Antenna requires direct grounding

[prcguy]

Do you really need to peel/tear off the bottom of the mag mount (even if it's just a thin aluminum sheet like on Larsen mag mounts) for the adhesive copper sheet to produce a better vehicle ground plane? Or can you just stick a circle of copper sheeting to the existing thin bottom cover and get the same benefit mimicking a permanent mount?

I peel off the original plastic sheet and replace with self adhesive copper sheet so the mag mount body conducts to the copper foil which greatly increases capacitance to the vehicle body.

 

[merlin]

Do you really need to peel/tear off the bottom of the mag mount (even if it's just a thin aluminum sheet like on Larsen mag mounts) for the adhesive copper sheet to produce a better vehicle ground plane? Or can you just stick a circle of copper sheeting to the existing thin bottom cover and get the same benefit mimicking a permanent mount?

No, you can leave the protective sheet intact. When stuck on like a vehicle roof, the capacitance is like a short to RF

 

[merlin]

I peel off the original plastic sheet and replace with self adhesive copper sheet so the mag mount body conducts to the copper foil which greatly increases capacitance to the vehicle body.

I think if you measured it, there would not be a lot of difference

 

[cbehr91]

I've noticed the older Larsen mag mount have what seems to be a piece of aluminum sheet on the bottom of the magnet as opposed to a thin plastic sheet on newer ones.

 

[nd5y]

I've noticed the older Larsen mag mount have what seems to be a piece of aluminum sheet on the bottom of the magnet as opposed to a thin plastic sheet on newer ones.

I would have to go look at mine but I think all they did was change from transparent to white plastic film over the aluminum.

 

[prcguy]

I think if you measured it, there would not be a lot of difference

At VHF/UHF/800 not a lot but its about as close as you can get to a hard mounted NMO. On HF I use an 8.5X11" sheet of refrigerator magnet material and cover that with self adhesive copper sheet then bond that to a mag mount, usually a triple. In before and after tests on 40 through 10m its night and day difference where on air and antenna analyzer measurements show the same as a grounded mounted ball mount . Without the magnetic sheet its a squirrely RF hot piece of crap on the lower bands.

 

[cbehr91]

I would have to go look at mine but I think all they did was change from transparent to white plastic film over the aluminum.

I have a probably 10 year old round Larsen mount and there's just a layer of plastic film under the magnet.

 

[K6GBW]

Is that a Comet B10NMO? If so, what's the SWR on UHF, or are you even using it for UHF?