Originally Posted by jneutron
Originally Posted by DonH50
because typical small-gauge coax does not have the low resistance of speaker wire and may have higher capacitance and inductance
......(JN, please ignore the hand-waving, or elaborate if you wish but I am not sure it would help...)
Onwards - Don
Only thing to say is higher capacitance but lower
Oops, yeah, worded that badly. A coax may have higher C or L than normal speaker wire depending upon the design impedance, etc. Zo (characteristic impedance) = sqrt(L/C) for a lossless line. So you have to choose realizable L and C values for the impedance you wish. Higher-power (larger) transmission cables tend to have lower C and L than low-power cables, but there are (I am sure) exceptions to the rule... I have notes/texts and articles I could dig up tonight that compare parameters of various cables, but probably not worth it.
Thanks - Don
RG-58/U (small, 7806R) = 50-ohm, 0.209984 uH/m, 79.7283 pF/m, 24.9356 mohm/m
RG-59/U (small, 1186A) = 75-ohm, 0.318257 uH/m, 53.1522 pF/m, 146.005 mohm/m
7976R (large) = 50-ohm, 0.19686 uH/m, 82.3531 pF/m, 2.69042 mohm/m
- Note the lower capacitance of the higher-Zo cable, and much lower resistance of the larger cable. I have use a hi-Z cable for years as acheap interconnect just for the lower cpacitance.
5000UE (12 AWG) = 0.49215 uH/m, 78.744 pF/m, 5.2496 mohm/m
Little higher inductance, comparable capacitance, lower resistance than smaller coax and much cheaper and easier to find!