50? VS 75?

stecle

SatelliteGuys Pro
Original poster
Feb 17, 2010
363
193
Between the North and South Pole
I am going to be putting up a tower at my cottage in about a month from now. I will be installing an onmidirectional WIFI antenna and a discone scanner antenna. I know that the impedance of these antennas is 50?. My dilema is that I have several hundred feet of RG-11 left over from a MDU install, which of course is 75?, that I would like to use.

The research that I have done shows that the difference between these cables would be negligible on receive. This would be ok on the discone but the WIFI antenna both transmits and receives.

I would appreciate any feedback.

Thanks

Steve
 
"The research that I have done shows that the difference between these cables would be negligible on receive." - if you mean attenuation, then it will be not enough.
It will bring much more issues as reflections and you'll lost a lot of signal.

There is a method of matching impedance, but it will cost you for two of them - on each side of RG-11 chunk.
 
Here's one link that might help. Although at these frequencies the matching sections would be mighty short and we're talking minimum 4 extra connectors. I'm guessing the height of the antenna would trump the (close to 2:1) SWR, but the length of the coax run would trump any overall gain.

Could you possibly use a USB wireless NIC up on the tower and connect it to your home system with a usb to cat5 cable setup?

Using CATV Hardline for ham radio antennas
 
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I would but the shipping would kill me :D
 
If you are only recieving the difference would not mean anything. On transmit it would be different.I run all my comm recievers on solid copper quad RG6. My Icom75 on a 400 foot end fed wire can here around the world on SOLID cooper quad and my BCT15 on a scantenna two can pick up UFH from over a hundred miles away. I would worry about the quality of your 75 ohm cable than the impedance. Again though, if you want to transmit it is a differnt story.
 
Best bet for Wifi is to install the radio right at the antenna and forget about the feedline (well maybe add a short jumper if you have to). Shielded network cable is much more forgiving than feedline, and cost is likely less. Yes you want shielded cat5 or cat6 cable or your scanner antenna (on the same tower?) will pick up the noise from the network cable and/or radio.

The scanner will work with 50 or 75 ohms. I think good RG-6 would be fine.
 

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