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Freeview/SKY quality
I am aware that Freeview is being pushed so that we can all go digital
ASAP but if Freeview can use an ordinary aerial with standard coax then does this mean that the quality is less than satellite signal or are they both the same when they come out of the set top box. Are there any differences and should we be looking at a higher coax quality for Freeview Just wondering Mike |
On Sat, 4 Sep 2004 16:06:32 UTC, "Mike Saunders"
wrote: I am aware that Freeview is being pushed so that we can all go digital ASAP but if Freeview can use an ordinary aerial with standard coax then does this mean that the quality is less than satellite signal or are they both the same when they come out of the set top box. Are there any differences and should we be looking at a higher coax quality for Freeview Depends on the signal strength. You might get away with the old style coax in a very strong signal area, but there is no graceful degradation. Any noise and you can lose the whole signal as it dips below the threshold on digital. A new antenna and downlead is meant to make quite a difference. -- Bob Eager begin a new life...dump Windows! |
Bob Eager wrote:
On Sat, 4 Sep 2004 16:06:32 UTC, "Mike Saunders" wrote: I am aware that Freeview is being pushed so that we can all go digital ASAP but if Freeview can use an ordinary aerial with standard coax then does this mean that the quality is less than satellite signal or are they both the same when they come out of the set top box. Are there any differences and should we be looking at a higher coax quality for Freeview Depends on the signal strength. You might get away with the old style coax in a very strong signal area, but there is no graceful degradation. Any noise and you can lose the whole signal as it dips below the threshold on digital. A new antenna and downlead is meant to make quite a difference. I presume antennas do not degrade with time then so do you mean it is a different spec for Freeview? Also do you mean the downlead should be of satellite quality? Thanks Mike |
In article ,
Mike Saunders wrote: I am aware that Freeview is being pushed so that we can all go digital ASAP but if Freeview can use an ordinary aerial with standard coax then does this mean that the quality is less than satellite signal or are they both the same when they come out of the set top box. Satellite needs different cable because it's transmitted at much higher frequencies. This makes no intrinsic difference to the end result. -- *No sentence fragments * Dave Plowman London SW To e-mail, change noise into sound. |
On 4 Sep 2004 13:28:33 -0500, Mike Saunders wrote:
I presume antennas do not degrade with time ... Bad assumption. They do, or at least the connections do, unless the installer is very particular about sealing the cap and cable entry. Most cheapo "contract" aerials will have water in the connection box after the first shower of rain. ... then so do you mean it is a different spec for Freeview? Depends where you are. In some places the Freeview Multiplexes are not with in the same aerial group as the analogue transmissions, fitting an aerial the properly covers the required frequencies will help. Also do you mean the downlead should be of satellite quality? CT100 has considerably less loss than bog standard "TV Coax". The less signal you lose the better... -- Cheers Dave. pam is missing e-mail |
On Sat, 04 Sep 2004 19:45:01 +0100, Dave Plowman (News) wrote:
Satellite needs different cable because it's transmitted at much higher frequencies. cough Yes the downlinks are roughly 10.7 to 12.75GHz but the LNB on the wok down converts that to 950MHz to 2.1GHz (ish). 950MHz is above above Band IV/V so "TV Coax" wouldn't be particularly suitable. However the satellite Tx frequency does not go down the cable from wok to box. -- Cheers Dave. pam is missing e-mail |
"Mike Saunders" wrote in :
I am aware that Freeview is being pushed so that we can all go digital ASAP but if Freeview can use an ordinary aerial with standard coax then does this mean that the quality is less than satellite signal or are they both the same when they come out of the set top box. Are there any differences and should we be looking at a higher coax quality for Freeview Just wondering Mike IMO freeview is not all it's cracked up to be. I get excellent picture and sound quality, but there are annoying occasional very short sound losses. This may be due to sporadic electrical interference from elsewher in the hovel, but they don't warn you about it, and many boxes appear not to be protected, and the system is clearly more vulnerable. Also there are occasional pixilation artifacts on very busy pictures due to bandwidth restrictions. It is a way to get a picture across using less bandwidth, but having given the broadcasters a bandwidth knob with digital techniques, they're happily screwing it down all through the chain. (Look at the picture quality on BBC 24 hr news - 3 shades of pink, and textures otherwise achieved only by cheapo camcorders). You need a good aerial, and good downlead to minimise electrical interference, because digital does not degrade politely like analogue, but totally collapses. I'd stay away from it if you have decent analogue; it may improve after the switchoff, but not before You could post in uk.tech.digital-tv for mor info; I doubt if it will help but Bill the aerial man has a fund of good stories. mike |
On Sat, 4 Sep 2004 18:28:33 UTC, "Mike Saunders"
wrote: A new antenna and downlead is meant to make quite a difference. I presume antennas do not degrade with time then so do you mean it is a different spec for Freeview? Yes...maybe. I'm not a major expert on this (years since I studied antennas) but one factor is that the antenna should incorporate a balun to match the essentially balanced antenna to the unbalanced feeder. Older antennas don't have this, but it's more important for digital, to reduce noise picked up by the feeder. In addition, the channels used by digital may not be in the same range as the ones your original antenna was meant for. A wideband antenna seems to be the thing. Also do you mean the downlead should be of satellite quality? It needs to be properly screened (foil screen, not the 'low loss' wide mesh stuff. I think this subject was rehearsed here recently. There is some good stuff (and details of channels used by each mux, in your area) at: http://www.dtg.org.uk The postcode checker is a little pessimistic, but you can then (when you get the result page) find the transmitter in use and how far away, on what bearing, and the channels in use. The link isn't very visble, but it's the text "Link to information..." in the second shade box down on the right of the postcode result page. There are also documents that explain the antenna requirements in more detail. -- Bob Eager |
Mike Saunders wrote:
I am aware that Freeview is being pushed so that we can all go digital ASAP but if Freeview can use an ordinary aerial with standard coax then does this mean that the quality is less than satellite signal or are they both the same when they come out of the set top box. Assuming that you are getting adequate signal from both dish and aerial then the main factor that will determine the picture quality is the bitrate used to encode the channel. Alas bit rates are often selected for commercial reasons (i.e. low bitrate = more channels in a given bandwidth = more cost effective) rather than aesthetic ones. Freeview tends to give quite good picture quality on some channels - but less so on the ITV muxes. It is less good on fast moving scenes (i.e. football for example) where the bandwidth restrictions become more noticeable. Are there any differences and should we be looking at a higher coax quality for Freeview Something like CT100 cable will tend to give better results not only because it is lower loss (hence more signal at the receiver), but also it is less susceptable to picking up Interference (impulse noise in particular) than traditional "low loss" co-ax. The other thing to consider is that aerials do "age", in particular co-ax absorbs water which will attenuate the signal. This is particularly noticeable if your local region has channels allocated toward the top of the spectrum where the absorption effect of the water will be more noticeable. Aerials can also degrade, due to mechanical damage accumulated over time (birds, wind etc), and also corrosion. The larger higher gain aerials tend to suffer more. Seven years is considered a good lifespan for a high channel, high gain aerial. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
"Mike Saunders" wrote in message ...
Bob Eager wrote: On Sat, 4 Sep 2004 16:06:32 UTC, "Mike Saunders" wrote: I am aware that Freeview is being pushed so that we can all go digital ASAP but if Freeview can use an ordinary aerial with standard coax then does this mean that the quality is less than satellite signal or are they both the same when they come out of the set top box. Are there any differences and should we be looking at a higher coax quality for Freeview Depends on the signal strength. You might get away with the old style coax in a very strong signal area, but there is no graceful degradation. Any noise and you can lose the whole signal as it dips below the threshold on digital. A new antenna and downlead is meant to make quite a difference. I presume antennas do not degrade with time then so do you mean it is a different spec for Freeview? Also do you mean the downlead should be of satellite quality? Thanks Mike If you look out the technical standards i believe that Sky via satellite has a higher bit rate than terrestrial freeview, as the available radio bandwidth is less limited, so it should be a better picture. Also digital radio from satellite has a higher bit rate than terrestrial DAB so the quality is better. luggsie |
mike ring wrote:
IMO freeview is not all it's cracked up to be. I get excellent picture and sound quality, but there are annoying occasional very short sound losses. some boxes handle this better than others have noticed. The oldish pace DTVA fro example tends to introduce lots of clicks and squeaks when it gets glitches in the signal. Something like the Netgem however handles it much better. This may be due to sporadic electrical interference from elsewher in the hovel, but they don't warn you about it, and many boxes appear not to be protected, and the system is clearly more vulnerable. The QAM64 modulation scheme used on the ITV muxes is more vulnerable to this than the QAM16 used on the other muxes. Also there are occasional pixilation artifacts on very busy pictures due to bandwidth restrictions. It is a way to get a picture across using less bandwidth, but having given the broadcasters a bandwidth knob with digital techniques, they're happily screwing it down all through the chain. (Look at the picture quality on BBC 24 hr news - 3 shades of pink, and textures otherwise achieved only by cheapo camcorders). You need a good aerial, and good downlead to minimise electrical interference, because digital does not degrade politely like analogue, but totally collapses. To be fair, it does not degrade at all right up until you reach the threshold of the capabilities of the forward error correction used. At that point it begins to suffer drastically. Subjectively that can be more annoying if you only have a poorish signal, since the transition between a perfect picture, and pixels, clicks, and frozen images is more noticeable than a general covering of "snow" over what you are trying to watch. There are also some reception problems that digital is far better at dealing with like multi path, (i.e. ghosting). I'd stay away from it if you have decent analogue; it may improve after the switchoff, but not before Indeed, it ought to improve when more spectrum is made available. You also need to factor whether any of the channels not available on analogue are of value to you. You could post in uk.tech.digital-tv for mor info; I doubt if it will help but Bill the aerial man has a fund of good stories. Yup that is true, well worth a visit for that if nothing else. (do a google groups search on "riggers diary"). -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
luggsie wrote:
picture. Also digital radio from satellite has a higher bit rate than terrestrial DAB so the quality is better. Note that radio on freeview and DAB are unrealted technologies. Digital radio on freeview tends to sound much better than DAB (which is to be honest, crap!) -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
John Rumm wrote in
: You also need to factor whether any of the channels not available on analogue are of value to you. Har har. mike |
mike ring wrote:
John Rumm wrote in : You also need to factor whether any of the channels not available on analogue are of value to you. Har har. Why was that funny? -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
Mike Saunders wrote:
Bob Eager wrote: On Sat, 4 Sep 2004 16:06:32 UTC, "Mike Saunders" wrote: I am aware that Freeview is being pushed so that we can all go digital ASAP but if Freeview can use an ordinary aerial with standard coax then does this mean that the quality is less than satellite signal or are they both the same when they come out of the set top box. Are there any differences and should we be looking at a higher coax quality for Freeview Depends on the signal strength. You might get away with the old style coax in a very strong signal area, but there is no graceful degradation. Any noise and you can lose the whole signal as it dips below the threshold on digital. A new antenna and downlead is meant to make quite a difference. I presume antennas do not degrade with time then so do you mean it is a different spec for Freeview? They do degrade over time, mainly due to effects of weathering. Also do you mean the downlead should be of satellite quality? All cables lose a bit of signal per metre. Higher quality cables have less signal loss per metre than low quality cables. "Satellite quality" cable tends to be higher quality. So it all depends on how strong the signal is to begin with. All satellite signals are fairly weak, which is why higher quality cable should always be used with satellite. For terrestrial, it depends how close you are to the transmitter, etc. At my location I HAVE to use "satellite quality" cable (CT100) for freeview or I can't get a reliable picture. |
Dave Plowman (News) wrote:
In article , Mike Saunders wrote: I am aware that Freeview is being pushed so that we can all go digital ASAP but if Freeview can use an ordinary aerial with standard coax then does this mean that the quality is less than satellite signal or are they both the same when they come out of the set top box. Satellite needs different cable because it's transmitted at much higher frequencies. This makes no intrinsic difference to the end result. Not down the cable it isn't. The LNB on the dish downconverts the Gigahertz-range signal which comes from the satellite into something very close to normal TV frequencies. |
Indeed, it ought to improve when more spectrum is made available. You
also need to factor whether any of the channels not available on analogue are of value to you. Also, analogue doesn't support widescreen. If you have a widescreen television, or want to watch widescreen programmes on a 4:3 TV with black bars top and bottom, then you'll need some sort of digital TV reception. Christian. |
On Mon, 6 Sep 2004 10:51:12 +0100, "Christian McArdle"
wrote: Indeed, it ought to improve when more spectrum is made available. You also need to factor whether any of the channels not available on analogue are of value to you. Also, analogue doesn't support widescreen. If you have a widescreen television, or want to watch widescreen programmes on a 4:3 TV with black bars top and bottom, then you'll need some sort of digital TV reception. Christian. ... and thicker cable, or the pictures won't fit through it anyway. When I was three or four, I asked my dad what the things with spikes were for on people's roofs. He told me, quite reasonably, that they were to pick up television pictures - we had just got a set. In those days, the old Band 1 H-shaped antennas were very commonplace, so I naturally assumed that somehow the pictures were slotted into the top, were perhaps rolled up to go down the cable and then appeared on the screen - as if by magic. There was even a short film that was shown about how television worked which showed something like this for the transmission part so it never occured to me to think differently. However, by the time I was about 8 or 9, this had all changed. I can remember going to the public library and pulling out a book on how to build a radio set. I took it to the counter and gave it to the lady with my children's ticket (which was not meant to be for books "for grown ups"). The librarian looked down her nose at me and suggested that I would be better off with Janet and John or Noddy. I explained to her that I could read the book perfectly OK. She asked me to do so, which I did. Then thinking that she could catch me out, asked me to explain how a radio worked. I closed the book and explained how a superhet operated. She stamped the book and asked me if I wanted any others like it. ..andy To email, substitute .nospam with .gl |
"Mike Saunders" wrote in message ...
I am aware that Freeview is being pushed so that we can all go digital ASAP but if Freeview can use an ordinary aerial with standard coax then does this mean that the quality is less than satellite signal or are they both the same when they come out of the set top box. Are there any differences and should we be looking at a higher coax quality for Freeview Just wondering Mike The boxes are now so cheap that I bought one just to try. There are two TVs on the aerial and I found that a £5 amplifier from Asda (to feed the digibox which is on the end of a few metres of cheap coax) was the only upgrade that was required. The picture and sound quality is never less than excellent and invariably better than the analogue signal (whether compared against the amplified or unamplified signal). MBQ |
In article ,
MBQ wrote: The picture and sound quality is never less than excellent and invariably better than the analogue signal (whether compared against the amplified or unamplified signal). Hmm. On a *good* TV with a decent aerial, with the sound fed to an external system, I'd defy anyone to reliably tell the difference between analogue, NICAM, or Freeview - provided that source is mono. Picture wise, pretty well the same applies (apart from aspect ratio) apart from on the odd occasion the broadcasters are providing a superior source than normal. -- *Your kid may be an honours student, but you're still an idiot. Dave Plowman London SW To e-mail, change noise into sound. |
xenelk wrote:
All cables lose a bit of signal per metre. Higher quality cables have less signal loss per metre than low quality cables. "Satellite quality" cable tends to be higher quality. True... One of the main advantages of sat cable for Freeview is the extra noise immunity that you get with the double screening on the cable. You can have a freeview setup that has plenty of signal, but is plagued by impulse noise from vehicle ignitions etc. Making sure all connections, amps, splitters etc. are fully screened as well is a good plan. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
Andy Hall wrote:
"for grown ups"). The librarian looked down her nose at me and suggested that I would be better off with Janet and John or Noddy. Not as daft as it sounds though... When I was I guess about 10, I had a Ladybird book called "How to build a transitor radio!" ;-) ISTR it went through building a set in stages, starting with a basic crystal set (using a OA91 diode for AM envelope demodulation - about the last time I have used one of those), and then worked up to a regenerative design. The construction method was a little "unorthodox" with a wooden breadboard with a matrix of screws driven in, and the wires of the components trapped under screw cups. Alas the full design never did work, and I did not have access to the test equipment to trace it through correctly to work out why. (not helped by being a very old circuit design - many components were on the verge of being obsolete). -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
Dave Plowman (News) wrote:
Hmm. On a *good* TV with a decent aerial, with the sound fed to an external system, I'd defy anyone to reliably tell the difference between analogue, NICAM, or Freeview - provided that source is mono. Alas the freeview can sound worse on the poor bitrate channels. With a decent bitrate channel I have found it is about as good as NICAM when fed into a prologic decoder. There also seems to be a fair variation in sonic performance between the different freeview boxes. Comparing against analogue is a little more trickey - as you say you would have to limit your source material to mono which in many cases will also mean older analogue recordings etc. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
John Rumm wrote in message ...
There are also some reception problems that digital is far better at dealing with like multi path, (i.e. ghosting). I can vouch for this - I got a digibox for this reason alone. There is a churchyard full of very old, very tall trees near my house. The signal bounces off them causing quite bad ghosting on my analogue signal. As the trees wave majestically in the breeze so the little ghosts dance about on the telly. Anyway, the digibox has cured this and gives a perfect signal on channels 1-4 despite running off an aerial which looks like it may have been up there since the house was built in 1880. The other channels can suffer from signal degradation but they seem to broadcast unalloyed crap, so no loss there. |
Dave Plowman (News) wrote:
In article , MBQ wrote: The picture and sound quality is never less than excellent and invariably better than the analogue signal (whether compared against the amplified or unamplified signal). Hmm. On a *good* TV with a decent aerial, with the sound fed to an external system, I'd defy anyone to reliably tell the difference between analogue, NICAM, or Freeview - provided that source is mono. Picture wise, pretty well the same applies (apart from aspect ratio) apart from on the odd occasion the broadcasters are providing a superior source than normal. I will second that. Ok the DVD's are a tad sharper, but otherwse my analogue installation is almost totally free of defects and sharp and clean. as is my FM radio... |
In message , John
Rumm writes Andy Hall wrote: "for grown ups"). The librarian looked down her nose at me and suggested that I would be better off with Janet and John or Noddy. Not as daft as it sounds though... When I was I guess about 10, I had a Ladybird book called "How to build a transitor radio!" ;-) ISTR it went through building a set in stages, starting with a basic crystal set (using a OA91 diode for AM envelope demodulation - about the last time I have used one of those), and then worked up to a regenerative design. The construction method was a little "unorthodox" with a wooden breadboard with a matrix of screws driven in, and the wires of the components trapped under screw cups. Alas the full design never did work, and I did not have access to the test equipment to trace it through correctly to work out why. (not helped by being a very old circuit design - many components were on the verge of being obsolete). I had an (IIRC) Radionics kit Perspex matrix with mounted components with lugs which fitted into screws .. it sort of worked -- geoff |
In article , xenelk
wrote: So it all depends on how strong the signal is to begin with. All satellite signals are fairly weak, which is why higher quality cable should always be used with satellite. For terrestrial, it depends how close you are to the transmitter, etc. The screening is the reason for the cable requirement. Correct cable is required even if (and probably more so) you are 2 miles from the transmitter. -- AJL Electronics (G6FGO) Ltd : Satellite and TV aerial systems http://www.classicmicrocars.co.uk : http://www.ajlelectronics.co.uk |
Andy Luckman (AJL Electronics) wrote:
In article , xenelk wrote: So it all depends on how strong the signal is to begin with. All satellite signals are fairly weak, which is why higher quality cable should always be used with satellite. For terrestrial, it depends how close you are to the transmitter, etc. The screening is the reason for the cable requirement. Correct cable is required even if (and probably more so) you are 2 miles from the transmitter. Which was my point. I was just trying to explain it in simple terms.... |
"John Rumm" wrote
| Andy Hall wrote: | "for grown ups"). The librarian looked down her nose at me and | suggested that I would be better off with Janet and John or Noddy. | Not as daft as it sounds though... When I was I guess about 10, I | had a Ladybird book called "How to build a transitor radio!" ;-) .... | Alas the full design never did work, I'm glad you told me that; I had the same book but never tried making it up. Now I know it wouldn't have worked anyway, I don't feel I missed as much. Owain |
Owain wrote:
"John Rumm" wrote | Andy Hall wrote: | "for grown ups"). The librarian looked down her nose at me and | suggested that I would be better off with Janet and John or Noddy. | Not as daft as it sounds though... When I was I guess about 10, I | had a Ladybird book called "How to build a transitor radio!" ;-) ... | Alas the full design never did work, I'm glad you told me that; I had the same book but never tried making it up. Now I know it wouldn't have worked anyway, I don't feel I missed as much. I think one of the problems was the components used were so old in design that the spec had altered by the time I managed to find examples of them. The transistors used (can't remember the number at the mo) were in glass domed cases with a black finish (about 3mm diameter by 7mm tall). It also called up things like "postage stamp" type trimmers which at the time were difficult to find (although they are available again now!). -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
In article ,
John Rumm wrote: The transistors used (can't remember the number at the mo) were in glass domed cases with a black finish (about 3mm diameter by 7mm tall). Ahh. Red spots. ;-) -- *Sherlock Holmes never said "Elementary, my dear Watson" * Dave Plowman London SW To e-mail, change noise into sound. |
On Tue, 07 Sep 2004 15:36:39 +0100, John Rumm wrote:
The transistors used (can't remember the number at the mo) were in glass domed cases with a black finish (about 3mm diameter by 7mm tall). OC71 etc, though that was an audio type tranny. Nicely light sensitive if you scrapped the paint off. It also called up things like "postage stamp" type trimmers which at the time were difficult to find (although they are available again now!). When I was at the "building my first radio stage" (late 60's early 70's) getting almost any electronic part was hard. RS, Farnell, etc where way above the pocket money level. Tandy didn't do most of the things required for UK designs and what they did do wasn't that cheap. Maplin didn't exist... -- Cheers Dave. pam is missing e-mail |
On Tue, 7 Sep 2004 14:36:39 UTC, John Rumm
wrote: I think one of the problems was the components used were so old in design that the spec had altered by the time I managed to find examples of them. The transistors used (can't remember the number at the mo) were in glass domed cases with a black finish (about 3mm diameter by 7mm tall) OC81 comes to mind. I had some here till recently... Strange numbering system...followed on from the valve conventions. O was the filament coltage, and C meat it was a 'triode'....! -- Bob Eager begin a new life...dump Windows! |
In article ,
Bob Eager wrote: I think one of the problems was the components used were so old in design that the spec had altered by the time I managed to find examples of them. The transistors used (can't remember the number at the mo) were in glass domed cases with a black finish (about 3mm diameter by 7mm tall) OC81 comes to mind. I had some here till recently... IIRC, OC82 was an output transistor in an ally can. OC71 was the common general purpose type. -- *Never underestimate the power of stupid people in large groups Dave Plowman London SW To e-mail, change noise into sound. |
On Tue, 7 Sep 2004 19:02:44 UTC, "Dave Plowman (News)"
wrote: OC81 comes to mind. I had some here till recently... IIRC, OC82 was an output transistor in an ally can. OC71 was the common general purpose type. Thinking about it, I'm sure you're right. I remember filing round the base of the glass, removing it, getting the jelly off, scraping the glass clean....lo, a phototransistor (terrible characteristic, but...) -- Bob Eager begin a new life...dump Windows! |
xenelk wrote:
Which was my point. I was just trying to explain it in simple terms.... But you got it wrong. The need to use decent (i.e. well-screened) coax cable for DTT is much more to do with keeping impulsive interference at bay, than with the loss of the cable. At UHF most of the loss of a coax cable is 'copper loss' in the resistance of the conductors rather than dielectric loss. Thus it's mainly determined by the size of the conductors - almost always 1mm inner and about 4.6 - 4.8mm outer for the sort of cables we're talking about. There's not that much difference in loss between CT100 / WF100 type cables and single-braided coax over the length of a typical domestic downlead (at least not until you get to the really cheap & nasty cables with 30% braid coverage) - but there is a huge difference in the screening effectiveness and that's what matters. -- Andy |
Dave Plowman (News) wrote:
IIRC, OC82 was an output transistor in an ally can. OC71 was the common general purpose type. And the audio line-up in a good transistor radio of that era was an OC71 feeding an OC81D driver feeding a pair of OC81s in push-pull (transformer coupled in and out). For the RF side you had an OC44 self-oscillating mixer and two unilateralised OC45 IF stages. Nostalgia... -- Andy |
Dave Liquorice wrote:
OC71 etc, though that was an audio type tranny. Nicely light sensitive That was the beastie.... When I was at the "building my first radio stage" (late 60's early 70's) getting almost any electronic part was hard. RS, Farnell, etc where way above the pocket money level. Tandy didn't do most of the things required for UK designs and what they did do wasn't that cheap. Maplin didn't exist... I guess I was lucky... first got into electronics in about 1980, and lived 10 minutes walk from the one and only Maplin shop at the time. ;-) -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
Dave Plowman (News) wrote:
Ahh. Red spots. ;-) hmmm - had forgotten that til you mentioned it.... feeling old now ;-) -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
In article ,
Andy Wade wrote: IIRC, OC82 was an output transistor in an ally can. OC71 was the common general purpose type. And the audio line-up in a good transistor radio of that era was an OC71 feeding an OC81D driver feeding a pair of OC81s in push-pull (transformer coupled in and out). For the RF side you had an OC44 self-oscillating mixer and two unilateralised OC45 IF stages. Yup. Life was simple in those days. ;-) Not always transformer output, though - high impedance speakers were fairly common. I've got a working 'Good Companion' I bought as a kit with my first pay from the BBC. Micro alloy transistors and transfilters... -- *Why is "abbreviated" such a long word? Dave Plowman London SW To e-mail, change noise into sound. |
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