800MHz Ground Plane Radials

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dwh367

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A friend of mine is welding 4 3" inch long radials to the corners of a metal dash light bracket that I'm using for my magnetic mount 800MHz cell antenna. I have it mounted above an aluminum awning outside and I use it to monitor the new statewide trunking system here in Indiana. Can the radials be left straight out or do they need to be bent to a certain angle to acheive the best performance?

Thanks,
David H.
 

DaveH

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Ottawa, Ont.
Hey another Dave H....cool!

Officially, the radials of a ground plane antenna should be bent
down at about 45 degress. The impedence is around 35 ohms out
straight, and it rises to around 50 ohms bent down, but this is not
too much to worry about for scanner operation. I think bending them
down lowers the "radiation angle", which is generally better. You
could try it both ways.

Dave
 

ke5lvt

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plaquemine la
while the advice is very good and correct, you dont need a ground plain for an antenna that is not used for transmit. how ever it will not hurt at all.
 
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N_Jay

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MINDSHOCKER said:
while the advice is very good and correct, you dont need a ground plain for an antenna that is not used for transmit. how ever it will not hurt at all.
Unless designed with its own ground radiator (like an elevated feed antenna) a vertical antenna NEEDS a ground plane.
 

dwh367

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Owensboro, KY (Daviess County)
Update To Original Post

After reinstalling the bracket with ground plane radials attached and bent at a 45 degree angle, I did notice a slight improvement but nothing of major proporations. I was able to pull in one more distant tower strong enough for it trunk. It also is trying to pick up an additional couple of towers but the control channel signal strength is just too weak for the scanner to decode it. Thanks to everyone who gave me their input concerning this experiment.

David H.
 

ke5lvt

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plaquemine la
just an fyi some antennas do come with a built in ground plane (elevated feed). these antennas are used for cars or houses that have no ground plane of their own. like i said it is not needed but would not hurt.
 
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N_Jay

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MINDSHOCKER said:
just an fyi some antennas do come with a built in ground plane (elevated feed). these antennas are used for cars or houses that have no ground plane of their own. like i said it is not needed but would not hurt.
Nor do any good.
 

kb2vxa

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Hi DWH and all,

You've done all you can do under the circumstances, now leave it alone. Please ignore the radial vs. no radial debate, the no radial side needs to learn a bit of antenna theory. BTW, I'm using the same setup only my antenna is a trunk lip mount, makes no difference, it's still a groundplane.
 
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