Posted: 11/4/2008 9:00:36 AM EDT
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A long time ago, i remember hearing something about cutting coax at certain lengths. It was either in relation to the frequency, or core composition, or type of coax.
I remembered this the other day, and tried looking it up, but haven't found anything. Any truth to this? wife's tale? I've got to make a few jumpers for a mobile rig. |
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Doesn't matter.
This saying comes about from poorly tuned antennas. If your coax is getting RF current on the shield then changing the length will influence the SWR. Keep RF currents off your coax shield like a good station should and its a non-issue. ETA: Coax is also sometimes cut at specific lengths to make tuning stubs or phasing cables, the length will depend on the velocity factor of the coax and wavelength/frequency. |
| Coax line can be cut to specific lengths for certain purposes, either to adjust the phase of the signal or as an impedance transformer (usually 1/4 wavelength or a multiple thereof). For test purposes sometimes a cable is cut to a particular length so that when added to a wattmeter or other test equipment that it presents at the same position electrically as the original connection (1/2 wavelength or multiple thereof). 1/4 wave shorted or open stubs are also used as bandpass or band reject filters. |
