What to use for ground plane

Status
Not open for further replies.

obrien135

Member
Joined
Feb 4, 2012
Messages
26
I was using a 1/4 wave whip antenna with my10M rig, but with th new vehicle my wife doesn't want any scratched on the roof (it's a mag mount). I got better reception on my balcony with a different antenna. I was wondering if I could use the whip on the balcony with tin foil as the ground plane 2nd part of dipole. Would that be possible?
 

ka3jjz

Wiki Admin Emeritus
Joined
Jul 22, 2002
Messages
23,696
Location
Bowie, Md.
Tin foil won't work because it's non-ferrous. For the mag mount to capcitively couple to create the ground, you will need something ferrous about 8 foot square or so (that's approximately 1/4 wave on 10).

Mike
 

prcguy

Member
Joined
Jun 30, 2006
Messages
10,976
Location
So Cal - Richardson, TX - Tewksbury, MA
You could go with a tuned single wire attached to the ground of your mag mount 1/4 wave and make it a dipole but for a ground plane you would need at least two wires running opposite directions and preferably tuned 1/4 wavelength each.

You can use foil or anything conductive. If you were referring to aluminum cooking foil, that is very wide and would make a better ground plane than a wire of the same length. What is your balcony made of? Do you have a metal railing that could be used as a ground plane or counterpoise?
prcguy


I was using a 1/4 wave whip antenna with my10M rig, but with th new vehicle my wife doesn't want any scratched on the roof (it's a mag mount). I got better reception on my balcony with a different antenna. I was wondering if I could use the whip on the balcony with tin foil as the ground plane 2nd part of dipole. Would that be possible?
 

prcguy

Member
Joined
Jun 30, 2006
Messages
10,976
Location
So Cal - Richardson, TX - Tewksbury, MA
The magnet will not stick to tin or aluminum foil but there is no difference between aluminum, tin, steel, copper, titanium. etc, as far as using it for a ground plane. At CB or 10m frequencies a typical magnet mount is not big enough to effectively couple the ground side of the mount to the sheet metal under it.

For the OPs purposes of using the mag mount at home on a balcony he is best off making a direct connection from the ground side of the mount to whatever counterpoise he provides.
prcguy

Tin foil won't work because it's non-ferrous. For the mag mount to capcitively couple to create the ground, you will need something ferrous about 8 foot square or so (that's approximately 1/4 wave on 10).

Mike
 

Rred

Member
Joined
Nov 21, 2014
Messages
830
Mike-
As prcguy said, ferrous doesn't matter except for keeping the magnet in one place, and there are other ways to do that. Like, save the top of a large can, put that under the aluminum foil, and let the magnet clamp down on it. That will work.
What matters is that the counterpoise is a quarter-wavelength long in at least two directions out from that 1/4 wave antenna.
A couple (more would be better) of 1/4 wavelength pieces of copper wire from the hardware store, soldered to that same can lid (or a metal plate) and then used without the foil would probably be neater, cleaner, better way to go for repeated use.
 

obrien135

Member
Joined
Feb 4, 2012
Messages
26
THanks foralll of those suggestions fellows. I will try a few of them and make a post about how it worked out.
 

Ed_Seedhouse

Member
Premium Subscriber
Joined
Jul 10, 2010
Messages
572
Location
Victoria B.C. Canada
Tin foil won't work because it's non-ferrous. For the mag mount to capcitively couple to create the ground, you will need something ferrous about 8 foot square or so (that's approximately 1/4 wave on 10).

Mike
Not true. The only advantage of a ferrous metal ground plane is that the magnet holds it in place so it is more secure. This has *nothing* to do with the ground plane. The electrical coupling to the ground plane is by capacitance, not via the magnet (which is often ceramic since ceramic magnets are cheaper). Anything that will carry an electric current with reasonable efficiency will do fine as a ground plane.
 

jonwienke

More Info Coming Soon!
Premium Subscriber
Joined
Jul 18, 2014
Messages
13,314
Location
VA
all you need is a 1/4 wave counterpoise wire
This is a stupid suggestion, as it will try to refashion a 1/4-wave ground plane antenna into a 1/2-wave dipole.

You'll have impedance matching problems, as well as all of the issues you get driving a balanced antenna with an unbalanced feedline--high minimum SWR and RF radiating from the coax. And if the counterpoise wire isn't on the same axis as the whip, you'll have a weird asymmetric radiation pattern.

If your balcony is the top floor, just put up a base antenna designed for that purpose. It will work far better than a cobbled mag mount monstrosity. If not, a dipole has to be twice as tall as a ground plane antenna (1/2-wave vs 1/4-wave) and is therefore less suited to limited space situations.

A good ground plane doesn't have to be ferrous metal, it just has to be conductive, and preferably extend 1/4-wave or so in all directions from the whip. But if it's not magnetic, you'll need some other way to mount the whip, which goes back to just getting a base antenna anyway.
 

1hardyanimal

Member
Joined
Mar 11, 2017
Messages
34
Location
Durand,Mi.
"all you need is a 1/4 wave counterpoise wire" as MOTEX said or I have also in a pinch use a piece of metal garage shelving (after having the kids clear all of the paint cans off) from my garage. Only thing is as mentioned I think above, your rig is not "grounded" per say to the proverbial ground plane as it is in your vehicle, so perhaps their might be some issues of sorts to be had their?
 
Status
Not open for further replies.
Top