[OKDXA] Small Discovery...

[Nelson Derks]

I picked up a Scientific Atlanta cable box marked 'bad' at the Choctaw ARC
swap a few weeks ago for nothing more than a 'thank-you'. Interesting piece,
the only thing bad about it was that the VCO PLL would lose lock on some
channels. There's an itty-bitty little trimpot on the PC board feeding the
input module, and a quick tweak fixed that problem. Rock it back and forth
to find the range of adjustment, then split the difference. Works FB now.

But... Here's the nifty part: A classic cable box is nothing more than a
heterodyne frequency down converter. This one has a volume control on it.
How can you adjust only the audio level on a heterodyne down converter? Even
KD5DLL knows you can't...

Surprise! This one has a real-live demodulator and modulator inside that
takes the audio and video signals down to baseband before bumping them back
up to channel three. There are just two little 'bricks' inside plus the
power supply and display board. The video comes out of the input brick on an
RCA phono jack, but I haven't found the audio yet. Why am I telling you
this? A clever guy could break the connections and loop them through a set
of phono jacks so the box becomes a combo demodulator and modulator. The
only drawback is that it won't tune the high end of the UHF broadcast band,
but if you're after the 70cm ATV channels, it's good to go.

Pretty cool for a freebie 'thank-you' item... Ehhh?

- AC5UP