On 23 January 2017 at 17:29, Tim Shoppa <tsho...@gmail.com> wrote: > > Funny how people always want to put the words "dielectric" and "constant" > right next to each other but we know it isn't constant :-) > > Tim N3QE >
Yes. I will have to look into this, as I see some quite widely different values quoted for the dielectric constant of PTFE. I have an HP 4291B impedance/material analyzer http://www.keysight.com/en/pd-1000000857%3Aepsg%3Apro-pn-4291B/rf-impedance-material-analyzer?cc=US&lc=eng&lsrch=true&searchT=4291b and 16453A dielectric material test fixture http://www.keysight.com/en/pd-1000000508%3Aepsg%3Apro-pn-16453A/dielectric-material-test-fixture?cc=US&lc=eng To make a measurement of the permittivity of a material, the calibration procedure is a bit complicated, needing 6 or 7 standards, but at one point you need to use a dielectric of known thickness and known permittivity. I believe it defaults to 2.1, which is supposed to be what the bit of PTFE Keysight supply is. Needless to say I don't have that, and I'm not spending the best part of £500 for a bit of PTFE that's 1 mm thick. But I've seen values of Er of PTFE quoted from 2.0 to 2.2. Dave _______________________________________________ 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.