Grateful for any advice on my situation with a Digi Box, when i've just done a *factory-default* on a Humax HDR Fox T2, which I did because i was missing some TV channels.
I'm located in Finchley North London near a Relay Station, but my main transmitter is Crystal Palace.
When i did my factory default the BBC TV programs were rubbish (picture breaking up). I remembered some advice to use a 'splitter' to reduce the signal strength for some reason when doing the re-tune.
After re-tuning using the splitter the BBC stations as well as all the other stations seem to work OK. But I now get some HD stations in the channels numbered in the 800s' as well as the 100s. The HD channels in the 100s work ok, but all the HD channels in the 800s are still breaking up.
Grateful for any advice on what I might usefully do further. Thanks
Well Crystal Palace does seem to lose channels when I do a retune. I've found that doing a factory retune with no aerial, even though the box was reset first makes this better. I think though that your main issue is that you are getting two transmitters and the box is throwing them in as it finds them. If you are lucky they end up with the weaker ones up on the high channels but this does not always happen as I discovered here during a tropo lift last autumn. I guess an attenuator is not really what you want unless you know for sure that the signals from the relay are lower, which I'm guessing they are not even though they may be cross polarised. Does the box in question allow you to see the channels the multiplexes are on that you have in your main channels and if they are not the ones you want there, then you need some way to re order them. Trouble is after any retune things tend to get scrambled again. Brian
Unfortunately, not all set-top boxes give you the option of doing a manual tune (or maybe the facility is hidden somewhere in the menus).
If you have to do an automatic tune, rather than use a splitter, a 20db variable attenuator will give you better control of the signal level. I was in B&Q yesterday, and I saw they do one (£7?) - which, if you need one quickly, might be more convenient than getting one elsewhere online.
---------------------------------------------------------------------------------------- Ian thanks. Two questions: What function does the use of a splitter serve, I understand it weakens the incoming signal but what is the purpose of that please?
If I get a variable attenuator from b and q, what kind of adjustment would I want to be making with it? Thanks.
I mistakenly thought I saw someone advised inserting a splitter in the aerial feed (to lower the signal level) - but looking back, it must have been in another thread!
However, sometimes inserting a splitter in the aerial feed is suggested (as these are readily available). This will lower the TV signal level by
4 dB (6 for the cheap resistive ones) - and this might just may be sufficient to make the set-top box, when it's doing the automatic channel scan, ignore the unwanted, weaker signals and detect only the stronger wanted channels. Obviously, with a splitter (or any other fixed attenuator), you don't have much control over how much signal loss you put in (other than use more than one of them).
The variable attenuator (as suggested by Paul), enables you to control how far you reduce the signal. A variable 20dB attenuator will enable you to reduce the signal by a maximum of 20dB (1/10th of the original), so with a bit of trial and error, you should be able to persuade the set-top box to 'see' only the strongest channels, and ignore the rest. Once you've done the scan, you should remove the attenuator, and only use it again if you need to do another scan.
An obvious problem with the above is if the unwanted signals are stronger than the wanted ones. This might be the case if you want to receive the full complement of TV channels from the main transmitter, but a stronger local relay transmitter is offering a reduced number of channels (as many do).
As you see, it's all a bit of a fiddle. It's a lot easier if your set-top box or TV set does allow you to do a manual tune. To do this, you'll need to enter (in turn) the individual transmission channel numbers. For Crystal Palace (standard definition) they are 22, 23, 25,
26, 28 and 29, with 33 and 37 for high definition (see link):
The idea is to weaken the signals so that the weaker set (from the 'wrong' transmitter) are too weak to be stored. Meanwhile the stronger ones remain strong enough to be stored.
Trial and error until you achieve the above. Start at the max atten end.
The answer is simple - decide which transmitter you want to use and then go to this website to identify the channel numbers used by that transmitter. Write them down and keep the piece of paper safe for next time.
formatting link
Enter your postcode, house number and make sure you tick the box next to the detailed view option.
Now, reset all the channels and do an individual manual tune for each of the channel numbers identified.
If you can receive channels from more than one transmitter (my aerial can see four of the possible six) it is the only reliable way and given it is painless and easy to do, there is no reason not to.
Bought a variable attenuator on line for 3.15 inc postage. screwed it out for maximum resistance (less one complete turn out of five turns) and it eliminated all channels in the 800 range on the factory default/automatic retune.
Many thanks to all for helping me get good results.
For maximum reliability of the wanted signals try again with less attenuation, and again and again, until the unwanted signals reappear, then go back a step or two.
I usually leave it in as long as long as the wanted channels are plenty strong enough. People forget to use it when they do a retune, and it could help with 4G (etc) problems.
If you leave it in, and there's only a few dB between the wanted and the unwanted, if the wanted drop a little, they may become marginal, and you'll find that some channels drop out at times.
OK, so maybe leave it connected in circuit as a reminder, but turn it to minimum attenuation.
Maybe (when it's a case of severe overload). On the other hand, the relative levels of the TV and 4G signals won't change as you twiddle the attenuator. I suppose it depends on the mechanism of the interference.
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