In our contest station we installed a HI-Z 4-8 for reception in 80 and 160
meters. 80 meters is working wonderful, in 160 we have a problem. Our 80
meter 1/4 w vertical is located at about 400 feet from the center of the
Hi-Z. When we transmit in 80 with 1000 watts, we have a strong interference
in 160.
I have done all I could imagine to solve it, like blocking broadcast
interference with a low pass filter, blocking 3.5 MHz in the 160 meters
preamp input with a 160m bandpass filter, shielding the 160 meter preamp
with grounded aluminum foil and adding 1.5 mH RF chokes in the DC line and
.5 mF decoupling capacitors from this DC line to ground. Situation improved
a lot but still I have about S7 interference in the 160 m receiver, I
disconnected all the vertical elements in the system to check if there was
RF leaking on power lines and coaxial cables but there is none...
Could it be that the design distance to the 80m vertical shall be much
longer? or shall I try tuning the vertical elements to resonate on 160? I
have not found any reference to it in all the HI-Z documentation.
Anybody experienced this problem before?
Appreciate any help,
--
73,
Jim, HK1N
President DXARC - DX Colombia Amateur Radio Club
*Malpe**lo Isl. HK0TU 1990 & H**K0NA 2012 Team Member/ hk0na.com *
Araucaria DX Group
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