[Top] [All Lists]

[TowerTalk] Field Day Interference

Subject: [TowerTalk] Field Day Interference
From: Dennis W0JX <>
Date: Thu, 3 Jul 2008 19:52:15 -0700 (PDT)
List-post: <">>
Thanks to Frank, W3LPL, for the great ideas to minimize interstation 
interference on Field Day. Our station, NI8G, worked W3AO on at least 2 bands.
We did not have the luxury of the large circle. Our three antennas consisted of 
an 80 meter dipole fed with open wire, a 40 meter dipole, a twenty meter ground 
plane, and a six meter beam. The antennas were within a 200 foot circle. Our 80 
and 40 meter dipoles met his "end to end" criteria.
We minimized interference on 40 and 20 with coaxial stubs. Second harmonic 
interference was minimized by using a 20 meter,1/4 wave line section at the 
output of the 40 meter station, followed with a shorted, 40 meter quarter-wave 
stub connected at the input of a Drake MN-2000 tuner. At the output of the 20 
meter station, an open, quarter-wave 40 meter stub was used to reduce 
fundamental overload energy. We had no noticeable interference between these 
stations, nor did the 80 meter CW station bother the 40 meter station. A 
Johnson, 275 watt Matchbox was used on 80 CW, plus the other bands as needed.
We did have a problem when the 20 meter station was operating BPSK. Its second 
harmonic created significant interference on 10 CW but we just asked the BPSK 
op to stop Cqing when we needed to finish a Q.
The biggest surprise was how well the center fed, 80 meter dipole worked, 
especially on 10 and 15 meters. It was up high, almost 60 feet at one end 
sloping down to about 40 feet at the other. If we could have only one antenna 
on Field Day, the open wire fed, 135 foot dipole would be it.
73, Dennis W0JX/NI8G 


TowerTalk mailing list

<Prev in Thread] Current Thread [Next in Thread>
  • [TowerTalk] Field Day Interference, Dennis W0JX <=