405 line video of Test Card C recorded on JVC3320

[Murphyv310]

Hi.
Jeffrey it was only tested on the scope so whether it would work in practice I don't know. All gone now and sadly I accidentally sold my SCRF NTSC aurora instead of one of the mono ones.

[peter scott]

I'm surprised the NTSC 405 played well. One of the big problems with direct colour on VTRs (as against colour under) is that the subcarrier frequency jitters too much for the crystal based burst locked oscillator in the TV. I've seen this with PAL recordings on near-broadcast grade VTRs. They had the frequency response to  record the whole PAL signal but needed a specialised timebase corrector to stabilise the subcarrier frequency.

The head drum servo damping on my 3320 (or lack of) would not reproduce an accurate reference burst very well. The FS90B looks much better controlled.

Peter

[ppppenguin]

I very much doubt that direct colour on any helical scan VTR will give sufficient subcarrier stability to lock a crystal oscillator. There is a whole spectrum of jittter due to mechanical irregularities. Varies with basic mechanical design, machine alignment, servo quality, tape wear and heaven knows what else.

All non-broadcast VTRs (VHS, Betamax, V2000, U-Matic etc) used colour under to record composite video. This was mainly because of limited bandwidth, but it also simplified the process of recovering a stable colour subcarrier during replay.

By contrast, all broadcast VTRs that recorded composite signals did so directly**. The main ones were Quadruplex, B format, C format and IVC 9000. All used highly sophisticated timebase correctors to recover a stable signal that could be locked to an external video reference. Before digital video processing these TBCs were frighteningly complex. For example part of some TBC designs used variable LC delay lines to give the finest vernier correction. The capacitors of a convenional delay line were replaced by varicap diodes. The terminations had to be varied in sympathy with the delay to minimise reflections due to mismatch.

Later broadcast VTRs such as Betacam, BetaSP and M format had component YCbCr signal paths throughout. This solved a lot of problems. Then the world went digital.

To come right back to the start of this thread, where are we likely to find 405 line tapes today? Obviously we can make our own, as Peter has done. Many earlier non-broadcast VTRs would handle 405 as easily as 625, apart from any dropout corrector problems. The only intentional 405 formats were the Sony CV2000 with its horrible skip field recording process and the multistandard Quadruplex machines such as the Ampex VR2000. A very few people in world have working Quad machines. Fewer still have ones that are multistandard (405/525/625/819) and in working order. One such person, possibly the only one in the UK, is BECG chairman Paul Marshall.

**The digital D3 VTRs recorded composite signals. They were often used as a digital "drop-in" replacement for C-format.

[`FRANK.C]

Hi Peter
Thanks for testing the FS90B on record. It does very well.
I can keep an eye out for a FS90B if the VCR I have doesn't work out.

Frank

[Freya]

Amongst a few other interesting machines, they have an Ampex VR2000 at "The Box" Plymouth in the media display.
I have been playing with my NV-W1 which is comparable to the FS90B, results are very similar but without the breathing.

[peter scott]

The breathing was only with my old JVC 3320. The FS90B is quite stable.

Peter

[peter scott]

Hi Peter
Thanks for testing the FS90B on record. It does very well.
I can keep an eye out for a FS90B if the VCR I have doesn't work out.

Frank

Just for interest I thought I'd try recording 405 SVHS using a brand new SVHS tape. Unfortunately it didn't work at all although I don't think this has anything to do with the 405 line content because I discovered that my FS90B showed exactly the same refusal when I tried making a normal 625 line SVHS recording. So no confirmation of the SVHS 405 recording. :-(.

Peter

[ppppenguin]

A general point which is implied in this discussion, but perhaps not directly stated, is that successful 405 recording and playback depends on the absence of circuitry that relies on line length. The older the VTR, the more likely this is to be true. The drop-out compensator, with its one-line delay, is the first exception. So good quality tapes are important. Later VHS machines with more complex signal processing are more likely to have circuitry that depends on line length.