Reception Problems

[Black Hole]

I've been having reception problems the last few weeks, but it seems to be getting worse the last few days. I surveyed my signal detection from the system menu and for both tuners from the service menu, and the results were consistent but my viewing experience seems worse than this and there are intermittent dips:

Channel	Frequency	Signal/Quality	Transmitter	Mux	Sample Services
23	490	60/100	Mynydd Machen	BBC A	BBC 1 & 2 Wales
26	514	46/100	Mynydd Machen	D3&4	ITV Wales, C4
30	546	27/80	Mendip	Local	Great! TV
32	562	57/100	Mendip	BBC A	BBC 1 & 2 West
33	570	58/100	Mendip	ARQ A	Sky News
34	578	60/100	Mendip	D3&4	ITV West, C4
35	586	0/0	Mendip	BBC B	BBC 1 & 2 HD
36	594	50/10	Mendip	ARQ B	Yesterday, Classic FM
48	690	54/100	Mendip	SDN	Quest, Horror
55	746	58/100	Mendip	COM 7	BBC FOUR HD

What sticks out like a sore thumb is UHF35. Why should that one be zero? It used to be OK, even a week ago. UHF30 is low power and no surprise that it is 27%... what's surprising is that I get anything from it at all.

I have two antennae, one VP pointing at Mynydd Machen and the other HP wideband pointing at Mendip. Cables appear to be intact.

 

[sine24]

Posted today


Chris.SE
sentiment_very_satisfiedPlatinum
10:32 PM
John B:

You are predicted to get excellent reception from Mendip in your locale. Your problems are highly unlikely to be related to any of the mobile masts that you've mentioned. If there was interference from these masts it would be a consistent problem, not one that comes and goes.
If the problems were related to yesterday (evening primarily) and possibly some this morning, then it's most likely to have been the current weather conditions. There has been some Temperature Inversion/Tropospheric Ducting which has been disrupting signals in various parts of the UK for some.

Essentially it results in interfering signals from other transmitters in the UK or Europe reaching you and so your wanted signals are disrupted. It won't necessarily affect all multiplexes or necessarily at the same time if more than one. It can last for seconds, minutes, sometimes hours or longer.
Despite the incorrect spelling, this link does work - simple technical explanation

https://www.bbc.co.uk/reception/sites/default/files/inline-images/tropispheric%20ducting1_0.jpg

It's always possible these conditions may affect you again during the next 24hrs according to some current predictions but if they continue after tomorrow evening when they should have cleared, then it might be wise to make some basic checks.

I would check that your aerial seems intact and pointing in the correct direction (compass bearing 234 degrees for you, that's 9 degrees W of SW), and that your downlead looks undamaged (especially if it is old) and is secure and not flapping in the wind..
Also check all your coax plugs, connections, flyleads etc, unplug connectors check for corrosion or other problems and reconnect them. Flyleads are a common problem, try swapping/changing them.
Make sure you don't have any HDMI leads near unscreened/poorly screened flyleads/aerial leads especially if those aren't double screened coax as HDMI has been known to cause interference.

One other check you could do is to connect your aerial output direct to your main TV feed eliminating the DA in case that's playing up.

 

[sine24]

in response to this


Saturday, 1 January 2022
J
John B
5:23 PM
Recent problems with Mendip too. BA2 5DF. Recently lost HD completely (Ch.35) for which my set was showing very low signal strength and high error rates (has subsequently come good but still sometimes glitchy). Ch. 48 also showing low strength and some errors.

 

[Rodders53]

The most likely is interference (enhanced propagation due to high pressure weather conditions) but that should be reflected in the Freeview interference prediction numbers for your location's 100m x 100m grid square, at least to some extent.
Such interference is frequently worst around dawn and dusk and is unusual if it lasts an entire day and/or night.

https://www.bbc.co.uk/reception/hel...and-fine-weather-can-affect-your-tv-reception The BBC currently have no weather warnings, though (12 hours after your post).

How are the two antennas combined? I know of no suitable filtered combiner for the channels now broadcast from the two transmitters (although one could be custom made).
With a wideband combiner (splitter in reverse) the signals received via both antennas will potentially interfere... typically in an unpredictable way.
Try connecting each antenna direct to the PVR and repeating all the measurements for each (expect an uplift in S due to the likely 4dB signal increase)? It may help with your diagnosis of the problem.

 

[Black Hole]

Try connecting each antenna direct to the PVR

Very not easy!

I appreciate what you're saying, but this setup has worked for years and why should it suddenly notch at 586MHz? UHF35 used to have the same reception strength as the other Mendip services (ignoring Local) until a month ago. I thought about destructive interference from a co-channel, but there's nothing in the area I can attribute it to (eg Wenvoe).

I use a passive combiner, and that's why I take my Wales feed from Mynydd Machen (V) not Wenvoe (H). Nonetheless, it's worth trying to disconnect the MM feed just to eliminate it from the equation (and I wouldn't cry if I lost it completely).

Could this be 4G? Frequency seems too low. I'm thinking some kind of local emission though.

 

[Rodders53]

No 4G / 5G* signals are outwith the broadcast TV band --- so it's overloading of tuners and more often amplifiers that they affect. {* COM7 is closing due to 5G rollout, but isn't a problem for you despite being in a SFN}

No harm in obtaining and fitting an AT800 / LTE filter though as the losses are small (-1 dB insertion loss).

You're meant to be carded if a new local mobile appears though. See https://restoretv.uk/

No 700MHz clearance work / transmitter frequency changes have happened since August 2020 so interference problems will have been the same for over a year... But there has been more enhanced propagation HP weather about this winter, so it is possible it is the cause... though its very unusual to be all day and all night...


I notice that your ch 36 reception has very poor quality, too... Have you checked with neighbours to see if they are having problems (assuming they also use Mendip).

I'd be interested to see your full Freeview prediction numbers.

 

[Black Hole]

I notice that your ch 36 reception has very poor quality, too... Have you checked with neighbours to see if they are having problems (assuming they also use Mendip).

Yes, the notch seems to encompass that too. The neighbours are all on Sky/Virgin/BT (it's a plot)!

There was something in the paper last year about some village where an ancient TV was knocking out the broadband. Maybe this is broadband getting its own back!

I'd be interested to see your full Freeview prediction numbers.

Your wish...








I have no idea why Ridge Hill shows reception of COM7 and nothing else! Don't worry, I have nothing pointing in that direction.

 

[Black Hole]

Being a single-person household, I've never had much need for Favourites... but now I've found an application: by setting up one service from each mux in a Favourite set, I can quickly survey the current reception conditions!

 

[MikeSh]

this setup has worked for years

Faulty capacitor? (In the combiner)

 

[prpr]

My figures, averaged over both tuners on two HDRs on the end of my distribution chain are:
546 40
562 60
570 60
578 60
586 55
594 53
690 47
746 52

I did see 594 dip to zero once. It's interesting how tuners vary in the same unit, and between units. My main one varies between 55 and 66 on 3 muxes. The other is stable.

 

[Black Hole]

Faulty capacitor? (In the combiner)

I take it you mean like dry electrolytics? Not applicable.

 

[Rodders53]

Those figure suggest co-channel enhanced propagation is unlikely from Mendip as 99% of the locations within the 100x100m square are Served and interference is <1% of time (potentially still 3.65 days a year - but I'd suggest far less with the numbers).
Wenvoe is slightly better, of course with 100% of locations served to the <1% standard.

Ridge Hill is showing because ch 55 COM7 is a single frequency network and is likely to be constructively reinforcing signals at your location along with all the other ch 55s received.

I must say that I'm slightly surprised you haven't got BBC One Wales HD, BBC Two Wales HD & ITV Wales HD tuned in rather than the SD variants. ( i.e. using f.ch 29+ from Mynydd).
Neither do I know the antenna bearings to Mendip, Wenvoe and Mynydd Machen either... as I wonder if two Hp almost back to back might give better results overall?
NB You'll never, ever get the theoretical 26dB H-V signal rejection in real life (reflections cause polarisation shifts) if that's the reason you use Mynydd Machen.

Local interference is a possible, of course: nearby faulty 'hooting' antenna head amplifiers were a favourite source (and could occasionally travel a goodish distance) ... but I wonder if there's much need for such amplification in your locality? Rarely someone with a 'wireless' UHF sender and an antenna connected to the output (in error or deliberately)?
Finding the source can be a major headache and would need others nearby to have the same issue and report it to the BBC RTIS http://www.radioandtvhelp.co.uk/

Capacitors (ceramic types) exist in filtered combiners (aka diplexers) but you aren't using one https://en.wikipedia.org/wiki/Diplexer just a wideband splitter in reverse (all inductive parts).

 

[Black Hole]

Capacitors (ceramic types) exist in filtered combiners (aka diplexers) but you aren't using one

Of course, but unlikely to fail.

I must say that I'm slightly surprised you haven't got BBC One Wales HD, BBC Two Wales HD & ITV Wales HD tuned in rather than the SD variants.

I only use Wales when I want local news...

 

[Rodders53]

I only use Wales when I want local news...

Which is broadcast in HD from HD-equipped studios you lucky person.

Also the Wales BBC B mux(es) will provide mostly the same programmes as Mendip ch 35 BBC B (with some time shifted). There is the two nations EPG issue though that may cause recordings to fail?

 

[Black Hole]

There is the two nations EPG issue though that may cause recordings to fail?

That was fixed, supposedly. I can't say I have any trouble, but I do take precautions to ensure both EPGs are updated daily.

broadcast in HD from HD-equipped studios you lucky person.

News of the Senedd (stupid buggers playing king of the castle and wasting loads of money) in HiDef. Lucky me (underwhelmed).

I seem to have 35 & 36 back by rejigging the cabling. Either that, or an interfering signal has gone away coincidentally (yeah, right). 30 is still weak of course, but back to 100%. Maybe a bad connection was setting up a standing wave.

The sore point is the Fox+TV in my study (some way down the line, and IIRC via a booster), which is reading 0 across the board and led to me investigating signal strengths at the main TV in the first place. It means I can't potter on jobs while half-watching TV (about all it's good for). I suspect the booster has failed, but I will have to dig around in the roof voids to figure out what's going on – I set all this up maybe 30 years ago, so perhaps it's no surprise if an active unit has failed. The bedroom Fox+TV seems fine (reasonable, anyway), and that's also a long line away.

All the feeds go via the main TV, because at one time the VCR was there and all the TVs were downstream so recordings could be viewed from anywhere. I have plans to revise the system with a central distribution amp now analogue recording is not a "thing", but never got around to it. This could be the necessary impetus.

 

[Rodders53]

I seem to have 35 & 36 back by rejigging the cabling. Either that, or an interfering signal has gone away coincidentally (yeah, right). 30 is still weak of course, but back to 100%. Maybe a bad connection was setting up a standing wave.

Glad you've fixed it.
Cables and connectors are often the cause of problems.

Once had a similar issue after re-arranging my TV/AV equipment into a new rack... A linking RF cable got pulled partly out of the TV plug by my clumsiness. Only affected the HD mux from Tacolneston. If I'd had any worthwhile hair I'd have been pulling it out before I found the problem. Another reason to solder the centre core on Belling Lee plugs, perhaps? ')

 

[EEPhil]

I seem to have 35 & 36 back by rejigging the cabling. Either that, or an interfering signal has gone away coincidentally (yeah, right). 30 is still weak of course, but back to 100%. Maybe a bad connection was setting up a standing wave.

I’ve had problems like this, where fiddling around with the cable improves things. Then later, without me touching anything, it goes wrong again. Sometimes the Humax seems to interfere with itself messing up the picture but displaying no faults on the signal strength/quality. Powering down and restarting sometimes clears that problem. I thought it might have been a problem with one of the tuners - but when I managed to get the same set of multiplexes recording on the same tuners it didn’t happen. This is for the 5000T which is in a shoddy plastic box. The 2000T is in a metal box and not so temperamental. I suspect the Fox has a sturdier casing, so probably not a shielding problem. I now resort to recording certain programmes on both Humaxes and either on the tv itself or on my laptop. A pain in the backside - but sod’s law applies. Something I really want to keep will get ruined by the self-interference reoccurring. Ho, hum!

 

[Black Hole]

Glad you've fixed it.

Wont be fixed until the study is restored! The levels are still down on where they used to be though.

 

[Owen Smith]

Glad you've fixed it.
Cables and connectors are often the cause of problems.

Once had a similar issue after re-arranging my TV/AV equipment into a new rack... A linking RF cable got pulled partly out of the TV plug by my clumsiness. Only affected the HD mux from Tacolneston. If I'd had any worthwhile hair I'd have been pulling it out before I found the problem. Another reason to solder the centre core on Belling Lee plugs, perhaps? ')

I hate Belling Lee plugs and refuse to use them directly. I cable everything with CT100 and screw on F connectors, including the faceplates in the wall, and then use commercially available F to Belling Lee adaptors on the end of home made CT100 fly leads. Luckily my FM/DAB tuner actually has an F connector as the aerial input, since it's a combined FM and DAB input (software defined radio based tuner - Arcam DT91).

 

[prpr]

I cable everything with CT100 and screw on F connectors, including the faceplates in the wall, and then use commercially available F to Belling Lee adaptors on the end of home made CT100 fly leads.

Yep, me too. It makes putting splitters in so much easier.