[time-nuts] 50 vs 75 ohm cables
Poul-Henning Kamp
phk at phk.freebsd.dk
Thu May 10 16:52:50 EDT 2007
In message <E1HmBTB-0006jt-SN at febo.com>, John Day writes:
>So 75 ohms as we
>know it now is a compromise between the low attenuation 77 ohms and
>the 73 ohm dipole feed-point.
I can confirm that the choice of 75 Ohm for telecom use indeed
is because of the low attenuation. The first use of coax was
for "Carrier Frequency" systems, where a number of telephone
conversations were AM modulated on individual carriers, usually
4 kHz apart.
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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