EPG Jr. Hardware

[AriX]

Okay, so I may not have time to write all of the stuff down that I want to write down, because I really need to do some homework and I've been putting it off for a decent bit of time while researching this stuff.

Let's start with my hardware news:
I found another person who was lucky enough to grab one of the EPG Jrs that were being sold on eBay a couple (?) of years ago, and he was kind enough to ship me his EPG Jr. cart and data demodulator. The cool thing is that the demod he sent me is a different model than the kind I had - it was made by Zephyrus Electronics, like my other one, but is two years older (labeled 6/86 instead of 7-88), and has different branding. It's also in not-so-great condition. Both demods are labeled "UV-D-2", but mine also says "REV D" on it. I would guess that UV-D-2 means United Video Demodulator 2, where the original UV-D was likely designed for the Texscan machines rather than the Atari ones.
The new cart I got is dated "10/14/96", while mine says "5/11/90". The cart itself is labeled "DK-JR.PCB", while mine is labeled "DK-JR". My cartridge's select code is DKJR6, which I previously thought to be related to this marking, but it turns out it may just be a coincidence, since the new cart is NNJR6 (different from the ROM we have, which is NJJR6). Additionally, I sent an ex-UVSG guy a picture of my cart a few weeks ago, and he told me that he was actually the original designer, and later made a connection that I probably should have seen - DK are his initials. These Zephyrus boards cost United Video $125 a pop, which was much better than the original Wagener Communications boards that were used in the very beginning of the EPG Jr., which were larger and cost $800 each.

Here are pictures of the new hardware: http://www.flickr.com/photos/arixr/sets ... 023987739/

One of the pictures there is of a crystal labeled "5.52625 MHz", which fell off of the demodulator at some point. While I was looking to see where the part was probably meant to go on the board, I noticed that the same one was present on my newer revision of the board, which of course, was not very surprising. The back of the component on both Atari boards say "JAN". Then, I looked on the Amiga's data demodulator card, and noticed that it had two very similar crystals. In the EPG DATA trace, the crystal is labeled "5.52625 USCC", while the back says "9535". In the CONTROL DATA trace, there is one labeled "5.51125 USCC" (I'm pretty sure that's what it says, it's EXTREMELY difficult to see), and the back says "9533".

At that point, I remembered two posts (here and here) that swest77 made a while ago, talking about frequencies. Of course, the 7.237 MHz audio transmission referenced in the satellite chart he found does not match up with the 5.52625 MHz crystal I found, but swest also mentions that this chart originated in 1984, and I know for a fact that around 1985, UVSG began moving from Texscan-based EPG units to Atari-based units, additionally adding the Amiga-based machines to their product lineup only a few months later. I also know that the Atari/Amiga EPGs used a different data format than the Texscan ones, so it only makes sense that they would place the new data feed on a different audio carrier to make for a smoother transition. So I started searching around for slightly newer satellite charts, and found the "South Scanner Satellite Services Chart" (SSSC), which appears to have been well-maintained from 1991 through 2002.

Let's focus on the Electronic Program Guide for a moment, and ignore Prevue Guide. If you take a look at an early version of the SSSC, and search for WGN, you'll find it on Galaxy G5, transponder 7. United Video must have moved WGN to here at some point - Satcom F3, its original location, was retired by 1992. (I think WGN may have also been on Galaxy G1 from sometime around 1986 to sometime around 1991). The important thing to note is what's immediately below WGN, at 5.48 MHz -- "SuperGuide Data Transmissions". SuperGuide, of course, was one of the first interactive program guides, and was likely in competition with United Video's Electronic Program Guide. Therefore, I would say it is highly unlikely that UV would be carrying SuperGuide's data feed on their WGN satellite transponder. More likely, the person who compiled this list made a mistake, and put SuperGuide instead of Electronic Program Guide. In fact, even the most recent edition of the SSSC I could find, circa 2002, still has the SuperGuide Data Transmisisons listed on WGN's transponder, and although EPG Jr. was still running in 2002, I think SuperGuide was long gone. Wait a second though - 5.48 MHz is really really close to 5.52625 MHz. I don't know much about anything in this field, especially test equipment, so I'm just spitballing all over the place, but I would guess that if you're not being too careful or you don't have really exact test equipment, 5.48 MHz wouldn't be all too distinguishable from 5.52625 MHz. So, I'm thinking that's just another mistake on the SSSC's part.

Unfortunately, the Prevue side of things doesn't make quite as much sense. According to the crystals on my Amiga demod, the Prevue Channel used similar data carriers as the Electronic Program Guide. However, looking at the various editions of the SSSC, I notice "Data Transmissions" on the transponder basically everywhere but where I want to see them. Different versions report data transmissions on 5.20 MHz, 5.755 MHz, 5.96 MHz, 6.03 MHz, 6.505 MHz, 6.534 MHz, 6.58 MHz, and later "occasional audio" also on 6.58 MHz. I'm somewhat inclined to think that maybe they missed it somehow or something, especially given that according to the SSSC, the definition of a data transmission is "There are possible Telephone/VSAT/Data transmissions on the noted transponder. I notice a buzz in the audio or darkening of the screen without any FM Squared transmissions are a good tip to tell there may be some data transmissions such as VSAT or Telephones traffic."

The last thing to note on the Prevue side is that the Prevue Guide is originally seen on Satcom F4, but is later observed on both Satcom F4 and Satcom C4, along with a notice that "These services are gradually going to move off F4R and go to other satellites (common satellites to move to are Satcom C1, Satcom C3, Satcom C4, and Satcom F2R). Most of these should be gone by February 1993." Sure enough, in the next edition, Prevue is exclusively on Satcom C4, transponder 8. Like swest77 has said before, the audio carriers are 5.9MHz background, 6.2MHz right, and 6.8MHz left.

Whew. That took a while. No homework for me tonight...

Reference satellite charts:
1984 Chart
Volume 1, Issue 1
Volume 1, Issue 8
Volume 2, Issue 7
Volume 2, Issue 10
Volume 5, Issue 1
Volume 8, Issue 1
Volume 11, Issue 1

[tin]

Hmmm, very interesting stuff - sorry your homework got bumped!!

Aside from all the audio information, have you run the cart? Does it have any differences to the one we have dumped?

[AriX]

Hmmm, very interesting stuff - sorry your homework got bumped!!

Aside from all the audio information, have you run the cart? Does it have any differences to the one we have dumped?

Yep, the cart is the same "Revision 6" we're used to seeing, and did not have any noticeable differences despite the 6 year difference in the date. At some point I'll dump it and run a diff against the other two versions we have, which I just posted on the wiki. Note that these cartridges are socketed, meaning that the EEPROMs inside them can be swapped out easily. Most likely, the Revision 6 we keep seeing is not an early version, but actually the final version of the software. Also, I'm not sure if these carts support it or not, but I know that there were two main versions of the EPG Jr., one of which was upgradeable (EEPROMs rewritable) via software.

Also, the frequency I saw on the crystal is presumably not audio, but the data feed. I'm going to do a bit more research to see if I can figure out how exactly the data streams were transmitted; if I could modulate the correct feed onto 5.51125 MHz, I could capture the other end of the demodulator and figure out how this whole bit-banging thing works.