Attached is a pdf I put together for building the full wave loop antenna and the 2 loop array. Feel free to share this anywhere. I hope it is useful to somebody, need any help just drop me a line.
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pdf -building the full wave loop antenna and array-
- Thread starter xm49north7
- Start date
Shadetree Mechanic
Delaware Base Station 808
Thanks for sharing the details. I have been thinking about building a two element quad because I am too cheap to buy one. Then again, I don't have time to build one either. The full wave loop looks like it would go together quick and I probably have the stuff to make one already. I probably have two trees that are a half wave length apart. Now you got me thinking.
Go for it you will not be sorry, I had better luck with the 2 loop array than I did with 2 el quad or the 4 element spider beam. Loops just work for me. Super simple to build and tune, maybe a few hours work, I have even done them from extension cord wire in a pinch. There is just something about resonant antennas for me, they just seem to hear better, send better, are quieter, I just have great luck with them.
My first beam was a cheap copy of the PDL-II.
Was a LOT of fun.
Worked just fine - too . . .
Was a LOT of fun.
Worked just fine - too . . .
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Nice! How high did you end up going with the antenna, either singularly or as an array?
I got them both just a pinch over 36 feet to the feed point. I think this is a minimum for good antenna performance on any cb antenna.
xm49north7, this is just my opinion. I don't mean to be critical of your antenna experimenting and doing a very good job of presentation to boot...I can only encourage operators to experiment.
I made a couple of Eznec models based on your well presented ideas in your PDF file above.
However, my models show your Vertical Quad with a feed point impedance near 200 ohms even when resonant. I had to adjust your dimensions down in frequency (longer) into the CB band...just like you suggested we might.
I also made a model that set your feed point to Horizontal at 32', and the impedance was improved, showing about 60+ ohms for resistance at resonance. It shows a much better SWR and the gain is also improved. Again however, the resistance remained high even at resonance.
I also did not find making the center struts wider to help much in tuning this antenna to a much better match. The effort does tend to make the wires longer, but that change is minor compared to the mismatch.
I have several other conventional type Quad models, and they generally show high resistance (SWR) at the feed point as well, again, even when resonant. That suggest to me, that no amount of adjusting wire length or changes in height are likely to fix the mismatch without some matching device, which I don't think you've mentioned.
If I was to try this design, I would simply make the antenna into a Moxon. You could stay vertical, and both gain and match should improve markedly. The Moxon will also allow for direct feeding with coax...all you might need to do is decouple the antenna from the feed line and mast is as you've already suggested...use a coaxial choke when vertical for sure. Going Horizontal might not be so bad.
Below is a PDF image from William Orr and Stuart Cowan. It is in their book "All About Cubical Quads." On pages 64-65, you will see a topic "Unbalanced (Coxial) Feed Systems For The Quad Antenna." This is an old book, but it is my go-to resource for Quads. See PDF file below. Sorry this is printed in Landscape view. You can use the printer function at the top right side of the PDF file and make reading better.
I will post my 2 Quads and a Vertical Moxan models in another post.
I made a couple of Eznec models based on your well presented ideas in your PDF file above.
However, my models show your Vertical Quad with a feed point impedance near 200 ohms even when resonant. I had to adjust your dimensions down in frequency (longer) into the CB band...just like you suggested we might.
I also made a model that set your feed point to Horizontal at 32', and the impedance was improved, showing about 60+ ohms for resistance at resonance. It shows a much better SWR and the gain is also improved. Again however, the resistance remained high even at resonance.
I also did not find making the center struts wider to help much in tuning this antenna to a much better match. The effort does tend to make the wires longer, but that change is minor compared to the mismatch.
I have several other conventional type Quad models, and they generally show high resistance (SWR) at the feed point as well, again, even when resonant. That suggest to me, that no amount of adjusting wire length or changes in height are likely to fix the mismatch without some matching device, which I don't think you've mentioned.
If I was to try this design, I would simply make the antenna into a Moxon. You could stay vertical, and both gain and match should improve markedly. The Moxon will also allow for direct feeding with coax...all you might need to do is decouple the antenna from the feed line and mast is as you've already suggested...use a coaxial choke when vertical for sure. Going Horizontal might not be so bad.
Below is a PDF image from William Orr and Stuart Cowan. It is in their book "All About Cubical Quads." On pages 64-65, you will see a topic "Unbalanced (Coxial) Feed Systems For The Quad Antenna." This is an old book, but it is my go-to resource for Quads. See PDF file below. Sorry this is printed in Landscape view. You can use the printer function at the top right side of the PDF file and make reading better.
I will post my 2 Quads and a Vertical Moxan models in another post.
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Good stuff. I run 75 ohm coax, on the array with 2 loops, and 75/50 ohm on single loops. I have not had any issues on swr. But you do have to play to get it where you want it. I did build a vertical moxon, but had trouble keeping it tuned being made out of wire and sruts. I think aluminum tube would be required for a good moxon. I would love to do some horizontal polarization for the dx. I will do some more work next summer on my 2 loops, one will need some care by then. I am sold on loops. They just seem to work better than anything at my location, ability to get them up and maintain them, and money I have to play with. If anyone builds one, do post your results. I am sure there is tons of room to play with these. Thank you for all your efforts, do not ever be worried about throwing in on what I post. I am just a tinkerer, I was a master electrician by trade, so have wire in my blood. I enjoy wire antennas, and can usually scrounge most of my materials. I am slowly getting tower materials stocked up from friends and family dropping off bits, so perhaps some day a pair of loops on rotors will happen, that would be on my list for some fun. I am mostly retired now, this stuff helps fill my day here on the farm.