OCF antennas are very convenient as they will allow multiple bands of operation with a simple wire antenna which is fed off center with a 4:1 OCF Current balun with built in feed line choke,
RFI/EMI Solutions from KHz to GHz
The simplest, most cost effective DC power cord noise filter is a ferrite ring installed as shown in the picture (at the radio/device DC input) to stop DC feedback radiation back into the DC power line or into the radio/appliance to suppress common mode power line noise current on the DC power cord or to suppress common mode noise present on the power lines from degrading the performance of the attached device.
These chokes are cheap, easy solution for RFI issues. Just replace your existing power cord with these prewound cables and enjoy interference free operation.