With this video you have opened a whole new area of interest for me. As usual in your vids a difficult topic explained simply so us lesser mortals can understand. Thank you for sharing.
As for color TV in Europe, it was introduced around the same time that they were switching from various black & white VHF systems to 625-line UHF, but there were actually plenty of black & white 625-line TVs made as well -- so PAL color does have B&W compatibility just like NTSC. But what they didn't do was add color to their old VHF TV systems, because they were either too low-resolution (like the UK's 405-line system) or used too much bandwidth (like France's 819-line system).
Most of that went over my head , but the diagram demonstrated the principle perfectly. Thanks Dave. It reminded me of my cb radio days when we had 40 channels and some back street hackers could open the loop for a few more ‘private’ channels.
Another interesting technology was called SCPC and was used on analog satellites. Back in the day of analog satellite TV, the sound was places on sub carriers typically 6.2 and 6.8Mhz. There were others as well that could be anywhere above the highest frequency of video. My receiver could tune from 5.0 to 8.0 MHz for audio sub carriers. When the VC2 scrambling system was introduced the analog audio was encrypted on the data stream in the horizontal blanking area. This freed up the 6,2 and 6.8 carriers. On one of the channels on G5 they had I think it was CNN, and they had a bunch of sub carriers at 5.4, 5.6, 5.8, 6.0. 6.2, 6.6, 6.8 7.0, 7.2, 7.4, 7.6 and 7.8. Since these were mono 2 pairs were used for stereo. 5.4-5.8 was 1 channel, 6.0-6.2 the next ect. 6 commercial free channels. I have a bunch of recordings from one called "The new age of jazz" There was that one, a soft rock channel, country, hard rock and classical. These were subcarriers on video channels. There was however another block of hidden radio called SCPC (single channel per carrier) I used an outboard stereo processor. Now this would normally only tune the 5 - 8 MHz range used by the video channels. On an SCPC transponder the entire transponder was used for audio. So I had a converter that would convert 0-3 on one band, then 3-6 on the second, and 6-9 on the 3rd. That way with my outboard audio receiver I could just sweep up the band. Of course the same could be done with the ham radio like I demo'd on here. I actually did that first before obtaining the stereo processor and band converter (I wanted stereo sound) My old 10 foot dish was used more for music then TV back in the day. There were hundreds of radio programs available on SCPC. Of course all good things come to an end, and the digital era ended that. There are still plenty of un-encrypted audio feeds available on satellite right now. All you need is a dish and a digital receiver, but with all the streaming stuff available why bother unless you like the idea of music just flying in from space.
Not an SW radio. SW is AM, A communications receiver, such as a HF ham radio also has FM receiving capability. The subcarriers received off the discriminator are still FM modulared.
They were using SCA for reading for the blind service back in the late 80's early 90's here in the NJ & NY area. I worked with a volunteer group called the Telephone Pioneers, and we were modifying old defunct DOW Jones stock alert radios to receive the SCA reading for the blind. Not sure if they still do that anymore.
6 лет назад
Thanks for sharing your insight on the topic sir. My old 3rd gen Ipod (firewire) radio transmitter 'beats' sometimes.
This kind of video and when you repair stuff are absolutely the one I prefer. I clearly don't like when you review products, like for icstation since there are no skills involved. But it's only my opinion :) thank you for the good work and making me learn something.
olipito Well if people would stop blocking ads and allow me to make some money from the advertising then I wouldn't have to resort to product reviews to pay the Bills but with 60+% giving me the raised middle finger and some, even posting comments why they block ads the product reviews continue. There is another solution. I have had a patreon account for over a year which does nothing. The channel has to generate revenue simple as that. It either has to be from ad revenue, subscriber revenue or from sales commission from reviewed products. Since I don't see PayPal and patreon subscriptions going up, and the advertising revenue is down the only other option is to review products. I do have a bunch of items to repair. I just got about a dozen components and I will be getting to them soon. It has been too hot out there in the shop for the past month or so to work but as it cools down I will get to my latest haul which includes a couple of plasma sets and a bunch of vintage audio gear.
I built one of those SCA decoders, and it uses that same PLL chip. I didn't have good luck receiving anything with it though. It was pretty slick using a PLL's VCO to pick the audio off.
I used it for music on hold at the shop I worked at. The one I built worked pretty good. One station, CHQM FM had 2 SCA channels. 67KHz had elevator music, and 92 had a commercial free rock music service. I hadn't lisnened in many, many years and was actually surprised to find a local station still using SCA. Most of them now have HD audio on the sidebands now.
Long gone are the days when BBC used a 50khz ACS (Australia called it Ancillary Communication Service) on 3RRR in Melbourne. Electronics Australia magazine actually featured a decoder that could switch to all three frequencies used here. 67 and 92 plus one I can't recall that was lower than 50khz. Maybe 48khz.
Wenlocktvdx The one I built could tune down quite low but here the 3 used were 57 67 and 92. The one I built was from the "engineers notebook " radio shack sold back in the late 70s. I might still have that and it would be fun to review some of the projects in it. Will have to look and see if I have it. I have a few boxes of old documentation, service manuals ext in my storage locker. I am kicking myself as I had the entire Sam's photo fact catalog. A full file cabinet full of vintage manuals that I tossed out when I left the business in 2003. What I would do to get those back issues back If for nothing else other than to scan them all. I had hundreds of Sam's ans ecc manuals.2 full 4 drawer file cabinets overflowing with manuals.
In the late 80s and early 90s most providers of background music and other similar services began using satellite receivers because they could service a larger area as well as receive the programming directly from the original service (Such as Muzak) , so they no longer had to maintain a studio that played tapes of the program. SCA became mostly for audio books for the blind, but my guess is even this service is provided differently now.
A Software Defined Radio (SDR) can be used to decode SCA, using a 192kHz recording capable sound card. HDRadio (Hybrid Digital Radio), or IBOC is not on baseband (modulated signal), it are two blocks of digital carrier on both side of main FM channel (or AM/MW). HDRadio have a 400kHz channel bandwidth.
pksato Yes I am aware of this. Separate transmitter, however you do hear it in the baseband demod audio. I did show where it is on the baseband spectrum. However when iboc is used a radio station can not also have sca as the side bands from the digital signals occupy the spectrum. The exception is the 57khz RDS sub carrier. Being a low data rate text service that remains.
Setting a pll to the same frequency, then coupling the dc loop correction voltage through a blocking capacitor to an amplifier. Very clever :-D I used to use an old frg7700 receiver to listen for the i.f sections in faulty c.b radios. You didn't even need to connect direct to the circuit, just bring the antenna close to the stage. A very under rated tool the receiver.
What would interest me is if we can find a way to generate our own SCA-FM signals. I have many part 15 FM transmitters that I use for my experimentation, and I found a way to generate a CW signal in the 14 kHz to 16 kHz range and use proper audio filtering, and SDR analysis software, and a program called which is already available called Morse Code Agent where you can create a morse code to audio text messege at 15.330 kHz and play it back on the FM station in the part 15 collection. I use SDR Sharp to monitor the CW signals which are very narrow in bandwidth like any other CW signal. I would to take a step above and do more than just CW signals in the 15 kHz to 16 kHz spectrum, and also 50 kHz to 100 kHz spectrum. 15 kHz to 16 kHz is good for experiments when using your own part 15 FM transmitter. So there is more what you can on your part 15 FM station.
My problem also is that I cannot find the detector IF output from a DSP chipset FM receiver. That there is very challenging. That's why it's very easy to do these SCA-FM modifications with regular non DSP analog receivers and tuners. Have you found a way to modify a DSP chipset FM tuner?
Mark Anderson Yes I had the same issues with that decoder and had placed a bunch of resistors and caps to reduce the swamping from main channel. Proper sca receivers used high pass filters to kill everything below 50 khz.
I imagine they do. I used to hear Muzak playing in grocery stores and I knew it was SCA and no background noise. I actually fixed a CD changer for Muzak once. It was an NSM 100 disk, RS232 controlled changer and they had 3 of them for 300 special music CD's that played 24/7
Mark Anderson Musak as they call it was distributed many ways. Sca was one way. More common was a leased telephone line. The equipment is still in at the central office I work out of. The tie down blocks are still there but the programming has been gone for years. When the CD changer came out most of the services moved to CD. There was a record based system before that the seaburg 1000 that used special records. The reason "special" Cds were used with modified players was for song logging. Royalties are paid to the artist for every play. I remember shooting a wedding about 30 years ago now and the DJ was playing cassettes. During dinner while everyone was eating a police officer and a "suit" entered and headed over to the DJ table. After a few minutes the music went off and they carted off all his "bootleg" tapes and charged the DJ with public performance without a public performance license. It made for an interesting evening. No dance music. The DJ improvised. Since as part of the party they were doing karaoke they set up the karaoke system and guests had to sing to the happy couple. I layer found out the DJ was fined 40,000.00! The next time I worked with this DJ (I worked with him many times as we did package deals) he had boxes of CD all leased from power tracks. He said it was 100.00 a month 25 basically every weekend to play music which he just added to the cost of his gig. They dont mess around because about the same time this happened a restuarant in nanaimo got popped for playing recorded music in their establishment and got a similar fine.
Interesting, I did DJ work too, One guy I worked for had special tapes labeled AVLA. I made my own and I was illegal. I did not do it much and I had VHS Hi Fi masters of all my tapes. Yes music over phone lines, I used to work on jukeboxes in bars and one company called wired for sound did just that. Music came over satellite, cable TV, special 4 hour cassettes, or continuous loop tapes The CD changers Muzak had were from NSM and were usually used, minus the RS232 interface in jukeboxes. I also remember the special CDs and they sold them for roughly $1000 or so and you signed up for subscriptions to get a CD a month pop and one country. They marketed similar ones for jukeboxes with a proper universal title strip. It was ERG or Entertainment Resources Group. Yes Seeburg also was big in Jukeboxes, they did not adapt well to CDs. NSM made a whole new high speed changer, Seeburg took a 45 mech and added a CD player and hooked to a home stereo in the box or bought a Sony changer. Pioneer also failed miserably in the jukebox world. Seeburg went from number one in 45's to BK over the CD. Now most went under adapting to fully digital sound. I spent years in the coin op business and saw many connections to background music and DJ.
Mark Anderson That's right. It was a subscription and he got a few new disks every month. He would loan them to me to copy for myself. I was working in a restuarant a few years ago and they had one of the newer musak systems. It consisted of a single disk blueray drive and all the tracks were recorded to a 25 gig bluray disk. Owner said they sent him a new disk every 6 months. This was about 10 years ago now I saw that system. I am sure everything these days is hard drive based. The files in the bluray disk were encrypted some way because he loaned me an old disk to see if I could copy it and on my bluray drive I could see the space used but could not read any files. So they were using some non standard format that only their special player could read.
I don't think that we ever had this in use over here in Britain.If your homemade subcarrier broadcast decoder board had been working would it have given better audio than that heard with this video?
thepatsny The iboc channels are higher up on the baseband. I did tune them in. You could hear the buzz of the digital noise in the 100-300 range. Iboc extends the bandwidth to 400khz so 2 iboc stations can not sit next to each other. Unlike sca which is a sub Carrier fm modulated into the base band audio which is then modulated to the fm carrier the iboc signal is a separate transmitter that mixes in at the antenna for fm operation. The end result is the same, it appears as a sub carrier. Am iboc was done differently. Phase modulation of the carrier similar to how am stereo worked.
thepatsny Sca was and is used for digital signals. In addition to analog audio sca was used for digital services. Pagers, stock market ticker were the most common. Rds on 57 is still in use on many stations.
3RRR in Melbourne used to carry BBC World Service for subscribers on 50khz. Way back when SCA, known as ACS - Ancillary Communications Service, first appeared in Australia the magazine Electronics Australia featured a decoder that could select the three common frequencies, but not the 50 kHz used by BBC WS.
I did have a schematic as i built it. I will have to look. I built it in high school. I have boxes of old paperwork i am sure it is in there somewhere. Yes the discriminator output and mpx output is the same.
I dunno why but I sort of remember a Popular Electronics article with an SCA decoder, would have been from the 70s worldradiohistory.com/Archive-Poptronics/70s/1970/Poptronics-1970-12.pdf
Probably dumb? So if someone started a pirate style radio station. could build a system to transmit on the subcarrier as well. Like, have main music channel and local news and sport on subs? ANd could a radio chip in a cell phone pick them up with the right software?
12voltvids, WOW what a tutorial! Thanks for this. Part of it I knew, like the 19KHzl pilot for stereo. But I never put all the pieces together before. Because both AM and FM broadcasts are slowly going away in other parts of the world, it's hard to say how much longer it will remain relevant but fascinating nonetheless!! Also, did you pick up a new to you Tek 2465B scope? It's a nice one! 👍😁
Walt's Channel Thanks to HD radio in north America being the only standard accepted by the FCC analog am and fm isn't going anywhere because the hd signal rides alongside the analog carrier. The reason analog is going away in other countries is because their digital system is on a different frequency which allowed the government to auction off the old frequencies to other services to use them. That wont happen here because there is no spectrum recovered.
Walt's Channel The scope was sent in as s donation from a viewer. He also sent me his ct101 1.5" Panasonic color crt TV which I ended up buying to add to my collection.
@@12voltvids That was indeed Japanese radio at that station. I've heard the language spoken for myself and the station's audio seems to be similar to that from what I could tell.
I'd imagine that SCA has been done in by streaming audio over the internet. I'm sure the market for the audio is still there, but the delivery method has changed.
Right. I actually didn't expect to find anything at all on the band, so I was pleasantly surprised to find that Japanese station riding along on the CBC french service. Now music services are pretty much all streaming services. There are still plenty of satellite delivered private music services. Music Choice and DMX still operate on satellite as do department stores like Macys.
