Combining aerial inputs

nffc · 11-07-2005, 12:04

I have 2 set-top aerials pointing to two different transmitters... how do I combine them?

I've tried using one of those little y-shaped plastic things but that just makes the signal go poor. Anyone have any ideas? I need one for digital, the other one less so (the digital is fine) but it would be nice to have some decent analogue as well.

handyman · 11-07-2005, 12:06

is this for free view?

nffc · 11-07-2005, 13:22

I'll have to elaborate.

In this part of Nottm there are too many bloody hills which makes reception of analogue from the E Mids (Waltham) transmitter difficult.

Yorks and Lincs via Belmont is fine so i'm using that for freeview and it's fine- but I wanted to get Waltham for the analog (local news) so i put another aerial up (they're both set-tops) with a booster.

Now all that seems to happen is the second aerial swamps the signal on the Belmont aerial making both analogues look like a snowstorm. If I take the Y-splitter out both inputs are fine so obviously the Y-splitter isn't combining properly (it's supposed to combine and split aerial signals)... but then if I put the second aerial in alone I lose the RF-out from the video/digital...

there has to be a way to do this properly...

11-07-2005, 15:42

I imagine what is happening is that the signals from the two transmitters are interfering with each other - probably what you need is a switched combiner - i.e. like your Y connector, but allowing you to select which aerial feed is sent to the telly, rather than sending both. - I remember using something similar for my Spectrum

nffc · 11-07-2005, 15:59

Quote:

Originally Posted by homealone

I imagine what is happening is that the signals from the two transmitters are interfering with each other - probably what you need is a switched combiner - i.e. like your Y connector, but allowing you to select which aerial feed is sent to the telly, rather than sending both. - I remember using something similar for my Spectrum

More than likely... glad you said that cos that's what I'd thought too.

Although it would be nice not to have to faff with a switch... have to have a doss in maplin and see what there is :P

punky · 11-07-2005, 16:00

Quote:

Originally Posted by homealone

I imagine what is happening is that the signals from the two transmitters are interfering with each other - probably what you need is a switched combiner - i.e. like your Y connector, but allowing you to select which aerial feed is sent to the telly, rather than sending both. - I remember using something similar for my Spectrum

That is exactly right. You need a true RF switch to do it. All the old consoles (Megadrive SNES, etc) used to come with one, so that might be an avenue to look at if you can't find one. The newer consoles though come with auto switchers, so not really any good (plus they have moulded plugs).

bob_builder · 11-07-2005, 16:08

From http://www.wolfbane.com/ukdtt.htm:
The Belmont digital UHF channels are 30, 48, 57, 60, 66 and 68.
The Waltham digital UHF channels are 23, 26, 33, 42, 45 and 49.

From http://www.wolfbane.com/uktv.htm:
The Belmont analogue UHF channels are 22, 25, 28, 32 and 56.
The Waltham analogue UHF channels are 35, 54, 58, 61 and 64.

So there should not be any direct interference. However, as a lot of these are on adjacent channels they may be some overlap that could cause interference. Also, you will need to find out what channels your VCR, STB, etc. are outputting on.

punky · 11-07-2005, 16:09

This is what you want mate.

http://cgi.ebay.co.uk/ws/eBayISAPI.d...tem=8203901411

rockin_plumber · 11-07-2005, 19:06

If the Freeview box and the TV have scart sockets there is no need to connect the aerial out of the Freeview box to the TV....
Just connect the Aerial you are using for Digi to the Freeview box and then link the box to the TV with a scart lead....
And connect the aerial you are using for analogue to the TV....

Problem solved

nffc · 11-07-2005, 22:35

Quote:

Originally Posted by bob_builder

From http://www.wolfbane.com/ukdtt.htm:
The Belmont digital UHF channels are 30, 48, 57, 60, 66 and 68.
The Waltham digital UHF channels are 23, 26, 33, 42, 45 and 49.

From http://www.wolfbane.com/uktv.htm:
The Belmont analogue UHF channels are 22, 25, 28, 32 and 56.
The Waltham analogue UHF channels are 35, 54, 58, 61 and 64.

So there should not be any direct interference. However, as a lot of these are on adjacent channels they may be some overlap that could cause interference. Also, you will need to find out what channels your VCR, STB, etc. are outputting on.

I know those but thanks anyway.

What i think the problem is, is the *lack* of a coherent signal on the respective analogues super-imposing on the decent signal coming from the other input.

I'll have a look see if maplins or anywhere have an input switcher, that seems the best way,
__________________

Quote:

Originally Posted by rockin_plumber

If the Freeview box and the TV have scart sockets there is no need to connect the aerial out of the Freeview box to the TV....
Just connect the Aerial you are using for Digi to the Freeview box and then link the box to the TV with a scart lead....
And connect the aerial you are using for analogue to the TV....

Problem solved

In theory yes but:
- I'd like the RF out from the FV to send to my PC
- I'd like to use both regoins for teletext- the signal from Waltham isn't strong enough for viewing anything other than the local news

drgordon · 25-07-2005, 16:38

There is a problem with combining ANY signals from aerials pointing at adjacent transmitter groups - from reflected ie out-of-phase signal images; your antennae are picking up in a lobar pattern - stronger in the "forward" direction, where the aerial is pointed - but picks up some signal from the 180 degree opposite ie back of the aerial.

If you can put some shielding BEHIND the aerial (a water tank in the loft, in my case) it will block a lot of this. Essentially, any grounded metal plate NOT ELECTRICALLY CONNECTED TO THE AERIAL SYSTEM, but erathed to ground, should reduce the back-of-beam signal.

I am a licensed radio ham, and I use this to keep the signals from my 2m ham, DAB receiver aerial, massive high-gain FreeView aerial, and PC signals (wifi, etc) separated. I have main transmitters at Brighton and Isle Of Wight TV (analog & Freeview), a relay station a mile or two away, and most of the French coast using more power on the same frequencies, and only analogue TV on BBC1 & 2 is adversely affected - French TV seems to run 1000s of times the RF power that the UK use, and spread it around like a dose of pox!

If you really MUST combine, try using a frequency mux-demux unit, which combines multiple signals - look in most satellite TV mags for ads and reviews, they use them to combine the outputs of multiple satellite dishes to feed to multiple or the same receivers, and I don't thinkthey were _that_ expensive. But try shielding the rear of the beam first, e.g.

A ! F A
/ \ ! I / \
/ \ ! I / \

Transmitter SHIELD Your aerial Other transmitter

Dave G6ENT, with multiple aerial for multiple transmitters, receivers, etc

nffc · 25-07-2005, 16:46

Belmont is NE of here and Waltham is SE though, so surely eliminating the back-reflections wouldn't do much.... (plus, it kills the freeview)