Doctor D
2010-01-23 23:31:54 UTC
On the 3rd January I posted this note :
"A neighbour receives his signal from Sutton Coldfield. Using my Swires
Terry
at the foot of the downlead shows that signal strengths are good - analogues
hover in the mid 70 dBuV and all MUXes around 48-52 dBuV and receive a Pass
for quality. The aerial looks like a Blake DMX10W feeding a Fringe 22dB
masthead amplifier and a 2 set low gain splitter.
However, both his Freeview boxes refuse to decode anything on C44 or C47.
Both of these channels are also used by Malvern for different MUXes, and
Malvern is also available at this location. Could this explain the refusal
to decode, and if so why are C41, 51 and 52 unaffected? (they show 100%
quality and about 70% strength.)
Cheers
D."
and received helpful advice.
Today I had another go and couldn't improve matters with SC. C44 was still
showing about 51dBuV and a Pass on the meter and despite fiddling with the
configuration of masthead amp and distribution amp, neither Freeview box
would decode it. Ridge Hill and Malvern showed worse levels than SC, but
Lark Stoke showed encouraging levels with my test log periodic.
Historically, I had avoided using LS for several reasons. In this location
it suffers severe co-channel interference with Wrekin for analogue and gives
no analogue Five. It also requires a wideband aerial, but all analogue and 4
MUXes are in group A which is normally difficult with a wideband quad X
aerial. (This was a job on a very tight (nil!) budget.) There are no other
aerials on Lark Stoke in the village.
However, Lark Stoke is now giving all 6 MUXes at an average and rock solid
63dBuV and the analogues are about 78dBuV. Analogue co-channel interference
is visible, but I had to point it out to my neighbour! He's solving the
problem by getting another Freeview box for his remaining analogue only TV.
So, thanks to all who responded. I never found out why those two channels
wouldn't decode (analogue reception of them appeared free from
interference.) It probably was poor S/N ratio which the meter was being
unduly optimistic about, but the end result is very pleasing.
"A neighbour receives his signal from Sutton Coldfield. Using my Swires
Terry
at the foot of the downlead shows that signal strengths are good - analogues
hover in the mid 70 dBuV and all MUXes around 48-52 dBuV and receive a Pass
for quality. The aerial looks like a Blake DMX10W feeding a Fringe 22dB
masthead amplifier and a 2 set low gain splitter.
However, both his Freeview boxes refuse to decode anything on C44 or C47.
Both of these channels are also used by Malvern for different MUXes, and
Malvern is also available at this location. Could this explain the refusal
to decode, and if so why are C41, 51 and 52 unaffected? (they show 100%
quality and about 70% strength.)
Cheers
D."
and received helpful advice.
Today I had another go and couldn't improve matters with SC. C44 was still
showing about 51dBuV and a Pass on the meter and despite fiddling with the
configuration of masthead amp and distribution amp, neither Freeview box
would decode it. Ridge Hill and Malvern showed worse levels than SC, but
Lark Stoke showed encouraging levels with my test log periodic.
Historically, I had avoided using LS for several reasons. In this location
it suffers severe co-channel interference with Wrekin for analogue and gives
no analogue Five. It also requires a wideband aerial, but all analogue and 4
MUXes are in group A which is normally difficult with a wideband quad X
aerial. (This was a job on a very tight (nil!) budget.) There are no other
aerials on Lark Stoke in the village.
However, Lark Stoke is now giving all 6 MUXes at an average and rock solid
63dBuV and the analogues are about 78dBuV. Analogue co-channel interference
is visible, but I had to point it out to my neighbour! He's solving the
problem by getting another Freeview box for his remaining analogue only TV.
So, thanks to all who responded. I never found out why those two channels
wouldn't decode (analogue reception of them appeared free from
interference.) It probably was poor S/N ratio which the meter was being
unduly optimistic about, but the end result is very pleasing.