If the dielectric of coax cables causes them to have a velocity factor of .6, why would the jacket insulation be different?
Greg On Apr 13, 2011, at 9:28 PM, Patrick Shoemaker wrote: > Except in this case, assuming the shield is intact and good quality, we are > dealing with undesired currents flowing on the surface of the cable shield > only. At 100 MHz and assuming an aluminum foil shield in the cat5, the shield > metal is thicker than a few skin depths (about 8 um skin depth). So we > essentially have a solid conductor in open air, and if the insulation’s > relative permittivity is close enough to 1 to neglect (should be), the > velocity factor is close to 1. > > -- > Patrick Shoemaker > > From: [email protected] [mailto:[email protected]] On > Behalf Of Greg Ihnen > Sent: Wednesday, April 13, 2011 21:32 > To: WISPA General List > Subject: Re: [WISPA] Ethernet Cable for FM Tower Install > > In space (vacuum). Cables have a velocity factor. > > On Apr 13, 2011, at 8:42 PM, Patrick Shoemaker wrote: > > > And speed of light (c) = 300,000,000 m/s > > -- > Patrick Shoemaker > > From: [email protected] [mailto:[email protected]] On > Behalf Of Patrick Shoemaker > Sent: Wednesday, April 13, 2011 21:10 > To: [email protected]; WISPA General List > Subject: Re: [WISPA] Ethernet Cable for FM Tower Install > > Wavelength (m) = speed of light (m/s) / frequency (Hz) > > Avoid ¼ wavelength multiples. > > -- > Patrick Shoemaker > > From: [email protected] [mailto:[email protected]] On > Behalf Of Scott Carullo > Sent: Wednesday, April 13, 2011 14:54 > To: [email protected]; WISPA General List > Subject: Re: [WISPA] Ethernet Cable for FM Tower Install > > Get with someone who can tell you exactly how long to make the cables. You > don't want them any whole fraction of the FM wavelength freq or it will > compound your problem. Make them as de-tuned length as possible. > > > > I've had a coax in my hand not hooked to anything in the vacinity of a > high-power FM station and it was a resonant length and it got so hot I had to > drop it. > > > > Scott Carullo > > Technical Operations > > 855-FLSPEED x102 > > > > > > > > > From: "[email protected]" <[email protected]> > > Sent: Wednesday, April 13, 2011 9:39 AM > > To: [email protected] > > Subject: [WISPA] Ethernet Cable for FM Tower Install > > > > We are mounting close to a 50kW FM antenna and want to use heavy, > > double shielded cable > > for the runs to the APs since we've seen issues in the past. Fiber up > > the tower but will need > > 3-4 ft jumpers to the APs. > > > > Any recommendations? > > > > > > -------------------------------------------------------------------------------- > > WISPA Wants You! Join today! > > http://signup.wispa.org/ > > -------------------------------------------------------------------------------- > > > > WISPA Wireless List: [email protected] > > > > Subscribe/Unsubscribe: > > http://lists.wispa.org/mailman/listinfo/wireless > > > > Archives: http://lists.wispa.org/pipermail/wireless/ > > > > > > -------------------------------------------------------------------------------- > WISPA Wants You! Join today! > http://signup.wispa.org/ > -------------------------------------------------------------------------------- > > WISPA Wireless List: [email protected] > > Subscribe/Unsubscribe: > http://lists.wispa.org/mailman/listinfo/wireless > > Archives: http://lists.wispa.org/pipermail/wireless/ > > > > -------------------------------------------------------------------------------- > WISPA Wants You! Join today! > http://signup.wispa.org/ > -------------------------------------------------------------------------------- > > WISPA Wireless List: [email protected] > > Subscribe/Unsubscribe: > http://lists.wispa.org/mailman/listinfo/wireless > > Archives: http://lists.wispa.org/pipermail/wireless/
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