Simple De-emphasis/ MPX filter. - UK Vintage Radio Repair and Restoration Discussion Forum

Radio tirana · 16th May 2022, 9:13 pm

Hi, At Retrotech I purchased a few Temic 1894 FM tuner modules, Thanks Radiomobile

I set up a test circuit powered from a 9V battery with a 50K pot and 10K resistor to derive the tuning voltage, a metre of wire served as an antenna. Listening through headphones there was a click each time I connected to the MPX output, I think there might be some DC present so I added a 0.47uF capacitor in line. The modules work really well. I only require a mono output Has anyone had any thoughts on how I best filter out the 19kHz pilot tone and Subcarrier and also provide de-emphasis. Would a simple RC filter work well enough? although I won't be able to hear these signals I don't want to amplify them further.

Kind regards Tony

16th May 2022, 9:13 pm	#1
Radio tirana Pentode Join Date: Nov 2015 Location: Oxfordshire, UK. Posts: 171	Simple De-emphasis/ MPX filter. Hi, At Retrotech I purchased a few Temic 1894 FM tuner modules, Thanks Radiomobile I set up a test circuit powered from a 9V battery with a 50K pot and 10K resistor to derive the tuning voltage, a metre of wire served as an antenna. Listening through headphones there was a click each time I connected to the MPX output, I think there might be some DC present so I added a 0.47uF capacitor in line. The modules work really well. I only require a mono output Has anyone had any thoughts on how I best filter out the 19kHz pilot tone and Subcarrier and also provide de-emphasis. Would a simple RC filter work well enough? although I won't be able to hear these signals I don't want to amplify them further. Kind regards Tony