Dale, you won't believe it, but Lauren McKey handed me the transmitter, tubes and all, about five years ago. It's sitting on a shelf behind me.
Geoff ----- Original Message ----- From: Dale Leavens To: [email protected] Sent: Tuesday, November 27, 2007 11:38 PM Subject: Re: [BlindHandyMan] radio direction finding project As kids at the school for the blind we used to make low power transmitters in that way. We would look for a radio with particularly strong signals and tune it further by attaching a cristal set clipped to the tuning condenser to modulate the signal to produce a low power a m radio station. Some of our studios got rather sophisticated and might carry several hundred yards. That was before the days of Fm and I don't have any idea how we might have been able to make an fm signal. These days though one can buy small FM transmitters fairly affordably. My brother and later Geoff also had a small a m transmitter which was rather more successful, I think they were even able to transmit a signal over the school to the girls dormitory. Dale Leavens, Cochrane Ontario Canada [EMAIL PROTECTED] Skype DaleLeavens Come and meet Aurora, Nakita and Nanook at our polar bear habitat. ----- Original Message ----- From: Max Robinson To: [email protected] Sent: Tuesday, November 27, 2007 9:49 PM Subject: Re: [BlindHandyMan] radio direction finding project They were looking for the local oscillator in the receiver. Try this experiment. operate two radios side by side. If they are AM tune in a station above 1000 kHz. Then sweep the other radio through the lower half of the band. Exactly 455 kHz below the station you have tuned in on the first radio. You will hear a tone that descends and then goes back up again as you tune the second radio. The results are less spectacular with FM radios but you can still block out a station by tuning the second radio 10.7 MHz below the station you have tuned in on the first one. With TV sets it's not as easy to figure out as the channel numbers bear no relationship to frequency. Every modern receiver has this local oscillator. It combines with the incoming station to produce the intermediate frequency which is 455 kHz for Am, 10.7 MHz for FM and 42 to 48 MHz for TV sets. Stations have been known to do audience surveys by flying an airplane over the city with a receiver tuned 455 kHz above the stations transmitting frequency to see how many local oscillators they could hear. They won't all be on the exact same frequency because no two people tune a radio the same and no two radios are exactly the same. If you want more information on this subject visit, http://www.angelfire.com/electronic/funwithtubes/Simple_Superhet.html Regards. Max. K 4 O D S. Email: [EMAIL PROTECTED] Transistor site http://www.funwithtransistors.net Vacuum tube site: http://www.funwithtubes.net Music site: http://www.maxsmusicplace.com To subscribe to the fun with tubes group send an email to, [EMAIL PROTECTED] ----- Original Message ----- From: "Dale Leavens" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Tuesday, November 27, 2007 11:44 AM Subject: Re: [BlindHandyMan] radio direction finding project > Fair enough, but by walking around you are in fact calculating position by > comparing a series of points. > > The multi-elemented antennae such as the Yagi can be pretty directional > within tens of degrees but there are so many confounding factors like > signal reflection and absorption. > > When I lived in England they used to have television and radio license > police who drove around in vans pointing at houses looking for signals > they compared against a list of licensees to catch people operating > receivers with out paying for the BBC.I don't know what technology they > used but the signals are fairly weak and of course standing still. > > Dale Leavens, Cochrane Ontario Canada > [EMAIL PROTECTED] > Skype DaleLeavens > Come and meet Aurora, Nakita and Nanook at our polar bear habitat. > > > ----- Original Message ----- > From: Dan Rossi > To: [email protected] > Sent: Tuesday, November 27, 2007 9:23 AM > Subject: Re: [BlindHandyMan] radio direction finding project > > > Dale, > > Actually you don't need triangulation to locate a transmitter. Not at > least, if you can move. These fox hunts are done by walking around with a > loop antenna and listening for signal strength. I think you have to get > within five feet of the transmitter before it is considered a hit. > > -- > Blue skies. > Dan Rossi > Carnegie Mellon University. > E-Mail: [EMAIL PROTECTED] > Tel: (412) 268-9081 > > > > > [Non-text portions of this message have been removed] > > > > To listen to the show archives go to link > http://acbradio.org/handyman.html > or > ftp://ftp.acbradio.org/acbradio-archives/handyman/ > > The Pod Cast address for the Blind Handy Man Show is. > http://www.acbradio.org/news/xml/podcast.php?pgm=saturday > > Visit The Blind Handy Man Files Page To Review Contributions From Various > List Members At The Following address: > http://www.jaws-users.com/handyman/ > > Visit the archives page at the following address > http://www.mail-archive.com/[email protected]/ > > If you would like to join the Blind Computing list, then visit the > following address for more information: > http://jaws-users.com/mailman/listinfo/blind-computing_jaws-users.com > > For a complete list of email commands pertaining to the Blind Handy Man > list just send a blank message to: > [EMAIL PROTECTED] > Yahoo! Groups Links > > > > > > > -- > No virus found in this incoming message. > Checked by AVG Free Edition. > Version: 7.5.503 / Virus Database: 269.16.9/1155 - Release Date: > 11/27/2007 8:30 PM > > [Non-text portions of this message have been removed] [Non-text portions of this message have been removed]
