At the meeting last night, we were talking about adding an antenna to the trailer for packet work. Having two radios in close proximity on the same band can cause interference – this can be reduced by isolating the antennas.

Vertical separation of the antennas provides significantly more isolation than horizontal separation.

Attached is a one pager showing isolation expectation for various frequencies and distances, both horizontal and vertical. These numbers represent center to center separation of dipole antennas.

Review the numbers:
> 30’ vertical= horizontal distance ~400’. (54 dB)
> 20’ vertical = horizontal distance ~300’. (46 dB)
> 10’ vertical = horizontal distance ~50’. (35 dB)

How to read the charts? Go to the frequency and distances on the vertical separation to find the dB isolation. Now look at that same frequency and dB isolation to see the matching horizontal distance separation.

Dave, N9KMY