Freeview has said that high air pressure is the cause of disruption experienced during the Autumn by some of its users in England and Wales, and reported that it was unable to remedy the problem until weather conditions changed. Freeview said that the situation was “uncommon but unpredictable”.

Alasdair Lawrance

I’ve not heard of this before, has anyone?  I can understand the Heaviside layer and sun-spots, but high pressure?

Barry Bonner

I remember many moons ago when we were getting interference from France I had a chat with the ebullient Ian McCaskill about the cause and he referred to it as “tropospheric funnelling”.

Peter Neill

Peter noted a BBC internal email 01 November 2017 that said that some viewers and listeners may experience short term interference to BBC TV and Radio services.  This is due to a zone of high pressure which is moving slowly over the UK. High pressure can sometimes cause signals from distant transmitters to travel further than normal and cause interference, resulting in poor reception. There is no solution to this natural interference and broadcasters cannot prevent it.  

Bill Jenkin

This has been an issue since the year dot.  

High pressure has always caused reception problems. Don’t you remember those announcements at programme junctions about the weather causing interference? Usually in the Summer while we were having a heatwave.  

I suspect it may have got worse recently because of 4G mobiles using the same UHF frequencies as DTT (800mHz band or UHF bands IV & V in old money).

See this “Engineering Announcements” from the IBA in 1984:
         

John Howell

They used to call it “Continental Interference” but I imagine that would not be PC at the moment! (2017)

Ian Hillson

I seem to remember that high pressure was good for Sporadic-E long distance telly reception in the good old Band1/3 days and DX TV enthusiasts loved it!

Over the last couple of days some Freeview (DVB) channels have been giving blockines or even completely going away for a bit. I wish someone would explain things properly to me/us – is it because the signal is fading (as some newspaper articles imply) or too much signal from more distant digital sources causing ones telly to get confused.  I say this because the blocky ones were showing not much signal on the little thermometer indicator.

Terry Meadowcroft

I remember ‘Sporadic E’ caused by the Ionosphere dipping and directing distant foreign FM signals nicely down to earth where we are, made for some interesting but totally sporadic, rapidly appearing (and disappearing just as rapidly) stereo broadcasts in foreign tongues. I used to look forward to bouts of Sporadic E’. If I remember correctly it had some connection with sun spots.

Martin Dilly

From my time defending the nation from the red hordes on the north-east coast of Scotland, we sometimes found that we could reach the Norwegian coast instead of the usual couple of hundred miles with our 1957 radar. This may be relevant: http://www.radartutorial.eu/07.waves/wa17.en.html

Pat Heigham

That explanation is interesting, and I’m reminded of a trans-Indian Ocean cruise that I took in a very small ship.

We passengers were allowed on the bridge, and approaching the Cocos Islands (Indian Ocean ones) the ship’s radar was clearly showing the image long before we had visual on the land appearing over the horizon.

Radar/radio waves do bend!

Following on from the  radar over the Indian Ocean, we were at sea on Christmas Day, and in the afternoon, I chucked a long wire over a lifeboat, and tuned in my Sony radio, recording the Queen’s broadcast onto my Walkman.

That evening, at dinner, the escort manager (bit of a w**ker) made a great deal of a ‘special event’ – it was going to be a broadcast of the Queen’s speech via the ship’s radio. It didn’t work, as reception was lousy, so I just offered up my cassette to put into the boom-box.

Takes a BBC engineer to sort it!

=====

I also had a period in my youth when I was listening to overseas stations on a Sony shortwave radio, sending in reception reports according to the SINPO classification

	S	I	N	P	O
	Signal	Interference	Noise	Propagation conditions	Overall merit
	5-Excellent	5-None	5-None	5-Excellent	5-Excellent
	4-Good	4-Slight	4-Slight	4-Slight disturbance	4-Good
	3-Fair	3-Moderate	3-Moderate	3-Moderately disturbed	3-Fair
	2-Poor	2-Severe	2-Severe	2-Severe disturbance	2-Poor
	1-Barely Audible	1-Extremely strong	1-Extremely strong	1-Very poor propagation	1-Useless

 
 
and one gets back a QSL postcard from the broadcaster:

International shortwave broadcasters have traditionally issued QSL cards to listeners to verify reception of programming, and also as a means of judging the size of their audiences, effective reception distances, and technical performance of their transmitters. QSL cards can also serve as publicity tools for the shortwave broadcaster, and sometimes the cards will include cultural information about the country.

One afternoon at about 14:00, from a garden in the I.O.W. I picked up Radio Australia!  That signal must have bounced around the ionosphere quite a bit!

David Wagner

This so reminds me of “Hancock’s Half Hour” – “ The Radio Ham”  – “It is Ah Rainin in Tokyo”.

John Howell

Do you remember, “Wireless World”  used to publish “Short Wave Conditions” each month. They took the form of graphs to “… indicate the highest frequencies likely to be usable at any time of the day or night for reliable communications over four long distance paths…” but, as Pat points out, freak conditions could bring in stations from anywhere.

I did some shortwave listening while still at school, using a big 1937 vintage Murphy radio and no-one believed I had picked up stations from all over the world. So to try and prove my claims I found test transmissions from radio-telephone stations clearly stating their origin. Being a trainee anorak I started to collect them, then I  became a confirmed anorak by recording them, and now, as a senior anorak I still have the recordings ! (sample attached).

Alasdair Lawrance

That kind of thing is barely credible now, when you can Skype almost anybody, anywhere.

We had a large Marconi Radiogram with 2 short-wave bands (I think), and my ambition at one stage was to get an RCA AR88 or a ’No. 19 wireless set’ from some of the many stores in Lisle Street.

I used to be able to do Morse, as part of a Scout badge, but I wasn’t very good at it – still less so now, and I think it was a mistake to drop it as an official emergency communication medium.

Bill Jenkin

The big difference between things being “broadcast” online and from a twig sticking up into the air (or satellite) is that you can have millions of subscribers receiving from the twig and it doesn’t tie up any more resources for the broadcaster.  Whereas online, the more subscribers you have at any one time, the more you have to increase the bandwidth to accommodate them.   So it may be incredible that we still do it this way but it still makes sense.   You have a sudden mass increase in the audience online and the system will crash.

Ian Hillson

And if you do it via the twig, you can fade out Trump permanently – rather than just disabling his Twitter account for ten minutes.

Tony Crake

Before I appeared at TVC in 1966, I had been on Short Wave transmitters miles away in the wilds of Cumberland (as it then was called)  Weird area!  I was dying to go South !

None of the transmitters are there now, gone and dismantled for scrap (some of which is in my garage!) I managed to visit all the SW stations before they were dismantled.

Rampisham , Skelton and Woofferton ( which is still used by the owners Babcock to transmit some stuff for other people, not the Beeb) Its all done mainly on the Internet or via local FM/AM stations, the outgoing links by satellite or fibre..  (  I spent hours at Skelton monitoring General Overseas Service and pedalling on a BBC Bike around 300 Acres of Aerials!)  

Pat Heigham

Bernie gave me a copy of the wonderful documentary made by Richard Cawston:
“24 hours in the life of the BBC”.

But it was made in 1956 and attitudes were a lot different, then.  However, it served as a good example of the extent of the BBC’s output, showing the transmitting aerials being changed over, etc.

Geoffrey Hawkes

Thanks for this information as I’d been wondering why our radio seemed like it had gone off-tune and that explains it.

Years ago disruption to programme clarity was blamed on “cross channel interference,” usually during high pressure in summer. In my ignorance I remember asking a colleague how foreign transmissions managed to cross the channel and whether those on the other side got the same problem in reverse. The blank looks didn’t betray whether he thought I was trying to wind him up or had completely misunderstood myself.

It was a bit like the reply (not mine) about why radios get quieter and quieter the longer the batteries are in them. “…Well it’s because over time all the electricity in the batteries sinks to the bottom and it’s a good idea to take them out and give them a good shake…”

Tony Crake

We obviously have no radio amateurs in our midst…. UHF / VHF propagation enhancement is dependent on many factors, the weather being just one such factor: all these can affect  your TV enjoyment!