Over amplified signal

1028

Novice Member
I live in a block of 12 flats and I suspect my TV signal is over amplified. Transmitter is Winter Hill 20miles away and the coverage for my area Is reported as strong. The signal strength on both my Panasonic TV and Manhattan Freeview box is 100% on all channels but BBC HD and ITV have very poor signal quality, virtually at bottom of the scale with some picture breakup. I have tried an adjustable attenuator fitted prior to the box and TV which has absolutely no effect on signal strength or quality. I have tested the device on a friend's TV and signal strength moves up and down as the attenuator control is adjusted so I know it is working correctly. My question if anyone can help is, is it feasible to be so over amplified that the attenuator is having no visable effect?
Thank you
 

A1944

Well-known Member
It could be that the HDMI cable between the box and the TV is interfering with the signal from the aerial, it is a known problem.

Make sure that the HDMI cable is as far from all aerial cables as you can manage.

Yes, it can be difficult, but it might do the trick. No certainty, but may be your answer.
 
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winston2010

Well-known Member
Yes it is feasible that the signal is over amplified. That would give the symptoms you have. Who is responsible for the TV distribution? You need to discuss with them. Also check with your neighbours. They may have the same problem.
 

1028

Novice Member
Yes it is feasible that the signal is over amplified. That would give the symptoms you have. Who is responsible for the TV distribution? You need to discuss with them. Also check with your neighbours. They may have the same prob
It could be that the HDMI cable between the box and the TV is interfering with the signal from the aerial, it is a known problem.

Make sure that the HDMI cable is as far from all aerial cables as you can manage.

Yes, it can be difficult, but it might do the trick. No certainty, but may be your answer.
Thanks for the replies.. I understand that there could be an interference issue with the HDMI on quality but the fact that the attenuator is having no visible effect on the 100% signal bars on both tv and box displays is perplexing me!
 

1028

Novice Member
Thanks for the replies. I understand there could be an interference issue with the HDMI on signal quality but the fact that the attenuator is having no effect on the 100% signal strength on both tv and box readings is perplexing me! I'll speak to the management co just wondered f anyone had seen similar.
Thanks
 

Clem_Dye

Distinguished Member
Might be an iffy attenuator, perhaps? What happens if you use fixed value attenuators? When I’ve used them in the past I’ve always found them effective.
 

1028

Novice Member
Pretty sure the attenuator is OK. When used on a friends TV both the signal values go up and down as the attenuator is adjusted. Today I connected the attenuator through two Y splitters in series to try and reduce the signal strength further. The signal strength is still showing at max but noticed that the quality went slightly higher on the bar occasionally flicking to yellow / red rather than solid red.
 

Rodders53

Distinguished Member
Panasonic TVs - at least of a certain age - have a tendency to show the same signal level for a very variable input level - I reckon they present that after the built-in automatic gain control. My Panny gave 10/10 both before and after DSO where the power increased by 10x (10dB), for instance.

Ideally tuners require between 45 and 65 dBuV; many will operate fine with a bit more or less.

Most variable attenuators are max 20dB, with a few higher. Y-splitters 3.5-4dB each. So, your probably 27-28dB of attenuation before some 'effect' on the HD mux signal would suggest the socket output level is around 100dBuV, or a bit higher?

20 miles from WRH signals at an antenna (aerial) aren't going to be excessively high in themselves (50-60 dBuV/m field at 10 m agl??); so some seriously very high gain, cascaded, amplification will be being applied to get to those levels.

NB COM7 (BBC News HD channel) is at least 6dB below the main BBC B HD multiplex (BBC ONE HD, ITV HD etc.,.) so might be expected to work better with your attenuated signal (perhaps).

But DO talk to the Building Management Company and other residents. The system seems in need of 'fettling' with a professional installer and accurate signal meter.
 

1028

Novice Member
Thank you for the trouble you have taken to explain the technicalities. As I live on the second/top floor and have loft access I am tempted to install my own aerial without any amplification. Have read up on some aerial sites and I understand an A band or wideband Log type should be suitable for Winter Hill?
Thanks to all responders.
 

mikej

Well-known Member
As I live on the second/top floor and have loft access I am tempted to install my own aerial without any amplification. Have read up on some aerial sites and I understand an A band or wideband Log type should be suitable for Winter Hill?
If you put your postcode and house number into the checker on this site, it'll give you the recommended aerial type for Winter Hill.

Hopefully, the aerial group in both the before and after columns will be the same, as this should mean you can choose an aerial now without the risk of it being unsuitable at a later date.

For my location, an 'A' or 'T' (wideband) group aerial is recommended for Winter Hill. The second letter refers to it needing to be Horizontal or Vertical.

Note that you'll need a Group T or wideband aerial in order to pick up COM7 (which carries BBC Four HD, BBC News HD etc) on UHF 55 at the moment but this is due to close by the end of June this year, after which time a Group A aerial should cover all the available frequencies (the highest from Winter Hill currently being UHF 37), presuming that they won't introduce any new muxes higher than UHF 37 in the future.

There's a good explanation of the different aerial types here : Wideband / grouped TV aerials - A.T.V. Poles, Brackets, Clamps & Aerials
 

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