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Post by homerbb on Apr 28, 2012 8:23:20 GMT -5
This antenna photo showed up on a couple of sites I am a member of. The discussion centered around two things- 1. Have you seen this?, 2. Does it work as advertised? It is advertised to be a portable 11 meter beam. I entered the first discussion because one of the forum members emailed me asking whether I would be willing to make one and test it to answer the questions of its true nature. I told the second forum that I had said I would do this when I got some time. I'm inviting the OTRF in on the fun.   So far:
quotes from other places:
"I used copper tubing to put one together based on the posted specs. Until I get it out in the open air and coax on it I can't be sure, but suspended in the garage with a short jumper it does not approach a readable SWR on any frequency. I can not tell by any of the drawings whether there is more to the antenna than as described in previous posts. More to come with photos."
"Ok, I put it on a step ladder and hooked up the analyzer. Details later.
I also hooked up a small AM radio and listened, and got a radio check from a truck driver on ch 19: video to come of that.
It has an atrocious SWR, and the X=0 resonance is elsewhere.
Photos and more comments to come. I am due at work in 10 minutes."
"I want to add that I believe this antenna may have potential in a limited way.
I have used copper tubing because I wanted to reuse it for another project when done with this.
I have most of the aluminum strap to go exactly to the materials specs and will get the remaining piece to do it up and see. . ."
"Two quick photos and a video link to the first on-air test.
Where it shows X=0 resonance:
"
"Where the supposed center frequency is supposed to be - not quite there in this model:
"
"And a video link of the first test:"
In Touch - 2el Miniature Pulsar Antenna Homebrew |
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Sandbagger
Administrator/The Boss 
Posts: 6,247 
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Post by Sandbagger on Apr 29, 2012 11:43:49 GMT -5
This antenna photo showed up on a couple of sites I am a member of. The discussion centered around two things- 1. Have you seen this?, 2. Does it work as advertised? It is advertised to be a portable 11 meter beam. I entered the first discussion because one of the forum members emailed me asking whether I would be willing to make one and test it to answer the questions of its true nature. I told the second forum that I had said I would do this when I got some time. I'm inviting the OTRF in on the fun. So far:
quotes from other places:
"I used copper tubing to put one together based on the posted specs. Until I get it out in the open air and coax on it I can't be sure, but suspended in the garage with a short jumper it does not approach a readable SWR on any frequency. I can not tell by any of the drawings whether there is more to the antenna than as described in previous posts. More to come with photos."
"Ok, I put it on a step ladder and hooked up the analyzer. Details later.
I also hooked up a small AM radio and listened, and got a radio check from a truck driver on ch 19: video to come of that.
It has an atrocious SWR, and the X=0 resonance is elsewhere.
Photos and more comments to come. I am due at work in 10 minutes."
"I want to add that I believe this antenna may have potential in a limited way.
I have used copper tubing because I wanted to reuse it for another project when done with this.
I have most of the aluminum strap to go exactly to the materials specs and will get the remaining piece to do it up and see. . ."
"Two quick photos and a video link to the first on-air test.
Where it shows X=0 resonance:
"
"Where the supposed center frequency is supposed to be - not quite there in this model:
"
"And a video link of the first test:"
In Touch - 2el Miniature Pulsar Antenna HomebrewI would imagine that it could be brought into resonance in a similat way that a DF loop is matched. But based on the size, even with a good SWR, I can't see how something so much smaller than a 1/4 wave can have any usable gain. |
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Post by homerbb on Apr 29, 2012 15:34:32 GMT -5
I'm with you on the usability.
I will redo it according to the exact materials specs using aluminum flat bar instead of copper tubing just to see what's up. I said I'd check this out so I will. At least it's interesting.
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Post by homerbb on Apr 29, 2012 21:26:57 GMT -5
Ok. The latest, and despite my previous commitment to redo the thing to exact materials specs, perhaps my last. Redoing it to the exact specs was an extension of my belief that the antenna might have some possibilities as a portable system. That was based on some encouraging results and the video with a decent radio check I recorded. Of course, on some of the forums I said I did not believe it was a beam, and still don't. It is a dipole, off center fed. The feed system settles that - braid to one half the antenna, center conductor to the other. Simple. Today I decided to test a thought that occurred to me based on experience with other types of shortened antennas, NGPs (no ground plane) in particular. Those antennas have a single thing in common - they depend on the coax to be part of the radiating system. To test this idea I mounted the antenna just as before, but this time I inserted a coax choke one foot from the connection point of the feed line to the antenna to defeat any potential CMC, and thus prevent the coax from being a radiating element. Just as I suspected, anything remotely resembling a match, or resonance across multiple bands wasn't happening for me. It is my opinion that this antenna depends on the coax to be part of the radiator. Here is my personal conclusion: Can it be used as a portable antenna on 11 meters?Yes, but you must be careful of the coax length in order to get a match. Is there a special length to be used? I doubt it. Just so there is enough to get the job done should do. Too short a coax will not provide enough length to radiate at the 11 meters band. I suspect that conductive surfaces near it will likely affect it. Is the antenna a beam? No. It's a dipole - a split element, off center fed dipole. Should one buy one? If they wish. It isn't useless, and could be fun. It certainly doesn't use too much space as many 11 meter antennas tend to do. Would I buy one? Of course not, I already have one.  |
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Sandbagger
Administrator/The Boss
Posts: 6,247
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Post by Sandbagger on Apr 30, 2012 7:17:09 GMT -5
Ok. The latest, and despite my previous commitment to redo the thing to exact materials specs, perhaps my last. Redoing it to the exact specs was an extension of my belief that the antenna might have some possibilities as a portable system. That was based on some encouraging results and the video with a decent radio check I recorded. Of course, on some of the forums I said I did not believe it was a beam, and still don't. It is a dipole, off center fed. The feed system settles that - braid to one half the antenna, center conductor to the other. Simple. Today I decided to test a thought that occurred to me based on experience with other types of shortened antennas, NGPs (no ground plane) in particular. Those antennas have a single thing in common - they depend on the coax to be part of the radiating system. To test this idea I mounted the antenna just as before, but this time I inserted a coax choke one foot from the connection point of the feed line to the antenna to defeat any potential CMC, and thus prevent the coax from being a radiating element. Just as I suspected, anything remotely resembling a match, or resonance across multiple bands wasn't happening for me. It is my opinion that this antenna depends on the coax to be part of the radiator. Here is my personal conclusion: Can it be used as a portable antenna on 11 meters?Yes, but you must be careful of the coax length in order to get a match. Is there a special length to be used? I doubt it. Just so there is enough to get the job done should do. Too short a coax will not provide enough length to radiate at the 11 meters band. I suspect that conductive surfaces near it will likely affect it. Is the antenna a beam? No. It's a dipole - a split element, off center fed dipole. Should one buy one? If they wish. It isn't useless, and could be fun. It certainly doesn't use too much space as many 11 meter antennas tend to do. Would I buy one? Of course not, I already have one. Of course, the biggest turnoff for me, with antennas which utilize the coax shield as the counterpoise, is the potential for increased RFI issues. Not to mention the difficulty in maintaining a decent match near surrounding objects and the ground level. |
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Post by cbrown on Apr 30, 2012 9:42:48 GMT -5
I would imagine that it could be brought into resonance in a similat way that a DF loop is matched. But based on the size, even with a good SWR, I can't see how something so much smaller than a 1/4 wave can have any usable gain. I agree 100%. You could try coiled elements |
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Post by cbrown on Apr 30, 2012 10:11:24 GMT -5
Of course, the biggest turnoff for me, with antennas which utilize the coax shield as the counterpoise, is the potential for increased RFI issues. Not to mention the difficulty in maintaining a decent match near surrounding objects and the ground level. I has set up a 1/2 wave Big Stick Back in 1977 or so, and that antenna must have used the coax as a counterpoise. Since everything back then was wired, it bled into the intercoms, phone lines & TVs... it was a mess. |
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Sandbagger
Administrator/The Boss
Posts: 6,247
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Post by Sandbagger on Apr 30, 2012 11:34:10 GMT -5
Of course, the biggest turnoff for me, with antennas which utilize the coax shield as the counterpoise, is the potential for increased RFI issues. Not to mention the difficulty in maintaining a decent match near surrounding objects and the ground level. I has set up a 1/2 wave Big Stick Back in 1977 or so, and that antenna must have used the coax as a counterpoise. Since everything back then was wired, it bled into the intercoms, phone lines & TVs... it was a mess. End-fed 1/2 wave antennas (like the A99) are especially bad at near-field related RFI issues. Placing a blocking choke at the feedpoint can greatly reduce this problem. |
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Post by homerbb on Apr 30, 2012 16:37:56 GMT -5
Roger on everything above. With this antenna, however, placing a choke near the feedpoint cut the antenna dimensions because this can't operate 11 meters without the feedline radiating.
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Post by cbrown on May 1, 2012 8:14:24 GMT -5
End-fed 1/2 wave antennas (like the A99) are especially bad at near-field related RFI issues. Placing a blocking choke at the feedpoint can greatly reduce this problem. Ya, thankfully I was helped out by a local ham I used to take on 11M to who showed me how to make one. He was a great guy, became my elmer. |
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Post by cbrown on May 1, 2012 8:18:21 GMT -5
Roger on everything above. With this antenna, however, placing a choke near the feedpoint cut the antenna dimensions because this can't operate 11 meters without the feedline radiating. You'd probably be better off with a center fed dipole than that antenna. Especially since you can just coil up the dipole antenna and throw it in the back seat when you are done. |
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Post by homerbb on May 1, 2012 10:29:10 GMT -5
Yep, you're right. I was asked to sort this thing out so I have been trying to.
I may give it one more shot with some tweaks to it and then let it go.
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Post by cbrown on May 2, 2012 8:25:21 GMT -5
I'm all for experimenting, heck you may even stumble across something.
What was the point of the antenna? Small sized base beam or a portable beam for field work?
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Post by homerbb on May 3, 2012 9:21:05 GMT -5
It is advertised for use as a portable beam.
Although another fellow on another forum says he and his Elmer built one 40 years ago with slight dimension differences and it was somewhat directional toward the smaller loop, I still do not believe it to be a beam. The feed system says it isn't
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Post by cbrown on May 4, 2012 8:37:34 GMT -5
Just judging from what I can see, it looks like an offset fed dipole. A beam would require some sort of director I would think.
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Post by homerbb on May 4, 2012 22:29:40 GMT -5
Exactly. I say you see right.
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43irc177
Mudduck
43irc177 Australia good day
Posts: 2
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Post by 43irc177 on Nov 27, 2019 18:17:29 GMT -5
Hay guys hi from Australia
looking at a small been antenna but the problem ie room a quad is to big and VQuad is to big
even a maxon beem is to bam big to fit into where we are
so now im stuck
eany thing that hangs over the fence well you know how that works
is there anything out there for 11m band with a small boom
the most room i got is 1.5 feet
i think its going to be a gig ask steve
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Post by cbrown on Dec 4, 2019 13:00:05 GMT -5
The problem is you need some size for the 11M frequencies. I'm not aware of any small antennas that will work well transmitting.
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Post by daveyboy on Jul 16, 2020 16:37:39 GMT -5
Hay guys hi from Australia looking at a small been antenna but the problem ie room a quad is to big and VQuad is to big even a maxon beem is to bam big to fit into where we are so now im stuck eany thing that hangs over the fence well you know how that works is there anything out there for 11m band with a small boom the most room i got is 1.5 feet i think its going to be a gig ask steve |
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Post by daveyboy on Jul 16, 2020 16:40:11 GMT -5
I've built a pulsar beam. Boom is 1311mm long 2 loop elements drive 750 mm x 700mm.reflector 770mm x 700mm. It is for sale message me
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Sandbagger
Administrator/The Boss
Posts: 6,247
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Post by Sandbagger on Jul 16, 2020 19:13:33 GMT -5
Hay guys hi from Australia looking at a small been antenna but the problem ie room a quad is to big and VQuad is to big even a maxon beem is to bam big to fit into where we are so now im stuck eany thing that hangs over the fence well you know how that works is there anything out there for 11m band with a small boom the most room i got is 1.5 feet i think its going to be a gig ask steve Sometimes you just have to come to the realization that you can't get there from here. Beam antennas derive their performance from the number of elements and the length of the boom. More is definitely better when it comes to gain and rejection. If you try to shrink a beam down to fit in a small area, you lose all of the things that give the beam its advantages. At that point, you might as well put up a Imax 2000 and call it a day. |
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Post by yaesu101z on Apr 19, 2021 8:04:32 GMT -5
Hi Folks
I have build a Pulsar 27 myself, but i have change the dimensions a bit.
I am using 30 mm flat Aluminum and my loops is slightly bigger.
I have worked on 15 meters W8LR from Cape Town with 45 watts.
Remember, the big loop must be in the front, then lift the front 25 degrees up.
I use a Yaesu FC 902 tuner +/- 50 watts on 10 , 11 ,12 , 15 , 17 & 20 meters.
You will see on QRZ.com if you put my call sign in. But the solar flux must be more than a 100.
This is NOT a miracle antenna but it does work if you don't have the space.
Good luck 73's
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Post by yaesu101z on Apr 19, 2021 8:23:25 GMT -5
Hi Folks
Here are the schematic for the Pulsar 27.
I'm using a 15 meter RG58CU coax feed line.
73's Dan
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