Will a 4G filter solve my interference problems

Taxboy

Taxboy

Taxboy

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We started to get interference problems about a year ago on Freeview non HD ITV and associated channels. Had new aerial feed which seemed to solve the problem for about 3 weeks but then it came back. Spoke to the aerial guy who said it seemed like mobile phone interference an suggested I spoke to at800. Did this and computer said no.

The problem disappears if I watch any ITV channel though our dvd recorder so I'm guessing that it amplifies the signal in the box ?

Did a bit of digging online which suggested the problem might go away with the recent retune so I waited hoping this might solve the problem. Unfortunately it's still there so is this something that a 4G filter could solve ? If so any recommended makes please.

I was hoping to finally upgrade our very old 720p set in time for the world cup but can't get buy in from higher management until this is fixed. Any advice appreciated
 
What happens of the aerial feed goes direct to the TV (no recoder in loop) and you watch ITV?
 
Okay, so it's not the recorder adding it. That's good to know.

It's cheap enough to try a 4G filter. Ot won't hurt the system. All it does is block signals above ch59.

I take it you've checked the fitment of any aerial plugs?

Slightly more complex is atmospheric interference where a distant signal bounces off the underside of the ionosphere and reaches an aerial when it's beyond normal range. This is called Ionic Propagation. Normally see this at certain times of day though rather than constantly.

More likely is an aerial amp or power supply going intermittent, or a poorly ificshielded fly lead picking up interference, or a damaged cable acting as a notch filter where is affects only a specific frequency range.

Harder to diagnose issues could be the new Free view frequencies moving to a lower part of the spectrum where your current aerial isn't designed to work that well. Do you know how to use the TV tuning menu to see what channel your IT signals come in on to the TV?
 
lucid said:
Okay, so it's not the recorder adding it. That's good to know.

It's cheap enough to try a 4G filter. Ot won't hurt the system. All it does is block signals above ch59.

I take it you've checked the fitment of any aerial plugs?

Slightly more complex is atmospheric interference where a distant signal bounces off the underside of the ionosphere and reaches an aerial when it's beyond normal range. This is called Ionic Propagation. Normally see this at certain times of day though rather than constantly.

More likely is an aerial amp or power supply going intermittent, or a poorly ificshielded fly lead picking up interference, or a damaged cable acting as a notch filter where is affects only a specific frequency range.

Harder to diagnose issues could be the new Free view frequencies moving to a lower part of the spectrum where your current aerial isn't designed to work that well. Do you know how to use the TV tuning menu to see what channel your IT signals come in on to the TV?
Click to expand...

Thanks for that. I've tried swapping the leads from the aerial to the TV with others I'd already got but that didn't help unfortunately. The TV guy did make up a new lead when he put the aerial feed in as he said the cab,e he was using was better quality than I'd already got.

I'm afraid I don't know how to check what channel the ITV signal is via the TV but if you could offer generic advice on how to find out that would be great. I'm guessing it's buried in the tuning menu somewhere? If it helps we use the Tacolneston transmitter.

Thanks for taking the time to assist. It's much appreciated. I'm loathe to get the aerial guy out again as it costs me £45 a go and I get the feeling it's a bit like when the garage can't diagnose the fault in your car and they keep trying things in the hope of getting lucky
 
Tacolneston uses ch59 for Public Service Broadcast 2 (PSB2) and that's running at 100,000W which is very powerful.

https://ukfree.tv/transmitters/tv/Tacolneston

Check your signal strength via the TV tuning menu. In general, put your telly on to ITV, then go in to the tuning menu and select Manual Tuning. You might see something along the lines of:

Search Type: Digital Aerial

Channel: 59

Frequency: 778.00MHz (or 777.8 if the tuner isn't rounding up)

Signal Quality: (something here, a number or a bar of some wording)

Signal Strength: (something here, a number or a bar of some wording)
__________________________________________________________

Quality (Q) is the most important. You're looking for 60-100% - the higher the better

Strength (S) is less important. This part can always be boosted with an amplifier, but too much signal strength causes as many problems as too little. 40-60% could be plenty of strength to get a good solid lock. If you're maxed out at 100% then it might be that you have too much signal.

There are five other mux channels on your transmitter that are also running at 100,000W. These are:

PSB1 (BBCA) C55
PSB3 (BBCB) C50
COM4 (SDN) C42
COM5 (ArqA) C45
COM6 (ArqB) C39

and so the natural question is why aren't these affected too. The answer is probably to do with your aerial. The sensitivity of an aerial isn't flat and equal throughout the frequency range. Most have a profile with a hump. At some frequencies they're good, and at other frequencies they're poor.

For the last 15+ years the common aerial type being sold and installed has been the wideband high-gain. It sounds like the perfect solution; wideband makes it seem like it gets everything, and high-gain would suggest that it produces lots of signal strength; so who wouldn't want that combination? Unfortunately it's marketing ********.

Here's the profile for this type of aerial (black curve) compared to the flattest reception type - the Log Periodic (orange curve)

4LdC8M.jpg


Graph explained: Across the bottom axis are the channel numbers 21-60. The vertical axis shows the gain (amplification) of the signal due to the aerial. The black line is the gain curve for a decent wideband high-gain aerial. You'll notice the curve rises up as the channel numbers gets higher. Once you're up in to the high 50's then the aerial is producing its strongest signal. This aerial gets close to 12dBd. That number is on top of whatever the field strength is for your local area. This means that for C39 we get field strength + 9dB roughly, and for C59 we get something along the lines of field strength + 11.7dB

Depending where you are, you home might already be getting high field strength. Alternatively, your original installer might have put an amp on the aerial feed and that's boosting the strength. Either way, the gain at c59 could possibly be right on the upper limit of what the TV needs, then something changed locally that has tipped it over the edge. Maybe someone had some trees taken down in the direct line of sight from your aerial to the transmitter? Stranger things happen.

The point is that a decent installer should have a professional signal meter and be able to look at the relative signal strengths of all the muxes then balance any amplification or signal strength to ensure that there's neither too much or too little. There shouldn't be too much "best guess" or "suck it and see" in any service call. If they haven't got the right gear then they'll waste time groping in the dark.


This is my meter showing the relative levels for 5 of the Winterhill muxes. I'm using an un-amplified Log Period and I'm about 30 miles as the crow flies from the transmitter.

2momcG.jpg




Check out your signal levels to see if things are getting overcooked. Come back with the results.
 
Last edited:
Lucid

Thanks for the detailed reply. I had a look via the manual tunine menu an all the channels you listed are 10 an 10 for strength and quality, with the exception of CH 50 at 706 MHZ which shows strength 10 but no quality at all. Hopefully this may help narrow down the issue ?
 
you might want to check that the channels you are tuned too/watching are the from the muxes lucid listed, since if you had an automatic re-tune it could have taken some from another transmitter. (Aunt had this, and unscrupulous company sold her another aerial)

I guess you spoke to neigbours too.
 
Taxboy said:
I was hoping to finally upgrade our very old 720p set in time for the world cup but can't get buy in from higher management until this is fixed. Any advice appreciated
Click to expand...

Slightly OT but I suspect the best way to watch the World Cup will be iPlayer, as I'm almost certain they will beta tests HDR HLG 4k live broadcasts with the World Cup.
 
jpaul said:
you might want to check that the channels you are tuned too/watching are the from the muxes lucid listed, since if you had an automatic re-tune it could have taken some from another transmitter. (Aunt had this, and unscrupulous company sold her another aerial)

I guess you spoke to neigbours too.
Click to expand...
If you could steer me in an approximate direction on how to check the channels that would be great please. I seem to have an idea it's buried in the manual tuning menu ?

I did try an ask the neighbours but they are pretty much all satellite
 
jpaul said:
on a panasonic setup->DVB tuning->Signal Condition
tells me channel# for currently viewed station

-- what is the tv ?
Click to expand...
Thanks it's a very old 720p Panasonic. I can't fight my way to the back to dig out the model no at the moment

Based on this Ch55 = BBC 1 & 2, Ch59 = ITV, Channel 4 & 5, Ch42 = ITV 3, Ch45 = Dave, I can't find any programmes on Ch50 although in the manual tuning menu it's signal strength 10 but quality 0.

Have I mistuned
 
Taxboy said:
Have I mistuned
Click to expand...
if those stations are on those channels then it is tuned OK to tacolneston;
you could get film4+1 from Ch50, which has mostly full hd channels, but with an older HD ready/720 tv it may not have a dvb-t2/fullhd receiver

..... so lucids' advice stands,

but since it is only three weeks since install nonetheless, does not seem unreasonable the installer should guarantee his work and call by for free to diagnose problem.
it could be changing atmospheric conditions since the install that are causing the issue, which installer should have anticipated.
 
jpaul said:
if those stations are on those channels then it is tuned OK to tacolneston;
you could get film4+1 from Ch50, which has mostly full hd channels, but with an older HD ready/720 tv it may not have a dvb-t2/fullhd receiver

..... so lucids' advice stands,

but since it is only three weeks since install nonetheless, does not seem unreasonable the installer should guarantee his work and call by for free to diagnose problem.
it could be changing atmospheric conditions since the install that are causing the issue, which installer should have anticipated.
Click to expand...
Sorry if you've misunderstood, the problem has existed for about a year and I got fed up with call ingredients the guy out. I had hoped that with the retune the problem might have gone away but unfortunately not
 
Taxboy said:
Sorry if you've misunderstood, the problem has existed for about a year and I got fed up with call ingredients the guy out. I had hoped that with the retune the problem might have gone away but unfortunately not
Click to expand...
Did he turn up with a proper signal meter though?

You know your installer, I don't, so if I'm speaking out of turn then please forgive me. The aerial install industry has always been seen as easy money by those who really don't understand what they're doing but own a set of ladders and have a head for heights. Just because someone installs aerials it doesn't mean they have a good grasp of the engineering standards.

Digital made it easy to get an acceptable result with little real effort or investment in training. Analogue required more skill. It wasn't just in alignment but also in understanding issues such as multipath which caused ghosting, and choosing the appropriate aerial group for the transmitter, and potentially filtering away other transmitter interference. Anyone that was a cowboy soon got found pretty quickly if the install was anything other than very straight forward. A lot of that changed with digital, particularly after full DSO when analogue started to be switched off and digital power increased significantly.

Unlike analogue, where picture quality is determined by signal quality, Digital reception is sort of an "all or nothing" system: Below a minimum threshold there's no picture. But just above that the picture is every bit as good as if you've got the best signal quality. It's a get-out-of-jail-free-card for sloppy work. That lead to a lot of guys with a head for heights getting in to aerials to take advantage of the confusion surrounding Digital. It also lead to some unrealistic pricing for installs. The end result is situations like yours where it appears the installer doesn't have the right tools or knowledge to properly diagnose the issue, but you still end up sticking with him because of the sense perhaps that it's better with someone you know than taking a leap of faith with a new installer.

As a general rule of thumb, if your installer turns up without a meter, or with something like this

XNspHF.jpg
or worse still, one of these
k1sNOz.jpg


then they're not a proper installer; with all due respect to both professions, they're just a glorified roofer........or an electrician :D

The Fringe meter is actually okay for rough satellite dish alignment, but the SLX meter is about as much use as a chocolate fire guard, and that's being generous. Neither is any use though for proper system diagnosis, and that's how you end up with an aerial guy best-guessing what might be wrong in a system and wasting your time and money with inappropriate solutions.

Diagnosing remotely is always a challenge. Without eyes on a system and some on-site measurements then you're reliant on the info from the householder, and they may not always include all the relevant info. That's not their fault, they're not technical, but it still makes it more of a challenge.

Let us know how you get on with the attenuator. When you get it, put the TV on the tuning menu for the channel that has 100% Strength but 0% Quality, then with the attenuator in-line start at the lowest setting and gradually increase. If over-saturation is the problem then at some point you'll see the signal strength falling and should see quality increase. The optimum setting is where quality is highest.
 
Thanks Lucid for taking the time to assist with this. The aerial guy turned up with a signal box similar to the one in your earlier post rather than those shown above. If I explain the situation that may put it a bit more into context.
We moved into the house about 5 years ago and he fitted a new aerial plus booster box in the loft. At that time he said that the TV aerial leads installed in the walls were not of the same quality he would currently use. However the signals would provide a decent picture but just to be aware of this and also that aerial cables do degrade with time.

Everything went well until about a year ago when we started to get break up on the TVs upstairs and downstairs. He came out and fitted a new booster and this solved the issue for a couple of days at which time I couldn't get a picture at all on the downstairs TV - total pixellation. He came out and suggested that the aerial cable had degraded to the lounge and fitted a new feed which fixed the issue for a couple of weeks. This is when we.started to get the interference on ITV. I rang him up and said he had several calls so thought it was possibly mobile phone mast issues and referred me to at800. He said if this didn't help he could come out and have another look but would have to charge me a call out.

I'm guessing that I may be a victim of coincidences but given I could resolve the issue by turning on the DVD recorder it was something I could live with and I wasn't inclined to chuck any more money at that time
 
Another thing you might do -
if you have a decent piece of fly-lead with connectors you have checked, connect the tv directly to the aerial before the amplifier box -
lucid already suggestet this, but I had had an amplifier that failed in the loft.
 
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