Manual fine tuning of HD multiplex?

Tim.ivn

New Member
I receive my Freeview signals from Crystal Palace and my reception of the Standard Definition multiplexes is pretty much rock solid. However my reception of the HD multiplex (Channel 30) occasionally suffers from interference which interrupts the program I am watching. When I press MENU -> Settings -> System -> Signal Detection on the HDR Fox T2 when tuned into an HD channel, it shows the frequency as 546000KHz. However according to the ukfree.tv website, it should be 545800KHz. I have therefore attempted to enter 545800KHz into the Manual Search page on the HDR Fox T2 in the hope that doing so will give the HDR Fox T2 a stronger HD signal but when I press the "Search" button, it reverts to searching on 546000KHz. How can I force it to search on 545800KHz?

Does anyone know of an another way of combating the interference?

Thank you very much.
 

Ezra Pound

Well-Known Member
The C30 for crystal palace has an offset in place and is indicated by the '-' next to BBCB. This is usually done to avoid TV signal 'clashing' with others in the area, so C30 = 546000KHz and C30- (which is what is being used) = 545800KHz. Although some TV tuners can only be set to the non offset channels (in this case 546000KHz) it doesn't necessarily mean they are incorrectly tuned, because they can auto-offset themselves by locking into the 'found' frequency
BTW
This warning is currently place for the Crystal Palace Transmitter :-
"CRYSTAL PALACE transmitter - Over the next week Crystal Palace main transmitter: TV (digital) Liable to interruption"
 

MartinLiddle

Super Moderator
Staff member
I receive my Freeview signals from Crystal Palace and my reception of the Standard Definition multiplexes is pretty much rock solid. However my reception of the HD multiplex (Channel 30) occasionally suffers from interference which interrupts the program I am watching.
So what signal strength and quality is the Humax reporting?
 
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Tim.ivn

New Member
Dear Ezra and Martin

Thank you very much for your replies.

Ezra, what you seem to be saying is that even though the HDR Fox T2 is reporting a frequency of 546000KHz it may have, in a hidden manner, auto-fine-tuned to 545800KHz. Am I correct?

Also Ezra, thank you for pointing out the warning about the possible interruptions this week. I don't think however that they have anything to do with the interference that I have been experience on the HD multiplex because it has been going on since I purchased the HDR Fox T2 a few weeks ago. My previous Freeview PVR did not have HD.

Martin, the normal strength and quality of the HD multiplex is 65% and 100% respectively. I do not know what the values are when the interference happens.

Could the interference be anything to do with 4G? Could it be solved with a 4G filter or any other filter?
 

Ezra Pound

Well-Known Member
Hi Tim

Yes a TV tuner can 'capture' a signal within a certain range of frequencies, so when asked to 'look' at 546Mz will see the one at 545.8Mz and lock onto it, so obviously there would only ever be one frequency used within the capture range. It may help to narrow down when and for how long the interference occurs e.g. a the central heating / a fridge turning on every hour maybe or an interruption every few seconds. Your signal Strength and quality values seem fine as long as they are constant. 4G interference is much more likely nearer to the channels used which are channels 60 upwards so I don't think that is the problem
 
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Tim.ivn

New Member
Dear Ezra

I think that the interference is fairly sporadic. I can watch an HD channel for a few hours without any interference and then I will watch one program which will have three or four moments of interference. I don't think any of my own appliances are the cause because I have done experiments which seem to rule them out. Could it be an appliance belonging to a neighbour?

If the signal strength was somewhat stronger, would that make it more immune to interference?

Thank you very much.
 

Black Hole

May contain traces of nut
"Off centre" channel frequencies are pulled in by AFC (Automatic Frequency Control). Do not be concerned.
 

Ezra Pound

Well-Known Member
If the signal strength was somewhat stronger, would that make it more immune to interference?
Not necessarily, Thing to lookout for are things that cause a spark e.g. central heating thermostat, fridge thermostat, a car (though not normally a problem), the guy next door is welding again, overhead power lines for electric trains etc.

Another thing to try is the HDMI cable to your TV, It carries very high frequencies that have been known to interfere with TV reception, so try moving the cable or re connecting / replacing it.
 
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