Sharing a CCTV feed - is it possible

["Keith Doxey" <ukha@xxxxxxxxxxx>]

**** SORRY FOR THE REPOST. ***

Didnt spot the "filter modified subject line" until after
I hit send and didnt want it to get trapped again :(

****


Hi Pete,

> Thanks for the answer – sounds straightforward, but, sorry for being a
> dunce:
>
> a)       where can you get a modulator for less than £10 –
> Henrys/Maplin etc
> all seem >£25
>

Ah! You are right. Presumably because most equipment these days has AV
inputs, everyone has stopped selling "bare" modulators :(

Plan B.... find an old Analogue Satellite receiver (Pace are the best for
this) and either

1. rip the thing to bits to remove the modulator
(ONLY DO THIS ON UNITS THAT HAVE A TUNING SCREW!!!
Usually limited to Ch30-39. Units without a tuning
screw are electronically tuned Ch21-69 and wont work
standalone. )

2. Use the complete Satellite receiver.
Feed the Camera into the Decoder socket
Select "External Decoder" in the menu
Camera will then appear on UHF output
Connect either TV SCART or VCR SCART to PC


> b)       camera plugs directly into the capture board with no
termination
> resistor in line to remove. Does this mean I’m doing something wrong
> already?!
>

No. All Video circuits MUST be terminated by a 75 ohm resistor to achieve
the correct signal levels. Because of this, all equipment has a 75 ohm
resistor internally. Some equipment will allow this to be disconnected.
Your
capture card cant be unterminated without finding the resistor and removing
it. That is why I suggested   a bare Modulator as that would be high
impedance unless a 75 ohm resistor was added. Because you are connecting it
to an existing circuit it is already teerminated by 75 ohm and the signal
levels would be correct.

You may find that you can "get away" with a double termination.
Domestic AV
kit tends to be fairly tollerent  of incorrect levels (unfortunately as
this
has led to some prety rubbish kit being sold) whereas more professional AV
kit will show up the incorrect levels.

If you get stuck I might have a spare modulator in one of my many
"junk
boxes" as I have canibalised several old Nokia BSB receivers for the
cases
and kept a few bits out of them.

Regards

Keith