TV Aerial

[The Natural Philosopher]

one end of the cable has an analogue FM tuner...

the delays are too short for ghosting or other multipath issues: what you get in 'meters of cable' is a comb filter in the frequency response..

Delay in a cable is about 3ns/metre, so the round trip delay of 50 metres is 300ns.

HOWEVER remember both ends of the cable are correctly terminated. Its just that it has a 'load' in the middle that shouldn't be there.

So at the worst its not going to be a very high Q resonance from the two halves of unmatched cable.

What you are looking at in all probability is a +- 3-6dB ripple with peaks every 3Mhz or so. As against an overall 6dB loss with a passive splitter.

You MIGHT have noticed that on an analogue set in terms of loss of detail on the picture, but most wouldn't.

You wont notice it on FM audio unless you have the very highest spec kit and can do back to back comparisons.

And it will make no difference to DTB at all.

[Ian Jackson]

Adding a 2-way splitter and 15m of cable to one of its outputs isn't rocket science.

As I've already said, the cable will have a loss of around 3dB, and the splitter 4dB* - a total of 7dB at the end of the extension. If the signal level there is too low, use a low-gain 2-output amplifier instead of the splitter. Job done!

*A proper directional splitter, with around 25dB isolation between the outputs.

[Graham.]

I disagree with "Myth 3" It might have been true during the dual running period, but now digital is transmitting at higher powers post analogue switch off, it is reasonably safe to assume if there was a good signal for analogue with an aerial in the loft, it will be good for digital too.

If anything, digital is more robust than analogue, which came as surprise to many in the trade.