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Author Topic: RG-6 coaxial affect??  (Read 768 times)
KA5IWO
Member

Posts: 131




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« on: January 01, 2013, 10:38:48 AM »

I recently had AT&T Uverse installed and hated it, so I had it removed and went back to Directv.
The AT&T tech drilled a hole in my wall and ran a 2 foot piece of RG-6 through it to connect to my other
RG-6 that was originally for my Directv dish.

My question in this.
If I use the correct adapters to connect my RG-8x coax with pl-259's to the "F" connectors, how would this short piece
of RG-6 affect my current 40m dipoles operation / swr. I only run 100 watts or lower here.  I know of course the RG-8x is 50 ohms and the RG-6 is 75 ohms, but
will this short piece affect things that much? If so I can always cut it, pull it out and pull a piece of RG-8x in the hole instead.
Any ideas from the guys good with math / coax out there?? They sealed it rain tight, and it will be a chore to remove it, but I thought it would be nice to use the nice new hole they put in my outside wall.

Thanks. 73 / Happy New 2013 Year to all.
Kevin / KA5IWO
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W5FYI
Member

Posts: 1044




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« Reply #1 on: January 01, 2013, 11:24:57 AM »

It won't affect it enough to notice. Two feet of RG6 hardly makes a hill of beans on 40-meters, or any of the HF bands. Go ahead and use it, and have fun. GL.
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WB6BYU
Member

Posts: 13126




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« Reply #2 on: January 01, 2013, 12:47:19 PM »

Yes, it shouldn't make much difference at all.

You can see using VK1OD's transmission line calculator: 

http://vk1od.net/calc/tl/tllc.php

We can put a 50 ohm load on one end and see how the impedance changes
at the other end.  On 40m, the impedance is about 50.5+j5 ohms, for an SWR
of 1.1 : 1.  That won't make enough difference to worry about.

You can use this same approach to see the effect of different lengths of RG-6.
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