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Aerial amp & 4 way splitter

placebo effect.,

Reply to
The Natural Philosopher
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I wonder if we're seeing this the same way;!..

For the avoidance of doubt..

In any radio linking system which TV reception generally is the signal will be received by the aerial. There we have an opportunity to "gain" as much signal as possible of the wanted carrier. Once we have that then we need to transfer that to the receiver usually done by a downlead cable. Now most TV cables aren't that great some like decent Raydex satellite grade cables are relatively good whereas the open weave braided string sold in the sheds are not.

Now if you amplify the signal before the loss invariably in that cable then that will improve the available signal at the receiver.

But if we now amplify that after attenuation introduced by the cable loss then how does that improve the overall link signal to noise ratio?.

I'm just planning a 40 mile 1.5 Ghz radio link. Now in that I will use an aerial which has 15 dBi gain some 400 odd quid, a cable of some 10 quid a metre as the run is quite long now if I could use a 20 quid amp and a simple aerial then I'd do that, would it work as well?..

Reply to
tony sayer

I think that what is happening is that the digital TV decoder has a very narrow threshold and any improvement in the signal level despite noise can sometimes effect a decode whereas in analogue TV this was just extra noise..

Reply to
tony sayer

You must be using a rather good quality pro TV aerial then Charles;?..

In which case I'd have thought RG213 would have been a better bet;?..

Reply to
tony sayer

Locate the receiver close to the aerial and send at baseband?

Reply to
Dave Plowman (News)

So to translate that back to TV reception ... your answer would be to locate the STB on the chimney and drop a long composite/scart/HDMI lead down to the living room?

Reply to
Andy Burns

In article , Dave Plowman (News) scribeth thus

Some 50 metres up a mast;?...

Reply to
tony sayer

See the reply to Dave..

Tho having said that its being done on a daily basis, well sort of, imagine having to run waveguide down from a Sky dish;!...

Course most Sky dishes are easily accessible, this one isn't its up a tall mast and it'd be an aerial rigger in around best part of a 1000 a day to get at it;!..

Reply to
tony sayer

Ruggedised Log periodic. Domestic aerials would stand up to motorway driving when mounted on the roof of a vehicle.

Mechanmical strenght and fexibily were both required. URM43 worked well.

Reply to
charles

No - you site any needed head amp close to the aerial so the cable can be of a lower spec. All else being equal.

But a radio link is a different thing. Just in case you didn't know.

Reply to
Dave Plowman (News)

When going for maximum coverage with radio mics it was always best to situate the receiver close to the aerial and run the audio the long distance. But with a custom made rig I'd guess you'd situate it at the bottom of the mast and bite the bullet for an expensive feeder.

Reply to
Dave Plowman (News)

They type of noise is also relevant given the sophistication of the QAM modulation scheme used for DTV. Classical random thermal and shot noise would have less detrimental effect on it than the numbers alone would suggest, whereas phase noise, amplitude imbalance, and frequency shifts are likely to have disproportionately more effect - especially on the higher order coding schemes now commonly used like 64 QAM.

Reply to
John Rumm

I agree.

Bill

Reply to
Bill Wright

No idea as I didn't try it. But in the domestic setting it is still not uncommon to have to say to the customer, "Sorry, but (a) the pixellation is the set, not the system and (b) sorry, but the patterning on your analogue CCTV is the set, not the system. If you want to watch telly in the kitchen/kid's bedroom/gym go out and buy a proper telly."

Of the signal we supplied to the sets? Yes, and it was of course perfect. Several times we took our own Sonys in to demonstrate the difference. On one occasion this led to a bit of a barney between 'Estates' and 'Procurement'.

Bill

Reply to
Bill Wright

  1. The obvious: the signal is amplified before cable losses.
  2. Similarly: the signal is amplified before outlet plate and flylead losses.
  3. The signal is amplified before extraneous noise enters the system (via the outlet or the flylead or the RF link between recorder and TV), this noise originating from the TV set, the recorder, other items situated nearby such as games machines, laptops, nicad chargers, and so on.
  4. Some TV sets clearly add noise, internally, to their RF input. Often this varies a great deal with frequency.

There are many advantages to having generally strong signals. My rule of thumb is to be 3/4 of the way up between the noise and the cross-mod/intermod. Not well put, but you get my drift. Suppose you go to a largish communal system, for the first time. There are all sorts of problems. Snowy analogue (in house) in one flat, wavy lines on the analogue next door, DTT drop out here and there, etc. If signal levels are generally a bit on the low side (but theoretically quite acceptable; shouldn't really be a problem) and if there's a cheap way to lift the head-end output by 6dB, ohh what a difference! Of course the s/n ratio at every repeater is improved by 6dB, but even so the results can be magic, for a modest increase in level.

Then you get the screamer. "You've made it worse!" Look behind the living room telly for the far eastern multi-output amp that feeds the bedrooms and stick an attenutor in its gob, or replace it with a passive split.

Bill

Reply to
Bill Wright

I think you're a fool as well, so that makes us equal.

Bill

Reply to
Bill Wright

Wot, you nicked a tx aerial off the beeb and stuck it on your roof?

Bill

Reply to
Bill Wright

Often attenuation of the aerial signal is needed before the loft box. In that case it can be in the cellar. I don't like loft boxes by the way. The are based on the fallacy that you can add an in house analogue or digital signal without creating a clear channel with a notch filter and without filtering the output of the device that produces the analogue or digital in house signal.

Bill

Reply to
Bill Wright

So there must be some completely s**te sets out there, and back in the day we made perfectly good tuners with just a BC180 and a 181 ;!..

This wasn't one of HM 's establishments;?..

Reply to
tony sayer

All that is keeping the S/N ratio to where it should be before it hits the receiver..

Ho humm fun ..Not;!..

Bet your glad you've retired;)?>.

Reply to
tony sayer

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