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any difference in cables using lower power?

 
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any difference in cables using lower power?
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energy106
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Post any difference in cables using lower power? Reply with quote
I'm using quite low power, would there any difference, if you picked out a 75ohm and 50ohm cable with simliar loses and cut them both to the same lenght would there really be any difference in the signal?.

I am currently using about 500mw and a dipole aerial with 75 ohm co-ax, strong reception reaches about a mile to a mile an half. The only problem is there is a place just over a mile away where the land drops down, its only 35/40 meters at the top the signal is strong but at the bottom its entirely different. Increasing the power seems to be the only way of getting the signal down there, i tryed a different aerial afew days ago and actually managed to get the signal down there still on 500mw but would'nt you know it the signal every where else just tottally sucked, did'nt go half as far as a dipole.
Tue Sep 19, 2006 2:57 pm View user's profile Send private message
pcs
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Well, I say you're ok with 75 ohms. VSWR created is negligible.

I'd be more worried about the losses, if the cable run is long.

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Tue Sep 19, 2006 3:11 pm View user's profile Send private message Visit poster's website
energy106
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cable run is just less than 10 meters
Tue Sep 19, 2006 3:24 pm View user's profile Send private message
pcs
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10 meters can be a lot, if you use low-quality high-loss cable.

It can be the difference between using a good and bad antenna. Those dB quickly
add-up to several dB.

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Marko - PCS Electronics
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Tue Sep 19, 2006 3:34 pm View user's profile Send private message Visit poster's website
energy106
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Post Reply with quote
cable is quoted at 8.5db at 100meters, i'm presuming thats is 0.85db at 10 meters, there was a cable with a loss of 2db at 10meters that would obviously loose some of the signal because theres over a db in difference between the 2, but if the difference was just 0.2 of a db a fraction of a db would you notice anything? is there anyway to convert these figures into milliwatts?
Sat Sep 23, 2006 9:38 am View user's profile Send private message
pcs
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I suspect that these sat-tv cables are rated rather liberally/optimistically. I suspect
the actual attenuation could be much worse than 0.85dB.

But if in doubt, give it a try. Take SWR/power meter and measure how much power
you've got left after the whole cable run, it will be easy to calculate loss from there.

You'll need dummy load for this measurement.

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Marko - PCS Electronics
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http://www.pcs-electronics.com
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Sat Sep 23, 2006 10:25 am View user's profile Send private message Visit poster's website
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