IR TV repeater won't work with extension

[Lobster]

Just bought myself an IR repeater gadget - the idea is that you can stash all your AV gear in a cupboard out of sight, and control it all via a single IR receiver stuck to the TV. I bought this model:

(or

Now, my problem is that the cable on the receiver module (which I want stuck on the TV) is much too short for my application. So, I found a 6' headphone extension cable in my Useful Box, with identical 3.5mm plug/socket, and used that to extend the range of the receiver. But - it simply doesn't work at all using the extension cable.

I've checked the extension on a pair of headphones and it works fine. Also, there seem to be plenty of identical looking cables sold specifically for this extending IR receivers - eg

- so it doesn't appear to me that there's any fundamental reason why a longer cable shouldn't work?

I'd happily buy the above cable (ie

if I thought it would do the trick, but is there any reason why it should, if my current extension cable doesn't work? Can there be something different about their speos? I'm as confused as hell.

[Lee]

Only things that come to mind are that, maybe the wiring in the cable is crossed over - unlikely but you never know... and maybe the DC resistance of the cable is a bit high - fine for headphones but maybe not for carrying power.

Should be able to check both easily enough with a DMM :)

[Dave Liquorice]

Seems a bit odd but what signal is this cable carrying? Is it just a couple of wires to the photo receptor and thus expected to carry the detected modulation to the decoder circuitry elsewhere. IIRC that'll be a 40 to 100 kHz pulse coded signal maybe at lowish levels. Extra noise. induced hum, the loss in the cable at those sort of frequencies or messing up with the shape of the pulses could well prevent the decoder being able to decode the signal.

[Bob Minchin]

Cable capacitance could be knocking the edges off the remote control signals.

[Brian Gaff]

One other thing, is this really a three core cable or is it something I came across recently a 3.5mm four core cable with another ring on the plugs?

Also, what kind of data is it carrying as if its very high frequency, it could be that long cable runs simply attenuate it with their internal capacity. Brian

[Lobster]

On 02 Jan 2015, Lee grunted:

Well, bugger me, spot on!

I was worrying about cable resistance, frequency response, bandwidth widgets etc, when in fact Occam's Razor prevailed - despite being a packaged item with welded-on-plugs, the extension cable turns out to have been cross-wired.

Thanks for the advice and encouragement!