| Author |
Message |
    
Sofkow
| | Posted on Sunday, March 03, 2002 - 2:14 pm: | 
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Has anyone had any experiece with this antenna? I would like to know how well it performs and if it's a good 10/11 meter base antenna. |
307
| | Posted on Sunday, March 03, 2002 - 9:32 pm: |
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It is the BEST you can buy..I replace mine every two years just to maintain a clean antenna...I LOVE it... |
Sofkow
| | Posted on Monday, March 04, 2002 - 6:01 pm: |
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Thanks 307. One more Question. Can you give a ballpark figure on what legnth I should adjust the antenna sections to in order to obtain maximum performance on 11 meters? |
307
| | Posted on Monday, March 04, 2002 - 9:42 pm: |
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Actually , the instructions are right on the money...
307 |
Marconi
| | Posted on Tuesday, March 05, 2002 - 5:25 am: |
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Hey 307, what instructions? I have never seen any real instructions on one of the older or more modern knock-offs, have you? I have very comprehensive docs for my old original antenna but the antennas mentioned above are similar but are not exactly the same.
If you have some docs dated after about 1985 or in the 90's, I would like to have a copy for my files. All I have ever seen from the Italians is a one page jobber that don't say much. It assumes that you already know the antenna and how it goes together. Maybe you could post such on the forum in the proper section.
BTW, I am looking for docs to the original Astro Plane also. Would appreciate a copy from anyone.
Thanks,
Marconi |
Marconi
| | Posted on Tuesday, March 05, 2002 - 5:14 am: |
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Sofkow, I run an old Sigma. It may have been one of the original ones. It has only three legs in the bottom cone. As we speak, it is exactly 29'-5/8" long, from tip to very bottom. This bottom is the end of base pipe, below the feed point hub. This is the hub that supports the cone shaped ground radials and the feed point.
The stinger, from feed point to tip, is 27'-8.25". My radiator element pieces are tappered. They are individual pieces which are soltted at one end. This one uses hose clamps to secure each section. Each section in this antenna that has one piece fitting inside of another (tapper fit), has been dimpled for ease of installation. This suggest that the antenna was pretuned and marked. My antenna is true resonant at 27.400 with SWR = 1.12:1, resistance = 49 ohms, reactance = -0, as shown on an Autek VA1. This reading was made at the antenna feed point with the antenna on a 10' mast used as a test pole. With 75' of near resonant RG8U feed line the readings were very nearly the same when reading the Autek at the station end. An inline watt meter, with 5 watts of input, indicates a flat match at this resonant frequency.
Your antenna may also have these dimples. The stinger is likely a one piece job that telescopes out with pre-drilled holes to secure the sections. It probably has four elements in the bottom cone, and it may have an adjusting hub at the tip, with one or two small sections of tubing in and above this hub, used for length adjustment tuning between 10 and 12 meters. You could even have one that has ribbed tubing in the bottom section of the antenna. This was probably done to increase latteral strength of the light weight material in this more modern version of the original. I am not sure about the overall length of these 4 legged models, but they are probably somewhere around 30' to 31' feet for 11 meters.
I believe that the top section, the one with the small adjustable hub comes with enough material to cover from 10 to 12 meters, and I don't think the docs indicated what the proper lengths should be for anything. You will just have to trial and error adjust it unless you have a resonance meter.
BTW, I would recommend using SS parts, screws, nuts, and washers, including the set screws in the adjusting hub at the top, if you want this one to ever come apart easily. If your hub and SO-239 don't come pre-assembled, make sure your insulating aspects are correct.
Sorry to be so long, good luck.
Marconi |
307
| | Posted on Tuesday, March 05, 2002 - 11:18 am: |
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OOPS I was confused. I use the Alpha V-5/8. Big difference. I love Alpha...
307 |
Sofkow
| | Posted on Tuesday, March 05, 2002 - 3:42 pm: |
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Well..My sigma 5/8ths hasn't been delivered yet...but I hope it does come with readable instructions. Last time I put together a sigma, it was the 4, and the instructions were in Italian. They didn't help out much to say the least... |
Marconi
| | Posted on Tuesday, March 12, 2002 - 5:41 am: |
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Hey Sofkow, when you get your Sigma, describe it a bit and I will see if it resembles several around me. If it does, I may be able to get some measurements off it and get them to you as a starting point for your assembly. I have never seen good docs on any Italian made antenna.
Look guys, I have been very ill lately, so if you don't hear from me on some topic I may have been involved in, just let me know. I look in when I can and only then when I feel good.
See ya!
Marconi |
Marconi
| | Posted on Friday, March 29, 2002 - 8:26 pm: |
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Hey Sofkow, have you got your Sigma yet?
Marconi |
Rci2990
| | Posted on Wednesday, May 08, 2002 - 8:30 pm: |
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Are we talking about the avanti sigma 5/8th made back in the mid 1970s? If so i have one that i have been tinkering with. great antenna! Pretty good bandwidth too BTW but not like a a99 though. I like mine and i also run another avanti sigma the sigma 4. Both great antennas!!!!! |
Marconi
| | Posted on Thursday, May 09, 2002 - 8:42 am: |
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Hey Eric, after reading this thread over, I note that Sofkow is probably taking about a completely different antenna than I was discussing. My piece was about the Sigma IV and I think he is discussing the old original 5/8's that sort of looks like a Maco V-5/8 with a tubular tuning coil and an insulated stinger.
Just another senior moment down here in Texas, sorry about that 307. Hey Eric don't you have some info on the length of the old Sigma 5/8's.
BTW, I am sending you the information on the two new antennas I just got thru building. You should have it soon.
Eddie Marconi |
Rci2990
| | Posted on Thursday, May 09, 2002 - 11:33 pm: |
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Yeah i do! I just need to hook up my printer and my scanner so i can make you your copies.. bear with me though, i had to send this infernal computer in to the shop to get a checkup and i STILL have problems with it crashing for no reason. Another reason NOT to get a gateway! |
Marconi
| | Posted on Wednesday, May 15, 2002 - 8:05 am: |
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BTW, your package is on its way. Should arrive by weeks end 05/18. I never did find my old docs for the PDL II.
Eddie |
123upmichigan
| | Posted on Saturday, September 07, 2002 - 12:12 pm: |
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what are the trademarks of some of the old antenna's? i have a ground plane up right now that i was given and i cannot figure out what it is. the top stinger is 17 foot long, and it has a couple peices of wire shaped into a little ball on top. the ground radials look like elements from a moonraker. they are solid , have a connecting nut then they are smaller solid matyerial. they do not stick straight out but droop from the weight of the element. it talkes pretty good but i cannot figure out what kind it is please help me sam 123upmichigan |
Marconi
| | Posted on Sunday, September 08, 2002 - 1:10 pm: |
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123, sounds like it may be an old A/S Mighty Mag. Are the four ground plane radials short, about 60" overall? I think the ends of the GP sections on this one were SS wire or solid aluminum wire like you mention, but I don't recall the drooping.
I also recall one that looked a bit like the MM up in the air. It really did have some droop in the radials because I think it used something like 1/4 SS whips for the radials. It looked good up there, but I don't recall the name.
Marconi |
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