Issue with aerial

muffler · 10-01-2023 9:54am #1

Last week I got a guy to replace 2 rooftop aerials - Freeview and Saorview. He fitted a single aerial but shortly after a few channels stopped working. It turned out it was the HD channels that were effected. He then indicated that he would fit a high gain aerial this week. However over the weekend most of the channels were breaking up during rain showers including the SD channels with signal strengths of around 7 - 15%.

I'd be fairly sure he knows what he's doing but just to satisfy my own curiosity will a high gain aerial be good enough to replace 2 separate aerials?

The Cush · 10-01-2023 10:00am

What transmitters? How far away are they? are they roughly in the same direction?

What channels are breaking up?

muffler · 10-01-2023 10:26am

Saorview is from the transmitter near Ballybofey about 1.5km away and Freeview from Strabane which is approx 20 km. They are roughly in the same direction - at a guess about 25 - 30 degrees separation. Most of the available channels were breaking up or had interference to some degree during the showers. For example I was trying to watch a rugby game on TG4 but had to give up. Given the short distance and the clear line of sight to the Saorview transmitter I was a bit surprised.

The Cush · 10-01-2023 11:00am

Any idea what make/model hi-gain was installed?

At those distances I would have thought it wouldn't be a problem. What's the terrain like between your location and the transmitters?

How many TV points is the aerial feeding, any splitters or amps in line?

How was the signal previously with the two separate aerials?

muffler · 10-01-2023 2:55pm

https://www.boards.ie/discussion/comment/120088877#Comment_120088877

He is coming back this week with the hi-gain aerial as he had to order it.

Clear line of sight to both transmitters. Im looking straight at the Saorview transmitter and while I cant see the Freeview one during the day i can clearly see the red lights on it at night time and thats from the door step so no obstacles there.

The cable is coming into a wall socket and from there it is split and goes to 2 tv's. No amps.

The previous aerials have a bit of history. I had a thread here previously where I indicated we were loosing Saorview channels fairly frequently as was the next door neigbour. This loss of channels would occur on average every 3 - 4 weeks. The Freeview signal was mostly fine and we may have experienced a very slight break up in picture maybe once a year at most. The guy did say last week that the old aerials were useless now and that water had gotten into the cable or cables.

I do have full confidence in the aerial installer as he's been doing this work for 30 years or more but as I said earlier Im just curious to know if a single hi-gain aerial is generally adequate to replace two separate aerials.

Glaceon · 10-01-2023 3:00pm

Both transmitters are in different UHF groups so it would need to be a single group K aerial. At the distances you describe it should be OK.

The Cush · 10-01-2023 3:03pm

Based on what information you've provided the hi-gain aerial should be ok provided the cable is ok.

muffler · 10-01-2023 3:58pm

New cable was fitted so that should be ok. I'm just relieved to know the single aerial is fit for purpose. Thanks for the input guys and I'll update you if this doesn't work out as expected.

muffler · 15-01-2023 6:17pm

So he came out during the week and fitted the hi-gain aerial but after everything looked to be okay the Freeview HD channels disappeared again. He thought it was the splitter/booster so he removed the old one and put one of his own in. That worked but shortly after he left we lost the audio on the Freeview HD channels on one TV. Im not sure if the other was affected or not but a reboot of the first TV fixed that issue.

A couple of evenings ago the Freeview HD channels went again but did return later. Last night this happened again but they still havent come on yet. No problems with Saorview channels or the Freeview SD channels.

Im assuming now that there was nothing wrong with the old splitter as we never lost the Freeview HD channels when using it. There is a problem somewhere and Im just trying to figure it out myself but Im stumped.

One question I do have though. Why are the Freeview HD channels only affected and not RTE1 & 2 and TG4 which are also in HD?

Elvis Hammond · 15-01-2023 7:22pm

https://www.boards.ie/discussion/comment/120112315#Comment_120112315

The Freeview HD signal (DVB-T2, 256QAM) is a bit more 'fragile' than the DVB-T 64QAM used for Freeview SD & all Saorview iirc, so might be inclined to drop out first if signal quality is reduced for some reason.

Really if the aerial installer can't provide enough signal margin to deal with what I assume are normal small variations, he should just admit this, & either let you try someone else or forget about UK terrestrial. I mean, if he's just chopping & changing aerials, does he even have a signal meter?

muffler · 15-01-2023 7:54pm

https://www.boards.ie/discussion/comment/120112598#Comment_120112598

I couldnt agree more. I have to ring him in the next day or two to let him know how things are going as he has planned (might have already ordered one) to fit a 4 way booster (if thats the right term) similar to the old one I was using and take back his own 2 way booster which is basically on loan to me at the moment. I need to get this sorted and in fairness he seems to be as much in the dark about the issue as I am.

I have no idea if he used a signal meter or not but given the fact that the channels were all showing 100% on both strength and quality when he was here its probably not his fault regarding the problems.

Just as a brief recap. I contacted him initially to replace 2 aerials . Freeview and Saorview. The Saorview one was being replaced as I was constantly loosing those channels and as the Freeview aerial was ancient, (maybe 25 years+) I decided to get it replaced as it would be more cost effective when he was here. I never had any real issues with Freeview in the past including the HD channels and no bother with the 4 way booster/splitter.

He suggested a single aerial would do the trick and it looks like some of the neighbours have the same type of single aerial. But its quite a surprise now that the Freeview HD channels are dropping which hasnt happened in the past.

Just to update my earlier post ... the Freeview HD channels are back again.

TAFKAlawhec · 16-01-2023 3:41pm

If the installer is using a single "hi-gain" UHF aerial, then if it's the ones with the X-shaped directors these aerials tend to have a fairly narrow front lobe even for vertical polarisation, narrow enough that if the two TXs are approx 30 degrees apart there can be noticable differences in gain between the two sites depending on where the receiving aerial is pointing. Nevertheless if you were getting signals from both sites fine until fairly recently where an aerial replacement was deemed necessary then it's possible there might be issues elsewhere either within the chain. If the old cables were damaged & waterlogged, were they replaced with good quality ones (xx100 standard, with copper braid & foil)? Is there any probable pattern to certain channels appearing/disappearing? Is there a modulator somewhere in your setup (if there's an old analogue channel 36 modulator involved, it'll harm reception for the Freeview HD transmissions from Strabane on channel 35)? Another theory is that co-channel interference may be causing issues - this doesn't have to affect all relevant frequencies, and given that DTT reception is now more interference limited than ever before it's quite possible.

I have to say though that without being on-site to see the issues at hand, I can't think of what could be causing channel drop-out issues more than what I've mentioned above.

muffler · 16-01-2023 5:59pm

The aerial that was put up looks something similar to this

Never had any great issues with Freeview which surprisingly is the problem now. Loss of Saorview channels every few weeks was the reason for the change and I just decided to get the Freeview aerial replaced at the same time as it was there for a long number of years.. The old cables were removed and new one fitted.

Im not sure what a modulator is though. The set up is just the aerial on the chimney with a cable coming directly into a wall socket in the sitting rom. From there its connected to a splitter/booster. Thats about it.

muffler · 16-01-2023 8:04pm

So a couple of hours ago the Freeview HD channels went off air again. All remaining Freeview channels and Saorview channels are fine.

I have 2 Hitachi brand TVs in use. On one of them a quick double press of the "i" button displays what I assume is strength and quality of individual channels. There's just the 2 letters - S and Q. The S shows at 100% and the Q shows at 0%.

The other TV is a bit more awkward to get channels details but when I get there it states "signal level 100% and signal quality 0%"

Does that make sense? I would have thought that the signal level / signal strength would be at zero if the channel wasnt being picked up.

The Cush · 16-01-2023 8:37pm

https://www.boards.ie/discussion/comment/120116535#Comment_120116535

The aerial is a bowtie grid wideband, wouldn't consider it to be a hi-gain antenna though. Probably ok for that particular area where the transmitters aren't too far away.

High signal strength with zero quality, overloaded signal for that particular frequency?

What's the signal strength and quality readings for the other Freeview frequencies?

Too much signal can be as bad as too little.

The Cush · 16-01-2023 9:25pm

Can you connect the aerial feed directly into the TV without the booster/splitter to see what the signal levels are direct from the aerial without the amplification. With the amp in place you're not getting a true reading.

Elvis Hammond · 16-01-2023 9:32pm

https://www.boards.ie/discussion/comment/120116535#Comment_120116535

I assume he has the aerial mounted on its side relative to that photo, for vertical polarisation?

muffler · 16-01-2023 9:42pm

https://www.boards.ie/discussion/comment/120117160#Comment_120117160

So somewhere in the last hour the Freeview HD channels are back again. I checked the readings on the first TV and strength is shown at a constant 100% on all channels including the now returned HD channels. Quality is mostly 100% also but every 10-15 seconds it might drop to as low as 60% but most drops are in the region of 80% - 100%. The lower readings only show for maybe a second or two and I havent seen any physical difference on the actual screen.

muffler · 16-01-2023 9:44pm

https://www.boards.ie/discussion/comment/120117376#Comment_120117376

Ill see if I can get that done later. The old back isnt what it used to be so I'll get a bit of help

muffler · 16-01-2023 9:46pm

https://www.boards.ie/discussion/comment/120117403#Comment_120117403

Yeah, it's 90 degrees to whats shown in the pic. Sorry, I should have mentioned that earlier. Ill get an actual photo of it tomorrow.

Ten Pin · 17-01-2023 1:03am

Has the aerial got a filter for blocking mobile signals?

muffler · 17-01-2023 1:18am

https://www.boards.ie/discussion/comment/120118260#Comment_120118260

Sorry, no idea. Never knew such a thing existed.

muffler · 17-01-2023 1:24am

I got a chance there to check the signals on the second TV. All the Freeview SD and Saorview HD channels are more or less 100% on both strength and quality. However the Freeview HD channels are a bit different. Signal strength is staying steady at 100% but the quality is fluctuating from 1% to about 20% with the most common reading being around 10%. Odd thing is that I cant see anything wrong with the actual picture/graphics.

The Cush · 17-01-2023 2:13am

https://www.boards.ie/discussion/comment/120118297#Comment_120118297

These grid aerials are wideband type covering the full range of TV frequencies in a single aerial, starting at UHF 21.

Originally Group W up to UHF 69.

https://www.aerialsandtv.com/knowledge/aerials/tv-aerial-groups-widebands

As TV frequencies were allocated to mobile the grid aerial coverage moved down to UHF 60, Group T, to reduce inward interference from mobile.

https://www.freetv.ie/wide-band-grid-uhf-aerial/

TV frequencies were further reduced in recent times, down to UHF 48, Group K, but it appears a manufacturer in the UK no longer produce these grid aerials in that range, UHF 21-48.

The older grid aerials, Group W & T, could be susceptible to inward interference from the newer mobile frequencies. A filter can be fitted after the aerial to reduce interference if required.

Some aerials come with a built in filter but not these grid aerials.

In any case I don't think that's your problem as the other frequencies aren't affected.

The Cush · 17-01-2023 2:20am

https://www.boards.ie/discussion/comment/120118311#Comment_120118311

I guess what we'd like to know is what's the signal strength and quality like before the amplifier but without a meter of some sort that probably isn't possible.

TAFKAlawhec · 17-01-2023 7:05pm

https://www.boards.ie/discussion/comment/120116535#Comment_120116535

That's a type of phased array aerial often called a "grid", "fireguard", "colour king" or "billboard" aerial. In that photo it is horizontally polarised and when used to receive horizontally polarised signals, the forward lobe is fairly wide - this is why they're commonly used in places where you want to receive more than one TX station that aren't too far apart from each other, common in North America (where broadcasters sharing sites let alone towers or transmitting aerials aren't common especially outside the major cities) and used to be used a fair bit in the past where viewers tried to receive RTÉ/TV3/TG4 analogue signals (where RTÉ 1 & 2 were on UHF) and a local "deflector" using one aerial.

However when these aerials are rotated 90 degress for receiving vertical polarisation signals, the phasing of the four x-shaped dipoles ends up with a significantly narrower forward lobe compared to when it is horizontally polarised. As both Ballybofey & Strabane transmit vertically polarised signals, I assume this is what your installer has set it up for. For this reason, it's very possible that it is not collecting enough "signal" from the Strabane TX if the Freeview HD channels are dropping out.

These aerials are often called "high gain" but the bigger gains are generally at high frequencies whereas they are smaller at the lower frequency end (not much different to wideband yagis). Personally I'd try an aerial with a broader forward lobe for vertical polarisation, maybe a medium sized yagi or log-periodic aerial.

As someone else has also mentioned, if there are any nearby mobile phone masts they could also cause issues, especially since the grid/fireguard aerials I've seen still cover the top of the old UHF TV broadcast band that is now used for 4G mobile services. A low-pass or band-pass filter between the aerial and either the TV tuner or before a distribution amplifier can be fitted in and shouldn't cause any harm to check to see if it helps.

Finally, FYI a "modulator" in this case is a device that acts as a mirco-transmitter which takes video & audio and allows them to be viewed on televisions where they either don't have AV sockets or where running cables to these sockets are impractical. Modulators were very commonly used in the analogue TV days by being built in to VCR's, satellite receivers etc. either for use with old TVs with no other input socket than an aerial one, or to allow watching videos or satellite channels in another room. You can get external digital TV modulators, though they're not dirt cheap and if there was one in your system, you'd know.

muffler · 17-01-2023 9:40pm

https://www.boards.ie/discussion/comment/120118364#Comment_120118364

I tried to bypass the booster box this morning but couldnt manage it. There wasnt enough cable to run straight to the tv but I had hoped to join the main cable going to the booster with the cable from booster to tv but there were screw type connectors and I had no way of joining them.

muffler · 17-01-2023 11:36pm

Dont know if its relevant but there are several mobile phone transmitters located on or adjacent to the Ballynofey Saorview transmitter which is about 1.7 km from me.

In any event the main problem is the intermittent loss of the Freeview HD channels which never happened before with the old Freeview aerial.

31-01-2023 12:45pm

https://www.boards.ie/discussion/2058278974/issue-with-aerial

Well muffler, have you any updates re your issue? Since you appear to be having problems with your UK HD reception I'm wondering have you thought about going the satellite route to get them? There's more UK FTA HD channels now from 28.2E than via Freeview, such as the recent editions of ITV2, 3 and 4 in HD.

muffler · 01-02-2023 11:30pm

https://www.boards.ie/discussion/comment/120181666#Comment_120181666

To be honest theres pleanty on Freeview and Saorview for us. I have a Manhattan Freeview recording box and its great for recording the soaps for her good self. Theres a satellite tuner in the TV but its not really used but I might scan for some channels shortly.

Im keeping an eye on the Freeview HD channels. This is the 3rd consecutive day that they havent dropped but I dont want to tempt fate by saying the problem has been sorted. I'll wait another few days before confirming.

muffler · 08-02-2023 1:34am

Just to recap on the issue and provide an update. I got 2 aerials replaced (Saorview & Freeview) with a single aerial but that didnt work as the Freeview HD channels would drop daily. All other channels were fine. A week later I got a high gain aerial installed but once again the HD channels were still dropping. After another week the installer came back and turned the aerial slightly but this didnt work either.

Somewhere in the middle of all that he swapped an old splitter/booster I had with his own but the HD channels still kept dropping. This splitter was only being loaned to me so I bought a new one and used it. Before doing so I removed the screw type connectors on the cables and replaced with the push in type. That was 9 days ago and all channels have been working 100% since.

The only thing that changed was the splitter/booster and the cable connectors so one of those was the cause of the Freeview HD channels dropping but I have no idea why. Id be interested in hearing what the experts here make of all that.

Issue with aerial

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