| Author |
Message |
    
Cornfed
Junior Member
Username: Cornfed
Post Number: 40
Registered: 2-2004
| | Posted on Wednesday, March 17, 2004 - 6:52 am: | 
|
have my a99 on a tripod with 8ft mast over a metal roof building.....any installation considerations concerning this type of installation would be helpful....does the metal roof affect my radiation patern? can i use the roof as a ground plane? how would i configure this application?
any thoughts would be appreciated.
73 from the cornfield
mark |
Ozzie
Intermediate Member
Username: Ozzie
Post Number: 127
Registered: 11-2003
| | Posted on Wednesday, March 17, 2004 - 9:22 am: |
|
Leave it as is. At 8ft or a quarterwave the roof will already be acting as ground. Of course you could try it at 16ft higher than the roof. |
Cornfed
Junior Member
Username: Cornfed
Post Number: 43
Registered: 2-2004
| | Posted on Wednesday, March 17, 2004 - 10:58 pm: |
|
would 16 ft lower my angle of radiation...ya know,,enuff to make a difference? |
Bigbob
Senior Member
Username: Bigbob
Post Number: 1768
Registered: 12-2001
| | Posted on Thursday, March 18, 2004 - 5:23 am: |
|
Just try it as is and check reports from other stations.Unless you are a perfectionist and like hard work,then check to see if roof runs 36 feet in all directions from base,if it does then just use 36 foot mast,if not then fabricate stiff radials to extend out from edge of roof to 36 feet from base at 8 points equally spaced and use a 36 foot mast,you see where this is going,I suggest to just use as is,but that's me,I've been trying to live down a rep. for making my property a laughing stock by having so many ugly looking gizmos out for all to see,but then like I said thats my dilemma,you remember the movie Absentminded Professor?So think carefully,you can have a nice clean looking station as is or you can look for that last s-unit and become the but of everyones jokes,just some thoughts,I really hope this helps you decide.Bigbob |
Ozzie
Intermediate Member
Username: Ozzie
Post Number: 133
Registered: 11-2003
| | Posted on Thursday, March 18, 2004 - 9:16 am: |
|
Bigbob,
Shouldnt need any radials if the roof is at least 9sq feet in size. If it's not it's a small roof. Actually I have a friend here in town who has a roof mounted antenna (metal roof) that he uses from 10m down to 80m, good SWR, good radiated signal too. Heck we're less than a mile apart and he can hear signals that I barely know are there.
His antenna is a GAP antenna. |
Ozzie
Intermediate Member
Username: Ozzie
Post Number: 134
Registered: 11-2003
| | Posted on Thursday, March 18, 2004 - 9:17 am: |
|
Cornfed,
Thats a halfwave legnth and in most cases yes it would make a difference. |
Cm3885
Intermediate Member
Username: Cm3885
Post Number: 272
Registered: 12-2003
| | Posted on Thursday, March 18, 2004 - 1:09 pm: |
|
That sounds like a lot of work for an antenna up on the roof on a tripod.. Hey if you get out good and can hear i wouldnt worry about it at all...... |
Bigbob
Senior Member
Username: Bigbob
Post Number: 1772
Registered: 12-2001
| | Posted on Thursday, March 18, 2004 - 7:30 pm: |
|
The nine feet diameter(not square feet) refers to the counterpoise for a quarter wave radiator,I'm speaking of a ground radial system expressly to lower the takeoff angle of radiation,albeit this is above ground,but utilizing the large mass of metal below the antenna,diameter is more important here than square footage,36 feet is minimum. |
Ozzie
Intermediate Member
Username: Ozzie
Post Number: 137
Registered: 11-2003
| | Posted on Friday, March 19, 2004 - 12:19 pm: |
|
Try again. You hasve less thna that on a car. NOpe from tests done (while in RAAF) 9 square feet at 11m is the smallest groundplane area that will work effectively. Anything less is no good anything biger obviously helps but isnt really required. |
Radiodude
Intermediate Member
Username: Radiodude
Post Number: 394
Registered: 1-2002
| | Posted on Friday, March 19, 2004 - 11:07 pm: |
|
Throw the 99 away and hook the coax up to the roof then use a tuner and ..... chat away |
Bigbob
Senior Member
Username: Bigbob
Post Number: 1775
Registered: 12-2001
| | Posted on Friday, March 19, 2004 - 11:27 pm: |
|
Ground planes use folded radiators why not folded ground planes,I'm talking about improving the ground conductivity,but in this case it is above ground.You are talking oranges and I'm talking apples,there is no comparison,the ground plane for a 5/8ths or 1/2 wave is used for a completely different purpose than a 1/4 wave,the stick utilizes it to lower it's angle of radiation,1/4 wave uses it to work at all.That's what I'm saying,and that's all I'm going to say. |
Crafter
Advanced Member
Username: Crafter
Post Number: 982
Registered: 12-2002
| | Posted on Saturday, March 20, 2004 - 9:19 am: |
|
If we get the lowest angle or radiation possible do we win! Wonder if we could get sky miles? |
Ozzie
Intermediate Member
Username: Ozzie
Post Number: 140
Registered: 11-2003
| | Posted on Saturday, March 20, 2004 - 9:36 am: |
|
Bare in mind the A-99 is designed not to require a groundplane too.. |
Bigbob
Senior Member
Username: Bigbob
Post Number: 1778
Registered: 12-2001
| | Posted on Saturday, March 20, 2004 - 10:06 am: |
|
You know who,I'm with you,gone. |
