One of the significant problems with spring and summer DXing is the threat of lightning. I have made something which significantly reduces that threat.

I bought two large ferrite rods for experimenting some time back. What I did was set one vertically, which has minimum pickup of signals in itself. This is connected to the antenna coax. Another identical rod was positioned parallel to it, a couple inches away. This was connected to the receiver. The mutual coupling beween the two allows significant signal to be passed between them. In practice, I cannot see much difference in S-Meter level between this arrangement and a direct connection to the receiver. Since they are separated by about 2", the chance of a lightning strike jumping that gap is very minimal. Kind of like an isolation transformer.

One problem remains of the lightning strike generating a very intense wideband RF signal. A gas suppressor such as the Alpha Delta ATT3G50U or Diamond CA35RS should clamp incoming RF to a safe level. This is put in the coax leading from the antenna.

A couple of side benefits.. I notice conducted noise has dropped a significant amount, though noise from in the house is heard. Second is that it would be possible to put one rod (waterproofed, of course) outside and the other inside. The signal ought to pass through a normal wood wall just fine. Great for temporary hookups without drilling holes.

The two ferrite rods are about 20" long, though smaller ones would no doubt work fine. These have five turns of #14 wire connected to an SO239 jack. There is a ferrite choke between the rod and the jack. This provides a common mode rejection and effectively balances the connection.

This particular ferrite rod type works from below 100KHz up to the 80m ham band, slowly rolling off above that.

Hope it proves useful..

23 May 2007