Grounding the Antenna

[One Country Boy]

Having determined that the ladder on our 5th wheel is not grounded that well, I decided to add some grounding braid. The braid is tinned copper. I soldered copper lugs to the ends of the braid. The type normally used in battery connections, for smaller batteries in lawn mowers, etc... The braid connects to the base of the quick disconnect atop the ladder, runs down the back side of the ladder and terminates on one of the stabilizer jack mounting screws. I'm hopeful for some added performance.

[TXiceman]

A friend in Dallas clamps a High Sierra to the ladder on his motorhome. Since the ladder is not too well grounded the first time he used this set up, he temporarily grounded it to the frame on his coach with his jumper cables. Worked fine until he was ready to head home. Last I spoke to him, he had applied a more permanent ground arrangement.

Ken

[jagco]

Nice work Jim. Looks nice and tidy.

[One Country Boy]

Thanks... I guess I could have put a clamp at the bottom of the ladder and run across to that same grounding point. I could have saved about 10 ft of the braid. But, somehow it just feels better with the copper braid runninng all the way to the mount. Probably just in my head.

[One Country Boy]

Originally Posted by TXiceman

A friend in Dallas clamps a High Sierra to the ladder on his motorhome. Since the ladder is not too well grounded the first time he used this set up, he temporarily grounded it to the frame on his coach with his jumper cables. Worked fine until he was ready to head home. Last I spoke to him, he had applied a more permanent ground arrangement.

Ken

I thought about doing that when we were in the mountains last Summer Ken. I was going to attach a jumper cable from the ladder over to the metal water supply system. I never did, but that probably would have made an excellant grounding system. Especially if they had metal pipes all the way through the park.

[Alan, KØBG]

There is a common misconception with respect to RF and/or DC grounding, and its relationship (or lack of it) to a ground plane.

Just because you run a ground strap from the antenna mount (the ladder in this case), to a hard point on the vehicle, doesn't automatically make it a ground plane. In fact it doesn't.

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.

Yes, 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, and a ladder at the rear of an RV isn't it.

Alan, KØBG
www.k0bg.com

[One Country Boy]

Originally Posted by Alan, KØBG

There is a common misconception with respect to RF and/or DC grounding, and its relationship (or lack of it) to a ground plane.

Just because you run a ground strap from the antenna mount (the ladder in this case), to a hard point on the vehicle, doesn't automatically make it a ground plane. In fact it doesn't.

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.

Yes, 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, and a ladder at the rear of an RV isn't it.

Alan, KØBG
www.k0bg.com

Understood and I agree with you totally Alan. This was not a "common misconception", but rather a hopeful improvement to my receive capabilities and possibly improve the transmit capabilities as well. It is not even close to being the perfect antenna. Now, if I had an old style metal roof on the RV and mounted the antenna in the center, that would be a huge step in the right direction. Since our RV is constructed of fiberglass with a rubber roof, I'm working with what I have. It was only a mini-step, but I have to report it did improve both transmit and receive capabilities. Like I said, it's not perfect but it was an improvement, a noticeable improvement. I can ONLY work with what I have.

By-the-way, welcome to the forum Alan. Glad to have you aboard and look forward to your posts. Many nice guys on here, all trying to help one another and carrying on the practices of good amateur operators coupled with the RV and camping life style. We hope that you will check in often. I've exchange e-mails with you in the past concerning your website. I've also recommended your site to many amateurs.

[n5rtg]

Glad to see you are (or were) here, Alan. I have spent many hours studying your site -- a great help to me, and I am glad to refer friends there also.

I'm lucky to have an "old style" metal roof on my trailer, and I mounted my motorized antenna as low to the roof as I can. It works very well, though I'd be happy to gain more dx reports and wish I could do on 80m what the antenna is advertised for.

Anyhow, glad to see you here,

N5RTG Jim

[KL7V]

Your best bet here would be to deploy portable radials which attach at the antenna mount. If you have room, spread a few out in different directions and tie them off to whatever is available. They need to be longish for the lower bands. You did not mention the antenna or bands you work. Is it a non-conducting roof?

[N3LYT]

I use a HS screw driver antenna on the camper it's mast is grounded to the frame, the aluminum siding and the aluminum roof! I went all over this thing with a mega ohm meter after repairing some siding grounding issues amazingly tight. Works great 6 to 80 meters! I'm thinking some thin counter poise radials below the antenna on a fiberglass roof might be the answer.

[KL7V]

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.

[N3LYT]

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.

[wa8yxm]

"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.

[N3LYT]

Yeah I had a Toyota motor home and there were wooden blocks in the fiberglass that the ladder was bolted to.

[JNeeleyW6ZKH]

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.

[MartaJobs]

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.

pcb assembly cost

[NN5I]

Originally Posted by MartaJobs

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.

[N3LYT]

I guess the bottom line with a vehicle is ground loss not ground plane.

[NN5I]

Originally Posted by N3LYT

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.

[wa8yxm]

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.