Connecting 2 aerials on roof to aerial amplifier box (aerials pointing at 2 different transmitters)

darkovo

Great replies with lots of information, thanks everyone. I’ll have a detailed look into every suggestion and see what’s best to try.

Bendy_House

Worth getting/borrowing a signal meter? You might find that aiming the aerial very slightly to the side of the oak tree will give a better signal.

Or, you might not. But the starting point will be to get the 'aim' or each as good as possible.

Can you see the transmitters? A crude method is to use the signal meter in the TV itself, but that will involve a lot of 2-way comms!

darkovo

Bendy_House Yes have done the mobile phone call to other person watching TV and showing the signal status, I don't think a signal meter would be any different.

Rodders53

Different place on roof may see more round the problem tree.  Lower down may see under the canopy.

Was the aerial a grouped aerial for Belmont? (Group A exc ch 55 COM7 which closes next year anyway).

Signal Q being poor suggests reflections and/or 'standing waves' may be the issue (where some frequencies are reinforced and others attenuated.  Moving aerial higher/lower crab left/right and fore/aft can find a sweet spot where all wanted ones are roughly the same level.  Pro installers use a spectrum analyser style meter to do this.  But tree growth and autumn loss/spring regrowth of leaves can change the result.  
The grid aerial https://www.aerialsandtv.com/product/grid-aerial-2 can sometimes work OK in the presence of trees (the stacked dipoles, sort of, averaging out the signals at different heights) but it's group A gain is poor and that's what you need.

FYI by the end of next year 2022 the HD mux will carry regional news programmes for BBC and ITV (ch28 for Belmont, ch41 Emley), as well as the SD muxes.  Which may or may not help you?

darkovo

@Rodders53 both aerials are wideband.
Both attached to bungalow chimney stack on a pole, there’s nowhere else to attach them, the tree is massive.
I had a look at diplexers from your link, the 1st basic one isn’t sold by them anymore, so I looked on eBay and the 2nd connection is for satellite, not sure if that means 2 aerials leads will work on those diplexers?

This is all for a family member, and doesn’t want to spend much more money. Sounds like we may have to wait until the end of 2022 to see if it’ll be easier to adjust what we have to get it working as we want?

Rodders53

Nope a simple splitter in reverse won't work properly.  But they are readily available and will lose 4dB of signal from each aerial.  The issue is that the signals picked up from Emley on the Belmont aerial will interact unpredictably, and vice versa. 
e.g. https://www.toolstation.com/proception-wideband-tv-satellite-splitter/p66100
Such splitters used in reverse to combine the signals lose 4dB (over half) of the signal going in from each aerial.

You need a device with filters on the two inputs to stop that interaction https://www.aerialsandtv.com/product/diplexer-channel-38-uhf-uhf is the correct item.
Fringe, who make them, no longer hold stock but make them to order in minimum orders of 20 units.  They aren't used very much nowadays.
They also don't lose as much as a simple splitter in reverse (but some loss is inevitable) just 1dB except near the ch38 crossover 'dip' - see the graph on ATV's site.

BUT you need to get the Belmont aerial working better first.  Under the tree canopy may be gutter level or even lower, affixed to a fence in the garden possibly?  

It might be worth experimenting with a masthead amplifier (if you had one so no cost).  But amplification must be done within a metre or so of the aerial.

Ensure the two aerials on the roof are at least one metre apart (they can interact unpredictably if closer). (Unless they are rear-end-mounted and pointing virtually 180 degrees apart.)

Frankly though, if they don't need the wanted local news live, use iPlayer.  Satellite would be the next cheapest option.  Some TVs have satellite tuners built in?

darkovo

@Rodders53 OK thanks again. I’ll start to look at the satellite option, the tv does have a satellite input as well, so if I can find a cheap dish or loan one for a test I’ll try that next.

*j*

Probably not worth trying to borrow a dish, considering the faff of accurately aligning it.  

A freesat dish kit is pretty cheap, £32 for a 60cm it....https://www.ebay.co.uk/itm/333424370657?hash=item4da1a423e1:g:dGwAAOSw1hZd58St

or consider an 80cm dish to give a stronger and more reliable signal for not much more....

https://www.ebay.co.uk/itm/352876923846?epid=2262606308&hash=item52291a8bc6:g:MloAAOSwmU9d5oD6

Much the same price as using splitters, combiners and amplifiers.