Sorry - I was talking about signal strength only, the lowest figure you get on non freeview channels is an indication of the quality of your amps...

No probs,

I didnt see any with 0 signal strength, the lowest was Channel 36 with a Strength value of 29 & a Quality value of 0.

Glenn.

If that's the case, your feed has a 29% noise floor so you can take that off your signal strength, ie 73% only gives the humax 44% signal to play with...

73% shouldn't be overloading it - I have 92% on average and all is well.

From what I've read 8-10db gain on the masthead amp is usually enough to overcome the strength loss incurred by the cable [between the aerial and your wall socked]. Masthead amps should usually only be used to increase the signal enough to overcome losses further down the wire [including the impedance/resistance of the wire] as they boost the noise as much as they boost the signal.

IMO if everything in the system is double screened (right the way up to the aerial, and all the way down to the Humax [including the fly leads]) then the only possible source of the interference is the aerial itself. I don't know enough about aerials to know if there *is* a type that won't pick up mower "noise" but mine definitely does . You could ask your neighbour to fit a surpressor to their mower but if, like me, you are surrounded by neighbours with petrol mowers, then you're in for a hard time convincing them all to sort out their shoddy kit!

Geebee.uk - just to calrify - here's a portion of my channel scan.

ch28 - signal strength 60 - analogue
ch29 - signal strength 27
ch30 - signal strength 56 - digital
ch31 - signal strength 21
ch32 - signal strength 61 - digital
ch33 - signal strength 26
ch34 - signal strength 56 - digital
ch35 - signal strength 13
ch36 - signal strength 18
ch37 - signal strength 27
ch38 - signal strength 16
ch39 - signal strength 20
ch40 - signal strength 0
ch41 - signal strength 29 - digital
ch42 - signal strength 0
ch43 - signal strength 0
ch44 - signal strength 29 - digital
ch45 - signal strength 0

ch40,42,43,45 have zero signal strength, so no noise from my amps, so the 29 for ch41 and 44 is clean and I have no reception probelms.

My old adjustable amp wouldn't let me get below 12, and I had nothing but trouble.

Does this indicate that the amp is noisey then?

As its relatively new should I return it for a replacement unit?

Or could it be something else such as poor connection on the aerial, slightly off tune, i.e. the aerial needs repositioning?

I'm on the fringe for reception, could this just be the noise being amplified?

How do you identify the channels as Anologue or Digital?

Glenn.

Probably, you can prove it's not the incoming aerial feed by disconnecting at the amp input and rechecking the noise floor. You should really fit a 75 ohm terminator to the amp input to be sure you are not picking up crap.


Horses for courses, you stated the amp is set to about 20% - 30% so it's too powerful for you location. I would disconnect it and see what you get. From the figures you quote you may not need it at all.


I'm puzzled, did you go on the roof to remove the old amp - or is it still up there? Since the amp needs to be as close to the aerial as possible, I would have thought you would have fitted the new one up the pole.


No - I have a much lower signal than you but I use amps that are not introducing noise.

Amps rarely compensate for a weak freeview signal. In my case, my very weak signal can be resolved by the Humax, but my immunity to noise (lights, lawnmowers etc) was poor.

Doubling the signal with a quality amp effectively halves the noise, but if you couldn't get a signal before you amplify, you won't get one after.


With the Humax - high signal with high quality = digital. High signal with zero quality = analogue.

Wolfbane will tell you which channels in your area are digital. ukfree.tv will show you both analogue and digital.

Its at this setting at the moment because i turned the gain down to see if the interference dissapeared. It has been set higher, about 50% i would guess. I arrived at this setting by watching the signal strength on one of the channels whilst turning the gain down. This was the optimum point before the gain reduced dramatically, I guessed increasing the gain beyond this point could have the effect of overloading the amp.


Just done this experiment tonight;
With NO MASTHEAD or DISTRIBUTION amp in circuit the signal strength on a valid channel is at about 41%, quality 100%. An invalid channel has Strength 18%, Quality 0. Digital picture was acceptable, but the analogue channels were very noisey with "Five" being the worst with a small square that traversed across the screen

With ONLY the DISTRIBUTION amp in circuit the strength is boosted to 73%, quality 100% on a valid channel. On an invalid channel the Strength was 25% and Quality was 0%. Digital picture was OK, but analogue was slightly better than before.

With ONLY the MASTHEAD amp in circuit the strength was about 60%, quality at 100% on a valid channel, but an invalid channel showed strength of 18%, quality of 0%. Digital picture OK, but analogue was as with distribution amp only, slightly better than before.


With BOTH the Masthead and distribution amp in circuit a valid channel shows 73% Strength with 100% quality. An invalid channel showed 63% strength and 0% quality.

I conclude from this that adding each amp into the circuit boosts the unwanted noise on an invalid channel, but contributes to a better quality analogue picture. I could dispense with the Masthead amp at the cost of analogue reception but as I still use a TV with Analogue only I need to have the best available picture.

I must repeat this experiment when more time is available as this was very much conducted "In between" SWMBO recording schedule and some of the figures don't seem quite correct (I didn't have time to write them down so this was very much from memory). I may be able to retune the analogue channels to get a better reception and dispense with one of the amps. At full digital switchover, I guess my issues will go away as the indicated power increase for the Mendip transmitter is 10 fold, but this is not until 2010!



I agree, masthead is best positioned closest to the aerial. Theres only one masthead amp in circuit, when the aerial fitter replaced the aerial, i retained the old amp to keep cost down, as he said there wasnt anything wrong with it, but I had it fitted just inside the loft so i could change it later at my convenience. I have later changed it to the Labgear PUH111.

Glenn.

I must confess - I abandoned analogue when setting up my system as my location makes it impossible to get decent analogue reception.

A line drawn from Durris to Rhumster Forest finds me smack bang in the middle and as Durris analogue uses Rhumster Forest's digital frequencies and vice versa, analogue suffers badly from patterning.

It is feasable that the spectrum in your area does not have any dead spots, at least you know that without the amp you can resolve a signal, so mimimal amplification for distribution may all you can get away with.

Roll on DSO.