Atari 800XL RF cable (and I/O cable availability?)

tony duell ard at
Thu Jan 22 23:47:46 CST 2015

> 1) When hooking this up to a TV via the RF input - is there any "magic"
> involved, or will a suitable braided co-ax TV cable with a phono connector
> added at the Atari end do?  I know it "works" because I lashed one up

Maybe... The modulator output is nominally 75 ohm, and should be linked to
such a piece of coax. European TVs have a 75 ohm aerial input, often on what
we call a 'Belling-Lee coax socket', so it's just a cable. US TVs, I am told, may have
either a 75 ohm coax input, often on an F connector, or a 300 ohm balanced input
(for parallel twin feeder cable) on a pair of screw terminals. For the former, just
connect it up. For the latter you may need a matching transformer, aka a 'balun'
(BALanced to UNbalanced converter). I am pretty sure you can buy these, but
it must be possible to wind one if you can get a suitable core

The European switch box is just a switch. The US one I have somewhere has
screw terminals for the aerial input, a bit of twin feeder for the output and
IIRC a phono socket for the computer RF input. There is a balun inside.

The switch is special too. It is designed to minimise RF leakage from the 
computer to the aerial, since linking an aerial to the computer modulator
output would make a very low power TV transmitter. How far it would be
detectable I do not know, but the FCC (or whoever) take a dim view of 
such things.


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