3.16k constant in simple_fm_rcv

GNU Radio
1

This is a question primarily for Marcus D. Leech (aka patchvonbraun):

In your simple_fm_rcv project, you have a “Multiply Const” block that
contains the constant 3.16k whenever stereo is enabled. I presume this
is
used to amplify the level of the “L - R” signal to reach the ideal level
of
separation between the channels. How did you arrive at that constant,
i.e.
what is it based on? I haven’t been able to find any official spec that
explains how much the L-R signal should be amplified. Thanks in advance.

Ethan

2

Ethan

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As I recall, I just kind of arrived at it empirically…

3

Ethan
I think part of the reason for that (hey, I wrote this thing last summer
:slight_smile: ) is that you end up having to multiply a bunch of signals together
that are
individually something like -10dB down, so you have to make up for
that somewhere.

The thing really did start out simple. Then I added stereo, and tried
to improve the sound quality, and then…

–
Marcus L.
Principal Investigator
Shirleys Bay Radio Astronomy Consortium