[time-nuts] Non-impedance matched antenna cables

Bruce Griffiths bruce.griffiths at xtra.co.nz
Fri Jun 13 10:09:05 EDT 2008

Javier Herrero wrote:
> Then, if the input is 50 ohm, at least the reflections in the other 
> extreme of the Thunderbolt + cable (i.e., at the antenna side) should 
> not be so bad... I'm afraid that since the cable is alredy routed using 
> the inside-building tubes (in fact it uses the tubing destinated for the 
> TV antenna) is not so easy for me to adjust the cable length :)
> Yes, I was also surprised by the use of F connectors... and that made me 
> suspect (with surprise) that the GPS input were 75ohm, but I must 
> confess that I did not read more ;).
> The antenna I'm using is a Motorola mainly intended for vehicle 
> mounting. Surely not the optimum antenna... but not bad results with the 
> Thuerbolt nor the M12's. I've another antenna, but is a cheap one with 
> magnetic base, only used for a nixie clock :)
> Regards,
> Javier

Its a relatively trivial matter to adjust the cable length just connect 
an additional short lenght of cable to bring the length to the correct 
However you will need to measure the in place cable length using TDR or 
other suitable technique.


More information about the time-nuts mailing list