Contrary to your thoughts, this is not
the thread for a VHF radio
/ VHF radio
range / VHF antenna
/ VHF coax cable questions.
There are threads on these subjects, or you could simply start your own thread....it takes no more clicks of the mouse, doesn't take any more time, and doesn't cost any more money
(it's still free!). LOL
If you wish to look at VHF (and AIS) radio range and radio propagation, as well as details on cable loss (and why it usually will make no, to little, difference), have a look at these threads that deals directly with that.
Please read those threads, and you'll have a much better understanding of the systems and issues....(and, why being "sold" low-loss cabling is just a way to taking more of your money!)
And, then either start your own specific thread here, or ask questions in those threads that are on-point.
Until then, to be clear you haven't provided enough info to completely answer your question, but the quick, short answer is:
It's likely your friend either has some receive issues (possibly RFI), and/or you both have antenna
pattern issues, as you mentioned you have an AIS
antenna sitting next to your VHF antenna? (this is very bad engineering, and is discussed in detail in other threads, have a look....)
Again, this is not the thread for this discussion....HF radio is not VHF radio!
[But, I personally have a great deal of VHF comms experience....both engineering and real-world operations....it's just that this is not the place for that discussion.]