On 27/11/2014 01:04, Ross Archer wrote :

On your roof antenna, is there any kind of transformer/balun between the antenna wire + ground and the lead in wire/coax/ladder line?

There's something tricky about coax you probably know, because you grounded your antenna.

People often think that coax is a magic noise cure because the shield prevents signals from getting into the center conductor from the outside. But there's something very tricky that happens because signals can travel along the OUTSIDE of your shield just like any hunk of metal.
Noise which hops on the outside of your coax in the shack can be conducted outside to the vicinity of your antenna, where the antenna "legitimately" picks it up and sends it down across both the inside of the shield AND your center conductor just like any other signal your antenna picked up. Then the noise you tried so hard to eliminate is still making it into your gear.

So grounding, especially near the antenna, is important. As you knew but for the benefit of anyone who didn't

-- ross AF6BV



Hello Ross

Yes it is grounded AND I use a home-made balun between the antenna wire
and the coax inside the house. (Equivalent to circuit C as shown here :
http://www.dxing.info/equipment/impe...er_bryant2.doc)

Certainely far from perfect, but so far it has the best signal/noise
ratio in my place, better than the commercial antennas I mentioned earlier.

Charly