AIS Antenna?

[Leigh]

Hi,

I now have the  RTL-SDR.COM USB SDR AIS receiver for my RPi3-Sensehat setup (see bragboard)

It came with both a mini and larger (maybe each arm nearly 1m long) version of a 'V' telescopic antenna.
I have read in another thread that the mini one is for FM radio, will the larger one work for AIS?

Or should I get another VHF antenna to mount on the pullpit?


Or can I use a splitter (for example this one) with my existing VHF antenna at the mast top?


Thanks

Leigh

Yes you can use a splitter. There is nothing wrong with a modern well engineered splitter but as somebody said it will cost you money. 

This one from Vesper Marine is excellent https://www2.vespermarine.com/antenna-splitter-sp160

You really want you AIS antenna at the masthead for best performance.

You could put one another VHF antenna on the rail as a spare but I would still have the splitter. It is better to carry an emergency VHF antenna securely in a locker than have it mounted as if you loose your rig there is a fair chance that your spare VHF antenna is going to get swept overboard too. If you know how to make an emergency VHF antenna then there is only the need to carry some stiff wire. 

Typically you would make a 1/4 wavelength antenna. 

The formula is the speed of light (300x10^8 m/s) / frequency in MHz

3x10^8 / 162x10^6

=

300 / 162

=

1.8519m which is the wavelength of 162MHz so this has to be divided by four

1.8519 / 4 = 0.463m = the length of your antenna. 

Typical marine VHF antennas are longer than 1/4 wavelength and have loading coils at the bottom to give better performance but a 1/4 wavelength like this on the stern will work fine in an emergency.

Thanks Chris