Freeview muxes 55 & 56 - the future?

prpr

Well-Known Member
Their long (medium?) term plan is to get us all onto fttp, which we'll pay for, using subscription services, which we'll pay for (and still get adverts), and off the airwaves so they can be used for more mobile services, which we'll pay for.
And people moan like b*ggery about paying £150 or so for the licence fee. They really won't know what's hit them in 5 or so years' time, but at least they'll have (no) choice over paying a lot more to some other fat companies...
 

Black Hole

May contain traces of nut
In the absence of a gospel I'll clutch a straw, because if there is a plan for 55/56 they are keeping it close and it's flipping annoying.
"This bypass has to be built and it's going to be built"
"Why?"
"It's a bypass. You have to build bypasses. You can't stand in the way of progress."
"I'm game, we'll see who rusts first"
"Do you know just how much damage it will cause if I let this big yellow bulldozer roll over you?"
"How much?"
"None at all."
 
OP
MikeSh

MikeSh

Well-Known Member
"This bypass has to be built and it's going to be built"
"Why?"
"It's a bypass. You have to build bypasses. You can't stand in the way of progress."
"I'm game, we'll see who rusts first"
"Do you know just how much damage it will cause if I let this big yellow bulldozer roll over you?"
"How much?"
"None at all."
Errr ... WTF :dunno:

(But I'll have whatever you're on - it sounds fun :) )
 

MymsMan

Ad detector
The Freeview channel plans are filed along with the bypass plans
“But the plans were on display…”
“On display? I eventually had to go down to the cellar to find them.”
“That’s the display department.”
“With a flashlight.”
“Ah, well, the lights had probably gone.”
“So had the stairs.”
“But look, you found the notice, didn’t you?”
“Yes,” said Arthur, “yes I did. It was on display in the bottom of a locked filing cabinet stuck in a disused lavatory with a sign on the door saying ‘Beware of the Leopard.”

― Douglas Adams, The Hitchhiker's Guide to the Galaxy
 
OP
MikeSh

MikeSh

Well-Known Member
Going back to the origin of the thread, I think I have solved it.
Looking at that web site I'd consider replacing your amp (the one in the red box). It is clearly unscreened in those pictures, which probably means it was designed for analogue TV. So as well as issues with interference getting in due to lack of screening, it may have a higher noise figure than is ideal or other issues that didn't matter for analogue but do for digital. You can also get a single output amp and not connect up the output that you acknowledge you don't know where it goes.
I was going to do the above and had bought a new single output amp which had a marginally higher spec gain than the current one. Before I got round to swapping them COVID-19 arrived and SWMBO decided that as she might be holed up in her room for months she needed TV in there ... so the second output on the amp was back in play (I've run a new cable to where it is needed).

While wondering what to do now about the amp change I hit upon the brilliant, but entirely obvious solution - put them in series.
I did contemplate various issues that might arise with this (short-circuited PSUs, earth loops, ... ) but decided there was only one way to find out. I also realised that I didn't need any more amp on the group A, only the E, so that's what I've done - A aerial direct to diplexer, E aerial to new amp and then diplexer, diplexer to 'main' amp and then off to the users. Doing this also means the diplexer is between the two amps, providing a bit more electrical separation (possibly).

Seems to work so far, but obviously I'll be watching it. At the FOX level I'm now getting the ch 55 & 56 signals (E) at around 70% which is the same as most of the ch 20-30 muxes on the A aerial.
 

Owen Smith

Active Member
70% seems to be a good signal level for the HDR Fox T2, more than enough for it to be happy but not so much you're saturating the input stages. If muxes go below 60% I try to do something about it.

One problem with the daisy chained amps is each one adds noise. 4db is a typical figure. The noise from the first amp is then amplified by the second which can cause issues. But at least by putting the new amp before the diplexer it may be able to filter out of band noise out to some extent.

You say the new amp is better gain spec. Gain is not everything, you want to look at the noise figure as well (the lower the better) and how well screened it is.
 

Black Hole

May contain traces of nut
Daisy-chaining amps doesn't sound the right way to go to me, but whatever works!

I have a real hotch-potch here, inherited from analogue days and piecemeal extensions through the eaves/loft spaces when I replaced one-aerial-per-socket with a combined feed from two aerials (West [Mendip] and Wales [Mynnydd Machen]), plus a security camera feed in through a modulator (an old VCR), via the VCR in the sitting room - all TV points could view BBC1 (West and Wales), BBC2 (West and Wales), ITV (West and Wales), Channel 4, C5, S4C, the security camera, and the VCR output (which could be switched to its SCART input and thus send the output from an analogue PVR).

However, the roof spaces take the long way around, so there (was) also a multiplicity of booster/splitters (powered from the lighting circuit), and strategic attenuators where it proved necessary. (I had a similar arrangement running before I left my parental home, but conveniently there the house is a standard box rather than a rambling dormer bungalow, and there is a useful void running the height of the house where the soil pipe is boxed in.)

The security camera still works, but I have to switch the TV to analogue to view it (and they don't make it easy). The VCR and PVR are practically useless, but still sitting there "just in case". One of the boosters went down, so I took it out of circuit and lost the feed to the kitchen (bypassed it to the master bedroom).

Before Maplin went to the great hobby workshop in the sky, I picked up an 8-way distribution amp. My plan is to consolidate TV, phone, and Ethernet distribution into one wall cabinet on the landing (everything coming in gets routed to there as its first stop, then distribution fans out from there on single destination links). Maybe with this lockdown, if I can source materials...

My foray into sending audio down Cat5 was a great success, but I suspect it wouldn't be up to UHF (pity)!
 
OP
MikeSh

MikeSh

Well-Known Member
One problem with the daisy chained amps is each one adds noise.
Yes, I thought about that. But in the end, as long as I wasn't going to damage anything, I was happy to give it a try. As said, I'll be monitoring it to see if there are any problems with sound or picture.
 

Owen Smith

Active Member
As said in my OP mine struggle below 40. There are obviously some other factors at play.

Is it really any different to daisy chaining FOXs as was suggested?
The gain in the FOXs isn't that high, it's only enough to compensate for the insertion loss of going into the box and back out. I suspect the gain is in the 3 to 6 db range but that's a guess. This should allow the gain to be done with a lower noise figure, but whether it is I don't know.

Whereas separate amps are normally 12 or 13 db, and some are 23 db which as I understand it are internally two stages of 13 db but then you have to de-rate the result by 3db for reasons I don't understand.

Rule 1 with RF amps is use as few as possible to get a working system. Zero is the best value, work up from there as needed.
 
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