Topband: Common-mode noise/long buried feedline runs

[Tom Rauch]

> OK; best to suppress common-mode at the feed-point; agree.
> What about long feedline runs...buried? My 80 , 160 xmit 
> antenna's and
> Beverages each have at least 300 foot coaxial feedline 
> runs, buried about an
> inch below ground. Should I ...also.... suppress at the 
> shack end and in
> what recommended manner?

You only need to suppress where there is a less-than-perfect 
shield connection or the potential for one. That long cable 
run can be buried or ten feet above ground and it won't 
matter.

Many of my cable runs are over 1/2 mile and the cables are 
dead when the antennas are disconnected. They are partially 
buried but have at least 1000 feet above ground, sometimes 
several feet above ground where they cross a creek or road.

If you think you might get a bad connection on the shield at 
the shack then you might consider a common mode choke in the 
shack. Or if the run is short  and you think noise from the 
shack might be conducted outside to the area of the 
antennas, then you might want to suppress common mode 
leaving the shack AFTER the cables pass through the entrance 
grounding panel (we all are safe and have them, right?) on 
the way out to the antennas.

I choke the shields of my phono plug connections with beads, 
but that is because the shield grounds are sometimes less 
than perfect with the friction fit connection.

73 Tom