Channel 5 signal quality

C

chicky

Member
My Satellite Setup
Dell PC + Twinhan sat-CI PCI card + Hauppauge WinTV Nova-t PCI card
My Location
England
Hi all.

Since installing a new WinTV Nova-t PCI card a few weeks ago I have noticed that the Channel 5 signal detiorates significantly during the day and starts to freeze then disappears altogether later in the evening. In fact I had to scan the channels a few times just to get it registered.

Admittedly I am using an old analogue ariel but is this problem I'm getting with Ch5 a common symptom outside of London? I'm in the Brentwood area about 40km from the Crystal palace transmitter. Also I understand from various other threads that loads of other people have trouble with ch 5. Is this because it is transmitted at a lower signal strength than say BBC1? Is this likely to be resolved when the Analogue signals are turned off in a few years?

Last question...is a nice new digital ariel likely to sort out this issue?

thanks
C
 
is your aerial connection to the PC the only TV connection you have your house? or do you have other TV points in the house? if you do are then feed from a AMP or a non powered splitter? what i would say i am sure other people may differ on this if you have got more than 1 TV point i would turn off all the other Tv connected to the TV points and then try CH5 on your PC and see how its if its still bad i would suggest replacing your feeder cable and also replace your aerial with a new 1 as newer aerials have a much better pick up than the old analogue puppys and with Ch5 you need all the help you can get to get a discnet signal unless your not far from the transmitter!!.

if you problem is cured when you try running the PC on its own i would suggest buying a powered amp and connecting all you TV points to that as this will stop the drag on your aerial and inprove your signals about the house.

hope this help you oout:)
Cheers Chris
 
Thanks Chris. Actually that makes a lot of sense. As you guessed the ariel connection to the PC is shared with another telly and also goes via a common amp/splitter.

Incidentally I was having problems last night getting digital stations on a new digital DVD recorder in a different room fed via a separate ariel source and amp/splitter - and I did what you were suggesting and that fixed it.

So I'll try feeding the PC direct from the ariel and take the amp/splitter out of the equation and see if that has an affect. I'll let you know how I get on.

thanks again.
C
 
No Worrys Chicky i would say a power AMP is the way forward and that will stop all your signal losses etc and will def inprove you TV reception in every room

take it eazy now
Cheers
Chris
:D
 
Chris and all.....just to keep you up to date.

I tried various reconfigs last night regarding the amp/splitter and the various inputs/outputs to telly and PC - even losing the amp/splitter altogther - and the long and the short of it is I still need the amp/splitter in place. Without it I get no picture at all on the digital PC card. Next I think I'll try sourcing the signal from our other 'better' ariel (again with and without the other amp) and see if that makes a diff. Will keep you informed...C.
 
Depending on the aerial, you may be getting the Ch5 "multiplex" at a lower level than the other Muxes, hence at a higher error rate, in which case there's no remedy except to upgrade the aerial!

Check this by looking at signal quality (NOT strength!) on a known good channel, eg BBC1, then compare with that on Ch5, there's probably a significant difference.

In general, not always, you should:

1) Not use a splitter at all, if avoidable.

2) If using a splitter, use a passive low loss one, and do not use an amplifier, because this increases the bit error rate.

(Having said that, people do all sorts of things, whatever works! ....).

For more info, see my Freeview guide:
www.satellites.co.uk/php-bin/forum/showthread.php?t=43646 .

If the aerial isn't good enough, then an amplifier will probably make things worse, as it will increase the bit error rate.
 
Cheers Spiney....yes I think it's the dodgy ariel that needs replacing. I was hoping there was going to be a magic button to press that could have fixed it but now it looks like I may have to spnd some cash to get it fixed.

As I said in my previous post I'm going to try and use our good ariel first but if that fails I'll get a new ariel. thanks.
 
Whether you can get a particular DTT mux (multiplex) depends entirely on bit error rate (ber). This in turn depends on:

1) Aerial
2) cable losses
3) splitters/amplifiers
4) receiver sensitivity (some are better than others, which matters a lot for digital tv, which is "all or nothing").

sometimes, the newer muxes are transmitted "out of band" (of previous analogue aerials), so get received at a lower level. Although this doesn't apply to Crystal Palace, at that distance you probably need a better aerial!

Amplifiers ALWAYS increase the received ber. Sometimes an indoor "signal booster" can compensate for a poor aerial, but only in high signal strength areas, where some of the signal can be "thrown away".

Have a look at the DTG guide, particularly at the "digital cliff" bit:
www.dtg.org.uk/publications/books/r_book2.pdf .

(looking again at that DTG guide, I can see that the Crystal Palace Ch5 mux is at the extreme edge of the group A aerial passband, so yes, Ch5 would probably be received at a slightly lower level on older aerials. Which might explain why it only works with the amp in place. To find out what's happening, check the effect various things have on signal "quality", or look directly at the ber figure).
 
Thank you Spiney for taking the time to explain this to me. I think I mostly understand the issues now.

Just for your information my current setup is as follows...

Roof mounted ariel - there when we moved in 6 years ago but it looks like it's been there for a loonge than that.

Perhaps a 20 foot ariel cable run from roof to downstairs ceiling (actually comes down into garage where the amp is sited).

Amplifier/3 way splitter feeding old portable telly (another 15 foot away from amp) and PC (10 foot away from amp).

The portable telly does get a snowy picture without the amp, but a very clear picture with it on channels 1 - 4. channel 5 is still grainy.

The PC (with a Hauppauge WintTV Nova-t) gets no picture without the amp but a clear picture with it - except ch5 again which is rarely available, and even when it is available it freezes.

As per your advice I shall check all the components again (that I can get to) and make sure they are ok as best I can. I'm not exactly sure how to check the signal strength and quality on the PC precisely but I'll have a dig around.

If I don't get any joy I'm going to try and link up to another rooftop ariel we have, but if that doesn't improve things I'll get a professional in.

Thanks again.
C
 
Can you take a picture of the amp in the garage?

Do you get a much better picture on the other aerial?

Where does the cable for the other aerial run and does it feed more than one point?

PS. Whereabouts are you and which transmitter do you receive your signal from?
 
Rolfw...I'll try and get a picture and get it posted up.

I would say there is a slightly better analogue picture from the other Ariel, although Channel5 is a bit grainy again, but it does pick up all the digital channels no problem on a set-top box and DVD recorder. So I guess the signal is better. Also this "good" ariel does point in a slightly different direction to the "bad" one. Say 5-10 degrees clockwise as compared to the "bad" one.

The cable for the "good" ariel actually takes a longer path path to the "bad one" one. i.e. From roof to ground level level (20+ foot?) then into another identical 3 way amp/splitter feeding a nearby digital dvd recorder and a separate digital TV 10 foot away. Pictures on both sets are clear on all channels.

We are in Brentood, east of London by 20+ miles, and I think our nearest transmitter is Crystal Palace, 27 miles away according to Wolfbane.
 
Sounds like the answer is to forget your old antenna, intercept the cable from the good antenna and insert a masthead amplifier and two/three way splitter, or a four way masthead amp, it can be powered from any of the rooms by means of a 12v power supply.

Channel five from CP is broadcast at the same power as the other channels, but is actually not on the main mast, but a little lower on the old Croydon mast about a mile away, so will be slightly lower signal because of this. It may also be that your antenna is grouped to cut off at channel 33 (analogue BBC2) so anything above this will suffer.
 
Interesting, Rolf, I didn't realise London Ch3 mux wasn't from main site!

Maybe we'd better explain to Chicky, a masthead map is still an amp, but with a low noise figure, maybe 1.5 dB, so increases ber much less than a typical indoor "signal booster" with 6 dB noise figure, but a masthead amp should go as close as possible to aerial.
 
Thanks again rolfw/Spiney....I'd never even heard of one of these masthead amps before, and I wasn't aware that the CP signals were from different masts.

I shall try and implement what you recommend and will be sure to let you all know how it goes.

C
 
Good selection of masthead amps at _http://www.jwhardy.co.uk/
Even if you don't buy one from there, good for a browse!
 
spiney said:
Interesting, Rolf, I didn't realise London Ch3 mux wasn't from main site!
Click to expand...

No, I was referring to Channel 5 analogue spiney.:)
 
Sorry, Rolf, that was a typo, I did mean ch5!
 
Thanks...I'll take a look. I feel like I'm (almost) an expert on amplifiers myself now after all the research I've done into it over the last few days. I didn't realise it was so complicated.
 
I have attached a picture of the amp/splitter. Sorry the pictures not too good but there's no natural light in the garage.

Anyway, the make is Maxview (think it came from B&Q about 6 years ago), and the only config changes you can make to it are via the "wheel" on the right. You have to turn it between "strong signal areas" and "weak signal areas". To get any picture on the PC I have to turn it as far as it will go clockwise towards the "strong signal areas" end. Actually I find this a bit confusing as I assumed we were in a weak signal area. Anyway, clockwise it is!

I'll post an update on what happens if/when I switch ariels when I get chance to try it.

Hope that's useful.
 
I've replaced an awful lot of those amps, they are probably one of the worst around for noise, so if you are starting off with a substandard signal, they will only make it worse. Best to concentrate on the good aerial. :)
 
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