17-03-2017, 05:02 PM
(17-03-2017, 04:46 PM)pwdrive Wrote:(17-03-2017, 04:26 PM)Nowhere-Man Wrote: There is this here:
http://www.radio-electronics.com/info/rf...inator.php
The subject comes up a lot on various forums.
That's a classic layout for the ratio detector, the two diodes shown in opposition (facing the opposite way) the Foster Seeley has the two diodes facing the same way as it were, also the Foster Seeley needs a limiter stage before it, that's in the form of an extra IF amplifier stage, the valve in that stage limits the amplitude of the signal fed into the discriminator by clipping the signal and thus removing any unwanted AM component from it such as interference.
Lawrence.
Do you think it will help me? Last night I felt like my brain was going through a grinder. It does get clearer as you ponder it but, as I said, there have been times I needed to just go back and look at the very basic theory. I even had to go back to AM a little because often in the FM tutorials they compare bandwidth to AM. One thing I did see with fresh insight was how at a resonant frequency (say in am), the current will drop off at resonance according to the value of the series resistance. That is, either broad or sharp. ARRL does have some information on FM and PM but it comes pretty late in the book. Sometimes ARRL doesn't offer the best explanations but other times it can be useful.
