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All posts by Simon

Below are all of Simon's postings, with the most recent are at the bottom of the page.


Uh oh. I have just retuned (and tried manual retuning) a modern digital TV in central brighton - aerial on the top of a tall block of flats - and have a very weak reception of BBC One and Two on freeview. Everything else is as it should be.

Any suggestions?

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GB

@KMJ,Derby

Thanks for your response.

I can confirm that the problem is only with the BBCA mux. I have all the channels on this mux but they are totally unwatchable.

The "auto tune" function picks up BBCA on C60- (so Whitehawk hill). I'm physically closest to Brighton Central but cannot tune into anything on C41 (or C24 for that matter).

Pre 7-March I used a small amplifier in-house between the flat and the TV. The problem I am now having is the same whether or not I use the amplifier.

Signal Quality: 65%
Signal Strength: varies but always >90%

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GB

Dave: is BBCA being transmitted on full power now (after part one of the switchover)? Or will that happen at part two?

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GB

Retuned. Now I have broken picture on all freeview channels (only BBCA was affected before). Do I conclude that excessively high signal is to blame and get myself an attenuator? Seems difficult to believe...

Sadly can only get signal from Whitehawk Hill. Nothing from Rowridge or any repeaters.

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GB

Hi - I posted this a week or so ago but don't think anyone picked up on it. Apologies for posting again - but I'd really appreciate some advice!

I live in a block of flats at BN1 4UJ, which share a common aerial. From the height of the block I'm assuming that the aerial has uninterrupted direct line of sight with the transmitter at Whitehawk (I guess about a mile away).

Prior to DSO we received an adequate signal for all Freeview multiplexes to work perfectly on a 2 year old Toshiba TV (with digital receiver built in).

After the retune at DSO stage 1 we suffered serious picture and sound break-up on the BBCA Mux only (the one that had moved). All the old freeview channels worked fine.

After the retune at DSO stage 2 we now suffer serious picture and sound break-up on all the freeview channels. (Though I should be clear that it tunes in to all of the channels on all of the multiplexes with no problems.)

The Managing Agents in the block say that the signal strength at the amplifier is spot on. I know of some flats which are also suffering the same problems. But there are some other flats (sharing the same aerial) which are unaffected.

Ive tried using a variable in-line attenuator (in case the tuner was being saturated) but I can only degrade the picture/sound quality, not improve it.

Im completely and utterly totally stumped. Advice please!

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US

Thanks. Appreciate your responses. And that makes perfect sense.

Any suggestions as to why some flats might not be affected?

My guess is that perhaps there are two distribution amplifiers? I don't know the system.

Don't know how I'm going to convince the mamanaging agents to fix it...

Simon

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GB

This is all really helpful. I'm very grateful for all the responses.

I don't think it's interference since it never appeared pre-DSO on any channel but now appears constantly on all channels.

I'm fairly certain I can rule out cable and satellite - we don't have either in the block. But it is possible that some flats may be using internal aerials, not the shared aerial.

We live at ground level tucked away behind quite a lot of concrete so I'm doubtful that an internal aerial would work for us, but if all else fails I will try this!

The flats affected and unaffected are distributed throughout the height of the building.

I've arranged to try my TV in one of the unaffected flats tonight.

And failing that I've booked a professional installer to come round and advise.

I'll let you all know how I get on!

Thanks again.

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GB

Just to feedback on progress so far:

I took my TV round to my neighbours flat this evening and plugged it into the same aerial outlet that he has been using successfully since DSO.

My TV worked fine!

However I also tried a secondard aerial outlet in his flat (in a different part of his flat and not normally used) and my TV displayed the same picture and sound breakup that I suffer in my own flat.

So my working theory is that the signal from the common aerial on top of the block might be split and sent via more than one distribution amplifiers around the building. At least one distribution amplifier is being saturated by the strong signal and then transmits a distorted (though strong) signal onwards around the flat. The amplifier in question may then only serve certain outlets in certain flats.

Problem is, for most people (including the managing agents) this sort of stuff seems like rocket science.


Jim: off to try sticking an 8" length of copper wire into the middle of the aerial input socket on my TV to determine whether my well-shielded ground floor flat counts as a virtual cellar or not!


Thanks again for all the replies. You are keeping me sane!

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GB

I owe you an update! In brief:

- installers came and measured the signal from the aerial outlet socket in my flat; it is strong but the signal to noise ratio is low - I don't the exact stats.

- apparently the distribution ampliefier is "old" and the cabling throughout the buidling is a "tapped" system - i.e. one cable runs throughout the building and has branches to each flat, rather than individual cables to each flat.

So I conclude that it is the distribution amplifier being overloaded by the strong freeview signal. They're going to look at replacing the amplifier.

In the meantime, I decided I would put the "8 inches of copper wire" claim to the test. And sure as you know, 8 inches of copper wire gives me a beautiful signal - despite the several meters of concrete between the TV and the outside world.

Now I'm worried what the 4kW from Whitehawk Hill is doing to my brain!

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GB

I'm not sure that we ever really worked out what was going on with the signal in my block of flats.

It seemed that the signal I was getting in the ground floor flat was stronger than the signal in some of the top floor flats (which was of good quality too). This suggests to me that there is a further amplifier somewhere in the distribution system and that it was this that was being overloaded and distorting the signal.

The solution has been to disconnect the main distribution amplifier so that it is an unamplified signal being distributed around the building (and then presumably boosted at some point by the secret second amplifier).

But there we go. A simple resolution in the end. Disconnect the amp.

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GB
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