attenuator

"Ian Jackson" wrote in message
...
In message , Roger
writes


You appear to misunderstand how a splitter works. A 4way splitter does
NOT reduce the signal by 8dB on each outlet.

Nonsense. With a 2-way splitter, the typical loss is 3.5dB at low
frequencies, rising to nearly 3.8 to 4dB around 860Mhz. Double these
figures for a 4-way.

I have never known one
to decrease a signal by as much as 6 times if you look at the log scale.

I'm not sure that I (or you) understand that statement!

I think he's a nutter.

Bill

I think we would need to know what distorted pictures means. is it blocky
freezing or what?
Brian

--
Brian Gaff -
Note:- In order to reduce spam, any email without 'Brian Gaff'
in the display name may be lost.
Blind user, so no pictures please!
wrote in message
news
I think that I need an attenuator for my DTV (set top box) receiver. I have
a four way splitter on the aerial and on three of the longest cable runs
all works OK. On the shortest cable run the picture is distorted. If I
create a 'poor' aerial connection on this short run the picture improves.
As you can see I know little about aerial systems and would be grateful if
anyone could advise me on a suitable variable attenuator I could try.
Obviously I cannot turn down the power on the splitter as then the longer
runs would be degraded. Many thanks.

Peter

wrote:
I think you missed the "turn down the power in the splitter", Bill :-)

around? You could have a faulty one that cannot automatically adjust its
sensitivity.

For variable attenuators, have a look at CPC (Google it). You might be
better to buy 6dB and 12dB fixed ones though. These are in the CPC
catalogue
as well.

Bill


--
PeeGee

Caradon Hill is my transmitter about 15 miles away in line of sight. I have
a loft aerial. Turned down the power on the splitter and it now works OK.
Amplifier on splitter is adjustable 0 - 20Db. Does this mean that the
signal was in fact too strong? I will have to see if other TVs on longer
cables will still function OK. Many thanks for the inputs.

Peter



I can't see how cable length alone could make enough difference. Most
boxes have a range of 80dB (say -80dBm to 0dBm). Typical attenuation is
20dB/100m, so you would have to have 400m for the signal to be too
strong at one end too weak at the other.

Most likely you have a faulty box, or one that just doesn't perform very
well. Also consider faulty distribution amp, connectors and any patch
cables (moulded jobs supplied with equipment).

--
Tony

You appear to misunderstand how a splitter works. A 4way splitter does
NOT reduce the signal by 8dB on each outlet.

Nonsense. With a 2-way splitter, the typical loss is 3.5dB at low
frequencies, rising to nearly 3.8 to 4dB around 860Mhz. Double these
figures for a 4-way.

I have never known one
to decrease a signal by as much as 6 times if you look at the log scale.

I'm not sure that I (or you) understand that statement!

I think he's a nutter.

Bill

You're not alone.

In message , Tony
writes
wrote:
I think you missed the "turn down the power in the splitter", Bill :-)

around? You could have a faulty one that cannot automatically adjust its
sensitivity.

For variable attenuators, have a look at CPC (Google it). You might be
better to buy 6dB and 12dB fixed ones though. These are in the CPC
catalogue
as well.

Bill


-- PeeGee

Caradon Hill is my transmitter about 15 miles away in line of sight.
I have a loft aerial. Turned down the power on the splitter and it
now works OK. Amplifier on splitter is adjustable 0 - 20Db. Does
this mean that the signal was in fact too strong? I will have to see
if other TVs on longer cables will still function OK. Many thanks for
the inputs.
Peter

I can't see how cable length alone could make enough difference. Most
boxes have a range of 80dB (say -80dBm to 0dBm). Typical attenuation
is 20dB/100m, so you would have to have 400m for the signal to be too
strong at one end too weak at the other.

Most likely you have a faulty box, or one that just doesn't perform
very well. Also consider faulty distribution amp, connectors and any
patch cables (moulded jobs supplied with equipment).

With the analogues present (which must really be hammering the front end
of the STB), I suspect you're being a bit optimistic about an 80dB
dynamic range. Even with the analogues switched off, but with the full
compliment of six muxes, I'm guessing it's more like 50dB at the most
(-25 to +25dBmV / 75 to 125dBuV / -73 to -23dBm?). But I could be very
wrong!
--
Ian