Can anyone identify this item?

s37d · Joined: 11 Nov 2007 Posts: 2

Can anyone identify this item? Not sure what it is.

gridnutter · Joined: 26 Apr 2006 Posts: 9

Looks like an attenuator....

Guest · Posted: Sun Nov 11, 2007 2:13 pm Post subject:

Ah, what exactly is it used for?

vtech · Joined: 08 May 2006 Posts: 1264 Location: USA

It is a cable filter

s37d · Joined: 11 Nov 2007 Posts: 2

So, what is the purpose of it and how/where does it hook up? ty

Guest · Posted: Mon Nov 26, 2007 12:13 pm Post subject:

torbjorn · Joined: 07 Jun 2007 Posts: 370 Location: Sweden

Those cable filters were used in some early cable tv networks for descrambling pay tv channels.
The scrambling scheme was very simple, as a strong interfering carrier was transmitted at a frequency very near the respective pay channel. An ordinary tv would get its RF stage blocked by that carrier, and the filter attenuates the carrier so it doesn't cause any harm.
Those filters were rented to the customers wanting to see the pay channels.

The drawbacks of that system were that it was not possible to scramble more than a few channels at the same time by that method, as a lot of strong carriers would cause intermodulation problems in the amplifiers of the cable network. And that it was fairly easy for anyone wanting to watch those channels without paying to build an DIY filter (in its simplest fashion, a suitable T stub of good quality coax cable).

At least in Sweden, no cable networks are using that scrambling method today but it was common in the early nineties.

hcs · Joined: 26 Nov 2007 Posts: 1

sorry, the pics arnt comming up on my computer
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