FAQ: Antennas

What is if I use the combination antenna instead of the existing VHF antenna in combination with the easySPLIT OCB and a further GPS antenna?

The combination antenna is easy to mount and works very well.

The quality of the reception is very similar to a regular VHF antenna. The difference is the height of the antenna in which the combination antenna is mounted normally.

A typical mounting place of the combination antenna is the railing at the stern of the ship. This “mounting” height is much less than the height of the masttop. In our practical use we found out, that the transmission range and the reception range is more or less the half. With our easySPLIT OCB and the masttop antenna you have a typical range of app 8nm for the transmission of your AIS data and app 25nm for the reception of other AIS data (Depends of course of the antenna and cable quality, as well as of the weather!) This is simply due to the reason of the physical effect of the VHF (Distance is line of sight and you know, as higher, as better).

“There is not such a good amplifier existing than a high mounted antenna!”

How can I see if my antenna connection to the easyTRX works fine?

It is not easy to give a limit for a good or bad antenna installation.

But here are some values which could be a guideline:

Fwd-Pwr Banten 1: 143
Fwd-Pwr Banten 2: 154
Fwd-Pwr Discone: 145
Fwd-Pwr no antenna: 34

Rev-Pwr Banten 1: 31
Rev-Pwr Banten 2: 15
Rev-Pwr Discone: 23
Rev-Pwr no antenna: 26

VSWR Banten 1: 4,6
VSWR Banten 2: 10,3
VSWR Discone: 6,3
VSWR no antenna: 1,3

Explanation of the table: When you start the Link2AIS program and look at the “Maintenance / Modem Data”, you can see the “forward power” (Fwd-Pwr) and the “reverse power” (Rev-Pwr).

1.) Please wait until the easyTRX has transmitted a message.
You can see that when the values are changing.

2.) Then divide the fwd-pwr by the rev-pwr values. You see that ratio in the VSWR-rows.
VSWF means “voltage standing wave ratio”

In the last row there is a value below 3 (VSWR no antenna: 1,3). That means it is bad. Of cause, because we had no antenna connected.

The other three columns show typical values, which are all perfect.

Conclusion: If the VSWR value is higher than 3, you have a good antenna installation and good cable connection.

What should I consider during the installation of my Antenna?

Please follow the link below for installation instructions. This will show you what to look for and what are the usual mistakes.

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