Re: signal loss


Alan Sewards <alan.sewards@...>
 

Hi Robert,
I have seen TV dishes around here flexing so much in the wind that the
opposite sides come within a few inches of each other! This is during the
strong gusts of the mistral (which happens to be blowing as I write). My own
dishes are largely screened from the wind, so I do not suffer from these
problems (the mistral is a W to N wind and I have a nice sheltered spot
facing south for the dishes). I suspect that this is the cause of your
problem. Not much to do but replace the dish with a stiffer one or find a
more sheltered place for it.

Best regards - Alan

----- Original Message -----
From: "Robert Moore" <rsmoore@liverpool.ac.uk>
To: <MSG-1@yahoogroups.com>
Sent: Tuesday, October 07, 2003 3:39 PM
Subject: [MSG-1] signal loss


Serious loss of signal - 7 october 2003
***************************************

List members may have seen earlier exchanges on this topic on the
SatSignal list.

Today I have experienced a very large number of missed segments, very
substantially more than those recorded by David Taylor. Since installing
my equipment I have had no problems until today. Excellent reception in
fact.

Setup4PC shows that my signal quality - normally steady at 69 - 70% is now
from time to time fluctuation wildly - including one instant switch from
100%
to zero percent (with consequential 'Out of Lock' message). It is
regularly
dropping to low 60 per cent and sometimes to 30 - 20 - 0 per cent.

Uncorrected blocks run into thousands


I am in a very exposed position 165 metres ASL with nothing between the
back of
my dish and the Mull of Galloway. Dish seems solid enough, very securely
bracketed on an end wall in the only position where my house can see
MSG-1.
There are trees on the whole of my south side and I assumed these to be
the
culprits. But I spent some time checking with a sighting inclinometer:
MSG-1 is
at 26 degrees of elevation from here; at ground level the tree tops are
not
moving above 24 degrees of elevation - and the dish is about 3 metres
above
ground level.

Wind is blowing at about force 5 but gusting to 6 and occassionally 7. I
was
beginning to wonder if the dish itself is actually flexing and causing a
loss
of signal to the block. The wind is directly into the convex side of the
dish
but I'm not sure of the aerodynamics of one of Dave Cawley's finest.

I'm getting variations to in sig qual low 60s in relatively calm patches.
50s to low 40s with quite modest gusts (surely not enough to flex a dish?)
Slightly more wind knocks me down into the red - but not consistently.
Strong gusts take the signal right down, including zero - but not every
time.

Have now spent some time gazing up at the dish. Brackets are, as I said
before,
'rock solid' but in the strong gusts the mounting pole and dish oscillate
a
little (presumably if they did not the bracket would be torn out of the
brickwork!). Perhaps my signal loss derives entirely from the dish
shaking? But
there must be millions with TV aerials - would they have problems with a
shaking dish? But I think the flexing dish hypothesis must be rejected!

The apparent randomness of the relationship between signal loss and force
of
wind might be explained by the duration of the gust and the relative
oscillation frequencies of the pole and dish. Luca's comments noted
(thanks
Luca) and also David's reply.

Is there anyone else out there having a similar problem?

Robert Moore



------------------------------
Professor Robert Moore
Department of Sociology, Social Policy
and Social Work Studies
The University of Liverpool
Eleanor Rathbone Building
Bedford Street South
Liverpool
L69 7ZA

tel and fax: 44 (0) 1352 714456


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