Menu buttonMENU    UK Free TV logo Help!
securesearchsettings

 

 

Click to see updates

What is the Inversion Effect and why does it effect my Freeview TV reception?

What is the Inversion Effect and why does it effect my Freeview TV reception?

What is the Inversion Effect and why does it effect my Freeview
published on UK Free TV

Under normal circumstances, the signals from each television transmitter can only be received by those homes and businesses that have aerials that have a direct line-of-sight to the transmitter.

(The Inversion Effect is also known as "Tropospheric Ducting")



The part of the signal from the transmitter that is directed upwards simply escapes into space and are lost.

When there is high atmospheric pressure (BBC Weather - UK Pressure chart) as the sun heats up the ground the warm air gets trapped underneath the colder air higher up. At the point where the warm air gets trapped under the cold air this creates a layer that is, in effect, a mirror for the television signals.



This means that signals that would otherwise be impossible to receive can suddenly effect your television reception.

The digital television signal uses a format called COFDM (coded orthogonal frequency division multiplexing) and this incorporates the ability to ignore reflected digital signals.

However, analogue television signals did not co-operate with each other and the picture quality is reduced. The very weak digital signals that were used before digital switchover for Freeview were badly effected by interference from reflected signals from adjacent analogue transmissions.

I recommend you look at the Tropospheric Ducting Forecast for VHF and UHF Radio and TV page for a current forecast - yellow, orange, red, and pink indicate that conditions are perfect for the effects listed above.



All questions
Freeview: yes the service is free except for the cost of two set top boxes - on1
Will analogue radio be switched off at the same time as analogue TV?2
Why has Men and Motors disappeared from my TV?3
My sound has high frequency distortion and sibilants - is this normal or do I h4
How can I Receive Freeview on two TVs using one Freeview box 5
In this section
My Freeview box has no EPG, is blank on FIVE, ITV3, ITV4, ITV2+1, has no sound o1
I have now lost all signal can you tell me what the problem might be?2
I have a Durabrand cg5660-m and I need the lock key code!3
My ITV/C4 Freeview channels have disappeared - what can I do? Is it my SCART ca4
My high gain aerial can't get all the Freeview channels I expected5
What are the aerial types about? Are they high-gain?6

Comments
Thursday, 7 June 2018
S
StevensOnln1
4:39 PM

Jon Dooley: Firstly, no one on this website has anything to do with any broadcaster or transmitter company. The transmitters do not reduce their power level overnight. If the problem is only happening overnight, the most likely explanation is that you are suffering from electrical interference being emitted by something in your home (or a near neighbour) which is operating on a timer and probably has an electric motor.

link to this
StevensOnln1's 2,089 posts Platinum Platinum GB
Tuesday, 12 June 2018
J
Jh
11:39 AM Preston

Lost itv1 no signal , bbc 1 OK, Bbc news hd channel poor signal pixelating. Area pr3 1tb

link to this
Jh's 1 post GB
Jh's: Freeview map terrain plot frequency data R&TI Service digitaluk trade DAB coverage
S
StevensOnln1
2:17 PM

Jh: Have you checked for any loose or damaged cables or connections behind your TV? Do not attempt to retune.

link to this
StevensOnln1's 2,089 posts Platinum Platinum GB
Select more comments

Your comment please
Please post a question, answer or commentUK Free TV is here to help people. If you are rude or disrespectful all of your posts will be deleted and you will be banned.







Privacy policy: UK Free Privacy policy.