OT - period TV channels

[AMc]

So can a new codec/firmware not be installed in the DAB radio, as it can in a computer?

Not in many of them - if you're rich enough to by TAG kit then possibly, but most radios/freeview boxes etc. have their capabilities burnt into the chips when they're made ... forever.
A computer has a general purpose processor that can be programmed to do more or less anything you want providing it can do the sums fast enough to keep up.

 

[Penners]

if you're rich enough to by TAG kit

That's a big, fat NO!

But thanks for the information.

 

[robgil]

Fm was/is broadcast in a lossless format, any dab broadcast that has been compressed will never be as good, thats obvious isnt it?
It might not become apparent when listening to the radio on a little portable jobby but when using some decent hifi equipment the difference is quite noticeable. Even my old Leak Troughline far out performs any dab receiver.
To take an analogue or any other lossless format then compress it is still taking away information from the source and reproducing what is left, the argumant is that up until a certian point the information taken away cant be heard anyway but in my view that point is well above 320p kbs, I've got Mp3's here in 320kps and the Flac or Wav files they came from sound ten times better.

If Dab radio could broadcast Flac or Wav files I might entertain it.

 

[MdB]

Fm was/is broadcast in a lossless format, any dab broadcast that has been compressed will never be as good, thats obvious isnt it?
It might not become apparent when listening to the radio on a little portable jobby but when using some decent hifi equipment the difference is quite noticeable. Even my old Leak Troughline far out performs any dab receiver.
To take an analogue or any other lossless format then compress it is still taking away information from the source and reproducing what is left, the argumant is that up until a certian point the information taken away cant be heard anyway but in my view that point is well above 320p kbs, I've got Mp3's here in 320kps and the Flac or Wav files they came from sound ten times better.

If Dab radio could broadcast Flac or Wav files I might entertain it.

FM broadcasts frequencies from 30Hz to 15kHz so doesn't cover the entire audio range. It is also broadcast in analogue so by definition it is lossy. Digital conversion of an analogue signal is also lossy in both frequency range and dynamic range. However, once it is converted a digital signal can be lossless from that point on if a non lossy transmission system is used (such as CDs put in the post). If a lossy digital transmission scheme is used (such an in DAB or MP3s) then the quality will depend on the settings chosen. With DAB is appears that the compression algorithm choice is poor and the amount of compression chosen is too high also which gives a lower quality overall compared to FM. If a better compression algorithm was used and / or a low compression ratio was used then digital radio is capable of being better than FM due to the losses in quality of the FM signal whilst it is broadcast. Unfortunately, it doesn't look like this is going to happen.

 

[robgil]

This makes interesting reading http://www.digitalradiotech.co.uk/articles/DAB-vs-FM-sound-quality.php , and as a comparison a random flac file off my hard drive plays at 1024 kBit/s, Fm plays at 728 kbps so I would assume Fm to be a lot better and closer to source than a 128 mp2 dab broadcast.

 

[AMc]

I do love that site - I remember when they dropped all reviews of 'full size' DAB tuners on the basis that there was no HiFi source available any more.
It's clearly written by someone who knows his/her stuff but the vitriol undermines the information somewhat.

I used to listen to XFM on FM radio when we lived in London when you could often pickup nothing but pirate radio. When I got my first DAB tuner it was to deal with that problem - it came into its own when we moved to the sticks.

There are no FM stations I want to listen to here - at all - so the objective or subjective difference in quality is academic to me - I wouldn't want to listen to Radio2, BBC Norfolk or Heart if it were in 7.1 DTS HD with 3D glasses

 

[robgil]

The poetry program on BBC4 can be quite funny at times, not that the poems are funny, just the idea of listening to it.
BBC2 has some decent stuff sometimes. Cant do with Radio1 and all that kind of garbage , Stop!..........carry on. Same songs over and over again and it takes three DJ's to be entertaining enough to bring a spark of life into the brain dead. That radio Norfolk is just plain weird. Bungalow radio.

 

[Penners]

once it is converted a digital signal can be lossless from that point on if a non lossy transmission system is used (such as CDs put in the post)

I love the idea that CDs in the post can be regarded as a radio transmission system. I shall immediately call the BBC and ask them to post me today's news.

:wink:

 

[MdB]

once it is converted a digital signal can be lossless from that point on if a non lossy transmission system is used (such as CDs put in the post)

I love the idea that CDs in the post can be regarded as a radio transmission system. I shall immediately call the BBC and ask them to post me today's news.

:wink:

http://en.wikipedia.org/wiki/Sneakernet

Real term with real life usage.

 

[AMc]

We used to chuckCD-Rs across the office for excellent data transfer speeds - access rates could be limited if you were already listening to a music CD esp. if you didn't hear the warning shout before a disc skidded across your keyboard

 

[Me!]

I'm having a problem with the aerial lead to one TV in the house since the digital switchover that I would appreciate some advice on please.
We have a normal Yagi type aerial in the loft pointing at Tacolneston. It has about a couple of feet of coax to connect it to a 6-way splitter, only four of which outputs are used. The feeds to TVs from three of the four outputs work fine, but the fourth does not. No matter which of the outputs I connect the problem feed to, and even if I disconnect all the other three, the troublesome one still doesn’t give any signal in its target room. I have also moved TVs between rooms to test different ones on different aerial sockets, so I am convinced that it must be this one particular length of coax that is causing a problem. BUT, when I test the length of coax with an AVO 8 (a period multimeter!) I get a resistance of only about 1 or 2 ohms from one end to the other of both the core and the screen. I have also tested to make sure that the core isn’t shorting to the screen and that is fine. So, can anyone please tell me then why a perfectly good signal that is going in one end of the cable, is not coming out of the other?
Thank you.

 

[MdB]

My guess (and it is only a guess) is that the cable is squashed or kinked at some point. This is won't change its DC properties (what the AVO is measuring) as its screen isn't shorted to the main conductor but it will change its properties at 500MHz that the TV signal is at. In particular, a kink will change the characteristic impedance of the cable which will cause a some of the signal to be reflected back up the cable. I doubt a kink would make a great deal of difference to a strong signal but it might be enough to stop a weak one from working.

 

[Penners]

MdB knows about this stuff - I don't. But to my amateur way of thinking he has highlighted one point that is perhaps worth reiterating. Splitting your TV signal four ways is pretty optimistic. I'd be inclined to do two things:

1. Replace the dodgy length of coax.

2. If this isn't 100% satisfactory, fit an amplified splitter.

 

[Flyfisher]

It does sound like the particular run of coax. When reading the original post I assumed that the splitter in question was a powered (i.e. amplified) version, but Penners raises a good point about passively splitting a TV signal six ways - it's not a great idea unless you live under the transmitter. :wink:

Measuring the DC resistance of the coax is really only half the story because the signals in question are very high frequency (ultra-high, actually, hence 'UHF') and can be attenuated by poor quality coax cable or long cable lengths or even by the cable being kinked or otherwise damaged.

Is the coax cable in question much longer than the other working cables?

The thing with digital television is that picture qulity will remain very good until, suddenly, it breaks up and disappears completely. The old analogue transmissions would become progressively noiser ('snowier'), which could give a clue about the signal strength. So, in this case, it could be that the offending coax cable is just that bit too long, or perhaps damaged in some way, that enough of the signal is being lost that the TV cannot decode the digital signal at all.

 

[Keithj]

If the splitter doesn't contain an amplifier, I'd be surprised.

If you've proved that particular run of coax doesn't work (by plugging into different outlets on the splitter, and the problem moving with the cable), and if you've checked that the terminations at the two ends are correctly soldered, then I'd replace the coax. Satellite TV coax is pretty cheap these days, and is a lot better performance than that dreadful "aeraxial" stuff that was the norm when I was a lad.

 

[Penners]

if you've checked that the terminations at the two ends are correctly soldered

Soldered? That surprises me. I've never seen TV aerial coax with soldered plugs on the end. Should they be?

The only coax I've seen in recent years is screened with wire mesh and Kit-Kat wrappers, and the plugs screw on the end in the usual way.

 

[Me!]

Thank you for the suggestions. The coax run that isn’t working is probably about 10 or 12 metres long, and there is certainly another run of about the same length that was made from coax off the same drum and that one is OK. The connector at one end is an f-type so there is no soldering there, and at the other end is a standard coax plug that goes into the back of a TV, and that one has a good tight grub screw holding the core.
I’m sure the suggestions that the cable is faulty and needs to be replaced are correct. Unfortunately it isn’t an easy one to get to, so that isn’t the answer I wanted to hear!
We are about 15 miles from Tacolneston, so we do get a very good signal. The splitter is a passive one, and I did think that may be a bit over ambitious so that is why I did try the tests with all the other outputs disconnected and only the one problem one still wired up, but that still didn’t work. Having the other three outputs all connected and in use at once all seems to work fine as well. How do passive splitters divide the signal though in a situation where all six outputs are connected to TVs, but only two TVs are ever turned on at any one time? Does each of the running TVs get half the signal from the aerial, or one sixth of it? Sorry, that must be a really stupid question to anyone who knows the answer, but unfortunately I don’t

 

[Flyfisher]

It's sounding more and more like the cable run.

It might be worth disconnecting the splitter altogether and connecting the offending cable directly to the aerial cable to get the maximum signal down it, but I wouldn't be too hopeful because it doesn't really sound like a signal problem from the aerial given that all the other TVs works over similar lengths of cable.

With a passive splitter, the signal is divided equally between all connected TVs. I don't think it matters if the TVs are turned on or off, it's the fact that they are connected that matters. But, again, if the other TVs are working over similar cable lengths then signal strength is probably not the problem. being only 15 miles from the Tacolneston is clearly working in your favour.

I can imagine that replacing the cable is likely to be a problem. Before ripping out the existing one it might be worth making a length of new cable and running it down the stairs and across the floor to the TV, just to be absolutely sure before messing up the decor!

 

[Feltwell]

FF's suggestion of running a bit of cable loose to the TV first sounds like a good idea!

If the TV works on that, it may also be worth trying to replace the more accessible bits of the offending co-ax first, and see if that solves the problem. I know that jointing the cable is not ideal, but I'm presuming that some parts of your offending cable will be easier to get at than others - try replacing the bits that can be got at relatively easily first, jointing onto the not so easy to get at bits with proper co-ax connectors, which are very cheap.

Worst that can happen is that you waste a bit of co-ax cable and a few connectors. You could even move the TV back along the run, cutting the cable at accessible points until you find it works - perhaps a better idea if you've got a 14" portable than a 50" plasma though...... 8)

Final lazy option - do you really need a 4th TV outlet? If you do, is it one where a small indoor aerial would suffice if you've got a strong signal?

 

[Lime]

It is worth pointing out that since switchover the East's transmitters are now broadcasting at full power.

Digital tv can blank out or pixelate with a signal that is too strong too.
I have had to reduce the amplification on my aerial because of it.

It is also possible that the piece of coax in question is of a length that creates resonance and the tv end is a null point.
Lengthening or shortening may produce an improvement.