Before DAT became common in the late 1980s, a significant number of stereo location recordings and some live transmissions were made using the PCM F1 or 701 by the BBC. The Beeb had more spare video link capacity around the country than fully equalised stereo analogue land-lines. You could also bounce it via a satellite feed too. Sony designed the system to be tolerant of the automatic video gain input stages on video recorders from the outset so a video sender is a similar environment assuming the RF signal is robust enough. They did however recommend using the matching Sony recorder. The SPDIF failure to record is by design, it's trying to stop you making a second generation digital copy (the CD/DVD will have the copy prohibit flag set). This became such a problem for professional use that several companies (ASC Design ??) sold SPDIF bit strippers that toggled the copy bit and HHB sold modified 701s with the SPDIF circuit modified and XLR sockets. I got caught out several times when an F1 refused to transfer my own material especially when moving from AES originated digital to SPDIF (the SPDIF copy prohibit software incorrectly interprets an AES Pre-emphasis bit as a copy prohibit flag if set). For several years the main stereo audio path from Bangor in north Wales to Cardiff in south Wales was using the same video circuit used for transferring to Cardiff the TV news stories shot & edited in N Wales for broadcast later in the evening. It just required careful co-ordination of who was using the video circuit. A PCM 701 at each end did sterling work for at least 5-10 years. Fascinating to see old and very familiar technology being re-discovered.

Interesting experiment! Regarding the S/PDIF input the following. The Copy Prohibit flag is always high when this input is used. A digital copy is only possible with a source that allows digital copying. The digital output of a consumer CD player always has that flag high. The digital output of the CD player can be modified. But it is also possible to modify the digital input of the 601, allowing unlimited digital copying. I once did that to one of my 601s and it worked fine. It is recommended to connect the video transmitter to the Copy output of the 601. Then the best result is obtained. When a tape without copy prohibition is played and the Copy key is pressed, a stable and error-corrected video signal is presented to the copy output.

This is the way DAB should be. Nothing of compression or multichannel. Pure digital PCM stereo audio.

I was kind of hoping you'd stretch the link a lot further. What would be interesting now that you've put the vid onto KZread, can we take the YT video and feed it back into the F1 and decode the audio, as in finally HiFi sound via KZread.

OFFCOM the UK radio spectrum "custodian" have proposals to allow up to 1.5kW power from ham transmitters. If it happens this would be a great area for experimenation!

Nice setup, I have a few of these 2.4GHz video senders, the biggest problem is that radio band has mostly been taken over by WiFi making them kind of useless. I setup one to transmit the output of a computer, and received it by a handheld receiver/LCD monitor, boy does the picture break up as I move away from the transmitter. I shut down my WiFi, but it was not much better as everyone around me, neighbours etc, all have WiFi.

I think that the PCM-601 should accept digital audio from a CD player - this DVD player may have the DCP flag turned always on for some licensing/copyright reason.

@MrRadar

Ай бұрын

Yeah, it's likely the DVD player is hard-wired to set the Serial Copy Management System (SCMS) bit in the SPDIF signal. That was the electronics industry's attempt to placate the RIAA and other music company groups who were worried about the ability to make bit-perfect digital copies of their content by only allowing you to make one copy from the source media and disallowing subsequent copies made from that copy.

@gman83090

Ай бұрын

Or it could be the DVD player has macro vision copyright protection

@mateuszorlinski7334

Ай бұрын

@@gman83090 Macrovision modifies the analog video signal, not S/PDIF

@mateuszorlinski7334

Ай бұрын

@@gman83090 this is completely unrelated, MacroVision protects the video signal, and here he's trying to convert the S/PDIF stream. It most certainly is DCP/SCMS flag always on.

I wonder if the DVD player you're using has got macro vision copy protection

As a radio ham I wonder if that could be itilised over really long distances? Great video Tim.

@timf-tinkering

8 ай бұрын

No reason why not, with a powerful enough transmitter. Those video senders were only designed to work between rooms in a house, so I doubt they would go far.

@17lvlham

4 ай бұрын

I've developed FPGA-based decoder of this standard and should say: BW of video here is 2.65 MHz. Too much for HF, only VHF or UHF can carry it. Also it won't withstand multipaths well

@peterfardell9267

4 ай бұрын

Thats very interesting. Band Width is still too high for even for the UHF amateur bands (e.g.70cm)? Possibly OK on 23cm band (FSTV) I think@@17lvlham

@GeoNeilUK

Ай бұрын

@@17lvlham "BW of video here is 2.65 MHz. Too much for HF, only VHF or UHF can carry it. Also it won't withstand multipaths well" That's why we have DRM radio, a digital radio standard that was for broadcast but I don't tihnk anyone uses it other than hams. DRM radios cost an absolute fortune on AliExpress and I haven't seen a model that does both DRM and DAB+ which is what I would like, just to see if there are DRM broadcasts on short wave.