80's tube ENG cams fun

[J Ballard]

Wayne has done an excellent job outlining the problems of tube cameras for HD.

The first time I saw an HD (1125 line) camera was at the SMPTE Winter Conference in SFO in 1981, made by Ikegami and using Saticon tubes. The resolution was quite good, but the noise was obvious. Later, while at NBC, we purchased a 30mm lead oxide (PBO) camera, also from Ikegami, and this camera did not suffer the image retention of the Saticon camera, and seemed to have much improved noise performance.

I believe that the lead oxide tube operated at higher signal current, but it likely had a much improved FET head amplifier. In addition, some manufacturers played games with the gamma corrector near black by placing a reverse correction that clipped the noise. It was not correct, technically, but subjectively, it was much quieter.

Wayne mentioned the special FET from Sony (?) that was sought by RCA for its cameras, but they would not sell it to a non-Japanese manufacturer.

In the late 1980s, there was a desire in the US and Europe for a HD production standard other than 1125 interlaced, such as the Zenith 787.5 line system. Hats off to them. I recall RCA Laboratories telling NBC the next TV standard has to have two attributes-component coding and progressive scan.

So NBC, AT&T, and Zenith bought Bosch KCH-1000 flexible standard cameras with Saticons. By changing dip switches and many ROMS, you could operate the camera in interlace or progressive. The complete camera, including image enhancer, was almost $500K. I wrote the PO, and no one flinched.

AT this time, Bosch and Philips merged their broadcast divisions, and camera development moved from Darmstadt to Breda. There was a lot of bad blood between the two engineering staffs, so assistance from the new company was a problem.

Noise from the Saticon camera was always an issue, especially when the signal was sent to an MPEG encoder. We generally ran the camera at the lowest sensitivity possible-minus 6 dB. But the pictures were high in resolution.

Later in the evolution of tube cameras, the diode gun tube was introduced to improve resolution. That it did, but only static resolution. The beam size was so small that it was inadequate for the complete discharge of a 525 scan line picture. The net result was an after image on moving, high contrast scenes known as "stern waving." I recall seeing the actor Danny DeVito in white shirt and tux performing in front of a diode gun equipped camera-the image resembled an unterminated delay line or coax, but it was moving with the scene.
The best advice about pickup tubes came from Bob Neuhauser of RCA-the electron optics of a tube must match the scanning standard. He was so right.
This was all so long ago, but it seems like yesterday.

JB

[old_tv_nut]

Originally Posted by J Ballard

So NBC, AT&T, and Zenith bought Bosch KCH-1000 flexible standard cameras with Saticons. By changing dip switches and many ROMS, you could operate the camera in interlace or progressive. The complete camera, including image enhancer, was almost $500K. I wrote the PO, and no one flinched.

JB

A few more notes on the KCH-1000. It was very flexible, but not quite enough for the progressive scan. The viewfinder could not run at 47kHz horizontal and had to be redesigned. Also, the digital control circuits ran at 27 MHz. These took special high speed (for the time) CMOS ICs, so we had to buy them only from Philips to have stock for any repairs.

Zenith and their partner, AT&T each bought a camera, and with the modifications we were charged $800k apiece. These cameras also followed the same practice as Sony and others at the time, of reducing the video bandwidth to 22 MHz or so to reduce the noise, but we needed 32 MHz to get sufficient H resolution with progressive scan. We immediately discovered the 27 MHz digital clock and control signals were running all over the chassis, and spent a lot of effort adding shielding and grounds to get it out of the video.

We also had to design and build our own aperture corrector/edge enhancer to work with the progressively scanned signal.

Fun!