Need to replace my VHF antennas. Lighting stuck my Shakespeare Galaxy 5018 17’5” that is used for my primary VHF radio, both the antenna and radio must be replaced. My other antenna is a Shakespeare Classic 4018 19’2” used for my backup VHF radio. It is old and needs to be replaced. Here is my question: I am staying with a Galaxy 5018 for my primary, should I use a 5018 for my backup or stay with a 4018. One antenna is on the Starboard side and the other on the Port side of the boat. Can 2 antennas of the same length/height and 9db on a boat cause a problem.
I believe that as long as they are at least one wavelength away from each other there shouldn't be any interference between them.
I would also think that interferences - if any - should only materialize with both radios in TX, which I can't think why should ever happen.
We have dual 4018s on our Bert with no issues. Just installed dual 4018s (19'), 5309 (23') and a SSB 390 (23') on my buds Hatterass. No issues. But the big question; How far off shore do you wonder? IMO, every foot in height counts when your 30-40 miles from the horizon. All of those above VHF sticks are 9db, just height and price. Interesting, the 19 is cheaper than the 17. Shorter warranty. My last 4018's lasted over 17 years. Still worked fine, just looked like crud.
Handy LOS / radio horizon calculator: https://www.everythingrf.com/rf-calculators/line-of-sight-calculator
