Freeview Aerial issue

Ratcliffe950

Novice Member
Can some please help me out with a problem I’ve had since the introduction of freeview. Any mux at the end of the band has always had a really poor reception. Firstly it was all the bbc Chanel’s which used mux 61. These channels were unwatchable during the winter months and poor during the summer. So the signal strength is full but the quality is like 1-2 out of 10. They moved these channels to a different mux and all the channels work perfectly. So now the next highest mux is 48 and all channels on this are now i unwatchable. I had a new freeview digital Aerial fitted with a masthead amp. 3 tvs split from the aerial and all do the same thing. So the problem is whatever chanmd use the highest mux number suffer terribly with no signal for to no quality. I live near a 4g and 5g transmitter could this be the problem or is it over attenuation? Boosting the interference? Why does it only affect the highest mux? And more importantly how do I fix the problem or diagnose it without having to get on the roof. Please help it’s driving me crazy. It’s definitely worse in the winter months and wind and rain make it that much worse again.
 

A1944

Well-known Member
It may be that the "digital aerial" (which don't really exist) is not actually suitable for your location.
 
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Ratcliffe950

Novice Member
It may be that the "digital aerial" (which don't really exist) is not actually suitable for your location.
Thank you for your quick reply. Is there a way to known which aerial is suitable for a certain location, as I said the higher the number of the mux the worse the signal quality gets (signal strength always 10/10 for all mux’s). I believe it was a high gain (40+ Prongs/teeth) it was fitted by an aerial engineer. I believe because we had it fitted while analogue was still transmitting it may be now over amplifying the signal where the signal strength for freeview was lower until analogue was switched off. Am I on the right track or completely way off course ?
 

A1944

Well-known Member
If the signal strength is 10/10 on the highest Mux as you say then that sounds like the aerial is giving sufficient signal and so something else may be the cause. Maybe someone else can give better advice, though.
 

Rodders53

Distinguished Member
Location (approx) for the transmitter and estimate of signal strength there.

What reports 10/10 signal/quality (Make/model).
My Panny TV in Lowestoft reported 10/10 on all muxes (except the Norwich local TV which was not meant to be received there at all) both before DSO and after the 10x (+10dB) power increase that happened there. That was because it reported things after the TVs gain and error correction circuits.

My Humax PVR gave a very different set of results that I'd have to find if I needed to. ;)

Your issue sounds more like variable reception due to evergreen trees (moving in the wind and rain) to me? What is the outlook from your home that the aerial 'sees'?
 

Ratcliffe950

Novice Member
Location (approx) for the transmitter and estimate of signal strength there.

What reports 10/10 signal/quality (Make/model).
My Panny TV in Lowestoft reported 10/10 on all muxes (except the Norwich local TV which was not meant to be received there at all) both before DSO and after the 10x (+10dB) power increase that happened there. That was because it reported things after the TVs gain and error correction circuits.

My Humax PVR gave a very different set of results that I'd have to find if I needed to. ;)

Your issue sounds more like variable reception due to evergreen trees (moving in the wind and rain) to me? What is the outlook from your home that the aerial 'sees'?
Thanks for your reply. What I don’t understand is if it’s interference from line of sight like u say trees why would it only affect the reception one mux (48) all the other mux have good signal and quality (from my transmitter 4 mux are used to broadcast all the channels). I do live in a area where I am the lowest in elevation for the town. As a test to see what could be causing the bad signal i disconnected the power supply for the mast head amp at the primary tv. With it plugged in I got no Reception on all channels on mux 48. With it unplugged i got a picture on all the channels on 48 but the quality wasn’t the best probably around 60% although all channels were watchable. This is what makes me think it’s an over attenuation problem?
 

A1944

Well-known Member
Thanks for your reply. What I don’t understand is if it’s interference from line of sight like u say trees why would it only affect the reception one mux (48) all the other mux have good signal and quality (from my transmitter 4 mux are used to broadcast all the channels). I do live in a area where I am the lowest in elevation for the town. As a test to see what could be causing the bad signal i disconnected the power supply for the mast head amp at the primary tv. With it plugged in I got no Reception on all channels on mux 48. With it unplugged i got a picture on all the channels on 48 but the quality wasn’t the best probably around 60% although all channels were watchable. This is what makes me think it’s an over attenuation problem?
I don't think any transmitters have 4 Mux, either Freeview-Lite (3 Mux) or the full service (6 Mux or more).

As Rodders53 says, it would help if you could give an approximate location with the postcode of a nearby business or public building (but not your own postcode).
 

Ratcliffe950

Novice Member
Sorry I was guessing the amount of mux’s I thought all the channels were picked up on 4 but it’s got to be 6 from what you say. So the answers are:
My transmitter is dover
My closest location (not my actual home postcode) is TN23 5ER, approximately 20 miles from the transmitter.
 

A1944

Well-known Member
Ah, now that is an interesting one.

Checking the coverage on the Freeview site reveals that there is a second transmitter 2 miles away somewhere in Ashford using the same 6 channels as Dover, presumably as a Single Frequency Network (SFN).

Whilst I don’t think it should, I wonder if that has any bearing on this problem.
 

Kapkirk

Active Member
You will most likely be served by the Bluebell hill or Dover transmitters, things are continually changing atm with the introduction of 5g taking over some of the higher channels, so yes this COULD be the source of your issues. Modern aerials are able to reject 4g/5g better than older models.
There are currently works in progress on the Bluebell hill transmitter 5/12/21 which may cause loss of signal. If you have an distribution amplifier fitted the signal will always be shown as 10 even if the signal actually being received by the aerial is very poor because the tv is seeing an amplified signal so the amplifier will just amplify noise.
I don't know if you have the correct aerial fitted to your roof or what transmitter it is actually pointing to .. and if you have selected the CORRECT transmitter after doing your channel scan on the TV.
I would get on the to firm that fitted your aerial or perhaps another reputable aerial fitter in your area to reassess your system and change as required, you may need a different aerial and it pointing to a different transmitter.
 

A1944

Well-known Member
You will most likely be served by the Bluebell hill or Dover transmitters
Bluebell Hill is not an option as it does not use Ch48 for any Mux. It will be either Dover or Ashford.

Edit: The Ashford transmitter is shown as just north of the international railway station.
 
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Rodders53

Distinguished Member
Ashford and/or Dover (as both are H and bearings 68 and 94 degrees will be likely be within the acceptance angle of many aerials).
Ashford is a cardioid beaming WSW? from atop International House mb21 - The Transmission Gallery
500 W erp and 2 km away.

Dover at 17 miles 28 km Wolfbane predicts 50 dBuV/m field from Dover. But allowing 10 dB gain for a receive antenna, 20 dB gain for a masthead amplifier and, say, 4 dB loss for cables and terminations to a single outlet:
50+10+20-4 = 76 dB
Ideally receivers require between 45 and 65 dB. Any less and they may not cope (weak signal) more and they may overload. Better designs of tuner cope well even outside those parameters.

So overload is potentially a possible issue due to excessive amplification. That would have been possible pre DSO as well though (10dB power increase) at 66 dB!

Of course the 3 x PSB 33, 35, 36 at 80 kW erp are +3dB cf the Wolfbane numbers (79 dB today, 69 before DSO). The 3 x COMs 39, 42, 48 are only 40 kW (Wolfbane estimates based on the lowest power).
Generally lower frequencies propagate better than the higher, so I'd not expect only 48 (Arqiva B) to give problems?

Much, much more likely though is continental (or UK) transmitter interference during recent high pressure conditions?
Although trees' leaf dimensions can match certain wavelengths and affect one more than any other (higher frequencies are shorter wavelengths).

Signal level can be reduced by using attenuators: Splitters, amps and diplexers - A.T.V. Poles, Brackets, Clamps & Aerials
As Justin says they aren't too expensive and will probably prove if the masthead amp needs its gain reduced, if variable, or removing altogether when reworking the system.

Still unanswered is what TV/device is being used to measure signal level and quality ;)
 

Ratcliffe950

Novice Member
Ashford and/or Dover (as both are H and bearings 68 and 94 degrees will be likely be within the acceptance angle of many aerials).
Ashford is a cardioid beaming WSW? from atop International House mb21 - The Transmission Gallery
500 W erp and 2 km away.

Dover at 17 miles 28 km Wolfbane predicts 50 dBuV/m field from Dover. But allowing 10 dB gain for a receive antenna, 20 dB gain for a masthead amplifier and, say, 4 dB loss for cables and terminations to a single outlet:
50+10+20-4 = 76 dB
Ideally receivers require between 45 and 65 dB. Any less and they may not cope (weak signal) more and they may overload. Better designs of tuner cope well even outside those parameters.

So overload is potentially a possible issue due to excessive amplification. That would have been possible pre DSO as well though (10dB power increase) at 66 dB!

Of course the 3 x PSB 33, 35, 36 at 80 kW erp are +3dB cf the Wolfbane numbers (79 dB today, 69 before DSO). The 3 x COMs 39, 42, 48 are only 40 kW (Wolfbane estimates based on the lowest power).
Generally lower frequencies propagate better than the higher, so I'd not expect only 48 (Arqiva B) to give problems?

Much, much more likely though is continental (or UK) transmitter interference during recent high pressure conditions?
Although trees' leaf dimensions can match certain wavelengths and affect one more than any other (higher frequencies are shorter wavelengths).

Signal level can be reduced by using attenuators: Splitters, amps and diplexers - A.T.V. Poles, Brackets, Clamps & Aerials
As Justin says they aren't too expensive and will probably prove if the masthead amp needs its gain reduced, if variable, or removing altogether when reworking the system.

Still unanswered is what TV/device is being used to measure signal level and quality ;)
Thank you so much for your answers. I am a real novice so thank you for bearing with me. Ok here goes.
I am using my tv (panny. Flat screen) to read the signal and quality levels. I assume this isn’t ideal but it does definitely show a difference between the different channels in quality by a fair amount.
I am confident i am aligned to Dover transmitter. I was going to ask whether it was worth realigning to the ashford transmitter but you say I should be picking this up with the angle of the aerial to dover? A silly question probably but if this is the case how does the tuner decide which duplicate channel to use as ashford and Dover transmit identical information.
With all the calculations you did which I did manage to follow you are spot on I had the same set up pre DSO there was the same problem but worse interference (only difference was it was all channels on mux 68 as this was the mux for all bbc channels at the time. they moved all channels from 68 and other changes to free up the higher frequencies). These channels are now on 33 and are absolutely fine.
I have 3 tvs running split at the mast head amp all show the same issue.
 

Rodders53

Distinguished Member
MODEL of Panny TV?
I have one plasma that gives 10/10 for virtually and signal input to it. Another LCD has a more useful system with a bar graph (possibly marked %?).

But detail the numbers it gives for each of the 6 mux frequencies, please (easy to do as you can simply channel up/down to find them all on most Pannys).

So a masthead distribution amplifier (amp-splitter). That may only have 10 or 11dB gain e.g. Labgear WBOS4F/S or Proception PROMHD14M. Maybe something like 5-16dB gain if a variable. That will amend the numbers from above^^^ to further reduce the likelihood of overload.
A higher gain masthead followed by passive outdoor splitting (4 ways passive = -8dB ) would give similar numbers.

I really doubt it's overload as the higher power muxes should be affected more than ch 48 if overloading?

Dover was only 1kW erp on ch 68 for BBC on the 81 transmitter plan while Analogue was on. Three other muxes were 2kW (+3dB) and one 0.5kW (-3dB). Top channel aerial and cable losses suggest to me that it would be digital cliff edge lack of signal issues mostly. Thus, at DSO 80 kW was well over 20dB greater.

An attenuator would be easy enough to use and prove it is (or is not) overload. Toolstation have a variable one at £4.69 but will need f-tv adapters too.

Re-pointing the aerial: If getting in an aerial installer they should use a spectrum analyser signal meter to align the aerial to get best reception from one or other or both transmitters together (compromise direction) and ensure a signal within the (upper end of) the ideal 45-65 dBuV level on all the multiplex frequencies. That may, or may not, entail removal / adjustment / replacement of the amplifier-splitter system?
 

Kapkirk

Active Member
I usually recommend using Log Periodic 27-36 element aerial to your strongest transmitter, these aerials are more able to reject mobile 5g signals.
 

Rodders53

Distinguished Member
I usually recommend using Log Periodic 27-36 element aerial to your strongest transmitter, these aerials are more able to reject mobile 5g signals.
No they do not.

Logs are not especially directional, so unless the 5G is from directly behind they will likely receive the 5G well enough.

They are usually wideband W in design so 21-68 and where does 5G sit? 60-68 originally and now 49-68 with AT700 clearance.

They work by some of the element sizes matching the wanted frequencies (see the BBC R&D white papers on designs of them). So recent re-designs of some could be 21-48 group K by losing the shorter elements... so 'element count' (mainly a marketing tool in reality) will reduce.

None I've seen, so far, on sale are like that (yet).

Filters do a similar job (some say better) and some aerials - of various designs - already include filters for >ch60 and in time will do the same for >48. (The filter is simply added as part of the 'balun' design to match the folded dipole element impedance to 75 ohm coax.)

There's no evidence the OPs issue has anything to do with mobile phone 5G interference anyway.
 

Clem_Dye

Distinguished Member
The potential gotcha with a group K aerial is the inability to grab COM7 on CH55 effectively. It could be argued of course that if/when COM7 disappears in mid-2022 then it won't matter, but for now, is a group T might worth considering if COM7 is receivable and 5G is not an issue?
 

Rodders53

Distinguished Member
The potential gotcha with a group K aerial is the inability to grab COM7 on CH55 effectively. It could be argued of course that if/when COM7 disappears in mid-2022 then it won't matter, but for now, is a group T might worth considering if COM7 is receivable and 5G is not an issue?
Group K Yagi 18 as per ATVs choice of aerials is perfectly good to ch55 COM7 (and up to 60 his site says).
But again we have virtually zero evidence that a new aerial is needed by the OP (so far).
 
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Clem_Dye

Distinguished Member
Yes, and I trust ATV’s test results. Still, for COM7, we’re only, in theory, about 6 months from it disappearing. It will be interesting to see what happens. As for the OP, pass. :)
 

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