[sci.electronics] Sending video signals 100 meters

gnd@targhee.idaho.amdahl.com (Greg Darnell) (02/21/91)

I have a barn about 100 meters from my house where I plan to install a
video camera to monitor a mare about to foal in March.  I would like to
get the signals from the barn to the house so that we can watch from a
heated area.  I have signal cables from the barn to the house already,
with multiple extra pairs, both twisted and non-twisted; however, no
coax installed, and I can't put that in now because the ground is frozen.

So...
  1. Can I send the audio/video signals across twisted pair with an
     acceptable amount of loss/crosstalk?  Should I send it as raw video
     and audio, or modulated to channel 3?
  2. Are there other ways that might work better, such as an infrared
     link or some sort of RF link?  I have seen the VCR Rabbit but it
     lists range as 150 feet "under ideal conditions".  Could I add 
     bigger antennas to it and make it work?  The nearest neighbor is
     over 1/2 mile away so RF interference should not be a problem if
     the power is low enough.

Any help would be appreciated...
  Greg
-- 
 Greg Darnell    Amdahl Corporation    143 N. 2 E., Rexburg, Idaho 83440
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  INTERNET: gnd@idaho.amdahl.com

robf@mcs213f.cs.umr.edu (Rob Fugina) (02/22/91)

In article <9942@tetons.idaho.amdahl.com> gnd@targhee.idaho.amdahl.com (Greg Darnell) writes:
>  1. Can I send the audio/video signals across twisted pair with an
>     acceptable amount of loss/crosstalk?  Should I send it as raw video
>     and audio, or modulated to channel 3?

It would seem to me (and I may be wrong) that you could send audio and video
via just about anything...I would think even telephone wire would do...  then
just plug it all into the inputs of a VCR back in the house...

Rob  robf@cs.umr.edu

jgd@Dixie.Com (John G. DeArmond) (02/22/91)

gnd@targhee.idaho.amdahl.com (Greg Darnell) writes:

>I have a barn about 100 meters from my house where I plan to install a
>video camera to monitor a mare about to foal in March.  I would like to
>get the signals from the barn to the house so that we can watch from a
>heated area.  I have signal cables from the barn to the house already,
>with multiple extra pairs, both twisted and non-twisted; however, no
>coax installed, and I can't put that in now because the ground is frozen.

Service Merchandise has a "video rabbit" that uses 900 mhz RF to send
video/audio up to several hundred feet.  It is meant to allow
one to view alternative video sources from anywhere in the house.
Price is about $90 for a pair.

There are other "rabbits" that use twisted pair wiring to do the same
thing.  They predate the FCC's permitting RF rabbits and are generally
less expensive.  I think Radio Shack carries these type.

John

-- 
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mcovingt@athena.cs.uga.edu (Michael A. Covington) (02/24/91)

In article <2220@umriscc.isc.umr.edu> robf@mcs213f.cs.umr.edu (Rob Fugina) writes:
>In article <9942@tetons.idaho.amdahl.com> gnd@targhee.idaho.amdahl.com (Greg Darnell) writes:
>>  1. Can I send the audio/video signals across twisted pair with an
>>     acceptable amount of loss/crosstalk?  Should I send it as raw video
>>     and audio, or modulated to channel 3?
>
>It would seem to me (and I may be wrong) that you could send audio and video
>via just about anything...I would think even telephone wire would do...  then
>just plug it all into the inputs of a VCR back in the house...
>
>Rob  robf@cs.umr.edu

No, the inductance and capacitance of the cable will get you if you're not
careful. Remember that video (TV type) goes to 4 or 5 MHz, and what's more,
all frequencies in the range 30 Hz -- 5 MHz have to be passed equally well,
with no difference between the highest and the lowest.
  
  However, you can use a wire of any (reasonable) length if it's a 
  coaxial cable of known impedance, and the driver and receiver (at the
  two ends) are matched to that impedance. This is a way of making
  inductance and capacitance cancel each other out. It's what makes
  large TV studios possible.