Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!seismo!rutgers!ames!ptsfa!ihnp4!homxb!houxm!mhuxt!m10ux!braun From: braun@m10ux.UUCP (MHx7079 mh) Newsgroups: sci.electronics Subject: Re: Wireless Audio Link Message-ID: <174@m10ux.UUCP> Date: Wed, 18-Mar-87 19:34:23 EST Article-I.D.: m10ux.174 Posted: Wed Mar 18 19:34:23 1987 Date-Received: Fri, 20-Mar-87 05:06:27 EST References: Organization: AT&T Bell Labs, Murray Hill, NJ Lines: 37 Remember that an equalized phone line from the phone company will be considerably longer than 2000 feet. (And not even shielded!). The tricks used by the phone company to preserve the signal quality are to make sure the line is correctly balanced (with a transformer at each end) and that it is terminated with the correct impedance. Also, equalization is added to correct the frequency response. The most cost-effective thing for you to do would be: Make sure the cable is of a balanced construction (twisted pairs). Use good 600 ohm balanced transformers at each end. To improve S/N, increase the signal level. You must make sure that the amplifiers driving the lines are not being overloaded. 10 volts into 600 ohms is a reasonable signal level. Also make sure the receiving circuits are not overloading. Attenuation may be necessary. Use a good equalizer at the receiving end. A parameteric (as opposed to graphic) is probably better. This could be done for maybe 50-500 dollars, depending on whether you have to buy a lot of new stuff. Make sure the transformers will handle the signal levels without saturating. The little ones meant for microphones are probably no good. You might try begging off a local radio or TV station; this is the sort of stuff that piles up in their back rooms. For a driving amp, you could certainly use any reasonably good amp (>25 watts) meant to drive speakers. You might have to add source impedance (0-600 ohm resistors in series with the output). In any case, you will have to fiddle a lot with the various resistance values, gain, and equalization to get the best results. The reliability will be better that a STL, of course. -- Doug Braun AT+T Bell Labs, Murray Hill, NJ m10ux!braun 201 582-7039