UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - HA12411 FM IF chip

SteveCG · 12th Aug 2019, 1:00 pm

I tried my first multi-path experiment using the Trio tuner over the weekend. Using a dual beam 'scope I connected the output from pin 13 (tuning meter/multi-path) of the HA12411 chip to one channel of the 'scope and the input to pin2 (raw FM demodulator signal) of the AN115 stereo decoder chip to the other, and tuned to the local BBC Radio 1 freq. Altering the tuner input signal with an attenuator I was seeing what G8HQP_Dave describes: strong signal - constant voltage on pin13, weaker signal - fluctuations in the signal which approximated to the audio content.

I was intending to try the X-Y plot display style however the control to select this on my scope is jammed solid (so I discovered). Mind you since the display would collapse to nearly a spot with any silence in the audio (just leaving the 19 kc/s stereo pilot tone present), that could risk burning the 'scope's phosphor.

I'm going to think now about my next moves...

12th Aug 2019, 1:00 pm	#17
SteveCG Nonode Join Date: Jun 2009 Location: Herefordshire, UK. Posts: 2,495	Re: HA12411 FM IF chip - who used it? I tried my first multi-path experiment using the Trio tuner over the weekend. Using a dual beam 'scope I connected the output from pin 13 (tuning meter/multi-path) of the HA12411 chip to one channel of the 'scope and the input to pin2 (raw FM demodulator signal) of the AN115 stereo decoder chip to the other, and tuned to the local BBC Radio 1 freq. Altering the tuner input signal with an attenuator I was seeing what G8HQP_Dave describes: strong signal - constant voltage on pin13, weaker signal - fluctuations in the signal which approximated to the audio content. I was intending to try the X-Y plot display style however the control to select this on my scope is jammed solid (so I discovered). Mind you since the display would collapse to nearly a spot with any silence in the audio (just leaving the 19 kc/s stereo pilot tone present), that could risk burning the 'scope's phosphor. I'm going to think now about my next moves...