Odd Quadraplex Behaviour


Novice Member
Hi all, I'm in the process of a house renovation and have run double coax to a few points in the house with the aim of attaching them each to a quadraplex outlet. I've mostly done it because I could, I have no particular plan to use them for anything other than freeview but wanted the future proofing in case I decide I want satellite etc. in the future (unlikely but i'd rather regret the extra work etc. etc.)

As a stopgap whilst my DIY work steadly progresses I've had the TV hooked up to one of the quadraplex outlets for a while with a single coax running essentially all the way from the back of it to the aerial on the roof. No problems.

Last night I came to tidy up the outlet, which involved wiring in the other coax cable, which is not attached to anything at present. As soon as the other cable is inserted, the signal to the TV disappears.

I cannot fathom why this would happen, excepting a bad job of tidying up the screening on the 2nd coax, and even then it would struggle to affect the signal from the 1st coax, already successfully attached, I'd have thought.

So does anyone know what's going on, or should I just try another quadraplex to see if it's a fault? I wondered if I just need the whole arrangement attached to the correct mux arrangement at the other (aerial) end for it to work once both cables are attached but couldn't reconcile that with any kind of common sense given that there is no demux involved on the second coax (it's just sat 2 as i understand) Happy to be corrected.


Distinguished Member
Quadraplex is no longer used for $ky satellite installs as their Q system uses wideband signals occupying the IF of 290–2340 MHz.

Asked, I'd have advised to keep it simple and use separate cables for the separate services rather than lossy combiners and splitters. (Triax Quad plates lose <= 2.5 dB on TV, <= 30 on Sat 1 and <= 2.0 on Sat 2).

I can't explain the issue for sure.
But screens will be common and interference pickup on the outer might upset the signal quality.
Equally the main cable may have an intermittent connection to the wallplate?

Use the TV metering to measure every multiplex frequency Signal and Quality with/without the second cable connected to see if there's a pattern?

The aerial could be fed to the SAT2 socket perfectly happily (it's just a connector). No need to put the aerial through a (lossy) combiner for it to work with the filtered splitter plate.

Consider connecting aerial cable via sat 2 to repeat measurements?


Novice Member
For the record, the problem here appears to be that I actually orginally had the single coax going into the wrong input, but it worked anyway for the TV by itself, maybe due to some interference, or by design, there. Once I switched the cables everything works fine.


Distinguished Member
Thanks for the update.

Quad plates use a Belling Lee male plug for UHF out and female for VHF/DAB out.

IF TV worked when using a male-male lead then that was mainly by direct cable pickup on that fly lead, as the UHF signal would be severely attenuated by the filters in the triplex splitter on that female VHF/DAB output.
But such direct cable pickup is, by it's very nature, highly variable and unpredictable.

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