Aerial amp & 4 way splitter

[charles]

But a mast head amplifier is likely to be even better. Interesting, over the time I was involved in this game, tv front ends actually got worse.

[The Natural Philosopher]

I think modern electrobics is now at te state where 'noisy' front ends d9ont reduce costs.

The case for the masthead amp is simply if teh signal is very very weak to start with and you are hovering on the edge of reception ..mostly with digital its either OK or f***ed.

[The Natural Philosopher]

I suggest not recently though.

[The Natural Philosopher]

IN the end a low noise GASFET for 25p is a low noise GASFET at 25p. No reasons NOT to put one in the cheapest of sets and the most expensive of mastheads.

Even back in the 70s getting to within 3dB of thermal wasn't hard with FETS.

The problem was it cots a bit moe and set manufactures rightly worked out that if 90% of the customers are happy with a low gain set and te rest will buy and amp well that's OK.

Today is simply doesn't cost extra to make all the sets more sensitive

And with digital the idea is that everyone is within the reach of a strong local signal and those that are not are in ans case f***ed, amplifier or not.,

[meow2222]

No, s/n ratio in the tv/stb is determined by: aerial gain & local noise pickup noise introduced into the cabling noise figure of amp, if any noise figure of tv/stb front end.

I've already explained why aerial amps often make a difference.

NT

[Bill Wright]

Cheap sets often have terrible front ends. Not just 'sensitivity' but all kinds of weird intermodulation effects, and also pick up from the set's other components.

We had a customer who went out and bought 700 of the cheapest sets he could find. The distribution system carried something like 18 analogue channels and six muxes. The sets simply couldn't cope. Wind the level down: grainy pictures and digi drop out. Wind it up: analogue patterning and digi drop out. We had to reduce the analogues to nine (I think) before the sets would work, and even then there was patterning, grain, and drop out.

Bill

[Bill Wright]

I think radiated noise from other components worsened. Also there was a run of Sonys in the early 80s that needed a masthead amp everywhere except Emley Moor village! (I exaggerate)

Bill

[Bill Wright]

In practice, amplification of signal before the TV set, when the signal is weak, usually has far more effect than theory suggests.

Bill

[Graham.]

That's why loft boxes are best located in the loft.

[charles]

This used to happen with quite expensive analogue sets too. Somwhere on the north Wales coast a simple HP aerial could pick up 12 channels. Unviewable pictures

[tony sayer]

ISTR that P-HEMT devices are all the rage now;)..

Umm.. You might be guv where you are but go to south Wales or 'opp north and theres many still who aren't so well supplied or worse supplied by one of those simple relays with MUX'es missing like the Sandsend area that was supplied buy the Whitby transmitter but now no longer exists.

I think the residents now use Satellite;!..

>

[tony sayer]

In article , charles scribeth thus

Can you say in what way were they worse?..

[tony sayer]

So how did these sets get on in a more normal situation i.e. in a domestic setting with a normal rooftop aerial?..

Did you have a spectrum analysis of that at all Bill?..

[tony sayer]

In article , charles scribeth thus

Yes if that amp is up there before the lossy downlead feeder...

[tony sayer]

Can you suggest a mechanism for that Bill?..

[tony sayer]

yes:)..

By the cabling losses..

Which there will be..

In the right location they can but if the S/N of the original signal presented to the amplification device isn't as it might be then you'll make it no better...

[meow2222]

Its already ben explained in this thread

charles hope:

Yes if that amp is up there before the lossy downlead feeder...

And often if after. Its been covered already

NT

[tony sayer]

In article , Dave Plowman (News) scribeth thus

Yes, but its dependent on the problem you have. A poor reception area and/or a long downlead then yes, go for the masthead amp to overcome the losses introduced by that, and they can be quite high depending on frequency and general TV cables aren't that wonderful anyway.

However if you do have a good clean signal and then want to supply 20 odd tellies with that an amp before the splitting and the losses that'll introduce is correct for that application..

[charles]

They became less sensitive.

[charles]

Not lossy feeder - about 10m of good quality URM43.