Ajy network geeks on here? What does your setup look like?

[Daverw]

Just to clarify, LMR 400 very good spec cable, but its low loss, not no loss

 

[wonkywinch]

Just to clarify, LMR 400 very good spec cable, but its low loss, not no loss

Even it has losses of 0.23db/m, 20m will introduce a 4.6db loss so you'll lose two thirds of your signal down that coax.

Better solution is to put the amp at the top of the mast but that comes with the added complication of feeding it power and access to the sim card. Remember those little TV booster amps we used to put in our loft?

No such thing as "no loss" cable. In my last few house projects, I addressed this by putting a distribution amp in the roof space near to the antennas (satellite dish, FM, DAB & TV) then feeding the rooms individually from the distribution amp. The people who fitted the electronics to my boat (prior to my owning it) had put a TV antenna at the top of the mast but the masthead amplifier (clue is in the name) is in the cupboard behind the antenna socket in the saloon. As they say, garbage in, garbage out, so the amp only serves to amplify the noise coming down the line.

Trying to use a 4G antenna on the end of 20m of coax losses defeats any advantage of gain through height but let me know how it works out as I seriously wanted to do this myself but advised against wasting my money by friends in the telecomms industry.

 

[Karlsenkystfiske]

Better solution is to put the amp at the top of the mast but that comes with the add

Like putting the router inside the antenna cabinet? That seems to be an option!¨

 

[vas]

that drawing layout is a bit wrong (imho!)

Assuming a larger antenna that a router would fit inside (the one pictured is most likely not!), it would be from mast down:
Antenna with router in it
ethernet cable to the plotter/helm area
PoE brick that would power the router/antenna combo.
connection to plotter/whatnot