back to article Telly apocalypse foretold for 4G arrival fails to hit London: Brighton next

Freeview-watching Londoners are safe from 4G interference, with trials failing to elicit even a single complaint - thanks to the capital's comprehensive coverage and its use of a Freeview band well clear of invading 4G signals. The tests were carried out by at800, the body charged with spending £180m in mobile-network cash to …

COMMENTS

This topic is closed for new posts.

Dodgy amplifiers?

So far they've deployed 4G in areas with good signal levels, where generally amplifiers are not needed. When they deploy in fringe areas away from main transmitters, that's when they'll find problems. As the signals are inside what has been the UHF TV band, it's in the pass band, even ones that are TETRA proofed. Pity the poor folk getting a free filter, but then it needs to be fitted between the antenna and the masthead amp at considerable cost.

3
0
Silver badge

shock horror

Places where interferrence is unlikely because of channel allocation plan suffers no interferrence!

So, that's the laws of physics confirmed again. Well done.

5
0
Silver badge

Re: shock horror

Well the fear is something else. Real amplifiers don't just multiply the signal to amplify it, but they also have a non-linear characteristic. The stronger the input signal the stronger the non-linear distortions. (Think of clipping)

Now if such non-linear distortions happen, separate frequencies can mix. Just think about (sin(1.5x)+sin(1.6x))^2. It'll have lots of new components. LTE and DVB-T signals aren't simple sine waves, but more complex signals. If you have non-linear distortions it's nearly impossible to say if those aditional components will be relevant or not. It depends on how bad the non-linearity is, which depends on how close the input signal of the amplifier is in regards to the maximum input signal of it.

So it is hard to predict what's happening, and unfortunately most DVB-T receivers don't provide any decent debug features. It would mostly be a software issue.

1
0
Unhappy

Didn't know about the trial in Brighton

...but it might explain why FreeView reception has been particularly crap this week - jumpy picture, sound syncing problems. Reception is not particularly great where I live anyway, but has been notably worse of late.

I feel a snotty email to at800 coming on. Hummph.

0
0
Silver badge

Re: Didn't know about the trial in Brighton

Well it might be caused by that, but it's also likely that your reception always has been "on the edge" and now is just a bit below. Even though marketing makes you believe it, DVB-T is not some plug and play solution. Your antenna needs to be carefully aligned and the question of having an additional amplifier or not needs to be evaluated based on individual facts.

0
0
Stop

Tell me about this strong Freeview signal in London...

....as although now officially out of the smoke (but still inside the M25) I always had terrible reception compared to analogue in NW London (various places in Harrow and Brent). The awful reception in some places in NW London was the reason I first paid for Sky.

0
0
Holmes

"its use of a Freeview band well clear of invading 4G signals"

well... duh!!!

1
0
This topic is closed for new posts.

Forums