Com fer una emissora de TV molt senzilla
on: Sun 15 of Apr, 2007 [17:15 UTC] (15366 reads)
In the mid-1980s, I was involved in "micro television" that was a television counterpart of "Mini FM" radio. The easiest way was to use a RF module that was installed in every VCR and TV game machine at the time.
We used to have a slogan that every VCR could become a micro TV station. It was theoretically possible but in practice there were problems. Using a "antenna booster" or a hand-made booster circuit, the very week output signals (images and sound) of a RF module was led to an proper antenna. But there was a significant loss in the cable connection between the VCR and the booster.
So, I took out the module from the VCR and soldered it to the booster circuit. Meantime, I obtained RF module units both for VHF and UHF in Akihabara (radio market in Tokyo). Using an unit for UHF, I built UHF TV transmitters. Since there were many choices in frequencies of UHF, the micro UHF stations worked well.
Micro TV project in Shimokitazawa, Tokyo (1987) RealMedia People of Radio Home Run tried to watch the program that was "broadcast" at the square of the Shimokitazawa train station. Although the "broadcasting" was not so successful (too many snowy images and noises), the square became a temporarily convivial space by the "belief" that "we were broadcast." It showed how mysterious the wireless imagination is.
With the people of PARC (1993) RealMedia In the late 80s, I mastered the boosting method to use RF module and tested a mobile version of the UHF transmitter outside. It worked very well. Also, we enjoyed transmitting as a radioparty.
In 1994, Hank Bull and I had a NTV (non TV or net TV) project by using this method at Western Front in Vancouver. The Canadian plan of the TV channel starts from 55.25 MHz(ch.2) and the channel 3 (61.25 MHz) and 4 (67.25 MHz) that the ready-made VHF RF module for the American plan can select were open. It was a two week project to operate a micro television station at Western Front. It actually worked very well in 2 km radius. See the schematic (jpg) of the transmitter that I designed and used.
However, this type of attempts of micro television didn't continue so long. This was the difference from micro radio. Why? I think this has a lot to do with our habitual attitude to the video images. Even those who could be tolerant to "low quality" sounds was unable to keep watching snowy images of micro television. Few audience were interested in them as a video art or a television art, though.
The situation has changed now. Given the "perfect" technology of video manipulation and video synthesizing, "imperfect" and "immature" images of video are no more what they meant. Just as "lowtech" is no more the antonym of "high technology", "low" images would be more viable than "high" images in creative expression. Using computer, it is easy to make "low" images. But it is not so easy to create "low" images as a happening or by accident. Lowtech could do it more easily. Because lowtech always remains in the more or less relationship with our body that is the domain of accidents.
The micro television system that consists of RF module and the booster is perfect except the limited radius of service area. The RF module is technologically a complete and inexpensive transmitter. But it has only two selections of the channel. Given the technological perfection, it is very difficult to diverse the system.
How can we build a simple television transmitter by ourselves? One of the most delicate and therefore complicated sections of TV transmitter is for synthesizing the signals of images and the sounds. But if you give up the sounds, the circuit become far more simpler. If so, why don't you do it? Silent television is now more cooler, isn't it? So, as a first step, I will talk about how to build a television transmitter without sound and look for unique usage of it. Then I will go to an atempt to build a television transmitter with sound as simple as possible.
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