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I have obtained a couple more image dissector tubes for my collection. I now own seven image dissctor tubes... by definition. The dissector tube receives a lot of disprespect from people who do not understand its physical properties. Allow me to set the record straight. An image dissector tube, as invented by Philo T. Farnsworth, is an excellent image analyzing device for every application except real time Television!
Why? Because it does not use the property of charge storage as found in the iconoscope, image orthicon, vidicons, CCDs, CMOS sensors or their derivatives. The dissector is an instantaneous sampler. Instead of continuous velocity scanning, imagine a scan that works by stepping from pixel to pixel and dwelling for a finite time on that location. The dissector is an addressable photon counting photomultiplier tube that can do that trick very well. As the sampling position steps , pixel to pixel, let's say it dwells for 200nS. During that short time period, only so many photons will land on that spot. Like very light rain on a given square inch of ground. In that time, in a real world tv camera running at SD rates, only a few hundred photons will be counted. Forget HD rates. At high speeds, the dissector can only detect noise. Hences its low sensitivity in TV applications.
In a tube with charge storage, the photo site has the entire frame (or field) time to collect photons before being interogated by the electron beam or charge transfer pulse as in a solid state imager. This is typically more than a dozen milliseconds. That is six thousand times longer than the 200 nanosecond real time sampling of the dissector.
Now, slow the dissector down and install it on a satellite. Let it stare into the darkest parts of space and dwell on each pixel for one second. Though it would take 85.3 hours to scan a 640x480 pixel plane, It would be counting photons for tens of thousands of times longer than a charge storage tube of the same resolution, with the equivelant increase in gain. A charge storage tube would also become saturated by background noise (faint stray light, background heat, RFI or ionizing radiation) long before the scan could be completed.
Five of my dissetor tubes are precisely of this type. They are officially called steerable photomultipliers and they are used as star trackers in many spy satellites to this day. Remember, vacuum tubes are resistant to high radiation as found in open outer space or during an enemy nuclear attack of the satellite. So, Farnsworth's excellent invention serves where a part for mere entertainment purposes would be a dismal failure.
My last two image dissector tubes are true imagers. One tube is a one inch diameter with a form factor exactly like a one inch vidicon. The other is a two inch tube that will require winding a special deflection and focus coil in order to apply it. The star tracker tubes have a practical resolution of about 50x50 pixels. Maybe. The true imager tubes are much higher resolution. I can not quote a precise figure as I have no data sheets for any of them and IT&T (sole manufacturer of these tubes) custom built each type to (usually top secret) customer specs. We have a mystery to solve. The dissector is such a simple tube to apply, that I believe I can make at least one them produce pictures with not much effort. I believe the star tracker tubes would work well as a camera for 30/32 line mechanical TV and the full imagers would make great slow scan rate TV cameras. 120 lines at 24 frames per second anyone? Stay tuned!
Labguy's World has obtained a [Wesgrove VKR-500] longitudinal VTR. Made in England in 1965 and sold as a do-it-yourself kit! Formerly owned by John Fletcher. I only recently learned that John passed away 11 years ago. A restoration project for this recorder is inevitable. Please stay tuned.
Added a new project today. [5FPn CRT Tester] project. Obtained three tubes. 5FP5, 5FP7A and 5FP25. Had to make these old 1940s display tubes light up, focus and scan. Just to see the pretty colors of the various flourescent phosphors. Each optimized for a particular purpose. Enjoy!
Updated part 2 of the [color mechanical TV] project. The new high powered color LEDs are working extremely well. Visit the article and scroll down for the latest images. Enjoy!
THE FOLLOWING IS A LABGUY'S WORLD PUBLIC SERVICE ANNOUNCEMENT. IF YOU BELIEVE IN SAFE SPACES, TRIGGER WARNINGS OR SOCIAL JUSTICE, YOU ARE EXCUSED NOW.
"During times of universal deceit, telling the truth becomes a revolutionary act." ~George Orwell~
If you think Socialism is a good thing, you know nothing about socialism
America. So BAD people climb over, tunnel under or bribe their way through, our 15 foot tall walls to get into it. Just a thought after reading this morning's news headlines. What we scientists refer to as stark contrast. And virtually all of these people are fleeing.... you guessed it, Socialist Countries! The goal of Socialism is [ALWAYS Communism] and Communism KILLS! By the millions!
Don't let the root word "social" fool you. Karl Marx declared, "Call everything the opposite of what it is. The people are that stupid." This revelation should open your eyes. Socialism is anything but social. Your school teachers, and their communist labor union controllers, are/were ALL socialists. They lied to your from day one. You should be horribly offended at the way they raped your mind. Don't believe me? Name one conservative, or non-union, teacher still working in an American public school. Name the last time you learned how GOOD America is. No hurry. I'll wait. Picking up on the lack of balance in your education yet?
Who was [Karl Marx]? I rest my case!
The proof of America's demise will be this site being suspended for posting this truth. Check back often. If the site stays up, there might be real hope. Not our current Dicatator's false brand of hope. At this time, I still expect to die in a death camp. Bullet to the back of my brain box while kneeling on the edge of a mass grave. Like SO MANY before me. About 300,000,000 since WWII, not counting [Hitler's amateur tyrrany that killed ONLY 6 million people]. I will NEVER comply! I will not go silently. WWIII approaches.
Labguy. OK, so your are passionate. What the Heck does this have to do with Extinct Video Equipment?
Glad you asked! The collapse of the old Soviet Union was predicated by the wide spread availability of VCRs and FAX machines that allowed, for the first time in their history, communication of POSITIVE ideas into previously unreachable regions of the world. Ask anyone from Romania about their first contact with a VCR. They loved Chuck Norris over there! The soviet union loved Frank Zappa (count the statues of him in so many Russian town squares), our own American dissident who DID NOT end up in a prison camp for his contriversial views. VTRs, cell phones and faxes spread freedom and liberty. Imagine that!
God Bless YOU. God Bless America.
Best wishes to you and yours in 2016.
Another year has passed. This year, I hope to get my image orthicon camera operational and to begin or complete my [color flying spot scanner] project. The latter being several sub projects that will be combined together to form the entire system. There will be smaller projects too. Some more work on [color mechanical TV], my [amateur television (KJ6RNL) station], [cathode ray tubes] and more clever video circuits.
As a person prone to episodes of low grade chronic depression, my projects operate in a start-stop mode. The struggles with the old camera taxed me and I have become frustrated with it. It is a project that will be completed as I owe this to my dear friend, John Turner at [Turner Engineering] for his selfless help in shipping the camera to me safely from the east coast. If you need professional services, facilities and equipment for your professional and industrial television production needs, Turner is your only choice.
When I resume the IO camera restoration, hopefully soon, I must address a suspected instrumentation issue. I measured excessive current drain and have been stymied by this. I am unable to find a single thing to cause this condition. Then I started to think about the 8 dollar Chinese digital 100 amp ammeter I purchased on line. It never occured to me that it could be inaccurate. Did I mention the 8 dollars? You do get what you pay for.
The color flying spot scanner will consist of a premade commercial professional Telemation sync generator unit, a premade commercial professional Telemation NTSC encoder. Along with this is the "projector unit" which will contain the scanning CRT and support circuits. The optical unit will have a holder for 35mm slides, dichroic mirrors and three photomuliplier tubes with power supplies and preamps. This is essentially four partly separate projects.
Also waiting in the wings is a return to my 32 line NBTV mechanical television set. I have some more LEDs, diffusers and circuit ideas to test. My newest acquaintence, [James Hawes], has been discussing many good ideas with me via the new fangled electrical mail system. How many mechanical TVs use trichroic prisms to combine the red, green and blue light sources in color mode?
Can you believe it? The [Tiny Triniscope ] turns two years old next month! How time flies!
To see years 2007 to 2015 What's New pages, [CLICK HERE]. Scroll to the bottom of each What's New page to find a link to the previous year at the bottom.
Created: February 6, 2016, Last updated: February 6, 2016