My thoughts! about TeKaDe. by Peter Yanczer

At this point in time, over the years I have given much thought to TeKaDe, their activities and others pertaining to mirror screw television recievers. Those of you that have tried to research any activities on the subject of mirror screws, I am sure you will soon find as I have, that any road they take, is likely to be very short. There just isn't much information around.

In thinking about this situation, I have come to some conclusions that I would like to pass along, for you to accept or reject. Your choice. I"m sorry, I have no proof to offer!

In the very early 1930s, TeKaDe (which over the years had many other names) were into building radio sets, headphones and among other things, building and selling Nipkow disk equipped television kits. Around 1930 they hired a Hungarian television engineer Franz Von Okolicsanyi, who had previously been employed by another television engineer, Manfred Von Ardenne, whose main interest and effort was towards cathode ray tube television.

Mr. Okolicsanyi apparently had some ideas, for a new mechanical scanner of his own design. After a through discussion of his scanner with the TeKaDe people, they were satisfied to the extent that he was put in charge of a small group and given the task of further development of a new low cost television receiver for the home. It would be equipped with his scanner, the mirror screw.

Because of his previous work with M. V. Ardenne, Mr. Okolicsanyi was well aware of the current level of performance of cathode ray tubes used in a television application. He also was well aware of the many problems that still lie ahead. For example, cathode ray tube life was very short, some tens of hours at best. Manufacturing costs were very high and yields were low. There were difficult problems in many areas that had to be solved. For example... the phosphors (like the joke about the NTSC system (never the same color twice), ...the spot size limited pictures to about 100 lines or less, ...the deflection circuits (they started by using sine waves), ...the very high voltage (deadly 60 Hz) requirements and in general, ...the cost of the final receiver (out of sight). It could... and in fact did take years to solve these problems.

With Mr. Okolicsanyi's idea of using the mirror screw, instead of the cathode ray tube, none of the above would apply. The mirror screw provides it own vertical and horizontal deflection by simply rotating it. The light for the image originates with some sort of lamp. Neon (reddish/pink) was the first used. Early mirror drum scanners used an incandescent lamp (white) followed by a Kerr cell. This also worked well with the mirror screw.

The only component that had a high cost in a Okolicsanyi/TeKaDe television receiver was the mirror screw itself. Built on a small scale, hand made and very precise, the estimate for one piece would be hundreds of (1931) dollars. However, it is known that he considered having the mirror screw formed in molds, of Bakelite or a similar material, much like the large tuning knobs used on radios of that period. The reflecting surfaces would be electroplated with chromium. He stated that the price for mirror screws would be no more than two dollars each. But the quantities had to be large (~ 50,000). With such a mirror screw, TeKaDe could offer a respectable size picture (~ 4" X 5" ) with somewhere between 100 and 180 lines for a very low cost. But, since there was no immediate large market for television, it was impossible to justify the high startup cost of molding the mirror screws. In addition, the television line rate requirements (controlled by the German Post Office), kept changing in the upward direction. When they first started, about 100 lines were enough. In fact, TeKaDe built a few 90 line, small mirror screw sets for demonstration.

At the same time, there were at least a dozen engineering groups, in countries all over the world, working hard to develop an all electronic cathode ray tube receiver. One of the most important characteristics of a cathode ray tube receiver is that the picture line rate of the deflection circuits, can be changed up or down, by simply turning a knob. Therefore, it was easy to "up" the line rate as other portions of the circuitry were improved. (Not so when using the mirror screw! )

Which is exactly what happened. Before long, the new standard line rates was increased to 180 lines. The 90 line mirror screw was now obsolete/inoperable and therefore had to be replaced, with one built to operate on the 180 line format.

In the years 1934 and 1935, at the Berlin Annual Radio/Television shows, the TeKaDe 180 line mirror screw receivers, were judged to provide better and the best pictures of all of the televisions on display in both shows. Mr. Okolicsanyi was so confident, that he attempted to get TeKaDe to transfer all of their engineering people from cathode ray receiver activities to further mirror screw development. Mr. Okolicsanyi was present at the 1934 show and was telling anyone that was interested that, that was going to happen.

It didn't!

Within 2 years, there were signs that the line format would be raised again. Since the increases in the past were usually a doubling of the previous number, it was expected that the new rate would be 360 lines. To get ready for this, Mr. Okolicsanyi developed and patented some additions and changes to the standard mirror screw construction, that he felt would provide good operation on as much as 360 lines.

However, when the format change was announced, it was not increased to 360 lines. was jumped to 441 lines.

And that signaled the end of the mirror screw.



* Last thing heard about Mr. Okolicsanyi, was that he had left TeKaDe and was hired by Scophony.

* It has be determined that the first patent given towards the mirror screw went to Mr. D. B. Gardener, Filed September 17, 1928 in Los Angeles, CA.

* Your comments would be appreciated. Thank you.

* Todays date: 1/27/09