rg6 coax - AntennaRestrictions Forum at eHam.net

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eHam.net Forum : AntennaRestrictions : rg6 coax

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rg6 coax	Reply
by K9RLX on September 29, 2009	Mail this to a friend!
I have a question that maybe a couple people could share there opinions/thoughts on. Is it true rg6 coax has higher power handeling and lower loss then rg8x? Currently both my antennas are run with rg8x. My scanner I have rg6. I want to put up a secondary vhf antenna and a 20 meter dipole and maybe even a 40 meter dipole. I have 2 spools of rg6 just sitting in my garage if I could use that then I would save myself a lot of money from not having to buy more cable. Yes I know there is the 75 vs 50 ohm but I don't think my tunner is going to care and I would think the dipoles would match the rg6 better then the rg8 and the vhf antenna well that is only a secondary so if swr is 1.5 thats not a big deal even 2.0 is not going to hurt my rig. Curious to hear some other peoples thoughts on this. One last thing when i used the rg6 for my scanner I put a F connector on the cable then used a F to pl-259 adaptor. I found these adaptors online for like 3 dollars a piece and even have 2 spares laying around in the house.

RE: rg6 coax	Reply
by AA4PB on September 29, 2009	Mail this to a friend!
You won't have any problems with the dipoles (where a tuner is used). It could be an issue for transmitting on VHF, depending on the length of the run. While the SWR on a 50 ohm antenna will be 1.5:1, the impedance at the transmitter will change with line length because the 75 ohm cable will act as a transmission line transformer. If you can make the length a multiple of 1/2 wavelength (including velocity factor of the coax) then the antenna impedance (50 ohms) will repeat at the radio. The worst case length would be an odd multiple of 1/4 wavelength.

RE: rg6 coax	Reply
by K5NDB on September 29, 2009	Mail this to a friend!
What AA4PB said. He is entirely correct. I use it on HF with no problems and it is mucho cheaper and easier to find.

RE: rg6 coax	Reply
by K9RLX on September 29, 2009	Mail this to a friend!
Thanks, Just wanted to post and see what other peoples thoughts were before I ran them. I am going to set it up this weekend and see how things work. I will try and make the vhf a multiple of 1/2 wave and we will see how it works out. Thanks again!

RE: rg6 coax	Reply
by WB6BYU on October 1, 2009	Mail this to a friend!
Because of uncertainties in the velocity factor of the coax, it is difficult to cut it to a multiple of half wave simply by formula for a long cable and a short wavelength. Just make the cable long enough and check the SWR at the rig: if it is too high shorten the cable and try again. You'll want to check the SWR variation across the desired operating frequencies, since even with a 50' cable the electrical length changes by about a quarter wavelength across the 2m band. (This is even more of a problem with higher frequencies and longer cable lengths.) Another solution is to use 1/12 wave transformers at each end to convert between 50 and 75 ohms, using short sections of 50 and 75 ohm coax. Or, if possible, adjust your antenna to match 75 ohms, and the SWR should be usable at the shack end.

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