Base Using a decommissioned magmount for base st

[Limeybastard]

Was wondering if one could use a Wilson magmount ontop of a chimney cap if it were steel. Also would adding extending coax from the supplied 18' to approx 100' be of any issue?

I live on an HOA, thus thinking a magmount on thre chimney cap area would be less obvious to the eye and easied fhan going up an oak tree.

 

[binrat]

Personally, I would do a bigger counterpoise.

 

[M0GVZ]

Was wondering if one could use a Wilson magmount ontop of a chimney cap if it were steel. Also would adding extending coax from the supplied 18' to approx 100' be of any issue?

Yes you can but the groundplane would be the horizontal surface of the chimney cap which is far from enough and extending the coax to 100ft would definitely cause an issue as your coax would be the RF ground. Now normally this is a bad thing as it means your coax is forming part of the antenna RF ground but being aware that it does you can actually sometimes make it work in your favour and this is one of those times.

So here's how we're going to turn what is normally a massive no-no into a benefit for you by turning the coax into a quarter wave 9ft antenna radial and effectively turn your Wilson into a vertical dipole. What you'd need to do is make a damned good RF choke in the magmount coax starting 9ft from the magmount so that only the first 9ft of the coax forms part of the antenna. My personal choice would be to get hold of a FT240-61 ferrite toroid from and wrap 8 turns of the coax around that or even do that once then just after do it again if your coax was long enough to double up.

http://www.amidoncorp.com/ft-240-61/

Now if you don't want to do that then wrap 5 turns of the magmount coax around a 4.25" tube (don't double the turns as any change in the number of turns or the diameter of the coil alters its tuning and therefore its choking on 27MHz) but as I said, you want that to be starting at 9ft from the magmount.

Et-voila, you've turned the outside of the first 9ft of the coax braid into a 9ft radial for your antenna and you've choked off any RF from the rest of the coax to your rig.

Beware though this has limitations. You don't want to be using a load of power, certainly not more than 100W.