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fransis 8 ft moble antenna
- Thread starter Mr Clean
- Start date
The Francis CB-28 Amazer and the CB-50 Wheeler Dealer were both 8' antennas, and were NOT IDENTICAL. Both were "triple quarter wave" antennas (that's what Francis called them), in that they each had three separate copper wires encapsulated in the fiberglass. The difference between the two is that the 3 wires in the Wheeler Dealer are all the same length, while the wires in the Amazer are three slightly different lengths. Francis claimed that this made the Amazer resonant at three different frequencies thereby increasing the bandwidth (???). The Amazer was gray in color, and I think (not certain) that the W-D was available in red, white, or black. The CB-28 Amazer is the best mobile antenna I have ever used.
Mr Clean ... if you do get the antennas, and they're CB-28s, put me down for two. Thanks and 73s.
BTW... the antennas were packaged in long poly bags about 2" wide. They had a white paper foldover stapled to the top of the bag, and the printing on it was red, and sometimes orange.
- 399
Mr Clean ... if you do get the antennas, and they're CB-28s, put me down for two. Thanks and 73s.
BTW... the antennas were packaged in long poly bags about 2" wide. They had a white paper foldover stapled to the top of the bag, and the printing on it was red, and sometimes orange.
- 399
Hello All: The Francis CB-28 Amazer antenna worked so well, it was truly impressive. But the top fiberglass part of the antenna feel apart with age and time hitting everything.
I made a larger diameter fiberglass antenna that has a 8 gauge silver plated wire and a reinforced fiberglass base assembly and heavy duty metal connection base. But as with the Francis CB-28 Amazer it will surly come apart with time, but has taken all the hits quit well for the last 5 years. I may add a top fiberglass cover over the top of the antenna. Time will tell.
Jay in the Great Mojave Desert
I made a larger diameter fiberglass antenna that has a 8 gauge silver plated wire and a reinforced fiberglass base assembly and heavy duty metal connection base. But as with the Francis CB-28 Amazer it will surly come apart with time, but has taken all the hits quit well for the last 5 years. I may add a top fiberglass cover over the top of the antenna. Time will tell.
Jay in the Great Mojave Desert
Hey guys, I still have a WD. I did not know the antenna had 3 wires, but I found out when I had trouble cutting a 1/4" inch off to try and lower the frequency a bit...the wire was very tough and was not copper.
I manage to crush the tip similar to Jay's comment. I sealed it with little epoxy/FG and used a rubber tip.
It is very old and I can tell the antenna is badly faded and brittle looking.
I have always felt the antenna worked very well and it didn't bend over near as much as the SS whips.
I manage to crush the tip similar to Jay's comment. I sealed it with little epoxy/FG and used a rubber tip.
It is very old and I can tell the antenna is badly faded and brittle looking.
I have always felt the antenna worked very well and it didn't bend over near as much as the SS whips.
Jay -
I had the same problem with my Amazers too. The top inch or so would shred after hitting trees and such. I took the vinyl tip off of my second one when it was new, and replaced it with a piece of LEXAN polycarb tubing about an inch long. Lexan is really tough and took all of the hits without allowing any damage to the antenna.
As an aside ... I attempted to duplicate the Amazer myself, and the fiberglass section came out good, but I was never able to get it to stay in the metal base. I wish I knew how Francis did it. Too bad that Francis sold out to Barjan, 'cause I'd be running an Amazer on my mobile if I could get one.
- 399
Hello U399: Ok thanks for the tip there I will look into the LEXAN polycarb tubing.
I use a much larger base connection piece made from Hexagon (6 sided, 3/4 in dia) shaped steel, then drilled out to make a very snug tight fitting of the fiberglass thick walled tubing into the metal base connection piece, approx. 4 inches long, with the fiberglass end allowing the fiberglass to be held in a vice and the fiberglass forced in to the interference fit hole with epoxy, then with a heavy punch it is pinched/crimped on the metal in 2 or 3 placed to hold the fiberglass Radom. The wire is brought down the fiberglass thru a hole and soldered to the Hexagon steel base, that has been drilled and taped for the 3/8 inch thread. Another piece of larger dia fiberglass is placed over both the fiberglass whip/radom and the metal base and fiberglass and resin is applied to add extra support, as it will certainly need it.
The FA antenna also uses a interference type fit, epoxy and is crimped in three places I believe by some type of machine. The top the of the FA Fiberglass antennas has come apart or shredded about 12 inches or more, and I have not attempted to repair it.
With the 8 gauge wire at the top of the fiberglass, I put in a brass screw in there not so much to tune it, but to keep the water out. The 1/4 WL whip antenna has a very broad and effective bandwidth. I use a heavy duty spring and the mounting puck is thick Delrin and it is reinforced with sheet metal in the cab of the truck.
Jay in the Great Mojave Desert
399, I think the Patent shows the equal length wires in the Wheeler Dealer also shows to have different diameters wires for the radiator. IMO, this provides the added bandwidth and similar responses compared to the Amazer that has similar diameter wires but with different lengths. At least this is the way I read the patent. I have an Amazer version of the model, but I did not consider it in this post. I will check it out however if it works and maybe post a thread with it compared to the WD model here.
The hand written notes are my guestimates for wire dimensions that I used in the models.
Here at my models.
1. Francis WD with wires equal in diameter noted as model "b" in the title.
2. Francis WD with wire diameter that are not equal noted as model "d" in the title.
3. Francis model with a single wire radiator.
4. Francis Patent 3,541,567.
The added images show some wire diameters in the details for the wires numbered 1,2,3, the radiator.
The added SWR curves show resonance and the high and low frequencies that determine the <2.00:1 SWR bandwidth for each end of the frequency. I also noted the bandwidth results for each model. This design does suggest a better bandwidth, but as I usually find for these kinds of technical details...the difference is not that significant. I also note there is a difference in gain when I made the Francis with 3 wires of different diameters vs. the one with the diameters all the same.
I added the source data report that shows the match condition for each model and they all look nice.
One thing you might notice is the antenna length is not as short as the actual antenna shows to be...and that is strange but it may be easily explained if you think about it. My wires are not insulated (coated) nor are they surrounded by a fiberglass random. I have not tested this idea but this is what I would expect if I did...the addition of insulation and the random would make the radiator shorter.
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2 stage epoxy, like they use to bond aluminum reel seats to heavy fiberglass offshore fishing rods. Scuff up the surfaces to be mated, if possible groove the metal. (Wire wheel) You will want there to be a gap between the fiberglass and ferrule, use a thin strip of brown packaging tape to create a bushing between the ferrule ends and fiberglass blank. When done correctly the tape/bushing centers the fiberglass rod within the ferrule. (Gap between bushings is filled with epoxy, allow epoxy to thicken slightly after mixing and apply to rod between tape/bushings). Clean/degrease parts before applying epoxy. Epoxy will set in an hour and cure in 24hrs. Glue up with that and you'll need a small torch to get it apart again...
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I'm curious, do you think a helically wound fiberglass antenna would benefit from multiple antenna elements wound with insulated thermaleze wire? They would all be parallel, electrically isolated, base fed, and could even be different lengths....
Trees, as you might notice in my models above...my experience trying to model the Francis idea with straight wires was complicated enough.
I do recall that my models did tend to show the differences that Francis claimed for their design over a typical 102" - 108" whip, but as I recall the differences were minimal at best. I think I got close with my Francis Amazer or Wheeler Dealer model, but I'd have to go back an check those Francis models out to refresh my memory.
Is it your thinking to make the antenna much shorter by using wound coils? If so, I would think more difficult issues may pop up...aside from construction problems that rumor says probably happened to the New owner of these designs a few year back.
My experience with trying to model the FireStik did not pan out with my thinking, so I can say that I never quite caught on to the mystery of such designs as they apply to my understanding of modeling.
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I'm thinking construction problems arose from trying to cheaply mass produce. Affixing a fiberglass blank to a metal ferrule securely is more than simply slopping some glue. This maybe something not understood by corporate executives weighing costs over quality. Cheaper is usually viewed as better. The reality is, the pieces need to be properly prepared, fitted, (small air gap between pieces that will be filled with epoxy), and the correct epoxy must be used. This is all a little costly. If the goal is to mass produce an antenna that costs about $10 to manufacture, I don't think that's a realizable goal. If the goal is to make the best antenna possible, well, that can be achieved, but it will cost four times the amount of ten bucks. (Material and labor). I don't know that an $80 (retail markup) fiberglass whip competes well with the other offerings. Big air wound, metal coil antennas seem to be the demand.
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I might be wrong, but I think the objective with helically wound wire whips is to achieve the proper inductance to cancel the capacitive reactance introduced by shortening the antenna? Additional, closely spaced wire wound inductors, electrically isolated from each other should capacitively couple together? I'm wondering if there would be any field cancellation/reinforcement/gain exhibited by such an antenna?