Cable question

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spacenerd

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After my cable company installed new lines to my home they left me extra cable. It is labled TFC CATVX. Does anyone know if this would be usable with from my outside antenna to my scanner ( about a 30 feet).
Thanks,
Spacenerd
 

gmclam

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Antenna cable

Typically, cable used for television is 75 ohms. Cable used for (scanner) antennas is 50 ohms. The cable will "work", even if the wrong impedance, but it will lose more signal than it would if it was the correct impedance.

Now if you're only monitoring VHF, and the distance to the antenna is fairly short, you'll be OK. But the longer the cable, and the higher the frequency you're receiving, the greater the loss. My gut says if you are monitoring above 500MHz, get the best cable you can specifically designed for the job.

Good luck,
George
 

thewenk

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I have used 75 ohm coax for years (RG6 & RG11) and it works great. If it is 75 or 50 ohm doesn't make a significant difference when you are receiving--only when transmitting. Make sure it is RG6 and not RG59 cable. Also do a search on "RG6 Cable" on this site and you will find plenty of info on using 75 ohm coax.
 

gmclam

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50 Ohm or 75 Ohm

thewenk said:
I have used 75 ohm coax for years (RG6 & RG11) and it works great. If it is 75 or 50 ohm doesn't make a significant difference when you are receiving--only when transmitting. Make sure it is RG6 and not RG59 cable. Also do a search on "RG6 Cable" on this site and you will find plenty of info on using 75 ohm coax.
You are correct in that the cable impedance is more important for transmitters. You are also correct that there is less loss when you use a larger coax. But that was not spacenerd's question.

There is a reason that cables of different impedances are manufacturered. Otherwise, there would only be one for everything. The reason we match impedance is for maximum transfer of power. In other words, when there is an impedance mismatch, there is a LOSS. The loss in your situation might be slight because you are receiving signals which are already strong (or antenna with high gain or sensitive receiver, etc).

The question was whether or not the cable is usable for a 30 foot connection. The answer is certainly yes, BUT he will get better performance if he uses the correct cable. And yes there are many correct cables (all 50 ohms), which is why I suggested he get the best cable he can designed for the job (and not save the few dollars using improper cable).

Best regards,
George
 

kf4lne

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Use it, it will be fine. Many commercially made scanner antennas include RG6 coax for feedline anyway and many members of this board are using RG6 or other 75 ohm cables for feedlines with no problems. I am using RG11 for my scanner, about 50 feet, and I am able to hear radio systems in nearly 9 counties in northwest NC and Northeast TN, and thats an area larger than some European countries. I use RG6 for my WX radio and for my SWL antenna feedlines and I am even using RG6 to feed a couple of homebrew dipoles for use with 2 meters and MURS with an SWR below 1.3:1 and excellent results, of course a dipole is about 75 ohms anyway and can be fed with 50 or 75 ohm coax with great results.
 

1979lee

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Jun 24, 2005
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bakersfield, california
I am currently useing rs 75 ohm cable
25-Ft.Video Hookup Coax Cable (Black)
$13.99
Model: 15-1571
Catalog #: 15-1571
and i do have some loss , you see i went with this cable , for one because of the price , and also because i did'nt know about the ohm thing, but it works and is very strong ,
 
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