Want to resurrect your D/D2 MAC kit?

[fsphil]

On my Philips I can pick between PAL, flat and MAC deemphasis inputs through the menu. Works best on MAC option from the generator. In PAL it locks occasionally - similar to the video above.

Oh that's interesting. What I'm doing at the moment would be best described as flat. It should be possible to make an appropriate filter in gnuradio, just have to figure out how now...

 

[fsphil]

@fsphil - have you managed to transmit a full moving video in PAL or just a still image made up of y and uv parts?

Proper video VSB modulated with audio (mono + nicam), though the nicam sounded pretty awful (no pre-emphasis filter). Did a quick FM test too with an old Pace Sky receiver and that seemed to work fine. It's a similar collection of scripts to this one.

 

[Captain Jack]

Proper video VSB modulated with audio (mono + nicam), though the nicam sounded pretty awful (no pre-emphasis filter). Did a quick FM test too with an old Pace Sky receiver and that seemed to work fine. It's a similar collection of scripts to this one.

Any chance of sharing those too? Flow graphs and scripts.

 

[fsphil]

I'll try and collect them all together and make a github repo for them tomorrow.

There's a real-time encoder for PAL (just AM modulated, no VSB or FM) written in C too, but I haven't got sound working in that.

 

[fsphil]

I made a crude approximation of the Linear filter mentioned in the D-MAC spec, and it's done this:

There is still a little glitch every 3 seconds or so but otherwise that looks good.

 

[Captain Jack]

Well done, Phil! Can't wait to try it out on mine.

And everyone thought these things were obsolete ;)

 

[fsphil]

And everyone thought these things were obsolete ;)

We just need our own satellite now, anyone got Elon Musk's number?

 

[Captain Jack]

Are you planning on working on the sound part or is it too complex to mux it into the video?

 

[fsphil]

I'll certainly have a go at sound. That part of the spec is heavy reading, but one of the audio modes seem to be basically NICAM which I've already an encoder for.

 

[s-band]

Congratulations, I'm impressed. @Captain Jack @fsphil I found a copy of the IBA technical review no. 24, from 1988, which is a collection of 11 papers about DMAC. There's too much to scan so if either of you want it, PM me. The same applies to a NoS Philips STU902/5R BSB box.

We just need our own satellite now, anyone got Elon Musk's number?

For educational purposes only: Satellite TC Booster Via sat 3 Watt Buc 1025739 Rev 6 A018325b | eBay

 

[Captain Jack]

I haven't done anything yet... still waiting for my HackRF to arrive. Probably will try over the weekend.

@fsphil - did you manage to get your Github repo going?

 

[Vipersan]

I wont deny what you guys are doing is beyond me and my old grey matter ...but is nonetheless one of the most interesting projects I've read to date ..
I wish you guys every success ..and hope one day my old churchill mulitimac (decoder) will once again have a purpose ..
rgds
VS

 

[Vipersan]

Some internal pics..
If the chips idents would be useful to you.. I'll get some closeups.
rgds

..what I remember ..
Baseband in ...RGB out ..but had it's own UHF modulator..
Sockets on rear read Video out scart (receiver)...(TV out scart)...satellite receiver SCART/input)
gonna dust it off and power up this evening to see if it still works ..
lol

 

[Captain Jack]

I think decoders are more complicated than encoders!

 

[Vipersan]

Well ..after all these years it still powers up OK ..
As to the remore control ..
buried somewhere in this house/tip ...
If Sats UK TV ever goes live ..I'll make the effort and find it .

 

[Captain Jack]

Received my HackRF today. Sadly, no actual satellite receiver to test it with. Will pick up my ancient Pace MSS100 from my parents' tomorrow...

 

[Adam792]

Looking forward to reading about how you get on with the HackRF!

I hadn't seen about them before this thread, but I'm half tempted to get one myself to experiment with generating DVB-T/T2 signals which is apparently possible in GNUradio with one. Might be able to transmodulate some sat Multistreams as terrestrial through my home wiring.


Sent from my iPhone using Tapatalk

 

[Captain Jack]

I managed to transmit NTSC-ish test card to my TV but no luck with PAL (waiting for files from @fsphil).

DMAC is transmitting but totally scrambled when sent over normal UHF range. Will check with receiver tomorrow.

 

[Captain Jack]

OK, I need Phil's help here as I am not having much luck.

With the original .raw sample from your 'scope, I am getting an image out but there's no lock at all I tried various input types - PAL/MAC/flat and none are locking. Tried setting similar settings within the receiver but again, no luck.

I am having even less luck with the converted files to sample.bin - it's looks like it's completely unsynced... Not sure where to go from here.

 

[Captain Jack]

Oookay. After a lot of messing around with gnuradio, I managed to get a result of sorts. For a short period, it was locking on perfectly in "PAL" output from the receiver and "PAL" input in the decoder but then I've done something and it won't lock like this any more. Only locks on MAC input with flat output - and it loses lock every second. Not sure why but I don't have the technical knowledge to go much further.

Here's the result: