RF Components

Okay. I'll post there.

As for questions, I have a bunch but let me start with:

Can the channel of an agile modulator be set dynamically? In other words, can it be done via an interface from perhaps a server? For example, on one occasion, a video stream may be sent to channel 58 and the next time to channel 72 and so on.

Yes, I am familiar with the units that provide a "manual" interface. What I need to be able to do is tune the channel remotely and, of course, at a relatively low cost.

What about signal scramblers. Can the method to scramble a signal be changed dynamically? In other words, I could always allow, for instance, a signal to go out over channel 58 but sometimes it would be scrambled so that is could only be decoded by a specific decoder associated with a given line to a specific set and then at other times be encoded differently so that it could only be decoded by a different decoder associated with a different line. Does that make sense?

It looks more like CATV eqipment.

That depends on the design of the modulator. Some are remote controllable, others aren't. Most of the ones I am familiar with used dip switches or thumb wheels to select the channel. Either of these could probably be converted to a serial, ethernet, or custom interface. Some equipment had a connector the brought the control lines from the synthesizer out to allow a remote interface.

BTW, there was/is a Motorola chip designed for agile modulator applications. It didn't need a lot of support parts, like the older modulator designs. I can't remember the part number at the moment, but I'll see if I can find it.

That would depend on the scrambling equipment. I used the old Hamlin system years ago, and it had 256 possible codes, or eight different functions where you could select one of the eight, or any combination, including no scrambling. The manual showed the setup on a DIP switch, but it could have easily been modified for remote control. I had to return the manuals as part of the NDA.

What about on the decoder side? Can this be a "single code" decoder?

The idea, of course, is to keep cost low. I would imagine a scrambler as you decribed would be rather expensive (BTW: Do you have a ballpark for what something like this might cost). So the decoders (there could be hundreds) need to be cheap.

Michael, thank you so much for your responses. They are very helpful!

May be better on sci.engr.television.broadcast What is it you want to know?

Cheers.

Ken

There are literally tons of surplus cable decoders available for little more than scrap prices, along with the encoders. Cable systems are switching over to digital systems and removing all kinds of equipment that would work for what you want. Look around with Google for CATV repair centers, and don't forget e-bay. Ask your local cable company if they have any systems being upgraded that will have excess equipment. You will have to contact their corporate offices, but their local offices is the place to start.

Just so I am clear; I could, for instance, have a video signal coming out of a standard channel modulator and then into a switchable scrambler. From there, the line would go into a cable plant and then out to, for instance, three television sets. Each of the lines to the individual TV sets could have a simple decoder that recognizes one (and only one) of the codes from the scrambler. This would allow a signal to go out to all sets but was only "readable" by one. Later, the scrambler could be switched again (remotely) and then the signal would only be readable by a different of the three sets.

Is that how it works? Am I missing something? Is this a cost effective solution? One can only assume that a switchable scrambler would cost far more than the single decoders.

Once again, I really appreciate your help.

Best,

Chuck (from Denver)

The scrambling is done to the video BEFORE it goed to the modulator.

The descramblers worked on a single channel, and were generallly built into the same box as the cable converter to allow you to select the chanel you wanted. If it was a scrambeld channel, the unit had to be programmed to let you receive it. The other method is single chanel traps to filter out a channel someone isn't supposed to get, but some people will remove the trap. One name that comes to mind was Eagle, but there were other companies making single channel traps, along with ones that removed a block of channels.