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Znut
| | Posted on Saturday, September 21, 2002 - 10:09 pm: | 
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Hello,
I started a project a short while back to make a horizontally polarized antenna. It worked but I decided to turn it into a beam. If you check out the thread "11 Meter Full-Wave Loop Antenna" you'll get more detail on that.
Here's the specs.
The driven element is about 36 feet long.
The reflector is about 36 feet 2 1/2 inches. The boom is 6 feet 4 inches long. These are approximations. I will follow soon with pictures and more precise dimensions.
At about 8pm here in GA I had the antenna hooked up.
Made several SOLID contacts on AM and SSB. I even talked to Taz with good results.
Znut |
Taz
| | Posted on Sunday, September 22, 2002 - 12:20 am: |
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No doubt |
Marconi
| | Posted on Sunday, September 22, 2002 - 6:45 am: |
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Znut, good to hear your beam is working fine. I seem to recall the driven element was longer. Did you decide to go ahead and cut it? Just off the top of my head, the reflector dosen't seem to be long enough either, if your using the 5% larger deal that is probably considered to be a standard. Just not real sure about every quad however.
How far away is Taz from you?
Good deal, keep us posted.
Marconi |
Znut
| | Posted on Sunday, September 22, 2002 - 11:02 am: |
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Yes Marconi on both accounts. I did the calculations based on the "k" factor numbers you gave me and split the difference. Turns out what sounded like such a big difference in length is correct. I never realized how much of a difference the element diameter made on resonant length.
I left my notebook outside last night when I posted.
Driven = 36' 1"
Reflector = 37' 10 1/2"
I need to shorten them though. I'm getting pretty good SWR around 26.5 mhz, I haven't really plotted the curve yet. It is really broadbanded and even on channel 38 it was only 2:1.
Taz is like 1800 miles from me here in GA. I also made SSB contacts in CA and OR, these are the farthest I've talked besides U.K. Ooh! Speaking of which, it's about that time of the day.
Znut |
Marconi
| | Posted on Sunday, September 22, 2002 - 1:00 pm: |
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Well you are getting real close. A little shorter on the driven element and it should put you right in the middle of 11 meters.
How is the side and back rejection?
You will just have to play with the thing for a while to see about the rejection factor. If it is good, I would adjust it just like you do the radiator. Since you are close, I would work it a while to get a real feel for the rejection before making any adjstments. Then you will be better able to realize the effects of any changes you make later trying to get closer to where you want to work it.
Are you able to turn it now?
Good work!
Marconi |
Taz
| | Posted on Sunday, September 22, 2002 - 4:39 pm: |
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I think hes lying. He must have a laser500 over there with a 20k amp.
8lbs solid on my meter sounded great |
Taz
| | Posted on Sunday, September 22, 2002 - 8:23 pm: |
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he cut it long so it works better below thr reg 40 channels |
Sixtiesmania
| | Posted on Friday, October 04, 2002 - 9:51 am: |
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Hey Guys,
Very interesting BUT I know alot of people are thinking.... what is the best way to tune it?? ie gamma match, 1/4 wave of 75 ohm coax etc. Please let the rest of us in on this. Also, many years back I made my own gamma match for a 3 element beam that consisted of 2 aluminium sections with a pvc tube between the 2 telescopic sections and the 2 aluminium straps, sliding the tube in or out to tune it in. It worked well I recall, but for life of me, I cannot find the basic dimensions now of how to build one for 11 mtrs, OR dimensions for a basic 3, or 4, element beam. Anyone out there can help??? I am sure tons of readers would find this really usefull stuff. A nice alternate to paying big $$$$ for a decent antenna from a shop.
Cheers
Andrew
HV 739 |
Znut
| | Posted on Friday, October 04, 2002 - 1:01 pm: |
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Here are the basic mechanical specs.
The elements are made of 1/2 inch 75ohm aluminum hardline, the type you see attatched to the overhead powerlines to carry cable TV signals. The spreaders that hold the elements are made of 1 1/2" O.D. thin wall PVC. The boom is made of 1 1/2" high pressure (thicker wall) PVC.
The driven element, the one with the coax hooked to it is 35 feet 7 inches. It is capable of about 1 1/2 feet of adjustment but right now it is tuned as high as I can tune it without trimming the loop part. I have it fed at the bottom so it is horizontally polarized (flatside). I wound 9 turns, about 6 or 7 feet of coax into a choke right at the feedpoint to prevent the RF from radiating from the coax itself.
The reflector is 37 feet 4 inches. It is capable of about 3 feet of adjustment.
The boom is 6 feet 6 inches long.
The height is almost 21 feet to the boom. However, the bottom of the elements are only about 8 feet from the roof of my home with metal siding and metal roof. I don't think that is detuning the antenna too much though.
I have about a 1.2 to 1 SWR on channel 20. I don't know for sure if that is where the antenna is most resonant/efficient. It has nice bandwidth. SWR is under 2:1 from 26.45 to 27.65!
I will make a balun when I can get an analyzer on it and tune it more precisely and determine the exact impedance at resonance. I think this will improve the radiation pattern.
I don't really have any info about the gain or pattern other than the fact that it is directional. All of my results are based on DX. I have had some stations come in 5 or more s-units over my A-99. HR 2510's don't have a very nice s-meter. Yes, I do have a switch to do side by side conparison. When I find a local station with a horizontally polarized antenna I may be able to get an idea of what the radiation pattern looks like.
Overall I am very happy with the results. I used it this past Saturday during the DX-A-THON so there are 3 of you who have heard it on the air. 2 during the event Saturday and one other from a contact the week before, see related threads for details.
As promised, here are pictures.
Znut
(Oops, see 11 meter loop thread for pics) |
Znut
| | Posted on Saturday, June 21, 2003 - 1:55 pm: |
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Znut
| | Posted on Saturday, June 21, 2003 - 3:52 pm: |
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