Hi As long as you are running a sine wave, and you don't change cables, you can run just about anything. The phase errors / reflections will work themselves out.
50 ohm plastic dielectric cable turns out to be the best for power handling at reasonable loss. 75 ohm cable turns out to be the best for loss per mile. Telcom and TV people went with 75 ohms. People who ran transmitters went with 50 ohms. If you change the dielectric, you can get "best" cases at somewhat different impedances. 50 ohm cable works best / easiest with 50 ohm connectors. Mixing 75 ohm connectors and 50 ohm connectors is not a good idea. The inner conductors on the connector are often different diameters and you tend to break one side or the other. Given the cost of (cheap) RG-58 or RG-59, I don't see a big advantage to switching impedance to save money at 10 MHz. Down there the skin depth is what will impact your shield the most. The fancy extra aluminum foil layers don't have much thickness. Of course if you go to hard line then it's a whole different story... Bob -----Original Message----- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Chris Albertson Sent: Tuesday, February 07, 2012 3:19 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Why a 10MHz sinewave output? Related question: Assuming I'm using 10MHz sine wave. What's the best physical cable to use? Is there any good reason to use 50 ohm cable? What about 75 ohm? I looked at a schematic of my counter and it looks like the 10MHz signal hits some high impedance chip inside. RG6 seems like the way to go. It's double shieled and lots of cable TV parts could be used. On Tue, Feb 7, 2012 at 11:12 AM, Hal Murray <hmur...@megapathdsl.net> wrote: > > li...@rtty.us said: >> Thank goodness for that inertia. I can still cable up a 100Kcps sine wave >> standard to run stuff from "long ago". When I run into a box that uses a T1 >> signal for a clock reference - not so easy in the basement. > > How much gear is there that uses T1 for a clock input? > > Is there any interest in a board/chip/whatever that converts 10 MHz to T1? A > clean design using a decimal DDS should fit into a small FPGA, maybe a CPLD. > > -- > These are my opinions, not necessarily my employer's. I hate spam. > > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. -- Chris Albertson Redondo Beach, California _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
