Typical HF antenna signal levels?

[neazoi]

What are the typical HF antenna signal levels one could encounter from far away stations?

 

[betwixt]

Many many many variables to consider but I would consider anything less than about 1uV in to 50 Ohms to be 'weak'.

Brian.

 

[neazoi]

Many many many variables to consider but I would consider anything less than about 1uV in to 50 Ohms to be 'weak'.

Brian.

I have a simple transistor amplifier (posted in the other thread) which seems not to distort even at 1vpp input. Buffer shown in the schematic, but the output can be taken from the collector. Is this a "safe" input level to consider it as a better dynamic range amplifier?

--- Updated Mar 18, 2021 ---

How about 100mVpp, is it considered a high amplitude signal in antenna terms (even maybe from that received by nearby 100W stations)?

--- Updated Mar 18, 2021 ---

I have a simple transistor amplifier (posted in the other thread) which seems not to distort even at 1vpp input. Buffer shown in the schematic, but the output can be taken from the collector. Is this a "safe" input level to consider it as a better dynamic range amplifier?

--- Updated Mar 18, 2021 ---

How about 100mVpp, is it considered a high amplitude signal in antenna terms (even maybe from that received by nearby 100W stations)?

How about 10mVpp, are these really big signal levels?

 

[biff44]

microvolts, as said

 

[albbg]

Let's suppose to have the receiver antenna placed at a distance "d" from the transmitter antenna. Very roughly if one antenna sees the other one and the distance "d" is greater than the wavelength of the transmitted signal (to be sure to comply with the far field condition) the the path loss will be given by:

PL(dB)=-28 + 20*Log(d*freq) with "d" in meter and "freq" in MHz

the received signal will be given by:

Prec(dBm) = Ptx(dBm) + Gtx(dBi) - PL(dB) + Grx(dBi) where Gtx and Grx are the gains of the two antennas (neglecting the cable losses).

If, for instance freq=30MHz (that is wavelength = 10m), d=20m (transmitter very close to the receiver), Grx=Gtx=0 dBi and Ptx=100W (50dBm) then:

PL(dB) =-28+20*log(20*30) =27.6dB
Prx = 50+0-27.6+0=22.4dBm that is 0.174W

The received voltage will be given by Vrx=sqrt(P*R) where R is the load of the antenna that is 50ohm. Then:

Vrx=sqrt(0.174*50) = 3Vrms

If instead the same transmitter was placed 1km apart (but in line of sight): PL=62dB that is Prx=-12dBm that is 63uW and the voltage Vrx=56mVrms

As I said is a rough estimation.

Of course reversing the math you can calculate haw far have to be a transmitter from the receiver to meet the maximum amplitude you want. As you can see it depends from the frequency.