Hiya,
Does anyone here understand and perhaps you might explain the functional differences between an FM ratio detector and a Foster Seeley detector?
I understand they are similar but from the attached photos, a Foster Seeley has a connection from primary to centre of secondary (via a capacitor) whilst a ratio has no connection, only using a tertiary winding.
Also a Foster has diodes pointing in the same direction whilst a ratio uses diodes pointing in opposite directions.
I also understand the concept of phasors adding up to produce an output. But now, this is where my understanding FALLS DOWN....
On a ratio detector, how is it that the loosely coupled secondary produces a frequency sensitive output to one diode over the other diode? Why is one preferred to another? In any case they point in opposite directions so how would that work?
On the FS detector, I can see that both diodes point in the same direction so I'm guessing one diode is preferred to the other as each half of the secondary is tuned slightly off centre from the IF frequency (and so depending on the frequency shift direction, one half of the secondary will have the greater output)?
In both types of detector, why do we need a 90° shift in phase? Can't we simply have both halves of the secondary tuned either side of the IF frequency?
Kind regards,
Aidan.
Ratio ♤
Foster Seeley ♤
Does anyone here understand and perhaps you might explain the functional differences between an FM ratio detector and a Foster Seeley detector?
I understand they are similar but from the attached photos, a Foster Seeley has a connection from primary to centre of secondary (via a capacitor) whilst a ratio has no connection, only using a tertiary winding.
Also a Foster has diodes pointing in the same direction whilst a ratio uses diodes pointing in opposite directions.
I also understand the concept of phasors adding up to produce an output. But now, this is where my understanding FALLS DOWN....
On a ratio detector, how is it that the loosely coupled secondary produces a frequency sensitive output to one diode over the other diode? Why is one preferred to another? In any case they point in opposite directions so how would that work?
On the FS detector, I can see that both diodes point in the same direction so I'm guessing one diode is preferred to the other as each half of the secondary is tuned slightly off centre from the IF frequency (and so depending on the frequency shift direction, one half of the secondary will have the greater output)?
In both types of detector, why do we need a 90° shift in phase? Can't we simply have both halves of the secondary tuned either side of the IF frequency?
Kind regards,
Aidan.
Ratio ♤
Foster Seeley ♤