VHF Aerial - Rod or Whip?

[Freeloader]

I'm going to upgrade my onboard VHF from a handheld to a fixed unit over the winter but would appreciate opinions with regard to the most suitable VHF aerial.

I intend to mount the aerial on the radar arch but am unsure whether to go for a rod-type or whip-type aerial. I've always had the whip-type mounted at the masthead on previous sailing vessels but, until now, haven't had a fixed unit on a motor boat. Most boats seem to have the rod-type but is there a reason for this (lack of flex at speed?) or is it just for aesthetics?

 

[oldgit]

Probably precious little difference in performance.The expensive white glass fibre aerials are merely a hollow tube with a bit of wire rattling around inside.
Most Mobos have a long monster glassfibre antenna most raggies go for a little whip with a loading coil to reduce length. !

 

[Hugh Foulis]

I shall follow this with interest. I am a licensed ham so have a liitle bit of knowledge but also looked after the emergency PMR system in Cumbria and north Lancs. My preference is for rod on the basis that we could experience a reduction in propagation with whip if they were moving.

HF

 

[JSYmartini]

Masthead whip antennas tend to have a lower gain (db) ie a less focused "beam" to allow for the heel of a sail boat. The extra power from a high gain antenna isn't so important as a masthead antenna has got the height required for good reception/transmission. Typical gain for a masthead antenna would be 3db.

You can get whip antennas designed for motor boats but still usually only have 3db gain which coupled with lack of height aren't ideal for good comms.
Also, I've found that on a planing boat in a choppy sea, a whip tends to start whipping itself to destruction. Over on the Ribnet forum there's been many comments on the uselessness of the Vtronix rib raider whip antenna for example. Having said that, the Metz Manta used by USCG is pretty durable, had one on my rib for a few years now for AIS without any trouble.

In my opinion, the fibreglass antennas are more suitable for mobos, some are stronger than others but they tend to be longer which gives you the all important height to increase horizon distance. The gain should be higher, 6 or even 9db to help reach that bit further too. Pacific antennas are often highly rated and not too expensive. I've also got a Comrod fibreglass antenna on my rib which is right at the top end of the market. It's solid glass not hollow and mostly aimed at the military etc, RNLI use them on the B class ILB's.

All just one person's opinion of course!

 

[arawa]

Probably precious little difference in performance.The expensive white glass fibre aerials are merely a hollow tube with a bit of wire rattling around inside.
Most Mobos have a long monster glassfibre antenna most raggies go for a little whip with a loading coil to reduce length. !

My original 2.4m glassfibre antenna was broken during a recent crane-out. I was suprised to find that there was only 1.6m of aerial (which did rattle) inside.
Based upon advice from elsewhere in these fora I replaced the broken aerial with a Metz. First impressions are that there is a significant improvement in performance – and no rattle!

 

[Bilgediver]

I'm going to upgrade my onboard VHF from a handheld to a fixed unit over the winter but would appreciate opinions with regard to the most suitable VHF aerial.

I intend to mount the aerial on the radar arch but am unsure whether to go for a rod-type or whip-type aerial. I've always had the whip-type mounted at the masthead on previous sailing vessels but, until now, haven't had a fixed unit on a motor boat. Most boats seem to have the rod-type but is there a reason for this (lack of flex at speed?) or is it just for aesthetics?

If your radar arch is glass fibre etc then be careful that if you choose a whip it is not one designed to use the mast of a yacht as a ground plane. The rod antennas generally do not need ground planes.

 

[Freeloader]

It's a stainless steel arch but the arch itself is not grounded anywhere. Do I take it that I would need to fit a ground wire to the arch if I wanted to fit a whip aerial?

However, I am now leaning towards either the Metz whip or a GRP rod-type aerial - any suggestions for a good make? Incidentally, the ones that I have seen seem to come with fairly basic coaxial cable - do any come with a better quality coax?