AIS Signal Booster

[alexrunic]

a mate of mine has been asked to build a booster for an ais transponder on a small boat, would this be legal?

 

[dt4134]

There'll be a standard or two it has to conform to.

A quick websearch found this http://www.navcen.uscg.gov/enav/ais/AIS_standards.htm

 

[Watson47]

Not sure of the legalities, but all certified AIS transponders will be built to an approved specifiction & designed to operate to a designated criteria.

If the perceived issue is signal related, there are practicable steps to improve this by use of correct antenna & location of antenna. Also, correct wiring and connections.

 

[st599]

a mate of mine has been asked to build a booster for an ais transponder on a small boat, would this be legal?

Depends on what your Notice of Variation granting you permission to change the output stage of a type-approved system says.

It will have the maximum output power listed alongside a long text string which contains information on the transmission mode.

 

[MikeCC]

I'd be more concerned about why it was needed/requested in the first place. Out-of-the-box with a decent antenna setup should be adequate.

 

[lenseman]

a mate of mine has been asked to build a booster for an ais transponder on a small boat, would this be legal?

The big question is whether his AIS is a transmitter type which transmits his AIS code or whether it is just a receive only AIS?

If it has a transmitter, and he is intending to introduce a radio frequency power amplifier for this transmitter part of the AIS, then it is definately illegal. The reasoning behind these rules is that the 'new' RF power amplifier 'might', could possibly introduce (transmit) spurious signals in-band or out of band (2nd and 3rd harmonic or higher or probably intermodulation products) to which he might be totally unaware and it could also cause desensitisation or co-channel interference of other marine radio circuits in the near vicinity again he could be totally oblivous of these problems he might create. It can go spurious days or weeks after it has been manufactured so just because it 'works' day one . . . . !

I spend 25 years doing radio frequency enforcement which involved type approval of RF devices and many, many radio devices failed spurious emissions for 2nd and 3rd harmonic. The failure limit was -54dBm for spurious emissions which is a very very small signal BUT it is certainly enough to disrupt adjacent radio circuits in the near viscinity.

There would be nothing worst than sitting in a marina listening to Channel 16, or worse still, trying to sail out of a busy shipping lane, (eg: Portsmouth Harbour), and some guy arrives on his boat, turns on his AIS with illegal RF amplifier, and wipes out all the marine VHF radios within a 300 yard area. Yes it does happen!

RF signals eminating from any transmitter can be very easily seen on a spectrum analyser and if the enforcement officers from Ofcom or elsewhere (FCC) 'see' an AIS signal many many times greater than the normal level of RF output, then they will chase it down and hopefully eliminate it with possible legal implications. The equipment would certainly be seized and confiscated.

A 'booster' for a receive only AIS is perfectly acceptable. This would be similar to a masthead pre-amplifier which are regularly used in the TV band, 470-868MHz.

He would need one which would be suitable for the 156MHz marine band, but there again, if he needs one . . . why? If the antenna is good he should not need one whatsoever.

I hope this helps, the simple answer is to keep things simple.