sharing antennas

[anneranch]

After observing Field Day "class" of more that common "3A" I like to learn more about
how SAME antenna , build for specific band , is being shared between TX operating
simultaneously between many operating modes - say CW, SSB , FT8 etc.
Does this sharing technology has an official name ?
( If I know it I can ask Mrs Google...)
Similarly - how to prevent UNWANTED interaction between DIFFERENT same band antennas.
(It was not much fun for GOTA newcomers to overcame interference from "BIG guns " )

 

[tweiss3]

There are a handful of ways to manage this.
'
1 antenna, multi-station: This is done with an HF multiplexer. LowBand Systems makes a handful of different options, like this one: Low Band Systems PB-TP200 Low Band Systems HF Multiplexers | DX Engineering

Multi-antenna, multi-station, same or different bands: This is done a few ways. If using beam antennas on towers, its as simple as making sure the beams aren't pointed the same direction. If using other antennas, like inverted V, you orient them 90 degrees from each other in an attempt to create a null/polarization in the direction of the other one.

Multi-antenna, multi-station, same band. We did this scenario this year, we had two 40 meter dipoles. We put some separation between them, but they were inline, one was for CW, one for voice. On the CW station, we put a bandpass filter. On the SSB station, we used a tee, and added an open ended length of coax that put a 30db null of attenuation in the 3.5-3.65MHz range, which is a multiple of the 40m digital band, to help cancel out the CW station running on the other dipole.