Path: utzoo!attcan!uunet!zephyr.ens.tek.com!gvgpsa!gold!grege
From: grege@gold.GVG.TEK.COM (Gregory Ebert)
Newsgroups: sci.electronics
Subject: Re: low-level signals and long cables
Message-ID: <910@gold.GVG.TEK.COM>
Date: 12 Apr 90 16:38:46 GMT
References: <22845.2623bae8@kuhub.cc.ukans.edu>
Organization: Grass Valley Group, Grass Valley, CA
Lines: 26

In article <22845.2623bae8@kuhub.cc.ukans.edu> rsl09@kuhub.cc.ukans.edu writes:
>
>I have an application that requires sending low level signal (in mv range)
>down a  long cable (about 50 meters). The signal is bandlimited to about
>13 KHz. To avoid potential interference, I thought it would better
>to  digitize the signal and send digital signal, rather than 
>analog, down the cable.
>
>I was wondering if there is a product on the market that can
>digitize an analog signal, transmit  down a long cable, and 
>receive the digital signal at the other end of the cable.
>
>Any help or suggestion will be greatly appreciated. 
>
	Why not use shielded cable ? Your frequency is so low that you wont
	even need to terminate it for a 50m run. The only potential problem
	would be a *slight* attenuation due to lossy media, but I'm pretty
	sure that the loss of, say, RG58 or RG59 at 13Khz is zippo for 50m.
	You will, of course, want to avoid ground loops. Make sure that the
	coaxial shield is the ONLY ground path between the transmitter and
	the receiver - Never, never, NEVER connect your power supply ground
	to 'earth' in more than one location.

	I had ground loops in my homebrew system; it caused SEVERE RFI
	interference for about 1/2 block. Took out the ground loops, and
	there was NO detectable interference.