Google G3TXQ COMMON-MODE Dave WX7 G On Dec 6, 2012 1:40 PM, "Steve London" <[email protected]> wrote:
> My 160 meter shunt fed tower project is essentially done. However, I have > an issue with the 80 meter antennas hung off that tower. In a nutshell, the > current baluns (ferrite beads) feeding these antennas don't have enough > common mode impedance on 160 meters. They heat up, and the SWR of the shunt > fed tower changes as they heat up. > > After some reading, I think what I need are some RG8X toroid baluns, wound > on #31 ferrite material. If they are going to replace the existing bead > baluns, then they will need to be placed at the feedline/antenna junction. > However, if I want to completely isolate the 160 shunt fed tower from the > 80 meter feedlines, shouldn't I place the new baluns as close to the > tower-mounted antenna switch as possible, and leave the bead baluns in > place at the end of the feedline to choke off the 80 meter common mode > energy ? > > To add more complications for adding the RG8X toroid balun, my 80 meter > antennas are switchable 2 element wire beams, with each element fed with > 18' of RG-8. That dimension is critical, as it provides the proper amount > of capacitive reactance at the feedpoint to make the element a director. > > Comments ? > > 73, > Steve, N2IC > ______________________________**_________________ > Topband reflector - [email protected] > _______________________________________________ Topband reflector - [email protected]
