Omega Owners Forum
Chat Area => General Discussion Area => Topic started by: Martin_1962 on 09 January 2009, 21:20:07
-
It's that time of year, TV is unwatchable due to trospheric ducting, 4 multiplexes have been overpowered by Emley Moor crapalogue >:(
Luckily we do have alternatives, Sue is now watching Deadenders via BT Vision Replay TV, and a couple of timers are moved to the Humax HDR.
Anyway after some comments at work I have set up Hustle for record, using BBC HD for that. :y
Having 3 TV sources is very usefull.
-
trospheric ducting
wossat? :-?
-
Emley Moor crapalogue.
who? :-?
-
Telly is such a small part of my life i probably would'nt notice for a week or so, even then i'd just wait for it to come back on which it will do eventually.
No offence, i'm probably in the minority but telly is'nt high on my need list, hence i only have freeview....if that cost anything i would'nt have it!!!!! ::) 8-)
-
Lol, in simple terms.....
Consider a radio signal.....it works by line of sight between the transmitter/receiver.
Normaly a radio signal can not go a long way because of the curvature of the earth (20-30miles is typical) under normal conditions. The earth gets in the way!.
What happens sometimes is that you get an inversion where you have dry air on top of cold damp air... (i.e. fog!) and this creates a wave guide (a bit like coax cable) which means the radio signals can now effectively turn corners and in this case its the curvature of the earth.
The attenuation of the signal is often less to!
Hence you can get interference between say your local tv or radio station and one 100's of miles away that uses the same frequencies.
There are actualy some ways round it with careful aerial choice etc (its more common when the aerial is pointing over a large body of water i.e. The Wash)
-
This is when TV signals get carried a long way
See the analogue frequencies
http://en.wikipedia.org/wiki/Emley_Moor_transmitting_station
See the digital frequencies
http://www.aerialsandtv.com/suttoncoldfieldtx.html#SuttonColdfieldsChannels
-
Lol, in simple terms.....
Consider a radio signal.....it works by line of sight between the transmitter/receiver.
Normaly a radio signal can not go a long way because of the curvature of the earth (20-30miles is typical) under normal conditions. The earth gets in the way!.
What happens sometimes is that you get an inversion where you have dry air on top of cold damp air... (i.e. fog!) and this creates a wave guide (a bit like coax cable) which means the radio signals can now effectively turn corners and in this case its the curvature of the earth.
The attenuation of the signal is often less to!
Hence you can get interference between say your local tv or radio station and one 100's of miles away that uses the same frequencies.
There are actualy some ways round it with careful aerial choice etc (its more common when the aerial is pointing over a large body of water i.e. The Wash)
North Worcestershire, Sutton and Emley is a common occurance and won't get fixed until Digital Switch Over.
I could sort it in a few minutes with an axe and I doubt if many people would notice.
Sutton needs the same treament too!
-
Nah....you use a multi element array......this results in the interference signal being cancelled out. :y
Its an old technique they also used on some early radar to try to get round jamming etc and works well for TV
-
ahh i see..... um nope still confused, think ill stick to cars
-
For those who wish to have a fuller understanding of the phenomena ....
http://ecjones.org/propag.html :)
Ducting: On rare occasions, two or more inversions may appear at different altitudes. Sometimes certain radio waves can be transported between these two inversions. Therefore, this type of propagation is called "ducting" (or "tunnelling"). Records of over 2500km have been set due to such ducting on VHF and UHF. Unfortunately, the effect is usually confined to 2m, but it can occur as high as 1.2 GHz (usually along frontal systems), and it almost never occurs below frequencies of 50MHz. When ducting does occur on these frequencies, communication distances are typically in the range of ~400km. Inversions usually develop under the influence of high pressure weather systems when there is very little air movement. Also, low pressure systems may produce an inversion when a cold air mass collides with a warmer air mass (called a frontal system in meteorology). Inversions that occur along frontal systems support propagation along a line parallel to the weather front, and radio amateurs using frontal inversion often point their antennas parallel to the frontal system to take advantage of this form of propagation.
-
Lol, in simple terms.....
Consider a radio signal.....it works by line of sight between the transmitter/receiver.
Normaly a radio signal can not go a long way because of the curvature of the earth (20-30miles is typical) under normal conditions. The earth gets in the way!.
What happens sometimes is that you get an inversion where you have dry air on top of cold damp air... (i.e. fog!) and this creates a wave guide (a bit like coax cable) which means the radio signals can now effectively turn corners and in this case its the curvature of the earth.
The attenuation of the signal is often less to!
Hence you can get interference between say your local tv or radio station and one 100's of miles away that uses the same frequencies.
There are actualy some ways round it with careful aerial choice etc (its more common when the aerial is pointing over a large body of water i.e. The Wash)
Which is probably why i nearly put my fist thro the screen of the 'command' unit in the Viano early (posh name merc give to their stereo/phone/satnav units)
I pushed the 'station list' button, and its suppose to come up with the names of radio stations it can receive, it came up with load of BBC ones including BBC Wales, BBC Cyrwa (or summat like that!) and missed most of the local ones off the list >:(
It was only when I got to within about 1 mile of the transmitter of the local radio station i wanted to listen to.....it put it in the list of choices ::)
No chance of trying to select FM 107.7 manually, well if there is a way on the unit, god is the only one that knows how to ;D
-
Yep....often because the signal is leaving the transmitter via a duct, the reception close to the transmitter is shite!
-
That'll explain why the freeview has gone tits up and the sky is working fine then :y
-
That'll explain why the freeview has gone tits up and the sky is working fine then :y
Is is going to be a big problem when all TV goes digital? Before wh had sky we were on the old digital set up and often lost the signal due to certain weather conditions. To be honest it is about that is stopping me from dumping sky
-
That'll explain why the freeview has gone tits up and the sky is working fine then :y
Not tried my freeview tonight so dunno, still got the radio on....
Havent gone DAB yet.....coz i discovered my fav radio station doesnt transmit on DAB :(
But when i came in at 9pm it was foggy and -6C .....be some icy roads in the morning if it doesnt warm up outside!!
-
It is unlikely to make any difference when it goes digital as somewhere theere will be a Tv transmitter with the same frequencies as the ones used by your local station.
-
Nah....you use a multi element array......this results in the interference signal being cancelled out. :y
Its an old technique they also used on some early radar to try to get round jamming etc and works well for TV
How does this work then - when EM C4 is the same frequency as SC Mux1 and in a very similar direction?
-
That'll explain why the freeview has gone tits up and the sky is working fine then :y
Is is going to be a big problem when all TV goes digital? Before wh had sky we were on the old digital set up and often lost the signal due to certain weather conditions. To be honest it is about that is stopping me from dumping sky
No because the jamming stations will be closed down - in SC EM situation there will be no shared channels post DSO
-
My TV never seems to suffer (only ever watch freeview), in fact not really suffered since the CB days...
-
Plenty of ham radio activity around europe on VHF / UHF tonight by the looks of things.
"Put those damned antennas up" moves up a notch on Kevin's TODO list.
Kevin
-
Nah....you use a multi element array......this results in the interference signal being cancelled out. :y
Its an old technique they also used on some early radar to try to get round jamming etc and works well for TV
How does this work then - when EM C4 is the same frequency as SC Mux1 and in a very similar direction?
Because the interfering signal has a number of multipaths reaching your location which will be in and out of phase with each other due to it having travelled a long distance down a wave guide......add and subtract the signals on the antenna arrays in the correct manner and the interferring signal is cancelled out!
The wanted signal is line of sight which will be the dominant reception peek.....it will be unaffected
-
That'll explain why the freeview has gone tits up and the sky is working fine then :y
Is is going to be a big problem when all TV goes digital? Before wh had sky we were on the old digital set up and often lost the signal due to certain weather conditions. To be honest it is about that is stopping me from dumping sky
No because the jamming stations will be closed down - in SC EM situation there will be no shared channels post DSO
There will....given the large number of transmitters in the Uk and the small number of mux frequencies there will always be overlap.
It wont go post digital and as discussed before, digitl is more prne to multpath interference where as on analogue it would ahev been seen as a ghost image.
-
Nah....you use a multi element array......this results in the interference signal being cancelled out. :y
Its an old technique they also used on some early radar to try to get round jamming etc and works well for TV
How does this work then - when EM C4 is the same frequency as SC Mux1 and in a very similar direction?
Because the interfering signal has a number of multipaths reaching your location which will be in and out of phase with each other due to it having travelled a long distance down a wave guide......add and subtract the signals on the antenna arrays in the correct manner and the interferring signal is cancelled out!
The wanted signal is line of sight which will be the dominant reception peek.....it will be unaffected
Want to have a go then? ;D ;D
Too high for me!
Looks like 5 degree or so difference
-
That'll explain why the freeview has gone tits up and the sky is working fine then :y
Is is going to be a big problem when all TV goes digital? Before wh had sky we were on the old digital set up and often lost the signal due to certain weather conditions. To be honest it is about that is stopping me from dumping sky
No because the jamming stations will be closed down - in SC EM situation there will be no shared channels post DSO
There will....given the large number of transmitters in the Uk and the small number of mux frequencies there will always be overlap.
It wont go post digital and as discussed before, digitl is more prne to multpath interference where as on analogue it would ahev been seen as a ghost image.
Looking at the channels - the only real problem around here is Emley
-
That'll explain why the freeview has gone tits up and the sky is working fine then :y
Is is going to be a big problem when all TV goes digital? Before wh had sky we were on the old digital set up and often lost the signal due to certain weather conditions. To be honest it is about that is stopping me from dumping sky
No because the jamming stations will be closed down - in SC EM situation there will be no shared channels post DSO
There will....given the large number of transmitters in the Uk and the small number of mux frequencies there will always be overlap.
It wont go post digital and as discussed before, digitl is more prne to multpath interference where as on analogue it would ahev been seen as a ghost image.
Looking at the channels - the only real problem around here is Emley
Today possibly.
What you ahev to remember is that after the analogue switch off most of the digital multiplexers are being moved to occupy the old analogue frequencies.....
....plus some extras (there are far more multiplers than the 5 analogue channels)
So it will probably just be another one causing the issues!
-
Seen the post switch off allocations, should be fine, only Emley was anywhere near the power of Sutton.
That said I once picked up Newcastle DTTV
-
The trouble with the ducting is that power has little to do with it as the attenuation is small!
So you can get trouble with low power repeaters!
-
The trouble with the ducting is that power has little to do with it as the attenuation is small!
So you can get trouble with low power repeaters!
In the rough direction there is only Sutton Emley and Newcastle which are horizontal, vertical seems to have no effect
-
The trouble with the ducting is that power has little to do with it as the attenuation is small!
So you can get trouble with low power repeaters!
In the rough direction there is only Sutton Emley and Newcastle which are horizontal, vertical seems to have no effect
Yep but your aerial will also have side lobes and receive off the rear....
-
The trouble with the ducting is that power has little to do with it as the attenuation is small!
So you can get trouble with low power repeaters!
In the rough direction there is only Sutton Emley and Newcastle which are horizontal, vertical seems to have no effect
Yep but your aerial will also have side lobes and receive off the rear....
Not when there is a big hill between us and Rigde Hill ;D
-
Again makes no odds.....ducting does just that....it goes over and round hills!
-
Again makes no odds.....ducting does just that....it goes over and round hills!
Malverns seems to block well. Malvern TX was erected to fill in the dead zone.
Worcester is not covered by one transmitter different areas use diffferent TXes.
RIdge Hill, Sutton Coldfield, Malvern, Bromsgrove
Yes I do know all of the local TXes ;D ;D