Aerial signal variation during the day

[dal5band]

We have a very old TV aerial with the lead coming down in the garage. In the garage there is a uhf Y splitter with one feed going through the wall into the adjacent lounge to a TV only about 2 metres . The other feed goes across under the floor about 12 meters to a second TV in the kitchen diner.
At best the lounge TV reports a very good signal 100% and the second TV is also good at 93% in the evening.
But we get a strange effect where the signal goes right down to 30% (lounge) and 10% with pixelation in the kitchen. This is worst in the morning.
Can this be caused by atmospheric conditions or is our old aerial setup failing ?
(The percentage signal is as reported by the TVs)

 

[Wayners]

Damage to cable or poor connection on fittings is likely.
Look at neighbours setup. Are they having trouble?
Signal changes with weather but not that much that it will effect picture unless you are in a really poor signal area.
Check all connections starting at the aerial and working back.
Check cable condition especially if its going through anything and constantly moving with wind.
I think it's a connection problem. Well that's where I'd be looking..

F plug splitters are cheap and very good so hold that thought to illuminate that

 

[dal5band]

Thanks ! Checked again today and the signal is fine so it probably is the aerial or cable giving an intermittent fault.
I will change to f type splitter and other connections and go from there.

 

[foxhole]

Birds moving aerial ?

 

[Rodders53]

BBC Reception Advice were warning of High Pressure, weather related interference from 14th May.

High pressure may affect TV & Radio services across parts of the UK - 14th May | Help receiving TV and radio

High-pressure weather conditions are currently affecting some areas of the UK, causing problems to television and radio services. This is predicted to continue for a number of days.

www.bbc.co.uk

That is often a bigger issue around dawn / dusk times. Check what the interference prediction numbers are for your location https://www.freeview.co.uk/corporate/detailed-transmitter-information

How old is the aerial and cable from it. They will degrade over time when outside from wind rain and UV sun damage. Heating and cooling - expansion and contraction - can give connection changes in cables outside. Even drying out and condensation changes.

Picture of Y splitter labelled with a label of which cable goes where would be useful. (The number installed incorrectly is amazing).

 

[dal5band]

We moved here in 1987 and the aerial was already here ! So near enough 40 years. I am surprised it still works. In fact things got better when we went digital because you don't get ghosting. The UHF Y splitter is ok as it has 1 male (aerial input) and two female uhf (outputs to TVs). There are no markings so the only issue could be the upper frequency limit.
By the way we are in GU22 area in a good signal area. I think the signal itself was improved after digital maybe when HD came along ?
Just checked the transmitter info (Rodders53) and we are in a good reception area off Crystal Palace direct.

 

[Harry Bloomfield]

At best the lounge TV reports a very good signal 100% and the second TV is also good at 93% in the evening.
But we get a strange effect where the signal goes right down to 30% (lounge) and 10% with pixelation in the kitchen. This is worst in the morning.
Can this be caused by atmospheric conditions or is our old aerial setup failing ?
(The percentage signal is as reported by the TVs)

Sounds as if likely to be water ingress, into the coax. At 40 years old, you have done well out of the system, don't waste money on replacing splitters.

 

[catlad]

If you notice it next time it rains then it will be moisture getting in the cable or connections.

 

[bernardgreen]

then it will be moisture getting in the cable or connections.

Or more likely the rain drops are absorbing some of the energy of the UHF signal resulting in a reduced signal at the aerial

 

[Rodders53]

GU22 0NR postcode: minimal chance of enhanced propagation interference for CP or Guildford transmitters.
(Well there is a chance, 100% of locations in the 100x100 grid square are served so <1% of time, that'd be a worst case - 1% - of 3.65 day per annum or 87 hours in total. But in slots of a few hours at a time when conditions are right for interference to get in.)

Wolfbane has GUI at 64 vs CP 60 dBuV/m field at 10 m. So pretty strong signal levels and line of sight to both. Drop the receive aerial to bungalow roof 5m and CP is diffracted and 57 dBuV/m

If replacing aerial (group A for CP or group K for either) and downlead get reception of both checked out by the installer? CP will be more resiliently supported (with Croydon as backup site) of course although Guildford is now a 'main transmitter' line fed, duplicated kit etc.,.

 

[ericmark]

Isotropic propagation? Have you ever noticed the smoke from a chimney going up reasonably straight, then spread out? This is caused by cold and warm air and also forms a reflective layer for radio waves, if one is below the layer, then the radio signal can go much further than normal, but if the aerial is above the layer, it reflects the signal into space instead of to your house, a mast with aerials on it may have some above and some below the layer, so sometimes only affects one group of programs.

 

[Rodders53]

The refractive layer is far, far higher than any terrestrial antenna... even the transmit antennas at 1000 ft above ground. Tropospheric ducting is the effect. https://en.wikipedia.org/wiki/Troposphere (Isotropic has rather different meaning).

The frequencies / wavelengths are affected differently and hence land on receive aerials differently... but more important is if the source of long distance reflected frequencies share the same frequency(ies) as the wanted local line of sight transmitter when cancellation and/or reinforcement of the signal can occur (with a time delay between the two, due to the path lengths).