This topic

Aerial connection

hughat4gp — Thu, 05 Sep 2024 14:49:15 GMT

I have a BT Youview box set up with my main television. I wish to take the aerial connection to the television in the kitchen. Can I attach a Y junction box to the Youview box and have an aerial line from the Y junction through to the other television?

Re: Aerial connection

TimCurtis — Thu, 05 Sep 2024 15:48:27 GMT

@hughat4gp

Yes you can but the signal strength will be lowered slightly which may or may not be a problem.

Re: Aerial connection

Midnight_Voice — Thu, 05 Sep 2024 21:59:07 GMT

@hughat4gp @TimCurtis

The signal strength will be at least halved to each TV, possibly a little more than halved unless the Y adaptor is perfectly efficient.

But there is an awful lot of leeway to reduce a decent strength signal without it being at all noticeable, so subjectively it may very well be perceived as slightly.

If there is picture degradation though, you can buy an active splitter, mains powered, that will reamplify the split signals.

The rules of the Community forbid me from linking to examples of such, but Google is your friend….

Re: Aerial connection

TimCurtis — Fri, 06 Sep 2024 08:48:04 GMT

@Midnight_Voice

I've never supported your view that the signal is halved by a split and my experience suggest that's not the case but I don't wish to get into any discussion about it.

Personally I prefer the metal splitters that use the screw fitting rather than the simple "Y" types.

Re: Aerial connection

Midnight_Voice — Fri, 06 Sep 2024 12:49:00 GMT

@TimCurtis

The laws of physics are not merely my ‘view’.

Re: Aerial connection

TimCurtis — Mon, 09 Sep 2024 10:23:17 GMT

@hughat4gp

I really don't think there's too much to worry about by using a splitter as the following results of some testing I've done suggest.

I have a T4000 box , alongside a Panasonic recorder and Panasonic TV and I was making a couple of changes so thought I'd do a before and after using BBC1 HD and checking the signal strength shown on the T4000.

Straight connection - 96%

2 way split 94%

3 way split 92% and the TV shows 92% as well.

I do have a strong signal despite being 35miles from the Crystal Palace transmitter.

I couldn't find anything after a brief google search that supported @Midnight_Voice contention of a 50% loss and I think my results support my suggestion of perhaps only a slight loss of signal by splitting.

The signal being received by my setup is already split as I feed 2 rooms via the single aerial.

The splitters I use are metal ones with screw thread connections made by either Labgear or Antiference.

I also checked the signal using an aerial signal checker which should only a very slight degradation over the 3 scenarios.

By the way signal quality - the important figure - remained at 100% throughout.

Re: Aerial connection

Midnight_Voice — Tue, 10 Sep 2024 09:17:36 GMT

@naylor2006 @TimCurtis

But as we are debating splitters:- 3 dB is 50% reduction, so we need to look at signal losses in dB;

You could look at the cpc farnell com mercury bx38 high grade low loss tv aerial splitter/combiner, which shows an average loss of 2.5 dB.

Or the screwfix labgear coax male to f plug 2 way t splitter, described as ‘Low Loss’, but with a simply appalling 12 dB return loss in the detailed description which would come out at about 94% signal reduction.

Not that I believe either number, especially as what the Screwfix example shows and what it describes are two different things, but it shows that a little Googling will certainly bring up dB loss figures.

I don’t believe the first one, because if you had two outputs at 2.5 dB and recombined them, you would actually have a stronger signal than the input signal, so your passive splitter would be acting as an amplifier!

And I don’t believe the second one, because it is too poor. 3.5 dB would be a good, and achievable, result.

You can’t rely on what TVs report, as the scales aren’t linear; but the numbers you are getting explain why, subjectively and objectively, we experience nothing like the 50% loss the splitter introduces.

A signal meter, such as is used by an aerial installer, should show accurate numbers though.

I know in the world of music amplification, that splitters don’t introduce the same losses as in TV aerial connections, because the impedances at the two ends are very different; but on 75 ohm aerial cabling, no such factors should intervene.

Re: Aerial connection

Jones_01 — Mon, 09 Sep 2024 17:02:30 GMT

@Midnight_Voice

Return loss is different from insertion loss.

Return loss is the ratio of the input power to the power returned, so the higher the value the better.

Re: Aerial connection

Midnight_Voice — Mon, 09 Sep 2024 18:15:17 GMT

@Jones_01

OK thanks, yes, what I know as Reflection Loss. Definitely a good idea to minimise that.

So I wonder why that splitter only quoted that, and not the rather more important insertion loss?

Re: Aerial connection

Jones_01 — Wed, 11 Sep 2024 17:29:23 GMT

Halving the signal strength sounds a lot, but in practice a drop of 3dB isn't much.

There are several internet posts about this, but the recommended signal strength seems to be between 45 and 65dBµV at the TV outlets.

So in theory, assuming that the OPs signal is at the top end of the range, the aerial cable could be split six times, giving 32 outlets, before the lower value is reached.

As @TimCurtis said, there isn't much to worry about by using a splitter.

Re: Aerial connection

Midnight_Voice — Wed, 11 Sep 2024 18:24:02 GMT

@Jones_01

Indeed, I put my trusty variable attenuator in my signal chain, and turned it up while watching the signal strength on my BBC HD 101. For a long time, it stayed at 100SS/100SQ, and even with max attenuation, it only went to 92SS/100SQ. And that was the maximum 20 dB down.