| Author |
Message |
    
Mikefromms
Intermediate Member
Username: Mikefromms
Post Number: 194
Registered: 6-2003
| | Posted on Tuesday, June 08, 2004 - 6:00 pm: | 
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I've really been paying attention to how my receive signals vary in my mobile in different spots. Lately, it has come to my attention that when I go over a bridge that has open air underneath and long distance to the earth beneath the signal goes up about 2 s-units. Pretty interesting, huh? Anyone else ever notice this, and why do you suppose it happens? Does the takeoff angle on the antenna response to the distance below the bridge and become lower? Just thinking out loud. You have to agree I have come up with an original post this time. he..he..
mikefromms |
Ca346
Advanced Member
Username: Ca346
Post Number: 816
Registered: 8-2003
| | Posted on Wednesday, June 09, 2004 - 12:27 am: |
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Mike you have really got to get a life..... It must be all that steel being used as a super ground plane??? |
Mikefromms
Intermediate Member
Username: Mikefromms
Post Number: 196
Registered: 6-2003
| | Posted on Wednesday, June 09, 2004 - 4:57 pm: |
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That's what a friend of mine said on the cb last night. Get a life? I am one busy dude. But I take time to smell the roses. I observe little things, like towers, antennas, and bridges that make your signal jump up, LOL.
mikefromms |
Triplecguy
Intermediate Member
Username: Triplecguy
Post Number: 159
Registered: 12-2001
| | Posted on Wednesday, June 09, 2004 - 5:33 pm: |
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DOn't crucify me if I am wrong, but I am relitively sure that it is the reinforcing steel or rebar in the concrete that makes up the decking under the asphalt, acting a reflector. I have really noticed it on 2m and 440 as well. I don't know if the open air under neat is a factor, but why would their be a bridge if their wasn't open air under it anyway? I don't know, but yes you are noticing something that is definately improving signals. |
Lowpowerhal
Intermediate Member
Username: Lowpowerhal
Post Number: 249
Registered: 7-2003
| | Posted on Wednesday, June 09, 2004 - 7:20 pm: |
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Mikefromms and Triplecguy ? When you go over the bridges is it ground or water underneath? a lot of times a bridge will be built to higher elavation also.Intresting question, I will take notice from now on. |
Tech8541
Moderator
Username: Tech8541
Post Number: 217
Registered: 12-2003
| | Posted on Wednesday, June 09, 2004 - 11:20 pm: |
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i think lowpower hit the nail on the head. i picked up in the 1st post here that you said the ground was far beneath the bridge, meaning you are higher up in the air.
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Mikefromms
Intermediate Member
Username: Mikefromms
Post Number: 198
Registered: 6-2003
| | Posted on Thursday, June 10, 2004 - 7:41 am: |
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Yes, there is air underneath (he..he) and distance below the bridge. I think it is interesting how the signal reacts on the bridge. Now, this isn't the Sanfrancisco Bridge or a even a large bridge, this is a small county bridge.
mikefrommms |
Rob5mike
Intermediate Member
Username: Rob5mike
Post Number: 119
Registered: 7-2002
| | Posted on Thursday, June 10, 2004 - 11:34 pm: |
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Mike I have noticed this for years and have wondered why? Triplecguy,Most bridges I have crossed have had open air under them too!
Mike |
Mikefromms
Intermediate Member
Username: Mikefromms
Post Number: 200
Registered: 6-2003
| | Posted on Friday, June 11, 2004 - 5:23 pm: |
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Maybe build a house over a bridge area to increase output and receive on a closed road. Now that's taking a hobby too far. Or maybe we could give new meaning to "going parking."....
nOt!
mikefromms |
Tech833
Moderator
Username: Tech833
Post Number: 739
Registered: 8-2002
| | Posted on Monday, June 14, 2004 - 1:34 pm: |
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The metal and concrete in the bridge makes a good ground plane and improves your antenna's effectiveness on receive. With air underneath, if the bridge is narrow enough, your transmit takeoff angle would be improved in the directions to the sides of your car. |
