HF and VHF antenna proximity

[Paul Elliott]

Originally Posted by senormechanico

OT, Am I correct in my calculation that a 2.4 gHz Wi Fi antenna on opposite sides of the mast (about 9 inches apart) from a VHF antenna is not going to be affected?
What about the VHF antenna?



Thanks,
Steve

The WiFi antenna is still in the near-field of the VHF antenna, and so sill be exposed to somewhat high levels of RF. But the frequencies are again so far removed that I doubt there will be an issue.

I am assuming that your WiFi antenna is actually a full WiFi transceiver, with ethernet providing the data and power. Even in this case the electronics should be shielded enough to eliminate any problems. You may need to put a ferrite choke on the ethernet cable, but I doubt it.

Even though there is the mast between the two antennas, the VHF antenna will still "see" the close-by WiFi antenna (The VHF wavelengths are much longer than the mast diameter), but I doubt that there will be any significant interaction with respect to antenna tuning or interference.

[senormechanico]

Both antennas are at the masthead. Does that make a difference?
I have not seen any problems, although only use them one at a time.
Would either cause directionality problems?

[Paul Elliott]

Originally Posted by senormechanico

Both antennas are at the masthead. Does that make a difference?
I have not seen any problems, although only use them one at a time.
Would either cause directionality problems?

I seriously doubt it. The WiFi antenna is substantially shorter than what would be needed as a directional element. Perhaps too close for that as well -- the distance needs to be around 28 cm for a director or 46 cm for a reflector, and the length still isn't right. It might cause some slight resonant frequency detuning, but I don't think enough to be noticed. By the same principle, the VHF antenna dimensions are way too long and distant to act as a directional element for the WiFi antenna. I think it's all OK.