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Post by Boomer on Nov 17, 2017 5:00:09 GMT
I was having a discussion with a radio friend.. With a 3 meter antenna system on a roof top, would there be any difference in radiated power if the same length of radial was run on top of the roof, or right under the roof in the attic?
That would be for the usual wooden roof and shingles, and with the idea that some might have a vent or skylight where radials could be run into and kept out of sight.
Boomer
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Post by Deleted on Nov 17, 2017 13:33:44 GMT
Elevated Radials
It is my understanding that with a vertical antenna the radials need to be exactly horizontal to be most effective.
Mounting poles on the outer boundaries of the building to support horizontal radials is the way to go.
With a normally tilted A-frame roof the choice would be to lay the radials on the attic floor which would require some amount of ground lead with the vertical antenna on the peak of the arched roof.
Probably the ground lead would increase the field strength and I consider anything "below the roof" to be "in the ground", although other engineers hate me for saying that.
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Post by Druid Hills Radio on Nov 17, 2017 16:30:26 GMT
Elevated RadialsIt is my understanding that with a vertical antenna the radials need to be exactly horizontal to be most effective. Mounting poles on the outer boundaries of the building to support horizontal radials is the way to go. With a normally tilted A-frame roof the choice would be to lay the radials on the attic floor which would require some amount of ground lead with the vertical antenna on the peak of the arched roof. Probably the ground lead would increase the field strength and I consider anything "below the roof" to be "in the ground", although other engineers hate me for saying that. DHR POKES HIS NOSE IN: Sloping the radials at 45 degrees varies the feed point impedance. |
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Post by Deleted on Nov 17, 2017 17:34:37 GMT
Sloping radials radiate, so would have to be considered part of the antenna.
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Post by station8 on Nov 17, 2017 19:24:31 GMT
Howdy all: Here's what I did.Two different test.
Note: range varried in test do to setup,tx used,etc.
Test 1
Using a rangemaster 1000 with a different gnd setup.
Tx was approx 6 foot of gnd level,about 10 feet from sea level.
1) I took 10 awg solid copper wire with insulation on it.
2) I soldered in a loop ( like a hula hoop ).
3) attached loop on the gnd terminal on the tx.
4) had the loop horizontal to the gnd.
5) loop was about 5 foot of gnd.
I saw good result in my test.
Test 2 Talking House 5.0
This is a vertical antenna/gnd test setup.
I also tested an antenna base at 9 feet in air and right below that I placed
The gnd wire 12awg at the same length of the ant.
The results where also good in the range.
In my conclusion as long as good construction ethic's are implemented
You can have above ground systems with very good results.
Happy trails
Station 8
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Post by Boomer on Nov 18, 2017 13:43:33 GMT
Station8, is that WLW's tower, it hit me that it kind of looks like it.
It's good to note the extra distance to the radials if they're under the roof, and the farther distance from the radiator, plus the extra length on the lead-in, and how it could change the tuning or field strength.
What I was thinking of with my friend was the interaction between radiator and the radials, with or without the intervening roof. I wondered, since surrounding objects like buildings and trees affect the 3 meter antenna easily, would the roof affect the interaction of the fields between the antenna and radials, if the radials were inside?
My intuition says antenna and ground in this setup should both be in the same open space. When I posed that question, my friend's reply was to think it would be fine to have indoor radials, because after all, many stations bury their radials in the soil under an antenna, but I thought there could be something more to it in the case of roof + radials, so I decided to ask you guys.
Station8, good tests, you've done a lot more than I have with Part-15 tests.
Boomer
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Post by station8 on Nov 18, 2017 17:25:04 GMT
Howdy all: I cant remember who ant it was but i like that style of antenna,
650 wsm uses the same tower as well.
Now try to answer your question on gnd radials inside a home, well that's
Can go either way do to I have done testing with it indoor and outdoor setup
With the same equipment / antenna /gnd system.
Again it all depends on your location,antenna,gnd,height,noise level,
Tx your using ( not all tx works the same ).
When I tested the rangmaster 1000 with original ant on a indoor/
Outdoor test they both worked fine but I did better in a house
When I did a drive test. I saw about a 1/4 mile range difference.
When I tested a range master with a new design antenna I built
I basically had the same range indoor and outdoor,but
Being outdoor it show slight more range then the indoor
Setup.
Here is just a couple of example that I did I tryed to keep
The setup exact to each other except the location and that
Was a 20 feet difference.
The only way you will know if it will work for you or not in your
Area is to experiment and try it out.
If you came to the ALPB meeting you can ask me questions
It would be a lot easier to talk then type and I could fill
Your head up allot do to my test where NOT computer software
Test but real world test!
Happy trails to you
Station 8
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Post by Deleted on Nov 28, 2017 16:36:17 GMT
Given a wooden roof with shingles there will be no difference between radials on top and radials in the attic and routed along the roof.
Adding radials might even decrease field strength compared grounding through the house AC wiring. I can analyze this given these parameters:
Grounding configuration without roof radials
Length and the number of roof radials
The slope of the radials
Dave
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