Is there a way to create an FM stereo multiplex signal with a 19KHz pilot tone using QSPICE? If so, I’d like to use this signal to test a Portus and Haywood stereo decoder. This revised design was published in Wireless World magazine in March 1978. I understand that an FM multiplex signal is an AM double sideband signal with a pilot tone at half the subcarrier frequency (although I’m not entirely sure what this means). I have NEVER created this signal myself and would not have a clue how to even start. Is this even possible in a simulator, let alone in QSPICE? I have decided to try QSPICE as it can use digital logic (the design includes a 7474 D-type flip-flop as well as discrete NPN and PNP transistors). If the signal has been created in LTSPICE is it possible to adapt it? Thanks.
I haven’t looked at that since, the 1970s, but I thought it was FM. After decoding to baseband, the low frequency was Left+Right and a higher band was Left-Right. The pilot was to decode the Left-Right. It’s probably easiest to implement as a C++ device, since otherwise the d/dt of the instantaneous frequency is hard to keep track of the impact due to the chain rule that makes a simple-minded notion of instantaneous frequency not so correct.
I have found this Tektronix application note which may shed some insight
Opps. That’s right, L+R is standard FM. The 19kHz pilot is to decode the L-R. Point being, you can decode FM stereo and get a good mono. But if you have enough S/N to lock onto the pilot, you can decode the stereo and mix L-R into the mono baseband and disco.
Here is a blog on generating a stereo FM multiplex signal using python and AWG
I leave this here for future reference, just in case I ever develop the skills to implement this in QSPICE using C++. This will take a LONG time as I’m a beginner programmer in C and I have a rudimentary knowledge of C++ and python. If anyone want to have a go, feel free. In the meantime, I’ll go over the basics of using C++ in this context.