Freeview and the ghost Channels -

[DerZwen]

Heya,

I just moved to Swindon and had to change from dvb-c to freeview. According to my landlady the former tenant first used freeview and later sky. The Sky box is still in the room but since I use my HTPC with a fairly standard monitor (19" with d-sub and DVI-In) to watch tv I can't use it. After spending the afternoon finding the best program to watch tv on the pc (for me mediaportal with tv-server) I had some issues with the aerial reception itself. TV-Server shows me a possible of over 50 programs. But I can only receive bbc 1-3 and ITV1 in a remotely watchable state. All the other are either not showing up at all or provide 1 picture every 2 minutes. I tried two different USB DVB-T Sticks and both had the same issues. The signal is provided by rooftop aerial and there is even a signal booster (and signal router) in the room - even though I have the strange feeling that the signal get's weaker with this thing on. Is there anyway I can improve the reception quality? I'm out of Ideas.
Postcode is SN3.
Help please

Sven

[Kymmy]

Signal boosters in the room can just make the matters worse as unlike mathead boosters they not only improve the signal but also the noise that the co-ax has picked up.. Also you will find an extreme difference in signal sensitivity between different freeview boxes..

Is the antenna itself digital capable? (just because it was used before doesn;t mean to say it is designed for digital) if it's an old analogue antenna then thier gain is normally lower and thier bandwidth capability is also inadequate.

[DerZwen]

Thanks for your reply,

that there are huge differences between the boxen became clear after the hauppauge hvr900 just found 12 Channels (and could only display 2) while this no name dual dvb-t gets the whole bouquet (but only shows 4). EPG data is transmitted for most of the channels.

Whether the antenna is digital capable: I have no idea. But I'll ask my landlady.

So the mathead booster might do the trick, even if the antenna is analouge?

thanks a bunch

Edit PS: That's the booster that's currently "working" http://images.maplin.co.uk/full/RT68Y.jpg

[Kymmy]

Edit PS: That's the booster that's currently "working" http://images.maplin.co.uk/full/RT68Y.jpg

As I said, if the booster is up near the antenna it's only boosting the recieved signal, but a booster down near the TV is boosting all the rubbish that the co-ax itself has acted as an antenna and picked up

BUT - A booster can only boost a signal that's there and strong enough to be boosted.

If the antenna is digitala nd has a high enough gain to pick up the signals in an area then you don;t need a booster.. There is a website out there that you can enter your postcode and it'll tell you which transmitter is closest, which channels you should be able to get and what sort of antenna you'd need. I'm sure someone will come along (Unless you want to search the older posts) and tell you which it is..

[DerZwen]

I think you mean wolfbane? I checked that out yesterday as I browsed through the forum. It suggested and amplified extra hi-gain. Well I'll talk to my landlandy and wait what she might suggest. I actually don't want to spend much money out of my own pocket :)

Thanks so far

[Chris]

Kymmy ... I don't wish to burst your bubble here but there's no such thing as a 'digital' antenna as such. All that is required is a UHF antenna of the correct group, with the correct gain, aligned to the correct polarity, to match whatever is being squirted out by the local transmitter. What works as a good antenna for receiving Freeview in Swindon, therefore, may not work in Preston. This is exactly the same situation as existed when we were in purely analogue days.

Sven, you need to start checking your whole set-up from the top down. It might be worth asking yourself at this point, why did the previous tenant switch from Freeview to Sky? Possibly because Freeview didn't work for him either? I wouldn't expect the landlady to necessarily know this (or admit it, if she does).

First you need to establish exactly what you need in order to get a good Freeview service in your area. To do this, visit the signal predictor at this website:

http://www.wolfbane.com/cgi-bin/tvd.exe?

Input your postcode and it will tell you which transmitter you can point at, which group areal you need, what gain it must have and the polarity to use.

Once you have that information, compare it with the aerial on the roof. First you have to ensure the thing is the correct group - that would be my first suspicion. You need to identify the colour of the plastic bung in the aerial's nose. The groups and colours are:

Channels - Group - Colour
21-37 - A - red
35-53 - B - yellow
48-68 - C/D - green
35-68 - E - brown
21-48 - K - grey
21-68 - W - black

If your aerial's group does not match the group being transmitted, then there's the problem. The solution is, ideally, to choose an aerial matched to the group your transmitter uses for Freeview. However, this may render it impossible to get analogue services, if those are on a different group. In that case, a wideband aeriel (group W, black) is required. This is where the misconceptions about 'digital' aerials comes from; a wideband aerial will receive all groups but the trade-off is that it has poorer gain compared to an equivalent-sized single-group aerial. So wideband antennas need to be larger to compensate. Most people who have had to swap their antenna in order to receive Freeview have swapped to a Wideband one, hence the tendency to refer to them as 'digital' aerials, even though they aren't. ;)

Of course, it may not be the antenna at fault at all ... can you check the run of coax from the aerial, down the wall (or through the loft)? Look for broken sheathing, or places where two lengths may have been (badly) joined with connectors.

As Kymmy has already said, your booster is also a potential issue. A booster next to the TV will be boosting all the interference picked up by your coaxial cable run, which, if the cable is old and of poor quality, could be considerable. To boost only the TV signals themselves, you need a masthead amplifier that sits right up there with the aerial. Failing that, an amp situated as close to it as possible - in the loft, if the cable comes down that way.

Anyway, go and check on those things, especially your aerial group and gain, and post back what you find.

[Kymmy]

Kymmy ... I don't wish to burst your bubble here but there's no such thing as a 'digital' antenna as such.

No fear there Chris ;)

I use Digital antenna as it has become very much to mean an antenna with a higher gain and frequency bandwidth (your color code of black) than the older antenna's used purely for analogue. The digital signal is spread along using more spot frequencies than the old 5 channels so the 'digital' antenna's tend to be more capable of recieving all the signal at the same gain.

I suppose it should really be 'digital compatible antenna' but yes there is very little difference but even a small difference in the design of a yagi can effect the gain, tuned frequency, bandspread and front to back ratio.

;)

[edit] Something the OP has to remember is that digital signals are more susceptable to breaking up on lower signal strengths than analogue due to the nature of the signal

[nodrogd]

Freeview reception in Swindon!! I hope you've got line of sight to Oxford. 30+ miles downrange so a hi-gain wideband aerial and amplifier a necessity.

[nodrogd]

No fear there Chris ;)

I use Digital antenna as it has become very much to mean an antenna with a higher gain and frequency bandwidth (your color code of black) than the older antenna's used purely for analogue. The digital signal is spread along using more spot frequencies than the old 5 channels so the 'digital' antenna's tend to be more capable of recieving all the signal at the same gain.

I suppose it should really be 'digital compatible antenna' but yes there is very little difference but even a small difference in the design of a yagi can effect the gain, tuned frequency, bandspread and front to back ratio.

;)

[edit] Something the OP has to remember is that digital signals are more susceptable to breaking up on lower signal strengths than analogue due to the nature of the signal

Unfortunately, the word "digital" is often used to justify a higher price. I'm stunned when I look around the rooftops nowadays. Some of the aluminum creations around wouldn't look out of place at a modern art exhibition. The basics are simple. Almost all TV aerials are based on the yagi principle(directors-dipole-reflector). You can only add a certain amount of directors (elements) as they become less efficient as you move away from the dipole. By the laws of physics, these elaborate designs work only slightly better than their bog standard yagi counterparts with straight rods. More money, weight, wind resistance, who needs it.

[Kymmy]

What's next I wonder, octal phased networks ??