sends an omnidirectional >radio pulse out at the same time it uses a phased array to sweep a >beam around at a known rate. The receiver measure the time between the >omnnidirectional and swept beam to give angle to transmitter. But VOR gives more information than requested: the person does not need to know that she is N, S, E, or W of the house, only in which direction the house is. That's easier. If you have a beacon transmitter at the house and a receiver with an antenna with a single sharp null (cardiod pattern), you have what the original poster wants. I have no idea about frequencies, etc. How about calling your local FCC field office? There have been some articles in ham magazines on direction-finding within the last couple years that might be useful; try _Ham_Radio_ magazine and QST. I recall an article on the "Double Duckie" antenna that has a sharp null - but the null is in two directions. Even so, it's fairly easy to resolve the ambiguity. By nature of its operation, the antenna puts essentially FM modulation on a CW signal, so you could broadcast a CW sig and she could hear the modulation and turn the antenna to null it... > >If power levels are below a certain level (100 milliwatts I believe) >or the signal is on on certain allowable experimental frequencies >(above VHF) then no license is needed. >----------
Ploni.Almoni@mailcom.FIDONET.ORG (Ploni Almoni) (06/08/89)
Alan - as long as you do it on 49 MHz or 27 MHz R/C channels, there is no problem --- if you can live with the low power. 49 MHz is 100 mw - good for 150 yards perhaps. 27 MHz (NOT CB channels) will get you a quarter mile range. As far as an accurate, sensitive, direction finder, portable, inconspicuous, the limit right now is about 30 yards. That's for portable. If you have a mobile installation, the range is much more. If you succeed in breaking the 30 yard barrier, my cousin Charlie the FCC inspector would like to talk sales and price with you!! -=Ploni=- -- Via apple!mailcom, Fido 1:204/444
Ploni.Almoni@mailcom.FIDONET.ORG (Ploni Almoni) (06/08/89)
Prem - see my reply of this date to Alan. There is no provision for "private beacons" except in 27 MHz R/C channels and 49 MHz low-power (non-licensed) channels. Anything except those requires special eligibility and licensing. The VOR is totally impractical for this purpose, unless you want to live at an existing VOR site. Contrary to your statement, operation of ANYTHING at VHF or UHF or higher requires licensing and eligibility ( which means that one has to meet certain requirements before a license can even be granted, such as specific types of businesses, etc.) except for mini-power stuff - 20 ft range. And again, there are no provisions for "private beacons". -=Ploni=- -- Via apple!mailcom, Fido 1:204/444