I might just try that, thanks.
I have another aerial in the loft feeding a 4 way splitter for each bedroom. The signals on the TVs in those rooms are all 100%, but none are HD, so I guess that's not a good comparator.
My Humax Forum » Freeview HD » FVP 4000T, 5000T
What's the latest software version?
(15 posts)-
| Fri 8 Jan 2016 23:00:12 #11 |
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I doubt SD v HD makes any difference.
The thing about digital TV is that a small amount of interference injected into the signal can cause major problems. For example, assume a value is is, in binary, 10000000000, which is 1,024.
Now let interference change just 1 bit.
If the last bit gets changed the value changes to 10000000001, or 1025, and it probably makes no real difference. But if the first bit gets changed, the value is 00000000000, or 0, and it makes a big difference.
Freeview digital signals have an enormous quantity of error correction built into them and, as long as the interference is coped with by the error correction, there is no effect. But let it get overwhelmed by even a tiny bit and the whole picture can collapse. There is no "graceful degradation" with digital signals - they are either above the limit and therefore excellent; or below the limit and awful. It's called "falling off the digital cliff" - one step too far and it's a really bad-hair day. See Cliff effect.
You haven't answered whether you are using fully shielded "satellite" coax (with a thin sheet of aluminium or copper completely surrounding the inner conductor) or rubbish old analogue TV coax (with a few thin strands of wire as a "shield", but which are doing virtually nothing to keep out interference).
I think that passive splitters attenuate the signal by half (in order to keep the characteristic impedance the correct value). A 4-way passive splitter presumably attenuates it to one quarter. I will be pleased to be corrected if I am wrong!
The best test is to connect the aerial direct into the tuner (take it up into the loft) and measure the signal strength and signal quality.
| Fri 8 Jan 2016 23:57:29 #12 | -
Thanks again
The cable is arguably the best you can get (supplied by my son who is a project engineer in the tv/radio industry. They design and fit out studios, OB trucks, etc., for major players such as BBC, Sky. And as he says, they don't muck about with cheap kit).
The cable comes straight out the aerial amp (in loft) into the Humax. So no dodgy interconnections.
Nothing to do with the 4 way splitter, which is on a totally separate system.
I'm going to try by passing the Netgear aerial amp, but to do that, I need to get hold of an F plug to F plug connector. Because the connections into and out of the amp are with crimped on F plugs. And I don't have a crimper to redo if cut off.
Incidentally, the non HD channels show on the Humax as circa 96% signal strength. And to the best of my knowledge never drop out. But I tend to watch mainly HD channels.| Mon 11 Jan 2016 20:02:41 #13 | -
JohnH77 - 2 days ago »
I think that passive splitters attenuate the signal by half (in order to keep the characteristic impedance the correct value). A 4-way passive splitter presumably attenuates it to one quarter. I will be pleased to be corrected if I am wrong!
See
| Mon 11 Jan 2016 20:10:35 #14 | -
Graham
Thanks! I see it's even worse than I thought - not the 3dB theoretical (ie halving the signal voltage) I assumed for a splitter, but 4dB in practice.
Loss through splitters at UHF :
2 way = 4dB 4 way = 8dB 6 way = 10dB 8 way = 12dB
It's a great site for information.
| Mon 11 Jan 2016 20:19:38 #15 |
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