signal amplifier

[jon cann]

hello
i have a little bit of picture break up on sky during very cloudy and rainy weather.
would this help clear(sorry for the pun) the picture?

Jon

 

[Robbo]

These amplifiers are for where the cable losses are significant enough to cause a problem, for example with a long cable run.
It will amplify noise and signal and add a little more noise in to boot, and probably make your situation worse.

Unlesss you do have a really long cable run, a larger dish is probably what you need, assuming that the LNB feed and alignment etc have been optimized.

 

[jon cann]

i have a 40m cable.... and the signal breaks up in bad weather.

 

[Robbo]

It depends on the cable type, but 40m may be very slightly on the long side.

I would certainly try some better specification cable, i.e one with a lower loss per 100m.

It may not cure your problem, but it certainly won't worsen it.

Different cable types are listed here:

http://www.cai.org.uk/asp/downloads.asp

Of the benchmarked cables,
100 type cables have the most loss, 165 has the least.

 

[rolfw]

What type of cable are you using for the 40m run?

If you are using standard 1mm core satellite coax, you may find that using 1.65mm core cable would help, gaining you probably 5 db more than normal cable for that distance.

I'm presuming that it is only the fringe channels like BBC and ITV which you are losing, as with the other channels, that sized dish should be more than adequate.

 

[dxsat]

Don't waste time changing the cable, or adding an amplifier, it will make no difference. 40m run is not a significant distance. I tried the cheapest cable I could get and laid it side by side with the most expensive over a run of 35m to a quad LNB. There was not a jot of difference in signal quality.
In Spain, the cause of the breakup is elsewhere, dish size, choice of LNB, weather, type of receiver. Could any one of these- but most certainly not the cable (unless you have used normal UHF co-ax.)
If break- up is only in bad weather the best solution is a bigger dish as there is insufficient rain margin.

 

[jon cann]

yes, bbc and itv are the only ones affected, as for the cable, i cannot remember what type i have, BUT, in the specialist SAT shop, I asked for good cable, not cheap crap....

 

[aba]

go for a bigger dish

 

[lovegroove]

I have a long cable run and one of those little gizmos was just the trick! They're not that expensive, so might be worth a try. P.S. when I say long cable run, I'm talking about 30m, but I am using very thin Ambitron PSF 1/7 LSO cable which I don't think is designed for the job.

 

[Robbo]

I have a long cable run and one of those little gizmos was just the trick! They're not that expensive, so might be worth a try. P.S. when I say long cable run, I'm talking about 30m, but I am using very thin Ambitron PSF 1/7 LSO cable which I don't think is designed for the job.

30m of the proper cable would have done the trick too

 

[satelliteman]

30 Mts of low loss cheapo cable = loss of who knows....

30 Mts of 1mm benchmarked cable @ 2 GHZ (2150 Mhz) = 8.7dB

This equates to 2.9 dB loss PER 10 Metres of cable (0.29 PER Mtr)

The window of operation for most receivers is 52dB to 77dB.

 

[Robbo]

The window of operation for most receivers is 52dB to 77dB.

dBuV I presume., Or is this total cable loss?:toke:

 

[satelliteman]

dBuV I presume., Or is this total cable loss?:toke:

dBuV yes.... just tried to simplify it for the non-techies

 

[Robbo]

dBuV yes.... just tried to simplify it for the non-techies

Thanks

and confuse the poor techies I prefer using dBm myself for the field I work in (50 ohm stuff, Not in the TV field)

 

[rolfw]

Most of the installation people I know (satellite and aerial) use db per microvolt, as do I, although some old school engineers still refer to 1volt and speak in plus and minus figures. I guess that it depends what you are used to.

http://www.scatmag.com/technical/db_conversionmeter.pdf

 

[satelliteman]

Good link Rolf, I couldn't be bothered to look over my SMATV notes. Bookmarked that page

 

[andy g]

Jon Cann,
I think the best way to settle this problem, would be to build a small shed under the dish and put all your satellite gear in there that should sort the problem.If that does not work cut down the apple tree.
best regards
andy g.

 

[Llew]

Not too small though, you'll need space for a sofa, a heater and a fridge full of Carlsberg

Llew

 

[lovegroove]

The type of installation that I have meant that I was restricted to using the really thin stuff.

 

[Zorba]

Which digibox/dish are you having the problems with?