Does highly sensitive radio receivers encounters less fading

[ofosot69]

I need to know whether the radio receivers that are highly sensitive, like having sensitivity less than 0.0224 micro volts for AM reception, encounter less fading than the others with less sensitivity?

Which specification of a radio receiver is responsible for mitigating fading?

 

[Papabravo]

Fading is caused by conditions in the D, E, & F layers of the ionosphere. These conditions can absolutely drop the level of a signal to undetectable levels. Nothing you do in a receiver can overcome the complete lack of a signal. Some relief is provided by an AGC (Automatic Gain Control)circuit, but these have a finite reaction time which does not allow smooth transitions between high gain and lower gain conditions.

There is also a limit to how sensitive you can make a receiver. There is a point called the noise floor where the signal has less energy than the noise cause by all the different sources including the cosmic background radiation. This level is about -176 dBm. There are methods for recoveing information burried in the noise floor, but they are for digital information, not audio..

 

[Ramussons]

Highly sensitive receivers can receive signals that are much lower in magnitude, so they can handle a wider range of signal fade.

 

[Nigel Goodwin]

Assuming we're talking shortwave or below?, the limiting factor is atmospheric noise - so there's no point increasing sensitivity beyond sensible amounts as it will make no difference. Once you get to VHF the atmospheric noise disappears, and the limiting factor becomes the noise level of the frontend of the receiver.

 

[RF_Burns]

If your fading is being caused by signal cancellation due to multi-path, this can be overcome by using diversity antennas and receivers. This is a common problem and solution on higher frequencies.

 

[ofosot69]

Fading is caused by conditions in the D, E, & F layers of the ionosphere. These conditions can absolutely drop the level of a signal to undetectable levels. Nothing you do in a receiver can overcome the complete lack of a signal. Some relief is provided by an AGC (Automatic Gain Control)circuit, but these have a finite reaction time which does not allow smooth transitions between high gain and lower gain conditions.

There is also a limit to how sensitive you can make a receiver. There is a point called the noise floor where the signal has less energy than the noise cause by all the different sources including the cosmic background radiation. This level is about -176 dBm. There are methods for recoveing information burried in the noise floor, but they are for digital information, not audio..

But I have tested too many AM radio receivers and only the expensive ones had a better reception with less fading.

 

[ofosot69]

Highly sensitive receivers can receive signals that are much lower in magnitude, so they can handle a wider range of signal fade.

Do you know any such expensive radio receiver that experiences less fading?

 

[ofosot69]

Assuming we're talking shortwave or below?, the limiting factor is atmospheric noise - so there's no point increasing sensitivity beyond sensible amounts as it will make no difference. Once you get to VHF the atmospheric noise disappears, and the limiting factor becomes the noise level of the frontend of the receiver.

But why in some radio receivers, fading is more?

 

[ofosot69]

If your fading is being caused by signal cancellation due to multi-path, this can be overcome by using diversity antennas and receivers. This is a common problem and solution on higher frequencies.

Which AM radio receiver is using diversity for SW?

 

[Nigel Goodwin]

But why in some radio receivers, fading is more?

As we've said all along, receivers with more sensitivity will experience less fading, as their AGC range is greater - but as we've also said, this effect is limited by the respective noise limitations depending on frequency used.

 

[rjenkinsgb]

Which AM radio receiver is using diversity for SW?

Diversity requires two or more antennas spaced apart by a significant distance in relation to the wavelength being received (so phase related fading that affect one has the other nearer a strong signal zone), plus a receiver that actually has multiple RF "receivers" internally & a system to combine or select the one that's getting the best signal at any instant.

For HF / short wave, probably only military or ones built by Ham radio enthusiasts. I've never seen an for general use, though they may exist.

It's quite common VHF and up, as wavelengths and antenna sizes are small - one common example is some types of multi-antenna WiFi access points or routers

 

[ofosot69]

Diversity requires two or more antennas spaced apart by a significant distance in relation to the wavelength being received (so phase related fading that affect one has the other nearer a strong signal zone), plus a receiver that actually has multiple RF "receivers" internally & a system to combine or select the one that's getting the best signal at any instant.

For HF / short wave, probably only military or ones built by Ham radio enthusiasts. I've never seen an for general use, though they may exist.

It's quite common VHF and up, as wavelengths and antenna sizes are small - one common example is some types of multi-antenna WiFi access points or routers

Any consumer radio receiver that experiences less fading?