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Post by homerbb on May 4, 2012 22:28:44 GMT -5
I've been tinkering around with an inductor, and a variable capacitor, and my dipole rejoined end-to-end for a 1/2 wave monopole fed from one end. I tried this coil/capacitor parallel coupling first and could get no where near where I wanted for a match, etc: Then I made this up: and paired it up with the capacitor: I was able to get very close to what I was looking for with a 1.1 SWR R60 X0 @ 27.567 27.400 was a 1.3 SWR and I neither wrote down nor photographed the MFJ readings so will have to do it again.
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Post by cbrown on May 7, 2012 8:46:12 GMT -5
I'd like to know the bandwidth you get with that with a 2.0 SWR curve.
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Post by homerbb on May 7, 2012 12:13:03 GMT -5
If I get to feeling better - allergies - I'll measure it for you
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Post by homerbb on May 7, 2012 17:44:24 GMT -5
I'd like to know the bandwidth you get with that with a 2.0 SWR curve. Here you go:
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Post by homerbb on May 7, 2012 18:13:11 GMT -5
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Sandbagger
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Post by Sandbagger on May 7, 2012 20:13:44 GMT -5
Wow... The compact disc-cap...... You sure are one heck of a fabricator.
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Post by homerbb on May 7, 2012 20:55:08 GMT -5
What I would like to do with them next is to use my small multi-tool similar to the Dremel and shape some discs into stators and rotors for a stacked set. The cap can be used with or without spacers because the CD's have a natural thickness to them
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Post by cbrown on May 8, 2012 9:01:12 GMT -5
If I get to feeling better - allergies - I'll measure it for you I hear you, I have the same thing happening here.
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Post by cbrown on May 8, 2012 9:05:17 GMT -5
What I would like to do with them next is to use my small multi-tool similar to the Dremel and shape some discs into stators and rotors for a stacked set. The cap can be used with or without spacers because the CD's have a natural thickness to them That would be something to see!
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Post by homerbb on May 8, 2012 11:06:37 GMT -5
It could be nicely put together, or crudely fashioned like the one above. A simple set of wooden clothes pins can help to keep the plates at the desirable positions. In fact, had I some wooden clothes pins handy the cap was to be held in place by them in the box. Screw two to three pins to the inside of the box by one half of the pins, then put the pins back together and slip the cap into them. Position the cap for best result and the cap never budges from tune.
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Post by homerbb on May 8, 2012 21:30:38 GMT -5
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Post by cbrown on May 9, 2012 8:55:17 GMT -5
Pretty innovative!
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Post by homerbb on May 9, 2012 23:45:42 GMT -5
Got it at 36'. gonna see if it works well or not.
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Sandbagger
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Post by Sandbagger on May 10, 2012 6:09:14 GMT -5
Got it at 36'. gonna see if it works well or not. Another successful homebrew project. However, I do not believe that this antenna will perform as well as some of the other configurations that you've constructed before. I've never been a fan of radial-less antennas, and prefer a ground plane design for best overall omni-directional performance.
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Post by homerbb on May 10, 2012 8:34:18 GMT -5
I agree with you Sandbagger, however, the non-radial end fed antenna is for me a matching challenge I hadn't tackled with successful results before. I had it to do sooner or later. I can hear well enough on it, but I'm not so sure it has the TX punch needed for the DX conditions prevalent in my area currently.
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Post by cbrown on May 10, 2012 8:49:23 GMT -5
Another successful homebrew project. However, I do not believe that this antenna will perform as well as some of the other configurations that you've constructed before. I've never been a fan of radial-less antennas, and prefer a ground plane design for best overall omni-directional performance. Ya, I agree. A radial-less design relies on using the coax as a counterpoise, which I never liked.
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Post by homerbb on May 10, 2012 14:24:39 GMT -5
Another successful homebrew project. However, I do not believe that this antenna will perform as well as some of the other configurations that you've constructed before. I've never been a fan of radial-less antennas, and prefer a ground plane design for best overall omni-directional performance. Ya, I agree. A radial-less design relies on using the coax as a counterpoise, which I never liked. I tend to agree with this, too. However, if you'll look closely at the photo you may be able to see the coax choke at the feedpoint . . .
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Sandbagger
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Post by Sandbagger on May 10, 2012 21:14:05 GMT -5
Ya, I agree. A radial-less design relies on using the coax as a counterpoise, which I never liked. I tend to agree with this, too. However, if you'll look closely at the photo you may be able to see the coax choke at the feedpoint . . . Yep, it's plainly visable. But while the choke can help limit coaxial near-field radiation, it doesn't help the fact that the antenna's radiation pattern (and gain) will be altered over that of a true ground plane design.
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Sandbagger
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Post by Sandbagger on May 10, 2012 21:17:55 GMT -5
I agree with you Sandbagger, however, the non-radial end fed antenna is for me a matching challenge I hadn't tackled with successful results before. I had it to do sooner or later. I can hear well enough on it, but I'm not so sure it has the TX punch needed for the DX conditions prevalent in my area currently. I can certainly appreciate and can relate to the need to "do it just to say you did it" aspect of projects like this. That's how you learn. I am reminded of the first time I built an amplifier. That was a very educational and fun project.
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Post by homerbb on May 10, 2012 23:49:08 GMT -5
I think I could build an amp if someone gave me the parts list and a 1, 2, 3 step-by-step book.
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Sandbagger
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Post by Sandbagger on May 11, 2012 10:02:19 GMT -5
I think I could build an amp if someone gave me the parts list and a 1, 2, 3 step-by-step book. Oh, you want a Heathkit! ;-) I had the schematic of a commerical unit and I just followed that, although I had to do a little "substituting" for those parts that were a litle tougher to find locally (and in 1975, there wasn't an internet to order from).
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Post by homerbb on May 11, 2012 22:08:33 GMT -5
LOL ;D Yeah, I guess so.
It would be a serious learning curve for me to know what to sub!
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Post by cbrown on May 14, 2012 8:36:23 GMT -5
I tend to agree with this, too. However, if you'll look closely at the photo you may be able to see the coax choke at the feedpoint . . . But that leaves you without a counterpoise, which should decrease the performance of the antenna. Might work if you move the choke 18 feet or so down the coaxial cable.
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Post by cbrown on May 14, 2012 8:37:47 GMT -5
Oh, you want a Heathkit! ;-) I had the schematic of a commerical unit and I just followed that, although I had to do a little "substituting" for those parts that were a litle tougher to find locally (and in 1975, there wasn't an internet to order from). Heathkits rocked! It also helped a lot if you had a good elmer to tell you what everything did.
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Post by homerbb on May 14, 2012 8:57:11 GMT -5
Yes, it leaves no counterpoise, but that was the point - to achieve a working half wave without counterpoise. I know, and am convinced an antenna is best with a counterpoise.
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Post by cbrown on May 15, 2012 8:55:46 GMT -5
Right. Without a counterpoise you are running an antenna with nothing to react against. Will it work? Sure. Will it work well? No.
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Post by homerbb on May 15, 2012 18:00:40 GMT -5
Not that it matters, but I took it down to put the Astroplane up and check it out as someone is interested in the AP. The AP is knocking the socks off that 1/2 wave and the .64 right now. It always has.
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Sandbagger
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Post by Sandbagger on May 15, 2012 18:06:51 GMT -5
Not that it matters, but I took it down to put the Astroplane up and check it out as someone is interested in the AP. The AP is knocking the socks off that 1/2 wave and the .64 right now. It always has. That's interesting. I was never impressed with the performance of the Astro Plane. I had one back in the mid 70's. I replaced a 1/2 wave Radio Shack ground plane with it, and it was no better in signal strength. About 4 months later, I replaced the AP, with a 5/8 wave GP and I jumped up between 1/2 and 1 S units to most of my daily locals.
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Post by homerbb on May 15, 2012 20:46:26 GMT -5
I notice that different folks in different places report different results with the AP. The bottom ring is at 45', making the top at 57'. The 1/2 wave was at 36' making the top about 55'. The .64 was at 32' making the top about 55' also. I suppose its height gives it an advantage of sorts, but then again, that has been the way of the AP. It shines with height. I wish I had it higher.
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Sandbagger
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Post by Sandbagger on May 16, 2012 6:21:31 GMT -5
I notice that different folks in different places report different results with the AP. The bottom ring is at 45', making the top at 57'. The 1/2 wave was at 36' making the top about 55'. The .64 was at 32' making the top about 55' also. I suppose its height gives it an advantage of sorts, but then again, that has been the way of the AP. It shines with height. I wish I had it higher. Mounting height was probably a big factor in why my results were as poor as they were. My original 1/2 wave antenna was mounted on 20' of mast. The AP was attached to the same 20' of mast, which resulted in the AP actually being lower in height than the 1/2 wave as well as the 5/8th wave that eventually replaced it. My location was also not very high in relation to the surrounding area. The combination of these factors is probably why I got the absolute best signal performance from the Sigma 4 (which replaced the 5/8th wave), while the AP was at the bottom of the barrel. Guys who lived on a hill and/or mounted their AP's up high, seemed to fair much better. On the other hand, they didn't do A-B comparisons between the AP and another antenna so we were just assuming that the performance was good based on comparisons with other people, which is probably not a good way to compare.
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