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Old 02-28-2019, 09:47 PM   #16
apollo16uvc
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Originally Posted by Notebook View Post
 Got some more comments from my friend:





BCD to me is Binary Coded Decimal, but with 40+ year old instrumentation recorder, it probably is something else.

EDIT:

This is the machine:
https://i89.photobucket.com/albums/k...psvxlyyvze.jpg

N.
Awesome Notebook, thanks for contacting him.

If I were to digitize each track, would it be possible to demodulate the FM track with a computer program? From what I understand, in order to demodulate an FM track you need a reference track. back in the day this was done with an analog circuit, but with today's computational power it should be possible to take the FM track and reference track audio files and process them?

Most documents talk about an FM track called 'SDCT' Sometimes the document doesn't give a frequency of this track, sometimes it says 13.5kc. According to the document the purpose of this track is timing.

Soon I will publish photos and scans of all tapes and their documents, hopefully this will clear things up.

---------- Post added at 09:47 PM ---------- Previous post was at 09:45 PM ----------

I have got great news on the new ESA tapes!

I have tested out three of the five tapes with a magnetic viewing solution, and all three clearly showed 7 tracks like the NASA tapes. This means they have not been degaused or overwritten with an audio recorder. The tracks look like raw telemetry, not computer tapes. One tape has a label that clearly says it came from a tracking station. I think we should be able to digitize these too eventually.

The tapes I have tested are:
TD-1 (Tape ID: 1117-09-08-B)
ESRO 1A (Tape ID: 800 645 08 10B)
HEOS A2 (Tape ID: 1115 06 11B)

I have made two videos on it in dutch.
First, a tutorial on how to make your town magnetic viewing solution.



And finally, a video where I visualize the magnetic tracks on 3 tapes:


I have attached some photos of the tracks to this message. I promise I will publish a big archive with detailed scans and photos of all ESA and NASA tapes currently in my possession.

I am interested to know if it is possible to determine the frequency of a signal by the macro photos, any ideas?

Best regards,
Niels.

Macro photos:
https://imgur.com/a/rnlJH9P

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Old 03-01-2019, 09:16 AM   #17
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Hello Niels, you are welcome again, if we come up with anything more will post it here.

FM on tape was used in the VHS format video tape, not in broadcast machines as far as I know.EDIT wrong FM was standard from late 2"(it was 40 years ago...)
My colleague knows far more about tape than me, I'll give him a call...

N.

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Old 03-01-2019, 09:37 AM   #18
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Most video tape formats used FM for the audio, like VHS.

Most of the NASA satellite tapes have the telemetry channel designated as 'Direct' but I think one or two documents also have a one of the two telemetry channels as 'FM'
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Old 03-01-2019, 10:22 AM   #19
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 Most video tape formats used FM for the audio, like VHS.

Most of the NASA satellite tapes have the telemetry channel designated as 'Direct' but I think one or two documents also have a one of the two telemetry channels as 'FM'
We are at cross-purposes here. I was only talking about the video system on broadcast tape machines. The two machines I know best are the
Ampex VR2000, and the Ampex VPR-2.

The VR2000 used the quadruplex system and recorded across the width of the tape. Early models didn't use an FM system for video.
The VPR-2 was heleical-scan and used FM from the first models.
Both well obsolete now, and hard to find.
Consumer machines I never worked on, so little info.

Will see what we come up with the instrumentation tapes.

N.
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Old 03-01-2019, 11:35 AM   #20
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 ...Macro photos (Large!)...
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Old 03-01-2019, 11:59 AM   #21
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 Site requires registration.
Fixed, link now points to an imgur archive with photos.

---------- Post added at 11:59 AM ---------- Previous post was at 11:48 AM ----------

I have finally finished v1.0 of the archive for the NASA satellite tapes.

Sat-53123114313-Version1.0 (Object photos, text file.)

Sat-GFORKS-314N003-Version1.0 (Object photos, documentation, Akai RTR sample, visualized tracks)

Sat-GFORKS-314N079-Version1.0 (Object photos, documentation, Akai RTR sample)

Sat-GFORKS-330N100-Version1.0 (Object photos, documentation, Akai RTR sample)

Sat-SNTAGO-120J827-Version1.0 (Object photos, documentation, visualized tracks)

Sat-SNTAGO-314J019-Version1.0 (Object photos, documentation)

Sat-WINKFIELD-330P001-Version1.0 (Object photos)
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Old 03-01-2019, 01:06 PM   #22
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More from L.
Quote:
Morning George, cloudy and damp down here.
Interestingly, for me at least, one of those tapes was manufactured by Pyral which was a French company who invented a particular method of applying the magnetic coating to the base material. Zonal Films, where I worked adapted and used it under licence, but that's off topic.
Very early video tape recorders used a mixture of 'direct record' and FM. Both RCA and the BBC produced linear (fixed head) machines running at something over 100 ips. Surprisingly 'direct recording' was used for the video, and FM for the audio, however these linear machines disappeared once Ampex demonstrated their 2" Quadruplex rotating head system. The first production machine was the VR1000, it produced far better pictures than the old linear machines, and overnight became the broadcast industry standard. The first VTR I worked on was a VR1000B made in the late 1950's, it used FM for video, direct record for audio. The next generation of Ampex VTR's was the VR2000 also using the quadruplex system. FM frequencies were from memory 7.16 MHz sync tip, 7.8 MHz black level, and 9.3 MHz for 'peak white', linear tape speed was 15.625 ips. Also a bit off topic.

The Pyral tape shown appears to be a mixture of direct, or saturation record, and FM. Although you can see some of the lower frequency components quite clearly, I'm not sure how well higher frequencies could be resolved. The FM recordings we made on that Honeywell Instrumentation recorder were only for 'in house' quality checking of our manufactured tapes. The FM carriers were fixed, and from memory no separate track was used for the carrier.

I'm not sure how successful recovering the data by the developing method would be, remember that 10.5" spool will contain at least 2,500 feet of tape, and that's a lot of developing. I also think, although cannot say for sure that the FM signal needs to be demodulated before digitizing. Maybe there is a clever piece of software out there to perform this task.
Regards, L

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Old 03-01-2019, 11:14 PM   #23
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 More from L.

Lots of great information, thanks notebook and L.

I think L misunderstood, the developing is not to digitize the contents. But to verify if there is anything on it at all, how strong the tracks are, and what kind of signals we can expect from each track.

Unless we are able to find a 7-track instrumentional recorder, I plan on using a 1/2 inch Otari 5050 8-track studio recorder. So far the speeds I have seen on documentation are selectable on the Otari unit, 7.5 and 15 IPS.

8 =/= 7 tracks of course, so I hope to accomplish this in two ways:

1. Move the 8-treack head to align one of the 8-tracks with one track on the 7-track tape. Repeat process for all 7 tracks until everything has been digitized.

Question: Are this many replays damaging to the tape, is head gap and track height indifferent enough to give adequate signal?

2. Get a 7-track head, from a broken instrumentation recorder, or a 7-track computer tape drive (Big mainframe reels) and make a head carriage assembly so it can be put in place of the 8-track reproduction head. Connect the 7 tracks to the normal playback amplifiers of the Otari, align 7-track head, and digitize all 7-tracks at once.

Questions: Is output from 7-track computer tape drive and instrumentation head close enough to the 8-track audio head so it can be connected to the Otari playback amplifiers without damage?

Is wiring compatible, was it always basically the same?

Where to get 7-track calibration/alignment tape?


If either one of these has been completed, we will be left with 7 WAV or FLAC audio files for each tape, digitized at 24bit/192Khz. These files contain the raw signals received from the playback machine.

I do not think recording an FM signal like this is problematic? it is just a wave form like any other audio signal right?

I do not think 'direct' recordings should be a problem, as no demodulation is required.

With today's computational power it should be possible to then take the FM wav file and demodulate it with a computer program. As long as we can find the modulation settings used.


Sorry for so many questions, and I am thinking far ahead here. This is so exciting.

Baby steps.
Niels
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Old 03-02-2019, 10:32 AM   #24
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We both misunderstood, thought you were going to build a hand-held bar-code reader style device and run it along your developed tape!

Personally, I think you should try and get a 7-track machine. If you try to modify an 8-track audio head that will be difficult. If it has a tape guide built into the head, you risk damaging the tape edge if you alter its height. If it hasn't you could use car mechanics "feeler-gauges" as shims to place under the head. Depends on the construction of the tape deck. As long as you don't alter the other tape-guides, you won't damage your tapes

For the rest of your questions, I don't know! I will pass them onto L. for comments.

You won't damage your electronics, the play-back pre-amplifiers will just be overdriven and distort if the flux density on the tape is too high.


I'll have a talk with L. about how a conventional tape deck will handle an FM signal. Depends on the carrier frequency and the deviation(how much the carrier signal changes with the modulation) as to wether it will get through the playback electronics.

It still needs to be demodulated after that.


N.
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Old 03-02-2019, 02:39 PM   #25
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Hmm, good call on the heads, I took a second look at the Otari MX5050 MKIII-8 headstack, and the rec and repro head seem to have skirts around them.

See here: https://reverb.com/item/10099682-ota...ack-head-block

It looks like the skirts are integrated around the head, so removing them is unlikely to be an option. Will this allow enough movement to align with every track?

I will be contacting some people who worked with IRIG equipment and hopefully know some units that are still around. I am not sure if I want to ship the tapes though.

I still think a good option would be to take a 7-track head from a broken unit and put it in place of the Otari 8-track repro head. Might need to machine a carriage assembly with spring-loaded screws to align it correctly. Doesn't sound too hard, right?

Could even have the carriage 3D printed, if it isnt used as a ground for the head?

I always though heads could be aligned by turning spring-loaded screws. The photos of the Otari heads don't seem to have this. Seems strange for a pro studio recorder not to have this basic feature? How would you calibrate your deck?!

Best regards,
Niels

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Old 03-02-2019, 03:20 PM   #26
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I really didn't work with multi-track tape machines, so my info is limited.

The spring-loaded screw arrangement was for the azimuth adjustment, making sure the head gap was at right-angle to the tape motion. I don't think any machine I worked on used that. All head and tape-guides on broadcast machines used locking screws after the tape alignment was finished.

Fitting a 7-track head onto your player could work, depends on the construction of course. You may find the head stacks have mu-metal shields around them:

https://en.wikipedia.org/wiki/Mu-metal
They were used to reduce external magnetic fields affecting the record/play head.
As you are playback only you could remeove these if it helps the mechanics.
Be carefull with them, they loose their "magic" if they are dropped or bent.


N.
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Old 03-02-2019, 09:52 PM   #27
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Didn't see the other images on your #25 above, and from image number 3 you can see the mumetal shields around the erase head on the left, and the record head in the middle.
They aren't tape guides, they are well clear of the tape path.

The playback head is on the right and unshielded.
In this case you can add metal shims underneath the pb head to find one of the tracks.

I'll have a chat with L. regarding the relative distance you would have to move the head.
For info, all tapes have a reference edge where track spacings are measured from, that can be the top or bottom depending on the standard.

EDIT just had more looks at you images, and each of the heads has a threaded part of the head base, above a dark insert in the head block. The dark insert is
also at the front of each head. Suggests this is an azimuth adjustment from below?

N.

Last edited by Notebook; 03-02-2019 at 10:43 PM.
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Old 03-02-2019, 11:39 PM   #28
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Once I get the recorder I will make some test recordings and visualize the tracks so we can determine how many mm we need to move the head. I'll take precise measurements to keep track of the adjustments.

The head without the shield is the erase head, properly don't want to switch those around!!!

See the MX5050 MK III 8 service manual at the bottom of this page:
https://www.analogrules.com/manuals/otari_manuals1.html



It looks like the head connects to a plug via wires, and those wires might be removable? so I may not have do cut anything. If they aren't removable, i'll have to use a soldering iron. Doesn't seem too difficult... (If I do a head transplant)

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Old 03-03-2019, 12:29 AM   #29
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Must admit the heads from left to right on your images are the erase head then the record head then the playback head on tape transport. That follows from normal tape construction.

If you look at image 1 the two heads to the left are the record/playback heads they both go to the same edge connector. They also have multiple twisted wire connection.
The head on the right has larger conductors and goes to a separate connector. That is the erase head. Note the fewer cables.


The head without the shield is the erase head, properly don't want to switch those around!!!
No its not, the erase head is always at the entry to the tape path.

N.







N.

Last edited by Notebook; 03-03-2019 at 12:53 AM.
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Old 03-03-2019, 09:15 AM   #30
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Hello again Niels.
Ignore much of what I wrote after 19:00 last night, it was a Saturday...

I can't open the rar. files, they need a password. Not important though as your .img in #28 shows a good drawing of the head-block.

I thought the head block was bolted to the chassis, but it has the heads "upside down" and on top of the tape-guides.

Just have to figure out how much you need to move the head to find the track you want, and see what comes out the audio channels.

Just for info, the only machines I saw in studios were Studer and Revox. Usually studio machines have XLR audio connections, others have RCA phono or DIN.
https://en.wikipedia.org/wiki/XLR_connector

N.
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