VHF AERIALS

[chubby]

The consensus for sailing yachts is a 1 m stainless steel whip at the mast head to get the advantage of height with a long run of coax.

Commercial vessels and motorboat seem to have the glass fibre aerials with I gather a brass conductor within.

On a ketch I have the option of using the mizen mast and I could fit a 2 m aerial with thicker coax and a shorter run as there is already a conduit outside the mast to take a radar and AIS cable.

So would I get any better reception with a full wave aerial mounted lower but fed by heavier duty coax? Or stick to the current masthead aerial: it was a Manta supplied by Salty John of this parish before retirement with the better quality coax he supplied but is about 10 years old now.

 

[andsarkit]

If you can get hold of a VSWR meter and it reads OK I would stick with what you have.
Many commercial boats and motorboats have an antenna twice as long which gives 6dB gain instead of the 3dB of a 1m yacht antenna. It does this by compressing the vertical beam pattern which is fine on a motorboat but not so good on a yacht which will loose the gain when it is heeled.
If you do a little searching you can find polar diagrams for various antennas and find out the dB loss at different angles of heel. You can also calculate the dB loss for the coax you intend to use and see if there is an overall benefit in a shorter better coax. I believe Salty John supplied RG8X coax with the Manta.
You say there is an AIS cable up the mizzen, in which case you don't want the VHF antenna in the same location as they need a minimum separation.

 

[AntarcticPilot]

For most VHF installations, the limiting factor for range is line of sight, not power or antenna gain. So in general a higher antenna will have greater range than a lower one.

 

[Porthandbuoy]

I have a ketch. VHF on the main, AIS on the mizzen.

 

[pandos]

Good reception can be a curse at times... In West Cork I was regularly getting broadcasts from the UK and French coastguard.

I have a manta mounted at the mast head and fancy (Italian? ) coax...