I have a USB digital tuner for my computer and get my signal from the Angus transmitter. However the signal is not all that strong but I can live with it short term as I only use it to watch something different from Sky. It is only one mux that is dodgy.
Even the analogue channels are not all that great. I really need a new aerial but when the Angus transmitter analogue is switched off I presume that the digital signal strength will increase.
If so, I will just persevere with my present aerial. So will the signal strength be increased?
>I have a USB digital tuner for my computer and get my signal >from the Angus transmitter. However the signal is not all that >strong but I can live with it short term as I only use it to >watch something different from Sky. It is only one mux that is >dodgy.
> Even the analogue channels are not all that great. I really > need a new aerial but when the Angus transmitter analogue is > switched off I presume that the digital signal strength will > increase.
> If so, I will just persevere with my present aerial. So will > the signal strength be increased?
> Dave
If you need a new aerial (why?) then get a new aerial. It matters not whether the transmitter e.r.p. is increased post DSO, your receiver will still work. If power was being reduced it would be a different matter.
> If you need a new aerial (why?) then get a new aerial.
Nobody *needs* to watch TV, clearly the O/P is willing to avoid the expense of a new aerial and put up with current reception problems for 10 more months if reception will improve at DSO.
Clearly reception will improve, if only one mux is currently difficult then at a rough guess the extra power post-DSO will be sufficient, even though the muxes are now and will remain in-group for a C/D aerial they will shuffle down from 56-68 to 53-61 which should help a little too.
Not all poor reception is due to low signals, it could be cross modulation, reflections or rain getting in the works or even physical damage to the aerial, and no amount of extra signal will help those problems, and when the switchover comes, you can bet your wotsit that.. A: all aerial riggers will suddenly be very busy, and B: you will find it does not wrk as it is and the prices will be higher.
Its Murphy's law, and for all those called Murphy, apologies.
Brian
-- Brian Gaff - bria...@blueyonder.co.uk Note:- In order to reduce spam, any email without 'Brian Gaff' in the display name may be lost. Blind user, so no pictures please!
>I have a USB digital tuner for my computer and get my signal from the Angus >transmitter. However the signal is not all that strong but I can live with >it short term as I only use it to watch something different from Sky. It is >only one mux that is dodgy.
> Even the analogue channels are not all that great. I really need a new > aerial but when the Angus transmitter analogue is switched off I presume > that the digital signal strength will increase.
> If so, I will just persevere with my present aerial. So will the signal > strength be increased?
>> If you need a new aerial (why?) then get a new aerial.
> Nobody *needs* to watch TV, clearly the O/P is willing to avoid the > expense of a new aerial and put up with current reception problems for 10 > more months if reception will improve at DSO.
> Clearly reception will improve, if only one mux is currently difficult > then at a rough guess the extra power post-DSO will be sufficient, even > though the muxes are now and will remain in-group for a C/D aerial they > will shuffle down from 56-68 to 53-61 which should help a little too.
I maybe only watch one or two programmes a week on CH 5 digital TV as the Angus transmitter does not have CH 5 analogue.
It is just that the aerial was erected before I got a garage built on the side of the house and it would need, so I have been told, scaffolding to put a better aerial up there.
I cannot even get subsidised cavity wall insulation because of that unless I pay for scaffolding.
That is the only use I make of the aerial as I have Sky+ and I watch it when there is a clash between what my wife is watching and recording at the same time.
I can live with it until analogue is switched off.
On Wed, 04 Nov 2009 23:54:08 GMT, "Dave" <d...@planet51.zzn.com> wrote: <snip>
>I have a USB digital tuner for my computer and get my signal from the Angus >transmitter. However the signal is not all that strong but I can live with >it short term as I only use it to watch something different from Sky. It is >only one mux that is dodgy.
<snip>
I regularly struggle with the Angus transmitter from which I am 16 miles behind some hills on a bearing of 62 deg. In theory Mux 1 should always be strong enough but it only takes a wet, misty evening (not uncommon in this part of the world!) for me to get the dreaded poor signal message on BBC1/2. I then sometimes find a retune picks up Durris satisfactorily. This 53 miles away on a bearing of 44 deg but transmits at 5x the power of Angus. I have a fairly new decent quality aerial of the right group properly aligned on Angus.
Why is it that DAB can amalgamate the output of several transmitters and when listening to a digital radio channel you can be receiving from more than one transmitter at a time but DTT signals all have to use different frequencies from different transmitters? Would it be possible technically for all transmitters in a given TV region to use the same frequencies and the total signal accumulated in some way?
> Why is it that DAB can amalgamate the output of several transmitters > and when listening to a digital radio channel you can be receiving > from more than one transmitter at a time but DTT signals all have to > use different frequencies from different transmitters?
Because the BBC use an SFN for their national DAB mux, but SFNs are not used for DVB-T in this country (apart from a few localised ones I gather).
In article <cutaf5d503iekqdreahn74mqcmk04k7...@4ax.com>, ChrisW
<ch...@chrisdeletethiswillsher.co.uk> wrote: > On Wed, 04 Nov 2009 23:54:08 GMT, "Dave" <d...@planet51.zzn.com> wrote: > I regularly struggle with the Angus transmitter from which I am 16 miles > behind some hills on a bearing of 62 deg. In theory Mux 1 should always > be strong enough but it only takes a wet, misty evening (not uncommon in > this part of the world!) for me to get the dreaded poor signal message > on BBC1/2. I then sometimes find a retune picks up Durris > satisfactorily. This 53 miles away on a bearing of 44 deg but transmits > at 5x the power of Angus. I have a fairly new decent quality aerial of > the right group properly aligned on Angus.
I also get a stronger and more reliable DTTV signal from Durris (78km away) than from Angus (27km). This also despite it being at the HF end of the band. Are the patterns of these TXs published now?
>Why is it that DAB can amalgamate the output of several transmitters
and when listening to a digital radio channel you can be receiving from more than one transmitter at a time but DTT signals all have to use different frequencies from different transmitters? Would it be possible technically for all transmitters in a given TV region to use the same frequencies and the total signal accumulated in some way?
There's a trade off between the amount of data that can be fitted in to a given bandwidth and the maximum distance between transmitters before the signals start to interfere with each other, rather than help each other. The numbers are wrong for Single Frequency Networks to work in the pre-DSO incarnation of DTT in the UK.
On 7 Nov., 17:39, "Bill" <wrightsaeri...@f2s.com> wrote:
> The numbers are wrong for Single Frequency Networks > to work in the pre-DSO incarnation of DTT in the UK.
> Bill
The maximum distance between two DVB-T transmitters is about 67 km before the signals start interfering rather than just adding in a helpful way. The 67 km comes from the product of the speed of light 3E8 m/s and the 'Guard Interval'. In the UK the GI is 28 usec = 8.4km (8k mode) while in Germany it is 224 usec = 67.2km
With DVB-T such a '67 km' SFN will have a bitrate of just 20 Mbps/mux and not the UK 24.13 Mbps/mux. (17% loss of capacity).
If you draw a map of the larger TX mast/towers in the UK - the distance between them is mostly well above 67 km. And new masts are very big money.
In addition, if very many transmitters used the same frequency in a very large SFN, the total signal from all transmitters more than 67km apart would increase the general background noise level - called SFN self interference. This problem is much worse with higher modulations e.g. 16/64-QAM than with the primitive low bitrate 4-QAM used by DAB (and DAB+)
Now enter DVB-T2 with its 16k and 32k modes, longer Guard Intervals, rotated constellations and very much better error correction codes. Now large SFN's is very much more possible for a DTT network.
The guard interval can be more than two times larger, but the capacity lost from SFN operation more like just 5-8%. With the GI in the range of 135-160 km it will only be very distant transmitters that need contribute to the self interference.
The UK do not have UHF channels allocated by the ITU (GE06) for a nationwide SFN in the UHF bands (470-790 MHz). One may think that channel 36 could (almost) be used. The channels 35 and 37 may also be able to cover large parts of the UK.
It is not easy nor inexpensive to implement such SFN's, but now it is for the first time technically not impossible.
>> The numbers are wrong for Single Frequency Networks >> to work in the pre-DSO incarnation of DTT in the UK.
>> Bill
> The maximum distance between two DVB-T transmitters > is about 67 km before the signals start interfering > rather than just adding in a helpful way. > The 67 km comes from the product of the speed > of light 3E8 m/s and the 'Guard Interval'. > In the UK the GI is 28 usec = 8.4km (8k mode) while > in Germany it is 224 usec = 67.2km
> With DVB-T such a '67 km' SFN will have a bitrate > of just 20 Mbps/mux and not the UK 24.13 Mbps/mux. > (17% loss of capacity).
> If you draw a map of the larger TX mast/towers > in the UK - the distance between them is mostly > well above 67 km. And new masts are very big money.
> In addition, if very many transmitters used the same > frequency in a very large SFN, the total signal from > all transmitters more than 67km apart would > increase the general background noise level > - called SFN self interference. This problem > is much worse with higher modulations e.g. > 16/64-QAM than with the primitive low bitrate > 4-QAM used by DAB (and DAB+)
> Now enter DVB-T2 with its 16k and 32k modes, longer > Guard Intervals, rotated constellations and very much > better error correction codes. Now large SFN's is very > much more possible for a DTT network.
> The guard interval can be more than two times larger, > but the capacity lost from SFN operation more like > just 5-8%. > With the GI in the range of 135-160 km it will > only be very distant transmitters that need > contribute to the self interference.
> The UK do not have UHF channels allocated by > the ITU (GE06) for a nationwide SFN in the > UHF bands (470-790 MHz). > One may think that channel 36 could (almost) be used. > The channels 35 and 37 may also be able to cover > large parts of the UK.
> It is not easy nor inexpensive to implement > such SFN's, but now it is for the first time > technically not impossible.
|
