So you aren’t going to mobile mount the 19-lb 1-kV-capable 23’ version? Ain’t that the point to a Sweet 16?
The Chuck Norris of mobile antennas: All bridges are drawbridges.
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So you aren’t going to mobile mount the 19-lb 1-kV-capable 23’ version? Ain’t that the point to a Sweet 16?
The Chuck Norris of mobile antennas: All bridges are drawbridges.
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Eddie
My antenna analyzer is packed away in storage as I am in the middle of a coming move so I am not able to do any in depth testing right now.
It may be after the first of the year before I can get things set up again.
73
Jeff
My antenna analyzer is packed away in storage as I am in the middle of a coming move so I am not able to do any in depth testing right now.
It may be after the first of the year before I can get things set up again.
73
Jeff
That's alright Jeff.
I found several of my VA1 analyzer test reports...testing my Francis antenna on top of my Marconi 4X ground plane that resembles a Starduster. See PDF file below.
These models were physically up 54' feet to the feed point when tested however. I also included a test with a 102" SS whip in a similar setup. The BW data point step rate for these paper reports were set at 17 data points from about 26 - 28 MHz. This made them much broader in scope than the Eznec models with a step rate of 47 data points from 25 - 30 MHz. The paper reports show the BW checked using an inline SWR meter at the TX end of the line. This data is at the bottom and you will see this makes for a more customary bowl shaped BW curve.
To be sure, my Francis model ideas above was intended as an attempt to simulate a mobile setup at 87" inches to the feed point.
I've read articles discussing compression techniques used for RF broad-banding purposes. IMO, Francis seems to talk a lot about bandwidth improvement, and no doubt, with minimal losses in gain. It's not hard for me to imagine Francis and his wife having the smarts to figure this all out using a slide-rule back in the day.
My 102" whip on the Starduster type GP shows 4.00 MHz BW in a model. If one pushed the <2.00:1 MHz limits a little, it could be claimed this model of the Francis is showing close to 4.70 MHz BW. Jeff. I only saw this irregular BW curve start happening after I made the adjustments to the dimensions that you provided. I think getting the model closer to the real dimensions helped show this characteristic. Thanks!
I will set the Eznec model to a BW data point step rate similar to that shown on my paper reports, and we'll see what happens.
Sorry about the paper reports I did with a pencil years ago. Over time and with some use, the print does not copy well. However, you can try using the PDF zoom feature to get a little closer.
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Eddie
I found the remains of the Francis whip today after much searching.
I will take pictures as soon as I get time and post them here.
It has faded but it was black.
Looks like 16 gauge enamaled copper wire.
More to come when I have time.
73
Jeff
I found the remains of the Francis whip today after much searching.
I will take pictures as soon as I get time and post them here.
It has faded but it was black.
Looks like 16 gauge enamaled copper wire.
More to come when I have time.
73
Jeff
Eddie
Have a look at this.
You can clearly see the 3 copper conductors that are encapsulated in the fiberglass.
I know the original ones were Orange. ( I think) but this may back up what I was told that later in production Francis started making them all triple quarter wave to simplify production.
I can get my digital calipers out this weekend and confirm wire size.
What say you?
73
Jeff
Have a look at this.
You can clearly see the 3 copper conductors that are encapsulated in the fiberglass.
I know the original ones were Orange. ( I think) but this may back up what I was told that later in production Francis started making them all triple quarter wave to simplify production.
I can get my digital calipers out this weekend and confirm wire size.
What say you?
73
Jeff
Attachments
Very good.
I checked my last model. I think that is the model where I changed the 3 wire diameters to 0.05466875" inches and the model started acting right for once. I also made the spacing between 3 wires 0.03125" inches. I also set these 3 wires starting at the center of the FG radiator. So this would make roughly 6 wires and 6 spaces for the full width = .0515625" inches. I think that is a little wider than the FG diameter at the base and for sure at the tip. I don't have my Francis antennas any more. I gave them to Dr_DX.
Can you see wires in the tip?
Here is the link to the full Patent for several ideas for the wire positions that Francis designed.
https://patentimages.storage.googleapis.com/9b/a7/29/7338be7e676742/US3541567.pdf
If if you can see one or several wires in the tip, are they positioned directly inline from the center to the outside, like shown in one of the Patent images above. or is there just one wire showing in the tip and the other 2 shorter wires are somewhere below the tip?
Or, are they positioned in a circle around the center of the FG as noted in one of the other images?
If can't see anything at the tip, can you see the wire positions in the FG by moving the fibers apart a little.
I designed my model to have wire positioned like below with all three wires are off-set to one side from the center.
I checked my last model. I think that is the model where I changed the 3 wire diameters to 0.05466875" inches and the model started acting right for once. I also made the spacing between 3 wires 0.03125" inches. I also set these 3 wires starting at the center of the FG radiator. So this would make roughly 6 wires and 6 spaces for the full width = .0515625" inches. I think that is a little wider than the FG diameter at the base and for sure at the tip. I don't have my Francis antennas any more. I gave them to Dr_DX.
Can you see wires in the tip?
Here is the link to the full Patent for several ideas for the wire positions that Francis designed.
https://patentimages.storage.googleapis.com/9b/a7/29/7338be7e676742/US3541567.pdf
If if you can see one or several wires in the tip, are they positioned directly inline from the center to the outside, like shown in one of the Patent images above. or is there just one wire showing in the tip and the other 2 shorter wires are somewhere below the tip?
Or, are they positioned in a circle around the center of the FG as noted in one of the other images?
If can't see anything at the tip, can you see the wire positions in the FG by moving the fibers apart a little.
I designed my model to have wire positioned like below with all three wires are off-set to one side from the center.
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Jeff, I only ran the Orange Francis and it had Wheeler Dealer printed at the base of the FG or on the metal part. I don't doubt the black one, but I don't see any ads that show any color other that Orange and Gray. I checked all the ads noted in the Way Back Machine software and found no black color there either.
Does your antenna have a name printed on it?
Can you possibly cut the fibers off and maybe see what the wire positions looks like inside that might look similar to one of the models in the Patent above? If so, maybe you could give me and idea for the space dimensions between the wires.
I will attempt to strip the antenna down some and see if I can get some more picture's of how it is constructed.
It is about 2 am here now and I just got in from work.
I have a lot to do over the next 3 days but I will see if I can make some time for this project on Sunday.
I will also try to get some measurements as to were the break is and attempt to get a clear picture of how the wire is placed in the FG.
Take care my friend.
I will keep you updated when I make some progress.
73
Jeff
It is about 2 am here now and I just got in from work.
I have a lot to do over the next 3 days but I will see if I can make some time for this project on Sunday.
I will also try to get some measurements as to were the break is and attempt to get a clear picture of how the wire is placed in the FG.
Take care my friend.
I will keep you updated when I make some progress.
73
Jeff
I don't what it is exactly about Francis antennas, but they worked better than anything co-phased during my trucking days, and they did not even need to be tuned.
I had a co-phased set of 4.5 foot mounted on my Freightliner. The 4.5 Francis antennas are rated at 175 watts. Had a DaveMade M400(1x4) that I bought around the late 90's, and the co-phased antennas handled the power out no problem. Talking skip was great with this setup. Longest contact I ever made was from Laredo, Texas to Hawaii on CB band. I got laid over in Laredo lots because my company had a main terminal there, so yes I had time to burn.
I will admit though one night I talked for hours upon hours because the skip kept rolling in, and I saw a trail of rubber cap oozing down the side of the antennas. Scraped the tops, and put new caps on, and never did see a rubber cap melting again.
I had a co-phased set of 4.5 foot mounted on my Freightliner. The 4.5 Francis antennas are rated at 175 watts. Had a DaveMade M400(1x4) that I bought around the late 90's, and the co-phased antennas handled the power out no problem. Talking skip was great with this setup. Longest contact I ever made was from Laredo, Texas to Hawaii on CB band. I got laid over in Laredo lots because my company had a main terminal there, so yes I had time to burn.
I will admit though one night I talked for hours upon hours because the skip kept rolling in, and I saw a trail of rubber cap oozing down the side of the antennas. Scraped the tops, and put new caps on, and never did see a rubber cap melting again.
Great. Just to be clear in my curiosity Jeff.
Right now, I consider your antenna may be constructed as noted in the image I posted above, Fig #8. I have the diameter for the 3 wires set close to 16 gauge wire. I'm not sure about the spacing between each wire however.
If I'm seeing these 3 dimensions, 3 wires and 3 spaces correctly and they occupy approximately 1/2 of the FG near the base...then I currently get a base diameter of a bit over 0.50" inch diameter. I think I remember you giving me the diameter as being close to 0.375" inches instead...so I still have my model's wire dimensions wrong, and the spacing needs to be smaller still, and this is getting the wires really close together.
Sorry Jeff, I know this gets confusing and I did not go back to this thread and rehash what has already been recently said. I'm going by my recollections, and at my age that can be dangerous.
Right now, I consider your antenna may be constructed as noted in the image I posted above, Fig #8. I have the diameter for the 3 wires set close to 16 gauge wire. I'm not sure about the spacing between each wire however.
If I'm seeing these 3 dimensions, 3 wires and 3 spaces correctly and they occupy approximately 1/2 of the FG near the base...then I currently get a base diameter of a bit over 0.50" inch diameter. I think I remember you giving me the diameter as being close to 0.375" inches instead...so I still have my model's wire dimensions wrong, and the spacing needs to be smaller still, and this is getting the wires really close together.
Sorry Jeff, I know this gets confusing and I did not go back to this thread and rehash what has already been recently said. I'm going by my recollections, and at my age that can be dangerous.
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Hard to beat the benefit of holding it in your hand from a picture, but it looks much smaller than 16awg?
I wonder if this design was as hard to engineer as it is to reconstruct
Good point 2NC995.
I read an article by Francis once that talked about the sell of his business. He talked about how difficult it would be for the new owner to manufacture this design without also buying the tools and setup jigs they had developed. It has been reported that the new owner had trouble in manufacturing just like the article noted.
So reconstruction for real or for modeling would seem to be difficult.
I have to assume that the Francis bunch had some good understanding of the math and science back when they developed this idea. I've commented before that they must have been using their slide-rule back then to help compute the math.
I can use Eznec to some degree, but I could not create an antenna design...without a lot more understanding of the math and science. So, at best I can only try and duplicate the dimensions, if the dimensions are available.
In this case maybe I was lucky and got close with some help from the Patent, but that too required me to make wild guesses. Now with Jeff's help and some better dimensions, I am trying some tweaking and maybe get even closer.
Thanks,
Hard to separate the technical things and any pure fluff in the patent, but they sure imply that both the size and spacing of the elements are of the utmost importance to the overall design. At least with respect to spacing, it sure seems to be proving true.
As always, I look forward to any new data on this topic.
As always, I look forward to any new data on this topic.
Audioshockwav, thanks for having saved an old, broken antenna, and now taking pics to re-construct the mental image.
I was very busy today and it has been pouring here so really no time to take any pictures.
Eddie
If there was anything printed on the FG it is gone.
Stamped on the chrome plated brass at the bottom is
Francis followed by the circle with a r ( registered trade mark )
Made in the USA.
OOH
Pat No 3541567
That's all.
On my calipers the wire Dia is 1/64 of a inch.
I did break apart the top broken off piece of the antenna and from that it "looks" like the three wires are offset to one side of the FG.
It is old, badly splintered and I had to basically crush the FG to see were the wires were.
At some point I would like to take a cut off wheel and slice it off and try to photo the end up close to show the position of the wires, but I was risking having my gonads chopped off just messing around doing this today.
I will post more as I have time.
73
Jeff
Eddie
If there was anything printed on the FG it is gone.
Stamped on the chrome plated brass at the bottom is
Francis followed by the circle with a r ( registered trade mark )
Made in the USA.
OOH
Pat No 3541567
That's all.
On my calipers the wire Dia is 1/64 of a inch.
I did break apart the top broken off piece of the antenna and from that it "looks" like the three wires are offset to one side of the FG.
It is old, badly splintered and I had to basically crush the FG to see were the wires were.
At some point I would like to take a cut off wheel and slice it off and try to photo the end up close to show the position of the wires, but I was risking having my gonads chopped off just messing around doing this today.
I will post more as I have time.
73
Jeff