Snow Go Area
 

I have been surprised to find that my reception of Freeview has not been
affected by the thick layer of snow on the roof, even though I'm using a
loft aerial in a weak signal area. Reception is fine for the usual four
muxes with no evident loss of signal on the STB indicator.

Shortly before Christmas I reported the complete loss of three muxes, and
attributed this to the layer of snow on the roof at that time. I also
suggested that the sub-zero temperature might be affecting the masthead-
type amplifier.

Having lost the same muxes a few days ago, when there was no snow on the
roof but the temperature outside was four degrees below zero, it is now
clear that the amp doesn't work well at a temperature much below freezing.
Reception returned to normal during the day as the loft space warmed up.
The signal here being not far above the "digital cliff", the loss of a few
dB in amplifier gain is enough to throw Freeview over the edge...

Ironically, even though the outside temperature is now minus 5, reception
is still fine. I'm sure this is because the snow on the roof is acting as
an insulator and keeping the loft warm. I've made a remote temperature
sensor so I can monitor the loft temp without going up there. Plugs into
the game port on my PC...

Conclusion: Reception of Freeview is fine here with sub-zero temperatures
outside, provided there is enough snow on the roof to insulate the loft :-)

Snow Go Area
 

In article ,
John Legon wrote:

I have been surprised to find that my reception of Freeview has not been
affected by the thick layer of snow on the roof, even though I'm using a
loft aerial in a weak signal area. Reception is fine for the usual four
muxes with no evident loss of signal on the STB indicator.

Shortly before Christmas I reported the complete loss of three muxes, and
attributed this to the layer of snow on the roof at that time. I also
suggested that the sub-zero temperature might be affecting the masthead-
type amplifier.

Having lost the same muxes a few days ago, when there was no snow on the
roof but the temperature outside was four degrees below zero, it is now
clear that the amp doesn't work well at a temperature much below freezing.

The temperature ratings of most capacitors do not include negative
temperatures.

--
From KT24

Using a RISC OS computer running v5.11

Snow Go Area
 

On Fri, 08 Jan 2010 13:41:26 +0000, Charles wrote:

The temperature ratings of most capacitors do not include negative
temperatures.

Which raises the point that presumably they have to use a special grade
of capacitors for satellites and space craft??

Snow Go Area
 

In article , John Legon
wrote:

I have been surprised to find that my reception of Freeview has not been
affected by the thick layer of snow on the roof, even though I'm using a
loft aerial in a weak signal area. Reception is fine for the usual four
muxes with no evident loss of signal on the STB indicator.

Shortly before Christmas I reported the complete loss of three muxes,
and attributed this to the layer of snow on the roof at that time. I
also suggested that the sub-zero temperature might be affecting the
masthead- type amplifier.

Alternatively, the cold is accompanied by a vertical profile in the air
density, etc, which is reducing the signal level at your location. So may
have nothing to do with your amplifier.

I have one DDTV box fed via coax from a small loft antenna. Most of the
time it works fine. But during the last week or two it keeps muting as the
signal level falls. No amps in the chain in the loft or outside. No
correlation with snow on the roof either.

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

Snow Go Area
 

In article , J G Miller wrote:
On Fri, 08 Jan 2010 13:41:26 +0000, Charles wrote:

The temperature ratings of most capacitors do not include negative
temperatures.

Which raises the point that presumably they have to use a special grade
of capacitors for satellites and space craft??

Yes. In general components for spacecraft have to go though special test
proceedures for such uses. As do the components for things like military
aircraft.

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

Snow Go Area
 

On Fri, 08 Jan 2010 15:29:39 +0100, J G Miller
wrote:

On Fri, 08 Jan 2010 13:41:26 +0000, Charles wrote:

The temperature ratings of most capacitors do not include negative
temperatures.

Which raises the point that presumably they have to use a special grade
of capacitors for satellites and space craft??

Years ago I worked in a factory producing TV signal distribution line
devices. As they were for outdoor use they had to work in any weather
conditions. Testing involved a range of temperatures to simulate the
extremes of weather. Some devices failed testing at the high
temperature but nothing ever failed because it was too cold. I don't
recall any special components being used.

Steve

--
Neural Planner Software Ltd www.NPSL1.com

Neural network applications, help and support.

Snow Go Area
 

On Jan 8, 1:03*pm, John Legon wrote:
Conclusion: *Reception of Freeview is fine here with sub-zero temperatures
outside, provided there is enough snow on the roof to insulate the loft :-)

I've never heard of a faulty masthead amp where the fault only showed
up when it was cold. Hot, yes. Coax cable sometimes shows up
temperature related faults. The most common happens in mid summer
during a hot spell. The cable goes OC mid-evening when the cable cools
down, having been very hot.

The next wave of bother will be in a few days, when the snow starts to
slide off the roofs, taking cables with it and hitting wall-mounted
dishes on the way down.

Bill

Snow Go Area
 

In article ,
Stephen Wolstenholme wrote:
On Fri, 08 Jan 2010 15:29:39 +0100, J G Miller
wrote:

On Fri, 08 Jan 2010 13:41:26 +0000, Charles wrote:

The temperature ratings of most capacitors do not include negative
temperatures.

Which raises the point that presumably they have to use a special grade
of capacitors for satellites and space craft??

Years ago I worked in a factory producing TV signal distribution line
devices. As they were for outdoor use they had to work in any weather
conditions. Testing involved a range of temperatures to simulate the
extremes of weather. Some devices failed testing at the high
temperature but nothing ever failed because it was too cold. I don't
recall any special components being used.

When I operated a survey vehicle for the BBC we found that our mast head
amplifier boxes, located and incorporating reed switches to take the amps
in and out of circuit which used a charged capacitor to change the contact,
on top of an extendable mast used to stop working when we drove in freezing
weather. RD, whose design they were, changed the capacitors to military
spec ones and our problems stopped.

--
From KT24

Using a RISC OS computer running v5.11

Snow Go Area
 

In article , John Legon
scribeth thus

I have been surprised to find that my reception of Freeview has not been
affected by the thick layer of snow on the roof, even though I'm using a
loft aerial in a weak signal area. Reception is fine for the usual four
muxes with no evident loss of signal on the STB indicator.

Shortly before Christmas I reported the complete loss of three muxes, and
attributed this to the layer of snow on the roof at that time. I also
suggested that the sub-zero temperature might be affecting the masthead-
type amplifier.

Having lost the same muxes a few days ago, when there was no snow on the
roof but the temperature outside was four degrees below zero, it is now
clear that the amp doesn't work well at a temperature much below freezing.
Reception returned to normal during the day as the loft space warmed up.
The signal here being not far above the "digital cliff", the loss of a few
dB in amplifier gain is enough to throw Freeview over the edge...

Ironically, even though the outside temperature is now minus 5, reception
is still fine. I'm sure this is because the snow on the roof is acting as
an insulator and keeping the loft warm. I've made a remote temperature
sensor so I can monitor the loft temp without going up there. Plugs into
the game port on my PC...

Conclusion: Reception of Freeview is fine here with sub-zero temperatures
outside, provided there is enough snow on the roof to insulate the loft :-)

What part of the TV band 4/5 is in use?..


--
Tony Sayer

Snow Go Area
 

In article , Jim Lesurf
scribeth thus
In article , John Legon
wrote:

I have been surprised to find that my reception of Freeview has not been
affected by the thick layer of snow on the roof, even though I'm using a
loft aerial in a weak signal area. Reception is fine for the usual four
muxes with no evident loss of signal on the STB indicator.

Shortly before Christmas I reported the complete loss of three muxes,
and attributed this to the layer of snow on the roof at that time. I
also suggested that the sub-zero temperature might be affecting the
masthead- type amplifier.

Alternatively, the cold is accompanied by a vertical profile in the air
density, etc, which is reducing the signal level at your location. So may
have nothing to do with your amplifier.

I have one DDTV box fed via coax from a small loft antenna. Most of the
time it works fine. But during the last week or two it keeps muting as the
signal level falls. No amps in the chain in the loft or outside. No
correlation with snow on the roof either.

Put it outside where it ought be !.. OK I know it costs;)..

Slainte,

Jim


--
Tony Sayer