[time-nuts] Non-impedance matched antenna cables

Richard W. Solomon w1ksz at earthlink.net
Fri Jun 13 23:16:00 EDT 2008

Sounds like an application just calling for "hard line". I have some 75
foot lengths of 1/4" Superflex that I'll have to drag out and look at.

73, Dick, W1KSZ

-----Original Message-----
>From: Mark Sims <holrum at hotmail.com>
>Sent: Jun 13, 2008 5:37 PM
>To: time-nuts at febo.com
>Subject: [time-nuts] Non-impedance matched antenna cables
>A while back I did a project that used a 100 foot piece of (supposedly) fairly good quality RG58.  I checked it with my TDR and then installed it in an outdoor application where it ran for a couple of weeks in good ole' Texas weather.  The outdoor connection was covered by a glass jar so water infiltration of the connector was not an issue.  Also the cable was not hanging, so stretching under its own weight was probably not an issue.  
>When the project was then over I happened to check the cable with the same TDR.  Its effective electrical length had changed by around a foot!   A half-wave of GPS is around 4 inches.  I think that most commercial coax is way too unstable to maintain that kind of precision in a real-world installation.  A .2% shift in velocity factor or cable length in a typical 100 foot run would be 1/4 wave of GPS signal.
>> ----------------------------------------
>Depends on the cable length and the temperature excursions it experiences.
>For short runs its well worthwhile.
>For longer runs the cable attenuation will help reduce the effect of 
>mismatches at either end.
>Instantly invite friends from Facebook and other social networks to join you on Windows Live™ Messenger.
>time-nuts mailing list -- time-nuts at febo.com
>To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>and follow the instructions there.

More information about the time-nuts mailing list