[ACARS] Filter & amplifier

Mon, 26 May 2003 11:49:39 +0200

Hi Carlos,
To get the best results is to connect the filter between the antenna and the amplifier. This is done for the following reason:
Right next to the VHF air band (which is from 108...136 MHz) is the FM broadcast band (88...108 MHz). Aircraft usually transmit between 10 and 25 Watts of power, while the FM broadcast band transmitters have output power ranging from 1 kW and up (often you'll find 100 kW of power). The filter between the antenna and the amplifier prevents overloading, which causes all kinds of spurious and other unwanted signals.

A good example is at my location: 
I use an Icom discone antenna, a FM broadcast band filter and an Icom IC-R7000. At about 3 km there is a transmitter site, which has several high power FM broadcast stations (up to 100 kW erp)!
With the filter installed I can listen to airport signals from an airport at about 30 km from here. When I remove the filter I don't hear anything anymore (due to front end overload).

I don't know your location, so the results might not be so drastic, but it is worth trying it this way!

73,
Marinus

-----Original Message-----
From: Carlos Abreu [mailto:[email protected]]
Sent: Monday, May 26, 2003 11:29
To: [email protected]
Subject: [ACARS] Filter & amplifier

Hi List

I have a question that I would like to ear your opinion:

I use for my ACARS listening a WATSON WRP-125 Pre Amplifier instaled after
the antenna and before a AOR ABF 125 filter, is  this the most correct way
to plug in ?
Or I must install the filter after the antenna and than the Pre Amplifier ?

How are your results for each situation ?

Brgds
Carlos

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