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folded driver
- Thread starter mb91w126
- Start date
RatsoW8
Supporting Member, W9WDX ARC Member - WD8T
Doesn't count as "folded" in the traditional antenna sense as I know it..those are just bent at right angles. I wonder what band the antenna is for and is there a call sign associated with Mick and Nigel?
MB this is the company that makes the antenna you may have already found it but if not here you go.
http://www.force12inc.com/products/11m-cb-yagi-beam-antenna-27-mhz-6-element-op-des.html
http://www.force12inc.com/products/11m-cb-yagi-beam-antenna-27-mhz-6-element-op-des.html
A link to the patent holders web site describing the technology...
They actually got a patent for what amounts to the driven element off of a moxon? They are even making claims that are very similar to what people report with moxon antennas... I wonder why...
Wow, the patent office must have been on an off day. They are not using any technology that hasn't been known about for decades, and I would be very surprised if someone somewhere hasn't put something like this together before. At best all they can do is claim that it was their idea to put the technologies together in this way.
Essentially the wires off the tips of the driven elements act as cap hats, which will have two effects in and of themselves. One, they widen the bandwidth. And two, they raise the antenna's feedpoint impedance, in this case bringing a naturally low feedpoint impedance closer to a feedline match.
They are also making the claim that because the wires at the tips of the driven elements are pointing the same direction that the radiation from them also oppose each other. What they don't tell you is that the currents at that point of the antenna are very small, and really won't affect the antenna's radiation pattern much at all anyway. As far as the opposed currents claim, you get a similar opposing current pattern if you take two wires at the tip of a single vertical antenna and point them in opposite directions. Horizontal radials below a vertical antenna do exactly the same thing as well. If you center feed a full wavelength square loop, two sides of the loop also do exactly the same thing.
They also seem to think that all losses in an antenna comes from SWR and matching, and they seem to think that this matching system will have no losses... I guess in their world there is no such thing as ground losses, and to them cap hats, which are admittedly pretty efficient, have no losses as well, which is clearly not true.
I'm sorry, I just find them getting a patent for that being very funny... Mind you I haven't read the actual patent, perhaps I should go look it up, maybe there is something in it beyond what one can determine just by looking at an antenna with this driven element... Somehow I doubt it...
The DB
They actually got a patent for what amounts to the driven element off of a moxon? They are even making claims that are very similar to what people report with moxon antennas... I wonder why...
Wow, the patent office must have been on an off day. They are not using any technology that hasn't been known about for decades, and I would be very surprised if someone somewhere hasn't put something like this together before. At best all they can do is claim that it was their idea to put the technologies together in this way.
Essentially the wires off the tips of the driven elements act as cap hats, which will have two effects in and of themselves. One, they widen the bandwidth. And two, they raise the antenna's feedpoint impedance, in this case bringing a naturally low feedpoint impedance closer to a feedline match.
They are also making the claim that because the wires at the tips of the driven elements are pointing the same direction that the radiation from them also oppose each other. What they don't tell you is that the currents at that point of the antenna are very small, and really won't affect the antenna's radiation pattern much at all anyway. As far as the opposed currents claim, you get a similar opposing current pattern if you take two wires at the tip of a single vertical antenna and point them in opposite directions. Horizontal radials below a vertical antenna do exactly the same thing as well. If you center feed a full wavelength square loop, two sides of the loop also do exactly the same thing.
They also seem to think that all losses in an antenna comes from SWR and matching, and they seem to think that this matching system will have no losses... I guess in their world there is no such thing as ground losses, and to them cap hats, which are admittedly pretty efficient, have no losses as well, which is clearly not true.
I'm sorry, I just find them getting a patent for that being very funny... Mind you I haven't read the actual patent, perhaps I should go look it up, maybe there is something in it beyond what one can determine just by looking at an antenna with this driven element... Somehow I doubt it...
The DB
As previously posted similar to a MOXON antenna.
The end of the driven element is bent back at a 90 degree angle and the spacing from the reflector will make a good 50 ohm impedance match, thus no need for a matching device.
Notice the balun at the feed point, Good idea to have one on a direct feed antenna.
No need for gamma, hairpin, or any other type of matching device.
The end of the driven element is bent back at a 90 degree angle and the spacing from the reflector will make a good 50 ohm impedance match, thus no need for a matching device.
Notice the balun at the feed point, Good idea to have one on a direct feed antenna.
No need for gamma, hairpin, or any other type of matching device.
Nothing new. Dick Bird G4ZU R.I.P and vk2abq wrote about this 40 years ago As noted the moxon is a derivative .If you can find Dicks article on critical coupling it is very interesting reading. Basically better bandwidth higher feedpoint impedance and still maintain a very high front to back ratio.
at HF, these antennas are much less subject to detuning due to ice buildup.
at VHF and above these folded antennas are also popular.
above 432 MHz is they are less detuned by water droplets, which once you get to 902-1296-2304 MHz is a pretty big issue.
at VHF and above these folded antennas are also popular.
above 432 MHz is they are less detuned by water droplets, which once you get to 902-1296-2304 MHz is a pretty big issue.
Agreed. I have never seen this design on a VHF or UHF antenna and only have seen it on one or two HF antennas. A true folded dipole element forms a complete long skinny loop. It has a step up impedance transformation of 4:1 meaning it has a self impedance of near 300 ohms. It is used a lot on commercial antennas on VHF as it offers an easy way to step up the low impedance drive point of a multi-element yagi and broader bandwidth.
I actually built a two element for 11 meters like this. I was playing around going to build a moxon and tried this design before i bent the reflector.
It does present a decent input impedance, cant say how it performed as i never put it on the test tower.
It does present a decent input impedance, cant say how it performed as i never put it on the test tower.
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