CB Antenna December 29, 2007, 09:14:23 pm Yahoo Message Number: 87656Do you have to use a non-grounding plane CB Antenna on a Lazy Daze aluminum roof? Does anyone have any recommendations as far as brands?Thanks for any help. Bud Hensley
Re: CB Antenna Reply #1 – December 29, 2007, 10:20:08 pm Yahoo Message Number: 87663"Do you have to use a non-grounding plane CB antenna on a Lazy Daze aluminum roof?"The aluminum roof makes a great ground plane--no special antennas required. The only thing you have to worry about is mounting, since magnet-mount antennas won't stick to aluminum.You can either mount the antenna on the luggage rails, or mount a piece of ferrous metal to the roof and stick a magnet-mount antenna to that. What' worked well for some of us is to get a 4" x 4" galvanized steel duplex outlet box cover--about forty cents at any hardware store--give it a coat of paint to prevent rusting, and glue it to the roof with Goop or Liquid Nails. A magnet-mount CB antenna will cling very firmly to that steel plate. :-)Andy Baird http://www.andybaird.com/travels/
Re: CB Antenna Reply #2 – December 30, 2007, 10:05:51 am Yahoo Message Number: 87669Quote Do you have to use a non-grounding plane CB Antenna on a Lazy Daze aluminum roof? Does anyone have any recommendations as far as brands? Bud, Fiberglass and aluminum RV roofs are a nightmare for optimum CB reception and transmission and are not considered a ground plane. If you are satisfied with minimal range a steel plate glued to the LD's roof may be sufficient. Firestik, http://www.firestik.com/Tech_Docs/CBs_%26_RVs.htm , offers both ground and non-ground plane antennas. I mounted my non-ground plane Firestik antenna on a solar panel and ran the cable through the escape hatch.The Firestik site is an excellent tutorial on antennas which is the most important element of your system.Malcolm Blue02MB
Re: CB Antenna Reply #3 – December 30, 2007, 10:58:29 am Yahoo Message Number: 87670Absolutely agree. A magnetic mounted CB antenna works great on aluminum skinned RV's. Been using a similar sk
Re: CB Antenna Reply #4 – December 30, 2007, 11:42:27 am Yahoo Message Number: 87673On Dec 30, 2007, at 11:05, bmwgt31995 wrote:QuoteBud, Fiberglass and aluminum RV roofs are a nightmare for optimum CB reception and transmission and are not considered a ground plane. Actually, the aluminium roof is a nearly perfect ground plane. It is just that magnetic mounts will not stick to it.-Dave '06 MB, Indianapolis
Re: CB Antenna Reply #5 – December 30, 2007, 03:19:04 pm Yahoo Message Number: 87678The Firestik tech document that Malcom pointed to asserts: "Copper and steel are excellent materials for ground plane. Fiberglass and thin aluminum sheets are not." However, their dismissal of aluminum as a ground plane material makes no sense from a physics standpoint, since aluminum is an excellent conductor--right up there with copper, and certainly better than steel. And searching the web, I was unable to find any other source that agreed with Firestik's statement. Quite the contrary--I found statements like these: "The one motorhome I owned which had an aluminum roof was so easy it was almost cheating to get performance from the HF antenna." "An antenna in the center of an aluminum roof will talk much farther." "aluminum works fine. Any conductive material can be used as a ground plane.""Aluminum may not stick to a magnet, but it sure does conduct electricity, and should work as a ground plane.""a tuned whip mounted in the center of an aluminum ground plane... provides optimum unity gain, omni-directional radiating patterns."Add to that Don and Dave's practical experience, as described in recent messages, and it seems pretty clear that Firestik was just plain wrong when they condemned aluminum ground planes back in 1996.Andy Baird http://www.andybaird.com/travels/
Re: CB Antenna Reply #6 – December 30, 2007, 03:45:22 pm Yahoo Message Number: 87679Quote "...their dismissal of aluminum as a ground plane material makes no sense from a physics standpoint..."Andy Baird Andy and others...Antennas, especially directional antennas, consist of one 'driven' element and additional 'reflectors'. In the case of the old rooftop TV antennas, you had a driven element and several directional reflectors which provided 'gain', or an increase in received signal strength in a given direction. Having a rotor was a big advantage because you could point the antenna array in the direction that gave you the best signal. With an RV antenna you have one driven element, the verticle 'whip', and the 'ground plane' is made up by the aluminum roof material. That in essence is your reflector, providing an 'omni-directional' or all direction array. It matters little what the material is but aluminum is a very good option.Steve S. Lazy Bones & Jiggs
Re: CB Antenna Reply #7 – December 30, 2007, 05:09:16 pm Yahoo Message Number: 87681"It matters little what the material is..." As long as it's electrically conductive, just to clarify. Fiberglass definitely won't work as a ground plane.Andy Baird http://www.andybaird.com/travels/
Re: CB Antenna Reply #8 – December 30, 2007, 09:16:36 pm Yahoo Message Number: 87687Quote "Fiberglass definitely won't work as a ground plane."Andy Baird AndyHad a K-40 mounted mid-ships on an International Harvester Scout with steel roof and have had several 'through the glass' antennas on an '84 and an '94 Ford Club Wagon (all steel of course). Some have a tendency to be directional, primarily toward the direction of travel. If you have a field strength meter you can determine the radiation pattern quite easily.Steve S. Lazy Bones & Jiggs
Re: CB Antenna Reply #9 – December 31, 2007, 09:30:30 am Yahoo Message Number: 87705My knowledge is both limited and dated on antenna tech. That being said, I had the impression that to form an effective ground plane, the antenna ground needed to have an electrical connection to the ground plane material. Drilling through a steel roof for a conventional mount makes that connection. Magnetic mount antennas on conventional steel-sheathed vehicles make the electrical connection to the frame in the CB mounting bracket, which is grounded. That comes with some loss in efficiency. On an aluminum roof that may not be electrically grounded to the chassis of the vehicle, the ground plane effect would be lost if a steel plate is glued (no electrical connection) to the aluminum to form the mount. The antenna would still work, but not nearly as efficiently as if the connection were there. I may be all wet on this, but I would love to learn more about it.
Re: CB Antenna Reply #10 – December 31, 2007, 11:14:02 am Yahoo Message Number: 87710If you consider the typical magnet mount antenna on the roof of a car - it works quite well. I'm sure that most folk don't scrape the paint off the roof to get a good ground connection. The magnet mount antenna generally has a foil covering on the bottom that is connected to the cable ground side. At high frequencies this acts as a relatively low loss capacitive coupling to the surface on which it is placed. The same would hold for the mount to the "glued down" plate. The dielectric gap may be slightly larger but the losses should still be negligible. I would welcome corrections from any engineers among you. I am just going on 50+ years of "ham" experience.Regards,ray--
CB Antenna Reply #11 – December 31, 2007, 11:45:35 am Yahoo Message Number: 87712Ray, you are correct. At radio frequencies, signals are coupled less by conductance and more and more by capacitive and inductive coupling. The resistive component of impedance to RF signals is minor.Tom Johnston, electrical engineer, Whidbey Island, WAQuoteIf you consider the typical magnet mount antenna on the roof of a car - it works quite well. I'm sure that most folk don't scrape the paint off the roof to get a good ground connection. The magnet mount antenna generally has a foil covering on the bottom that is connected to the cable ground side. At high frequencies this acts as a relatively low loss capacitive coupling to the surface on which it is placed. The same would hold for the mount to the "glued down" plate. The dielectric gap may be slightly larger but the losses should still be negligible. I would welcome corrections from any engineers among you. I am just going on 50+ years of "ham" experience.Regards,ray--
CB Antenna Reply #12 – December 31, 2007, 02:43:41 pm Yahoo Message Number: 87727Tom, are you saying that inductive rather than conductive connection establishes the ground plane when a magnetic mount is on a steel plate glued to the aluminum roof? If so, I think I understand. Thanks Ken
Re: CB Antenna Reply #13 – December 31, 2007, 02:57:58 pm Yahoo Message Number: 87729No he is saying the foil on the bottom of the antenna and the metal on the roof are the plates of a capacitor while the paint is the dielectric of said capacitor.. This capacitor is what makes the roof an fairly effective ground plane. Note not all antennas require ground planes... Antenna theory is a very complex subject and there are many more false statements and half truths out there than there is real information. Much of the truly false information has been spread by CB experts over the last 4 decades. Both well intentioned as well as those that are closely related to snake oil salesmen.Garry
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Topic: CB Antenna (Read 7 times)
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