| Author |
Message |
    
Captian_radio
Intermediate Member
Username: Captian_radio
Post Number: 182
Registered: 9-2004
| | Posted on Tuesday, April 17, 2007 - 6:38 pm: | 
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Has anyone ever seen or used one of these antennas,it shows that the overall length is 27 feet 7 inches.Looks impressive , just wondering if anyone has ever used one and how well it preformed and at over 27 feet in length how well did it stay up in high winds?
Robert L. Spicer
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Tech808
Moderator
Username: Tech808
Post Number: 13517
Registered: 8-2002
| | Posted on Tuesday, April 17, 2007 - 6:57 pm: |
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http://www.copperelectronics.com/cgi-bin/discus4/board-auth.cgi?file=/29/46621.html
http://www.copperelectronics.com/cgi-bin/discus4/board-auth.cgi?file=/29/71355.html
And Look to the LEFT of the Forum here and you will see:
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Edit Profile
Or CLICK on Search and type in: Avanti sigma 4 AV 174
and start reading.
Hope this helps,
Lon ~ Tech808 ~ N9CEF
CEF#808 ~ CEF HAM#33 ~ CVC#002
10-10 #61493 ~ 10-10 VP#2688
Tech808@copperelectronics.com
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Road_warrior
Senior Member
Username: Road_warrior
Post Number: 2082
Registered: 7-2004
| | Posted on Wednesday, April 18, 2007 - 10:29 am: |
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I personally used the Sigma 4 look-a-like antenna years ago. Doesn't handle winds, snow and ice very well. Quality wasn't very good. Had trouble with SWRS moving all the time.
It replaced a A-99. Out did A-99 by alittle bit. |
Marconi
Advanced Member
Username: Marconi
Post Number: 697
Registered: 11-2001
| | Posted on Thursday, April 19, 2007 - 10:10 am: |
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Robert, I have one of the original 3 element Sigma IV's and it is a great antenna. It is also probably much stronger than the knockoff sold today.
It does have a problem in design however. It uses a soldered on wire nut to attach the very long gamma rod to the SO-239 bracket at the hub. The wind works on this antenna pretty good and I am sure it puts a lot of stress on this solder joint and fitting. I have had to re-solder mine many times until if re-did the gamma connection.
Maybe that is why RW had SWR problems, the solder joint was cold and it moved in and out of short.
The resonant length setting of this antenna is crytical. I think it comes with enough material to tune between 25-29 mHz. I understand that the documentation is terrible and may not give you details about the overall length. The tappered tubing for my antenna was dempled on every section. This pre-set the section length of all 9 sections of the radiator and that was pre-marked to tune for the middle of CB. Even the location of the gamma rod tap point was dimple marked with 1/2" for adjustment only. My antenna assembled is a fraction less than 31' tall. I understand some have complained that they are difficult to tune because of the lack of good documentation. |
Maxgain
Junior Member
Username: Maxgain
Post Number: 28
Registered: 3-2007
| | Posted on Thursday, April 19, 2007 - 5:14 pm: |
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It' a half wave J-pole, with about 2 db gain. )(over a quarter wave ground plane) |
Tech833
Moderator
Username: Tech833
Post Number: 1663
Registered: 8-2002
| | Posted on Friday, April 20, 2007 - 10:59 am: |
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It's not a 1/2 wave J-pole. Get your tape measure on one for verification of my statement. |
Road_warrior
Senior Member
Username: Road_warrior
Post Number: 2091
Registered: 7-2004
| | Posted on Friday, April 20, 2007 - 8:14 pm: |
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I was always bringing that Sigma 4 copy down to re-adjust Swrs...lol.. |
Marconi
Advanced Member
Username: Marconi
Post Number: 698
Registered: 11-2001
| | Posted on Friday, April 20, 2007 - 8:56 pm: |
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Was there a little wire nut soldered to the back of the SO-239 that the gamma bolted to in order to make that connection?
Since all the gamma adjustments are fixed when tightned, what do you think was causing your antenna to get out of tune unless something was moving around?
Did the bottom section have ribs to reinforce the tubing? |
Road_warrior
Senior Member
Username: Road_warrior
Post Number: 2094
Registered: 7-2004
| | Posted on Friday, April 20, 2007 - 11:25 pm: |
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It got really cold out the year i had it up and the bottom section (hoop) aluminum split, cracked.
Winds broke the top section off.
I don't remember any ribs for reinforcing.
Not sure what was causing it to detune. Back then that was my first experience with a gamma match type antenna. So, long ago to remember. |
