Just Masthead on own - High Strength Low Quality Freeview Signal

[bendyplank]

Hey Guys,

I have just bought two Digifusion FVTR 100's - and I have them in different houses, about two miles apart. One house has a roof aerial and everything is fine and dandy. Even with a large aerial in the kitchen it does ok.

The other one, doesn't do well at all. It will pick up Emley Moor transmissions on UHF 40 and show those channels - but that restricts me to the ITV/C4 multiplex. All six Multiplexes can be found on UHF 46 but I get unaccaptable signal quality above UHF 40....

The problem house is using a loft aerial as the property is rented and the landlord refuses to have an aerial. The signal strength is high - 60 - 90% depending on orientation but the quality is terrible. Most of the time the box claims it is too corrupt.

I am using a high end wideband aerial - with amplifier. What is bizarre is I can remove the amplifier and the aerial from the masthead / diapole and get the same signal.... Its like the body of the aerial and amplification mean nothing !!

The signal strength remains high, so what is killing the quality of the signal - and why does the masthead work as well on its own as with its body ??

Anyone have any answers ?

[C.Wolf]

Hi, Welcome to the forum. With freeview I was told you need double screened coax and if using an amp it needs to be low noise as freeview is apparently severely affected by noise.
Clyde.

[bendyplank]

Hey there,

Thanks for the welcome ! I am a big AV freak on a budget - I kind of like getting a good system going cheap

Perhaps the coax is the problem. The booster isn't a problem - but it isnt a help either. I know UHF tends to attenuate quicker over channel 40 but I would have thought if that was the case I would have low signal strength, which I dont.

[Chris Muriel]

Maybe there is too much signal (causing overload) in which case an attenuator would be needed.
If your amplifier has variable gain, try turning the gain down.

Chris Muriel, Manchester

[LV426]

Originally Posted by bendyplank

all six Multiplexes can be found on UHF 46...

Just to clarify - that's simply not possible. All six multiplexes take up 6 UHF channel numbers always. At Emley Moor they are
(Mux - Channel - ERP):
1 - 52 - 10
2 - 40 - 10
A - 43 - 10
B - 46 - 10
C - 50 - 10
D - 49 - 4.0
...so I think you are misinterpreting something.

It is quite possible, as others have said, that your analogue signal is too strong and "killing" the digital tuner in your box. But the first thing to do is evaluate all 6 of those UHF channel numbers above.

[bendyplank]

I think I am misunderstanding something ! The aerial alignment section of my box setup is what made me think that it was 46 that contained six multiplexs - if I try and move the aerial so I can get a better reception on UHF 46 - I get six multiplexes - most of the room picks up UHF 40 only and I get one multiplex.

I can remove the amplifier from the setup and it makes no difference - literally the booster and aerial assembly make no difference to the reported signal strength and quality wether they are present or not !!

Its driving me mad - how can the lack of assembly and amplifier make no difference ? Is it possible for a signal measured at 70% to be too strong and causing bad signal quality?

[SamRadford]

A digital signal at 70% could mean that the (stronger) analogue signal is over 100% and therefore swamping the tuner.

The notes here might help: http://www.satcure.com/tech/freeview_problems.htm

[bendyplank]

Hmmm, I just tried a masthead powered amplifier today and exactly the same problems as a £5 set top aerial, a £50 loft aerial and a diapole - with or without booster. Signal strength 70% plus - quality 0%.

This is really annoying...

Am thinking of trying a caravan aerial now... Not sure how I can tackle analogue overwhelming the digital transmission though ? Any ideas ?

I agree with Sam Radford that the analogue signal you are receiving is causing "swamping" problems on your digital reception which is why if i read your post correctly a simple room aerial seems to be performing better?

Removing an amplifier I had installed some years ago to improve analogue Channel 5 reception made an enormous improvement to my DVB-T Freeview reception.

[bendyplank]

I've managed to have some success by replacing the aerial with a cheap self powered loop aeriel from Argos. Only missing out on UHF multiplexes over 50 now. Wierdly if i plug my booster between the freeview box and the self powered aerial I lose all the channels !!!

[maldonian]

Have you tried swapping the Digifusion PVRs?

How close is the rented house to Emley Moor? (Put the postcode in the Wolfbane reception predictor to find out.)

Is there a transmitter near the rented house? (i.e. a phone mast, a police station, taxi firm, etc, or any unusual aerial). Or is it close to an industrial site?

[bendyplank]

For those that are interested my new wonder aerial is a Bench silver powered loop aerial for Argos. Outperforming my £20 super aerial from a very nice shop near the Kremlin... Bizarre. I have swapped the boxes around, there is no issue there.

There is Chapeltown Police Station about 1/3rd of a mile away. The only multiplexes I now cannot recieve with my cheap argos aerial are those UHF 49 +.

Why this cheap aerial performs better is beyond me, but the signal is near perfect in terms of quality - something neither my other cheap aerial nor my expensive loft aerial could do. And that includes using a booster !!! the booster actually makes things worse.

Philex Large High Gain TV Aerial.
535/2069 - This is the aerial that is rubbish

This is the aerial that gets 4 / 6 multiplexes
One For All Amplified Indoor Aerial, with gain up to 40dB.
534/3243

Wierd....

[maldonian]

There is Chapeltown Police Station about 1/3rd of a mile away.

Chapeltown Police Station is 16 miles from Emley Moor and the predicted field strength there is 46 dBuV/m. Wolfbane recommends an amplified extra high gain aerial. And that's for an outdoor aerial mounted 10m above ground level (that's about chimney level on a two storey house).

Assuming the field strength at the rented house is similar (it's only 600 yards away), then your problem isn't too much signal. Your problem is not enough signal. I doubt if any aerial is going to work really well in the loft if the field strength above the roof is only about 46 dBuV/m. If you could persuade the landlord to let you put up a decent outdoor aerial you should see a big improvement.

Have you asked the neighbours what their Freeview reception is like?

EDIT added the word 'predicted'

[bendyplank]

Hey Maldonian,



I get 70% - 100% signal strength on virtually all channels, it is the quality that is the problem. Unless you are suggesting that the freeview box is not being correct in the signal strength it reports - because at 46dBuV that would seem to be the case.

I'm not sure if I said this earlier - but the roof aerial is out of the question. The landlord actually cut off the coax cable from the roof when we complained that the aerial needed reallignemnt after some strong winds !!!

NTL was then introduced and I am sure the landlady gets a comission from NTL as she has done the same in lots of houses.
Why would the cheap piece of plastic from Argos would outperform an expensive Philex loft aerial....

[SamRadford]

Philex has something of a reputation for selling cheap "eye candy" equipment. But in this case I think your problem is that the aerial is indoors. If you read the page I linked to (#7 above) you'll see a full explanation.