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HDR FOX T2 - does the tuner fall over at low temperatures?

prpr said:
I was right then :)
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So it seems! Apologies for not taking your advice earlier. All I can say in my defence is that I tried to make an assessment of which suggestions appeared the most likely to bear fruit - without knowing anything about the credentials of those making the suggestions. My judgement at the time - which turned out to be flawed but I which nevertheless believe to be defensible - was that a problem with the DA would affect the Humax and TV equally.

WT
 
grahamlthompson said:
Think you looking at it the wrong way. An amplifier adds noise as well as increasing the signal level. A splitter adds no noise just reduces the signal strength. Right way is use a splitter first then add a low noise amp to the input if you need it. Chances are your base signal is well above the 3.5dB loss that a 2 way splitter will introduce.
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I don't agree. Let:

Vs = signal voltage at the aerial
Vn = in-band noise voltage at the aerial
Vc = in-band noise voltage contribution of the cable
Va = in-band noise voltage contribution of the amplifier (at fixed gain)
Ga = gain of the amplifier (as a ratio)
Ac = attenuation of the cable (as a ratio, 1/attenuation = gain)

Signal + noise at the end of the end of the cable with the amplifier at the top:

Ga(Vs+Vn)/Ac + Va/Ac + Vc

So S/N = ( Ga.Vs/Ac ) / ( Ga.Vn/Ac + Va/Ac + Vc )

Signal + noise at the end of the cable (after the amplifier) with the amplifier at the bottom:

Ga(Vs+Vn)/Ac + Va + Ga.Vc

So S/N = ( Ga.Vs/Ac ) / ( Ga.Vn/Ac + Va + Ga.Vc )

Conclusion: given an amplifier I can either fit ahead of distribution or after it, I know which I would prefer.
 
Black Hole said:
I don't agree. Let:

Vs = signal voltage at the aerial
Vn = in-band noise voltage at the aerial
Vc = in-band noise voltage contribution of the cable
Va = in-band noise voltage contribution of the amplifier (at fixed gain)
Ga = gain of the amplifier (as a ratio)
Ac = attenuation of the cable (as a ratio, 1/attenuation = gain)

Signal + noise at the end of the end of the cable with the amplifier at the top:

Ga(Vs+Vn)/Ac + Va/Ac + Vc

So S/N = ( Ga.Vs/Ac ) / ( Ga.Vn/Ac + Va/Ac + Vc )

Signal + noise at the end of the cable (after the amplifier) with the amplifier at the bottom:

Ga(Vs+Vn)/Ac + Va + Ga.Vc

So S/N = ( Ga.Vs/Ac ) / ( Ga.Vn/Ac + Va + Ga.Vc )

Conclusion: given an amplifier I can either fit ahead of distribution or after it, I know which I would prefer.
Click to expand...

Did you look at the link ? (Justin knows a hell of a lot about antenna). He tests all hie aerials and produces gain curves for all of them.

If your aerial worked fine (to one point) on the lower power transmissions before switchover, the higher power transmissions after DSO should enable you to split the signal 4 or even 6 times and still end up with the same signal level at each TVs` input that you had before to the one TV. This is because the power was increased at switchover by about 10dB.

Thus, the moral of the story is, if you`re unsure whether to fit a (passive) splitter or an amplifier/"booster" [i.e. an amplified splitter] I`d go with a splitter because you always have the option to add an amp in front of it if required.
On the other hand, you can`t remove the amplifier part of the amplified splitter ! ? !
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grahamlthompson said:
Think you looking at it the wrong way. An amplifier adds noise as well as increasing the signal level. A splitter adds no noise just reduces the signal strength. Right way is use a splitter first then add a low noise amp to the input if you need it. Chances are your base signal is well above the 3.5dB loss that a 2 way splitter will introduce.

Best source of info for all terrestrial info is here. Link to splitters and amplifiers.

http://www.aerialsandtv.com/ampsandsplitters.html#Splitters

Check out the aerial choice info as well.
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But the link says (as you quote in a later post): "If your aerial worked fine (to one point) on the lower power transmissions before switchover, the higher power transmissions after DSO should enable you to split the signal 4 or even 6 times and still end up with the same signal level at each TVs` input that you had before to the one TV. This is because the power was increased at switchover by about 10dB."

The operative word there is "IF". I had an extremely flakey digital reception prior to DSO - having to revert to analog on occasions when it didn't work at all. I am, after all, pretty close to falling off the edge of Sutton Coldfield's coverage area!

WT
 
Watt Tyler said:
But the link says (as you quote in a later post): "If your aerial worked fine (to one point) on the lower power transmissions before switchover, the higher power transmissions after DSO should enable you to split the signal 4 or even 6 times and still end up with the same signal level at each TVs` input that you had before to the one TV. This is because the power was increased at switchover by about 10dB."

The operative word there is "IF". I had an extremely flakey digital reception prior to DSO - having to revert to analog on occasions when it didn't work at all. I am, after all, pretty close to falling off the edge of Sutton Coldfield's coverage area!

WT
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Power went up by 10dB at DSO. That's a lot. A 2 way splitter gives you about 3.5dB in loss but adds no noise. Presumably to bypass the amp you used such a device any way. So the amp and the pvr are both working fine with this loss. From the sound of it your amp is a distribution amp, these have much higher noise figure than the low noise type used in mast head designs. Have you tried removing the amplifier completely ?

If you then need amplification it should be a variable output masthead type located as close to the aerial as possible to avoid amplifying noise picked up on the coax downlead.

For example this one gives you 4 outputs, combined with quality splitters would easily support 8 devices.

http://www2.dastechnology.co.uk/shop/masthead-cw-psu/Vision-V201420-Variable-Gain-Masthead-Amp-PSU
 
MartinOnline said: ↑
One final point, as was pointed out to me once, the use of Capital Letters is the net way of Shouting - only to be used in extreme conditions.
Martin​
If you're referring to my line of caps proclaiming that the problem was fixed, I considered that that was justified because that bit could easily have been missed by someone speed-reading the overall message.

WT
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Again I feel that you are not accepting advice which is humbly offered . You have used capitals throughout your posts in this thread. They were used to emphasise your statements, but, as I tried point out sympathetically, the use of capitals in text will be read as shouting. Using italics offers emphasis without the shouting connotation.

Martin
 
MartinOnline said:
Again I feel that you are not accepting advice which is humbly offered . You have used capitals throughout your posts in this thread. They were used to emphasise your statements, but, as I tried point out sympathetically, the use of capitals in text will be read as shouting. Using italics offers emphasis without the shouting connotation.

Martin
Click to expand...

Fair enough. I spend a lot of time in text-based usenet groups where individual words are usually emphasised by enclosing them in asterisks. I haven't seen that done here, and the use of capitals to emphasise the odd word seemed like a possible way to go. [I think I have only once "shouted" a whole sentence.] If you prefer italics, I'll use them instead in future. Presumably acronyms are ok - or is "HDMI" shouting?

WT
 
I use a variety of emphases according to the situation, including the *asterisk* approach. On an iPad the edit tools are not available so I have to enter the BB tags directly, any combination of:

[i]italic[/i]
[u]underline[/u]
[b]embolden[/b]
[s]strikeout[/s]

eg Bold Italic Underlined

For more info click Help (near the top of each forum page).. BB Codes
 
Black Hole said:
I was stating the physics. Show me where I've got the analysis wrong.
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Basically ignoring the fact that at the antenna there is little noise so little noise to amplify and you have the highest signal to start with, so your source signal to noise is improved. A properly designed aerial will reject most unwanted signals, log periodics are especially good at this. Lower gain than a yagi but much cleaner.

At the far end of the cable which picks up most of the unwanted signals (mostly impulse), you increase the signal by say 10dB you also increase noise levels by 10dB. Passive splitting has little effect on signal to noise because signal and noise are both attenuated by a similar approx. 3.5dB. That's how communal installs are planned, you start with the cleanest signal at the source amplify it to cater for the losses in passive splitters and taps. Why do you think masthead amplifiers are used in fringe areas, simple they can be fitted at the aerial.
 
Show me the physics.

The equations I quoted assume nothing, and clearly show that regardless of the actual contributions of noise from the various elements, all things being equal a better end point signal-to-noise ratio is achieved by applying gain at the beginning rather than the end. If you fit a low-noise amplifier at the end, it would have been better (though possibly impractical) to fit an equally low noise amplifier at the beginning. That's why there are mast-head amplifiers: do you really think it's easier to fit and power one of those than a signal booster at the point of use?

Unless you can show the physics, anything else is a matter of opinion, but largely irrelevant now analogue has gone.
 
You both seem to be arguing from the same side...

Anyway, for anyone who thinks cable or attenuators are noise free, then think again. Everything has a noise temperature.
Go and read and understand some of the stuff here:
http://en.wikipedia.org/wiki/Noise_figure
http://en.wikipedia.org/wiki/Noise_temperature

And yes, amplifiers are better at the top end than the bottom of the distribution chain (overload and headroom issues notwithstanding) because of the loss/noise of the cable. You can't put back with an amplifier what has been lost en route.
 
Watt Tyler said:
My judgement at the time - which turned out to be flawed but I which nevertheless believe to be defensible - was that a problem with the DA would affect the Humax and TV equally.
Click to expand...
I'm afraid RF stuff is never that simple. Just because one device can cope with something doesn't mean another can. You have no idea what the differences are between the Humax and the TV in terms of signal handling capabilities. Nor do I. Just because one works doesn't mean the other will. This is especially true if something upstream has been overloaded, as it seems to have been in your case. Sometimes the outputs from the DA can be different to each other.
 
prpr said:
I'm afraid RF stuff is never that simple. Just because one device can cope with something doesn't mean another can. You have no idea what the differences are between the Humax and the TV in terms of signal handling capabilities. Nor do I. Just because one works doesn't mean the other will. This is especially true if something upstream has been overloaded, as it seems to have been in your case. Sometimes the outputs from the DA can be different to each other.
Click to expand...

What evidence do you have that something upstream seems to have been overloaded? I'm in a pretty poor signal area - on the outer fringes of Sutton Coldfield's coverage area, and the DA provided a gain of only 6dB. The amp with which I have replaced it has a gain of 12dB, and the signal strength reported by the Humax is still only 72% - and there are now no quality issues. So I can see no case whatsoever for suggesting that my problems were due to overloading.

WT
 
Watt Tyler said:
What evidence do you have that something upstream seems to have been overloaded? I'm in a pretty poor signal area - on the outer fringes of Sutton Coldfield's coverage area, and the DA provided a gain of only 6dB. The amp with which I have replaced it has a gain of 12dB, and the signal strength reported by the Humax is still only 72% - and there are now no quality issues. So I can see no case whatsoever for suggesting that my problems were due to overloading.

WT
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If you are referring to my original suggestion.

Never said I had any evidence, my post was purely speculation. At that time the only information you provided was that the indicated signal was not very high. A result entirely consistant as a result of over amplification. You did not provide any background information nor the requested key information using the DTG detailed view reception checker.

http://www.digitaluk.co.uk/coveragechecker/

Had you done so the anticipated signal strengths and recommended aerial types for transmitters you could use would have helped considerably.

Does it say amplified high gain is required ?

Getting confused now, didn't you say the Humax works fine without any amplification ? If so still every chance you don't need an amplifier at all just to feed two TV's.
 
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