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Old 12-14-2015, 12:29 AM   #11
KL7V
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Aluminum roof, well heck you are lucky. I wish my roof was aluminum. Did you bond the mount directly to the roof also? To improve things on 80, you can still deploy those portable radials, fan them out a bit and make them long. May not work so well in some RV parks I know. That is what I am going to do, use radials fanning out from the pin box mount.
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Old 12-14-2015, 08:18 PM   #12
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Yes it is connected to the aluminum window frame just below the roof line the roof is folded over the siding and clamped down with an aluminum bar full length of the camper. I went all over this thing with a maga ohm meter it's amazingly conductive. I have tried a 3 foot SS ground rod but I don't believe it made a bit of difference so I don't bother any more I guess plugging it in does at least as well as the ground rod. I do part time time electrical work for a local camp ground and have replaced and installed power pedestals and they get buried 4" deep.
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Old 12-15-2015, 11:43 AM   #13
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"Have determined that the ladder is not grounded that well"

Have determined the ladder is not grounded at ALL. It bolts onto fiberglass on my RV.
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Old 12-15-2015, 07:39 PM   #14
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Yeah I had a Toyota motor home and there were wooden blocks in the fiberglass that the ladder was bolted to.
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Old 12-17-2015, 10:24 PM   #15
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When I went to add some ground buss to my RV ladder, when I drilled the small pilot hole in the bottom of each vertical side, nice RUSTY WATER came out!! Shows they arent sealed too well, where the steps attach via screws to the vertical section. From each vertical section, I ran a braid bond to the frame of the 5'er. I run various vertical antennas off the ladder, i.e., Screwdriver, Hamsticks, etc. Oh yes, I did leave a small hole at the bottom of each vertical for a drain hole for any future water infustion.
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Old 03-20-2016, 02:00 AM   #16
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Actually there is a common misconception with respect to RF and/or DC grounding, and its relationship to a ground plane.
The best way to think about vehicle ground planes is simply this; it is the metal mass under that antenna that counts, not what's along side. The second part is, the more metal mass the better.
Also you can make contacts with the lossiest of antennas, as any Outbacker or ATAS owner can attest to. However, if you want consistent communications, then you need a decent amount of metal mass under the antenna.

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Old 03-20-2016, 10:15 AM   #17
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Quote:
Originally Posted by MartaJobs View Post
Actually there is a common misconception with respect to RF and/or DC grounding, and its relationship to a ground plane.
The best way to think about vehicle ground planes is simply this; it is the metal mass under that antenna that counts, not what's along side. The second part is, the more metal mass the better.
Also you can make contacts with the lossiest of antennas, as any Outbacker or ATAS owner can attest to. However, if you want consistent communications, then you need a decent amount of metal mass under the antenna.
Interesting idea, but no. The mass doesn't matter at all. What matters is the surface area of the metal under the antenna.

Not even that, really; it is the effective reflecting area (and its location) that matters. There can be holes in it, for example, which would reduce the actual surface area; but if the holes are small compared to the wavelength of the signal we're interested in, they won't reduce the effective reflecting area. That's why a copper screen is as good as a copper sheet.

Either the screen or the sheet can be ever so thin, though, as long as it's thick enough so that the surface resistivity is limited primarily by skin effect, which is pretty thin (thousandths of an inch) at HF.

Hardware cloth -- even chicken wire -- works pretty well, too, but isn't massive at all. The mass of metal is totally irrelevant.
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Old 03-20-2016, 07:17 PM   #18
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I guess the bottom line with a vehicle is ground loss not ground plane.
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Old 03-20-2016, 07:45 PM   #19
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Quote:
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I guess the bottom line with a vehicle is ground loss not ground plane.
That's one of the two important bottom lines. The other, of course, is the effect on radiation pattern.

My old friend Whit Griffith, N5SU (SK), whose career for decades was designing and building large HF station transmitters and antennas (Voice of America, Radio Free Europe, etc.) knew more about antenna efficiency and antenna patterns (not to mention HF amplifier design) than I know about everything I know about. He once ran an experiment with a large (large!) HF vertical. He calculated the radiation resistance, then measured the input impedance with one radial, two radials, etc., up to (if I remember) a hundred or so radials. This enabled him to calculate the efficiency of the whole antenna system at each step. Whit presented the results at the Dallas Amateur Radio Club in 1982 or so. He found that anything more than 25 or so radials yielded only a little improvement, but fewer than 10 or so caused the station, to a considerable extent, to cook worms instead of radiating a signal.

As Whit explained for those of us whose expertise didn't match his, the purpose of the radials (or other ground conductors) can be looked at as shielding the soil from your signal so the signal won't be absorbed in the soil and your transmitter's power be wasted cooking worms.
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Old 03-21-2016, 01:27 PM   #20
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Regarding the comment that a wire from teh antenna base to a hard frame point is not necessarly a "Ground Plane" ... true.> but it might (if long enough) be a counterpoise, which serves the same function.

That's why I like NGP antennas.
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