| Author |
Message |
    
Danusee
Member
Username: Danusee
Post Number: 79
Registered: 10-2004
| | Posted on Friday, August 23, 2013 - 9:00 pm: | 
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It is just a thought. If a person added length to the A99 would it tune out at the 3/4 wave length? I think I have the material to do it. Also I could tie off about 3/4 the way up with nylon string. If that worked it would be one bad antenna. Have you ever heard of or tried this? Please give me your opinion. |
Dale
Senior Member
Username: Dale
Post Number: 1954
Registered: 12-2002
| | Posted on Sunday, August 25, 2013 - 9:14 am: |
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adding lenth will change the resonance of the
antenna. or making it tune for 12 meters.
now you MIGHT be able to put a 102 whip on
top then you,ll HAVE to retune the rings on the bottom then maybe it might work.
dale/a.k.a.hotrod
cef426
cvc#64
454 [dx numbers]
38lsb
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Danusee
Member
Username: Danusee
Post Number: 80
Registered: 10-2004
| | Posted on Monday, August 26, 2013 - 6:32 am: |
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I read where on a 3/4 wave antenna the feed point will be out of phase. Also above a .64 wave length the pattern becomes distorted. I am off work for a few days and was looking for a project. Probably not this one. I have a Imax 2000. The best I have been able to do is one 18' radial (electric fence wire to nylon rope) in the directon I talk. Man it liked that! I get almost no swr movement on my needle over such a long range you would think my meter was broke. My tuning ring is about 3/4 the way up. |
Tech833
Moderator
Username: Tech833
Post Number: 2263
Registered: 8-2002
| | Posted on Tuesday, August 27, 2013 - 9:58 pm: |
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The A99 is already a 3/4 wave antenna (electrically) with the first 1/4 wave taken up in the coil at the base.
A full length 3/4 wave antenna will cancel 1/2 of it's own signal since the first and second quarter waves of the antenna are at opposing phase angles. The second and third 1/4 wave lengths are at correct angles. That means, a full length 3/4 wave antenna will have half the gain of a half wave antenna. In essence, 3 dB LESS gain than an unmodified A99.
See the "Antron 99 Exposed" article for the schematic and pictures of the antenna from the inside.
Your radio 'Mythbuster' since 1998
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Danusee
Member
Username: Danusee
Post Number: 81
Registered: 10-2004
| | Posted on Wednesday, August 28, 2013 - 9:08 pm: |
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Well that was interesting. Thanks Tech833. |
