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best way to measure effectiveness of ground?	Reply
by N0ZLD on September 18, 2008	Mail this to a friend!
What's the best way to measure if your antenna is adequately grounded? Maybe not 'grounded' per say, but I'm wondering if there is a way to measure if how you have your antenna and radio setup in your car is effective or not. Thanks

RE: best way to measure effectiveness of ground?	Reply
by N0ZLD on September 18, 2008	Mail this to a friend!
I should state that I'm not talking about the obvious, like your able to get out, work stations, etc. Is there a way to take a measurement and if it's within X range, then you have your antenna mounted effectively, etc.

RE: best way to measure effectiveness of ground?	Reply
by K0BG on September 18, 2008	Mail this to a friend!
Although there is some fallacy if it isn't done correctly, it is easy to do. You measure the actual input impedance of the antenna with an antenna analyzer. You then model the antenna with EZNEC or NEC4, and then adjust the ground losses in the program until the calculated input impedance is the same as the measured one. Then, readout the calculated efficiency. Some of the fallacies are correctly inputing the coil Q. Most folks way over estimate it. Real-world values are in the 100 to 300 range. Hamsticks fall below this range, and some large antenna are slightly above it. You might also want to visit my web site and read the Efficiency article. Alan, KØBG www.k0bg.com

RE: best way to measure effectiveness of ground?	Reply
by N0ZLD on September 18, 2008	Mail this to a friend!
Thanks

RE: best way to measure effectiveness of ground?	Reply
by K0BG on September 18, 2008	Mail this to a friend!
A few more comments. Far too many amateurs confuse DC grounding with ground plane. They're both important, but they aren't the same. The coax shield does indeed need to be attached to the antenna's ground plane as close to the base of the antenna as possible. If the surface the antenna is mounted over is poorly bonded to the rest of the vehicle, you can have a problem, and this is why proper bonding is a good thing. It just so happens bonding also DC grounds things, but its purpose is to provide a unified mass for the RF to flow through. Mounting antennas on trail hitch mounts (for example) places the ground plane next to the antenna, not under it as it should be. Running ground straps to the frame and/or body will not nullify the excessive ground losses, although it might make the antenna easier to tune. Alan, KØBG www.k0bg.com

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