[TowerTalk] Measuring Coax Length

[Dan Maguire via TowerTalk]

Jim wrote:
>>> An easy way to get close to the actual length is to put a connector on one end, leave the other end open, and measure the impedance with an antenna analyzer. At every frequency where it's some odd multiple of quarter waves long, it will look like a short. So sweep it with whatever analyzer you own, write down those frequencies, and do the arithmetic.

There's an expanded explanation of this technique, with illustrations, on one of the Zplots pages.  See section "Line Length via Quarter or Half-Wave Points" here:

http://ac6la.com/zpapndx1.html

So if your analyzer can produce a Zplots-compatible file, and you have MS Excel, you can let Zplots (http://ac6la.com/zplots1.html) do the math.  An alternative not requiring files or Excel is to use the "Conversions" button from the TLDetails (http://ac6la.com/tldetails1.html) program.  Either way, be sure to enter the frequency *difference* and not an absolute frequency.

Both Zplots and TLDetails are free.

Dan, AC6LA
http://ac6la.com