UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Does anyone know anything about "Modulation Depth"? (Philips PM5680)

inaxeon · 6th Oct 2022, 2:24 pm

Hello

I'm currently trying to throw together a setup to create an analogue telly Broadcast [by that I mean signal - not actual on-air transmission] (for fun). It's mostly based on Philips PTV gear (I have spammed these forums with links to my teardowns of them in the past).

The latest piece I'm trying to grapple with is a Philips PM5680 modulator ( https://www.radiomuseum.org/r/ptvphi...5680_all.html# ). Usual problem - no manual available.

I have one which is PAL-I capable but am a little confused about the modulation depth adjustment.

I think I understand with the vision carrier, it's the ratio between the amplitude of the carrier tone and the video signal and I can see this clearly on my spectrum analyser. Some reading suggests 90% "modulation depth" is a good starting point.

I'm a bit more confused about the audio side of things. It measures it in KHz instead of %. Basically I have no clue what this measurement actually is.

Anyone have any experience of this?

6th Oct 2022, 2:24 pm	#1
inaxeon Pentode Join Date: May 2022 Location: Odiham, Hampshire, UK. Posts: 128	Does anyone know anything about "Modulation Depth"? (Philips PM5680) Hello I'm currently trying to throw together a setup to create an analogue telly Broadcast [by that I mean signal - not actual on-air transmission] (for fun). It's mostly based on Philips PTV gear (I have spammed these forums with links to my teardowns of them in the past). The latest piece I'm trying to grapple with is a Philips PM5680 modulator ( https://www.radiomuseum.org/r/ptvphi...5680_all.html# ). Usual problem - no manual available. I have one which is PAL-I capable but am a little confused about the modulation depth adjustment. I think I understand with the vision carrier, it's the ratio between the amplitude of the carrier tone and the video signal and I can see this clearly on my spectrum analyser. Some reading suggests 90% "modulation depth" is a good starting point. I'm a bit more confused about the audio side of things. It measures it in KHz instead of %. Basically I have no clue what this measurement actually is. Anyone have any experience of this? Last edited by inaxeon; 6th Oct 2022 at 2:32 pm.