How does this active antenna work?

[neazoi]

Hello,
I have found this active antenna **broken link removed** (schematic at the end of the page) and I was wondering how does it work?

I can guess how the second transistor work, but I am confused of how the first transistor, the bas16 diode and the transformer work?

Also what is the expected frequency range (apart from what the author states) and it's gain, given that the vcc is 3v ?

 

[FvM]

I believe the promised X2 signal enhancement by the transformer isn't so essential for the amplifier, apart from this detail it's a buffer amplifier with high input impedance.

 

[neazoi]

I believe the promised X2 signal enhancement by the transformer isn't so essential for the amplifier, apart from this detail it's a buffer amplifier with high input impedance.

So the transformer is there in order to double the signal?
What about the bas16?

Any estimation of the gain of the preamplifier?

 

[FvM]

The diode is protecting the FET against ESD and other possible input overvoltage.

Voltage must be below 6 dB, hopefully it's greater than 0 dB. Antenna effective height and output impedance is the more interesting part of the problem.

 

[neazoi]

Voltage must be below 6 dB, hopefully it's greater than 0 dB.

You mean the gain of the amplifier, right?
0db is no gain, so what is the meaning of having the preamp in place? Maybe all the voltage gain depends on the transformer and the transistors are there as current amplifiers? (a guess)

 

[FvM]

Yes, I meaned to write voltage gain.

0 dB or even negative voltage gain can be still reasonable for a buffer amlifier with high input impedance.

 

[neazoi]

Yes, I meaned to write voltage gain.
0 dB or even negative voltage gain can be still reasonable for a buffer amlifier with high input impedance.

From your experience it this preamplifier going to do a significant difference in RX signal amplification?
In other words does it worth it to try?