parnass@ihuxz.ATT.COM (Bob Parnass, AJ9S) (01/31/88)
x CONVERT YOUR CORDLESS TELEPHONE TO 800 MHZ? by Bob Parnass, AJ9S Convert your cordless telephone to receive 800 MHz? Yes, I'm quite serious. How do you convert a 47 MHz cordless phone to 800 MHz? With a converter, of course! But you don't need a fancy $99 Hamtronics converter. All you need is the UHF tuner from a spare television set that was manufactured when TVs still covered channels 14-83. I used the solid state, tuneable UHF tuner from a cheapie JVC television set given me a few years ago. This tuner seems typical of the type available in TVs for the past several years. It uses a variable capacitor, not a varicap diode, to tune channels 14-83 (470-890 MHz), and convert them to an IF of 47 MHz. If 47 MHz sounds familiar, that's because it is the upper edge of the cordless telephone band. A cordless telephone is just a full duplex 46-47 MHz FM receiver and 49-50 MHz FM transmitter in the same case. Since I don't own a cordless phone, I used a scanner tuned to 47 MHz and connected its antenna jack to the IF output of the TV tuner. My tuner required a 300 ohm impedance antenna, so I placed an ordinary TV balun between the tuner input and my scanner antenna. The IF is pretty broad - at least 10 MHz, so I tune around on my scanner, rather than use the very coarse tuning control on the tuner itself. This tuner lacks an RF amplifier, so it's not as sensi- tive as a modern 800 MHz scanner, but I sure hear a lot of stations between 460 and about 890 MHz! My tuner works well when powered at 6-9 VDC, and since it only draws about 10 milliamps, I use a 9 volt alkaline battery. An article in January 1988 Ham Radio Magazine describes other TV tuners, and suggests ways to put them to good use. WARNING: Listening in on mobile phone conversations is now against the law. -- ===-===-===-===-===-===-===-===-===-===-===-===-===-===-===-===-===-===-===-=== Bob Parnass, Bell Telephone Laboratories - ihnp4!ihuxz!parnass - (312)979-5414
ron@topaz.rutgers.edu (Ron Natalie) (02/01/88)
WARNING: Listening in on mobile phone conversations is now against the law. So is telling people how to do it. Better watch out for the phone cops. -Ron