405 line recording.

[Station X]

channel405 wrote

Hello John,

A question about your 1980 recording if a may! How did you record that? Did you use a Sony 405 line CV2000, record baseband video from a TV onto a VHS, Beta or Quad machine! Did you record because you anticipated 405 was going off air 5 years later? I now this is a slight deviation from the original thread but this fascinates me, especialy as there aren't many original 405 line off air recordings around and home VCRs will still quite expensive even by 1985. And extracting a signal from a live chassis can be slightly precarious!

Regards

Tim

[peter_scott]

Hi Tim,

I think most (625 line) VHS machines are quite oblivious to line rate since they record complete frames, so you can record 405 line video signals directly into the video input of a normal VHS VCR and play them back with excellent quality without any modification what so ever. The only thing that doesn't work is the drop-out compensator, but if you use good tapes this is not a problem.

HTH

Peter.

[ppppenguin]

Generally, earlier VHS machines will be better on 405. Some later ones do know about the line frequency and will give trouble on 405. Peter is correct about the DOC so use good tapes.

It's still a better bet to buy a standards converter

[Heatercathodeshort]

Hello Tim,
My 405 line recordings were made between 1980 and 1982 using a standard VHS machine. At the time the JVC/Ferguson 3V29 series had just come out and all that was required was a 405 line signal source. This was obtained from a Bush model TV166 dual satandard set with the video signal taken from the anode of the PFL200 video amplifier via a small emitter follower stage using a BC108 transistor. The sound signal was taken from across the volume control in the normal way. The signals were fed to the audio and video input sockets of the machine and played back via a system 'A' modulator. The television was run from the workshop isolated supply. The video head slows to take into account the reduced line frequency and the servos lock fully,results are superb. I have made copies of the original tapes and they appear to be little degraded. Yes I did realise 405 was going off air and it felt very odd when the screens finally went blank on the old sets 25 years after I had first entered the trade. Never mind! They live again!
Regards JOHN

[Danny]

Before i was lucky to get a standards converter i used an old sony cammera i converted to 405 and used a ferguson 1690 as the monitor the results were a lot better after recording them with a ferguson 3V35 video but it is easy to record the output of a standards converter if it has video level output. but this is pointless if you own the standards converter! .
Danny

[peter_scott]

Originally Posted by Heatercathodeshort

The video head slows to take into account the reduced line frequency and the servos lock fully,results are superb. Regards JOHN

Hi John,

I think what actually happens is that the video heads traverse the tape at just the same speed as they do with 625 lines but you are writing fewer lines across each traverse. Likewise the replay speed is the same again and of course you get the same number of lines out that you put in (between frame syncs).

One thing that hadn't occured to me, until Darius mentioned it, is that when you record 405 lines on VHS you get proportionately greater bandwidth because you are devoting more tape to each line. So, if your VHS machine has 2MHz video bandwidth at 625 it will have 3MHz bandwidth at 405. 405 line definition is therefor much better than what we are used to with 625 lines.

Peter.

[ppppenguin]

When recording 405 the heads definitely do not slow down. The drum still rotates at the same speed, locked to the 50Hz field sync. The lower bandwidth of a 405 signal means that ordinary VHS can give very good results. The bandwidth of the VHS machine is unchanged. If it was 3MHz on 625 it's still 3MHz on 405. The difference is that 3MHz is virtually full bandwidth on 405 but on 60% of the 5MHz needed to fully record 625.

[oldeurope]

Good morning,
look at this thrad #3 it showes the resolution increase with 405 recordings.
https://www.vintage-radio.net/forum/...ead.php?t=1916

If your vcr uses an electronic delay ccd you can make a 405 detector and
change its clock frequency. I did this with my vhs successfully. An LED
showes the 405 at the front panel.

Some modern vhs are counting the lines for the head switch pulse
and the delay ccd is a part of one big video processing IC.
In this case you can replace the color XTAL by a tuned cirquit to
reduce the frequency. I made this with a Grundig SE41VPS and it
works very well.

Kind regards
Darius

[peter_scott]

Originally Posted by ppppenguin

The bandwidth of the VHS machine is unchanged. If it was 3MHz on 625 it's still 3MHz on 405. The difference is that 3MHz is virtually full bandwidth on 405 but on 60% of the 5MHz needed to fully record 625.

Hi Jeffrey,

True enough, I was getting carried away with nonsense thoughts and appologies to Darius for attributing those thoughts to him.

Peter.

[channel405]

Hello Chaps,

Thanks all for your input on this subject.

Sadly I was unable to afford a VCR in 1984 (being only 14 at the time and not given enough pocket money to buy one even an old Beta) as 405 was closing, but I did watch the last transmissions. With standards converters being (understandably) relatively high in price, video recordings are the best way to go. Like others here I find that modern VCRs (I used a Panasonic pro SVHS deck) produce a ghost image displaced to the left of the main image. I tried a Lo band Umatic once with my Sony 405 camera, and that produced a similar ghost image, though stretched. I put this down to the either the DOC or sharpening circuits. Otherwise the pic was brill!

Maybe the only way to record 405 then is to use an older pre HQ deck. Hmmmm, might be worth a look on ebay.......

Tim

[peter_scott]

Originally Posted by channel405

(I used a Panasonic pro SVHS deck) produce a ghost image displaced to the left of the main image.
Tim

Hi Tim,

I am using a Panasonic NV-FS90B SVHS machine without problems. By what percentage of the line is your ghost displaced by?

Peter

[oldeurope]

Originally Posted by channel405

Hello Chaps,

Thanks all for your input on this subject.

Sadly I was unable to afford a VCR in 1984 (being only 14 at the time and not given enough pocket money to buy one even an old Beta) as 405 was closing, but I did watch the last transmissions. With standards converters being (understandably) relatively high in price, video recordings are the best way to go. Like others here I find that modern VCRs (I used a Panasonic pro SVHS deck) produce a ghost image displaced to the left of the main image. I tried a Lo band Umatic once with my Sony 405 camera, and that produced a similar ghost image, though stretched. I put this down to the either the DOC or sharpening circuits. Otherwise the pic was brill!

Maybe the only way to record 405 then is to use an older pre HQ deck. Hmmmm, might be worth a look on ebay.......

Tim

No problems with Umatic here.
Verify that your black poch is long enough after the H-sync.

Darius

[Heatercathodeshort]

Hello,
Well you have got me head scatching with this one. The head on my 3v29 VCR playing 405 tapes does run around a third slower when playing 405 tapes as compared with 625 tapes. I checked this evening comparing two machines with a tape in each. Slowing the head down manually decreases the line frequency and likewise speeding it up will increase it. The difference in speed can clearly be seen. Any comments here? Always willing to learn something even at my age. Regards. JOHN

[ppppenguin]

That's really weird! The head drum rotation must be locked to field frequency, if only to keep the head switch in the right place at the bottom of the screen. Since 405 and 625 have the same field frequency, the drum must spin at the same speed.

[peter_scott]

Originally Posted by Heatercathodeshort

The head on my 3v29 VCR playing 405 tapes does run around a third slower when playing 405 tapes as compared with 625 tapes. Regards. JOHN

Hi John,

How are you measuring the drum rotation speed?

Regards,

Peter.

[channel405]

Hello Peter,

The Panasonic I am using is an AG7510 edit player for edit suites etc. I would say the ghost image is displaced to the left by roughly 40-50% or so. Could this be the difference between line duration i.e 100us-64us? Could this be a DOC delay line, but this should only happen if the FM drops because of a tape blemish/drop out etc and surely not be present all the time?

I've taken a photo, not too clear I admit. The symptom is clearer in the flesh, but as you can see to the left is an image though much reduced in contrast. If you look closely you can just make out a dark band from top to bottom just right of the centre of the picture. This is a non-"ghost image" affected part of the picture.

Tim

[ppppenguin]

There's a one line delay (64us) somewhere in the main signal path of that recorder. Possibly part of a comb filter decoder. If it's an SVHS recorder you could try using just the Y part of the S input. Otherwise I'm afraid that the recorder is not suitable for 405. You need something older and less sophisticated

[peter_scott]

Hi Tim,

I don't know how SVHS differs from VHS but are you using SVHS tapes or VHS?
Which ever it is have you tried the other?

Peter.

[oldeurope]

Originally Posted by ppppenguin

There's a one line delay (64us) somewhere in the main signal path of that recorder. Possibly part of a comb filter decoder. If it's an SVHS recorder you could try using just the Y part of the S input. Otherwise I'm afraid that the recorder is not suitable for 405. You need something older and less sophisticated

Hi, I agree with you Jeffrey.
But why does he have problems with U matic? What kind of Umatic was used?

John, you are right with drumm speed and line frequency but this does
not change the amount of lines. So if you reduce the speed playing
a 625 tape the V frequency will be reduced too.
This is why a vcr can not used as a standard converter.

Please remember the vintage VCR's. They had one big motor and an
inductive brake. Thus the speed can not change much but they play
625 and 405.
As Jeffrey toled the drumm speed is locked with the
CTL pulses on the tape and these are locked with the V frequency.

Kind regards
Darius

[channel405]

Hi Peter and all,

A though just occured to me when ppppenguin mentioned the Y signal, there is a switch on the back of the unit, at bit like the first generation VHS machines that alows you to select between B/W, colour and Auto. I'll try this in B/W mode and see what difference this makes. From memory, this not only disables the chroma but bypasses a comb filter which reduces the Y signal resolution to prevent beat frequencies with the chroma, am I on the right lines (excuse the pun)? So I should have slight increase in resolution in monochrome and possibly no ghosting, will report back.

The tape differences shouldn't make a difference, I think this is a playback phenomenon rather than a recording issue.

Daruis, thanks for your suggestion about the back porch with Umatic recordings. But if I remember the original 405 spec didn't include a porch before the H pulse, and as the camera I used is of 1966 vintage I don't know if the camera would be generating one. The Umatic I tried was a portable JVC Lo Band one, quite old but fully working. The picture was very good otherwise, its a much better system than VHS and there is no noise on recordings, even on 625 lines. These machines are good value now for this sort of thing as they a cheap, well made, far superior to domestic stuff and there are loads about. The ghosting effect was different to the VHS one, I'll dig a tape out and see if I can get a photo of it.

Tim