| Author |
Message |
    
Mikefromms
Intermediate Member
Username: Mikefromms
Post Number: 485
Registered: 6-2003
| | Posted on Wednesday, March 02, 2005 - 11:16 pm: | 
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I helped a fellow cber today, along with 3 other cbers, install an Imax 2000 on top of a tower with the 12 ft long huge TV antenna beneath the Imax about 5 foot. The TV antenna also has a booster on it. After the instalation and a few radio checks, it became apparent that the antenna had some directional qualities. After talking it over and thinking over the air, we all decided that the TV antenna must be coupling with the Imax. What are your thoughts, anyone?
Mikefromms |
Inspector
Intermediate Member
Username: Inspector
Post Number: 133
Registered: 12-2001
| | Posted on Thursday, March 03, 2005 - 1:01 am: |
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The TV antenna could be closer to ground-potential than the I-max. This could make the TV antenna act like an artificial ground-plane for the I-max...and it's elongated shape, lends to the directionality of the radiated signal from the I-max. Get a field-strength meter and map-out your radiation patern. |
Racer_x
Member
Username: Racer_x
Post Number: 91
Registered: 2-2005
| | Posted on Friday, March 04, 2005 - 6:37 am: |
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It's possible that RF is making it's way down to the TV antenna and causing the pattern issue.
Did you make a coil out of the coax with 6-8 turns of coax taped together in a coil and then taped to the mast? |
Yankee
Intermediate Member
Username: Yankee
Post Number: 405
Registered: 7-2003
| | Posted on Friday, March 04, 2005 - 1:15 pm: |
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I've often wondered myself if my TV antenna being just below my IMAX-2000 didn't have something to do with my transmitting pattern doing very good to the north, but not as well in other directions. My TV antenna is aimed due north to pick up Oklahoma City stations. I remember reading some place that a ground plane antenna makes an electronic mirror image of it's self and causing the TV antenna to make it a directional pattern. I'm on a hill out in the open with no obstructions. |
Mikefromms
Advanced Member
Username: Mikefromms
Post Number: 506
Registered: 6-2003
| | Posted on Saturday, March 19, 2005 - 9:22 am: |
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I want to resurrect this subject for more comments. Do you think a tv antenna 5 feet below an Imax 2000 without gp/kit can change the pattern of the Imax antenna?
Mikefromms |
Hotwire
Intermediate Member
Username: Hotwire
Post Number: 202
Registered: 1-2005
| | Posted on Saturday, March 19, 2005 - 10:45 am: |
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I think it would. Think about mobile antennas. Depending on where it is mounted on the vehichle you get different patterns. |
Slim1
Member
Username: Slim1
Post Number: 85
Registered: 4-2002
| | Posted on Sunday, March 20, 2005 - 2:45 am: |
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Yep;for sure Mike. You guys already have the proof at hand. Just as Hotwire said about antenna
placement. Pretty cut & dry isn't it?
As far as the VHF/UHF antenna amp goes,that shouldn't have any relevance to the "plane" affect.BUT,the coil winding as RacerX makes reference to will help cut/reduce interference to that particular Tv's antenna reception on the TV
set it's hooked up to! Believe me it DOES help. I tried my A99 w/and w/out the coil winding and it was much better(TVI) w/the winding present than w/out it.
Slim CDX285 |
