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What is the recommended cable to use for a fast PI mono coil? I've notice RG58 mentioned quite frequently, but I've also noticed mention of lower capacitance cable as well.
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What do you all think about RG-59? It is rated at a lower capacitance per foot than RG-58, and the diameter is still within reason.
I have read about egress issues with runs of RG-59, so I don't know if it may not be shielded well enough for a fast coil. What are your thoughts? Has anyone compared RG-58 to RG-59 in this application? -
RG-59 - good, but too heavyOriginally posted by hobbes_lives View Post
there is no need to use 50 Ohm cable, you can use lightweight TV or SAT cable without problem (even better on its own capacitance)Comment
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See the web link below for a good discussion about "cable capacitance".Originally posted by hobbes_lives View Post
http://www.quabbin.com/tech_briefs/tech3.html
Not only is low capacitance important, the shield material is also important so that it does not become a target itself. Also, any movement of the cable relative to the coil might be picked up as a false signal. It is important to secure the cable to the lower part of the coil to minimize it's movement.
My own rule of thumb relative to capacitance in the TX circuit of a mono coil is that for each 100 pf I can reduce from the circuit, including cable capacitance, I can sample about 1 microsecond faster. A shaft mounted control box offer the best opportunity to have the shortest coax cable from the coil. A 30" to 36" cable length, depending on your height, should be sufficient compared to a body mounted control box that requires 6' to 7.5' for the cable length.
Generally, coax cables with the higher rated impedance, have the lowest capacitance per foot.
When using a commercial coil housing (Hays Electronics), note the largest cable diameter that will fit the waterfroof seal that is provided, generally about .25" to .28" in diameter.
This information should get you moving in the right direction.
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