Re: LAA++ Questions, Transmitting and Raspberry Pi #raspberrypi


Chris Moulding
 

Hello Jack,

Good to hear that your loop and the LAA++ is working OK.

Answers to your questions:

The LAA++ is for receive use only.

The head unit contains an amplifier and other circuitry to isolate the loop from the amplifier and a common mode choke to isolate the amplifier from the coax cable so that RF signals and noise don't get into the loop.

When a loop is used with a LAA++ it acts as an aperiodic loop, in other words it is untuned and wideband and the amplifier amplifies the very weak signal induced into the loop by the electromagnetic field.

A magnetic loop antenna is usually a tuned loop where the inductance of the loop is tuned in a resonant circuit with a capacitor. To get a reasonable efficiency the loop has to be made out of thick copper pipe or similar.  The badwidth, if efficient, is very narrow typically 7-10 kHz at 14 MHz. The problem with a magnetic loop antenna is that even at low power the voltage and current flowing in the loop are very high. The magnetic and electric fields are also dangerously high close into the loop.

A few years back we investigated making a prototype HF magnetic loop for the amateur radio market but came to the conclusion that they are not safe. We decided not to sell them. Others may tell you different, maybe their antennas are lossy and don't generate the high electric and magnetic fields.

 Many different loop configurations can be used with the LAA++.. Welcome to your new hobby making loop antennas!

It isn't possible to transmit into the LAA++. It's a receive only antenna and it would damage the amplifier.

Regards,

Chris

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