One other point to make that has not been stressed. Field Day rules allow up
to 1000 foot diameter for all operations. (984 feet to be exact. They specify
300 meters or 1000 feet diameter)
That means if you use good coax and tuned antennas, you can spread the antennas
over a wide distance. Putting the antennas on the same tower or pole is likely
to cause interference.
Generally the rule of thumb is coax will have higher losses if the SWR mismatch
is bad, but you can use a very long run of coax to separate your antennas.
Many field days also spread out power and grounds, so that noise on one is not
radiated to the other, and battery operation is a really good way to isolate DC
power from each other.
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