[TowerTalk] Matched "Bury Flex" cables

[Jim Lux]

At 07:04 AM 7/14/2005, Keith Dutson wrote:
>John W0UN wrote:
> >Solid dielectric is much more controllable, but I even measure the actual
>phase shift for each delay line of solid dielectric coax, if the application
>is critical.
>
>For HF, the delay is likely not critical.  From reading the ARRL Antenna
>Book I understand phase errors up to 30 degrees for antenna phasing have
>small effects on radiation pattern and TOA.
>
>73, Keith NM5G


Indeed, phase errors of tens of degrees aren't going to have a huge effect, 
however, a transmission line length change of 30 degrees might have a 
radiated phase change much different. The reason is that you're not just 
using the coax as a delay line, because neither end is a well matched load. 
(Even if the individual antenna is a nice 50 ohm load when tested by 
itself.) The impedance transforming effect also comes into play.  At the 
junction point, neither coax is going to present a nice 50 ohms, but both 
will present  some reactive impedance, likely quite different, so the 
currents will distribute unevenly.