Posted: 4/7/2008 3:20:36 PM EDT
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Please help. What type and how much coax do you carry with you for HF and 2m ops? |
all amateur gear, like laboratory RF test and measurement equipment, is designed for use with 50ohm impedance cabling and accessories (splitters, directional couplers, and the like). moreover, with the exception of the stupid PL259/SO239 "UHF connectors", all common amateur radio gear is equipped with 50ohm impedance couplers (BNC, N, SMA, and so on). however, RG59 is designed for video applications and has a 75ohm characteristic impedance. in fact, almost all video and satellite related coax and fittings are 75ohm impedance. moreover, there are 75ohm variants of the BNC and 75ohm N connectors -- they have different diameter male pins and female receptacles due to the geometry needed for 75ohm impedance. so, the answer to your question is complicated. if you are not worried about SWR (it will range from 1:1 to 2:1 depending on coax length), are not concerned about power loss, you need coax in a pinch (say, for an emergency antenna application), and/or you can find common connectors that fit the slightly larger diameter, go ahead and use RG59. otherwise, use a proper 50ohm impedance coax like RG58, RG8X, RG213, 9913F7, LMR400, etc. -- with so many 50ohm types to choose from it seems silly to try to drive a square peg in a round hole. (to all the EE's in the crowd, yes, i know you can build matching networks and attach them to both ends of the 75ohm coax [as is commonly done when using CATV hardline for ham applications] -- but i don't think that the OP had that in mind). ps: NEVER EVER insert a 50ohm N connector plug into a 75ohm N connector jack. ask me how i know this!  ar-jedi k5dwj.com/ham_catv_hardline.htm www.repeater-builder.com/rbtip/matchingstubs.html www.n1bug.net/tech/catvline.html jonz.net/W3DHJ/catvhardline.html www.arraysolutions.com/Products/baluns.htm#50:75%20ohm%20Xfrm |