cellphone? interference to satellite IF

Some of you might remember me asking if anyone knew which Astra 28E
transponder NASN was on. The answer turned out to be D9S. The frequency is
11623MHz. Today I investigated the complaint that started me on this trail. A
very nice US citizen living near here in a large apartment complex had
intermittent reception of NASN. No-one else in the block had a problem, but
there again no-one else is American, and the other channels in the mux would
only be of interest to lunatics. When I asked the analyser to analyse D9S it
said that the channel power was just fine, but it refused to even consider
decoding the datastream. I turned the line power off, thus disabling the
polarity switch at the repeater. Exactly where D9S had been there was a large
spike, only a few dB below the transponder power. The IF frequency is 1873MHz.
I suspect a local cellphone mast. In theory nothing should get into the TV
system thanks to heavy screening, but of course that's theory for you. I walked
right round the block with a screwdriver shoved into the analyser's input. The
spike peaked at one corner. Above my head was a hideously rigged point-to-point
microwave aerial -- one of those things that looks like a length of pipe. Dunno
whether that was the culprit or just a red herring. Has anyone any experience
of this sort of problem?

Bill

Yes Bill, exactly the same thing here in coventry (bedworth to be precise),
and more interestingly it started at 5pm on a friday and finished between
9-10am on the following monday morning every week, across about 5
transponders, in a very small area, covering about 5 houses (outside this
the Sky boxes worked fine)

ended up resiting the dishes at ground level (etc.)after an unsuccsefull
visit from the RA investigation team who refused to attend when it was
actually doing it!!

Alan
telespeed


Bill" wrote in message
...
Some of you might remember me asking if anyone knew which Astra 28E
transponder NASN was on. The answer turned out to be D9S. The frequency is
11623MHz. Today I investigated the complaint that started me on this
trail. A
very nice US citizen living near here in a large apartment complex had
intermittent reception of NASN. No-one else in the block had a problem,
but
there again no-one else is American, and the other channels in the mux
would
only be of interest to lunatics. When I asked the analyser to analyse D9S
it
said that the channel power was just fine, but it refused to even consider
decoding the datastream. I turned the line power off, thus disabling the
polarity switch at the repeater. Exactly where D9S had been there was a
large
spike, only a few dB below the transponder power. The IF frequency is
1873MHz.
I suspect a local cellphone mast. In theory nothing should get into the TV
system thanks to heavy screening, but of course that's theory for you. I
walked
right round the block with a screwdriver shoved into the analyser's input.
The
spike peaked at one corner. Above my head was a hideously rigged
point-to-point
microwave aerial -- one of those things that looks like a length of pipe.
Dunno
whether that was the culprit or just a red herring. Has anyone any
experience
of this sort of problem?

Bill

Yes Bill, exactly the same thing here in coventry (bedworth to be precise),
and more interestingly it started at 5pm on a friday and finished between
9-10am on the following monday morning every week, across about 5
transponders, in a very small area, covering about 5 houses (outside this
the Sky boxes worked fine)

ended up resiting the dishes at ground level (etc.)after an unsuccsefull
visit from the RA investigation team who refused to attend when it was
actually doing it!!

Alan
telespeed


Bill" wrote in message
...
Some of you might remember me asking if anyone knew which Astra 28E
transponder NASN was on. The answer turned out to be D9S. The frequency is
11623MHz. Today I investigated the complaint that started me on this
trail. A
very nice US citizen living near here in a large apartment complex had
intermittent reception of NASN. No-one else in the block had a problem,
but
there again no-one else is American, and the other channels in the mux
would
only be of interest to lunatics. When I asked the analyser to analyse D9S
it
said that the channel power was just fine, but it refused to even consider
decoding the datastream. I turned the line power off, thus disabling the
polarity switch at the repeater. Exactly where D9S had been there was a
large
spike, only a few dB below the transponder power. The IF frequency is
1873MHz.
I suspect a local cellphone mast. In theory nothing should get into the TV
system thanks to heavy screening, but of course that's theory for you. I
walked
right round the block with a screwdriver shoved into the analyser's input.
The
spike peaked at one corner. Above my head was a hideously rigged
point-to-point
microwave aerial -- one of those things that looks like a length of pipe.
Dunno
whether that was the culprit or just a red herring. Has anyone any
experience
of this sort of problem?

Bill

Yes Bill, exactly the same thing here in coventry (bedworth to be precise),
and more interestingly it started at 5pm on a friday and finished between
9-10am on the following monday morning every week, across about 5
transponders, in a very small area, covering about 5 houses (outside this
the Sky boxes worked fine)

ended up resiting the dishes at ground level (etc.)after an unsuccsefull
visit from the RA investigation team who refused to attend when it was
actually doing it!!


So what goes on at weekends that might cause it? How odd.

Bill

Yes Bill, exactly the same thing here in coventry (bedworth to be precise),
and more interestingly it started at 5pm on a friday and finished between
9-10am on the following monday morning every week, across about 5
transponders, in a very small area, covering about 5 houses (outside this
the Sky boxes worked fine)

ended up resiting the dishes at ground level (etc.)after an unsuccsefull
visit from the RA investigation team who refused to attend when it was
actually doing it!!


So what goes on at weekends that might cause it? How odd.

Bill

On 13 Jul 2004 23:27:31 GMT, o (Bill) wrote:

Some of you might remember me asking if anyone knew which Astra 28E
transponder NASN was on. The answer turned out to be D9S. The frequency is
11623MHz.

After being down-converted by the (Universal) LNB, then that would be
sent to the receiver at 1873 MHz. You should keep in mind that the
receiver does not receive the signal at the same frequency as is sent
by the satellite.

Today I investigated the complaint that started me on this trail. A
very nice US citizen living near here in a large apartment complex had
intermittent reception of NASN. No-one else in the block had a problem, but
there again no-one else is American, and the other channels in the mux would
only be of interest to lunatics. When I asked the analyser to analyse D9S it
said that the channel power was just fine, but it refused to even consider
decoding the datastream. I turned the line power off, thus disabling the
polarity switch at the repeater. Exactly where D9S had been there was a large
spike, only a few dB below the transponder power. The IF frequency is 1873MHz.
I suspect a local cellphone mast.

That is highly likely, when 11623 subject to the 9750 L.O would be
downlinked to the receiver at exactly 1873 Mhz.

However, there is one thing that you can do to get around this
problem, provided that you have control over the 22 KHz tone signal in
your receiver of course.

As the second L.O in the LNB is 10600 Mhz. This means that this 11623
MHz signal can also be downlinked at 1023 Mhz. And watching it at this
frequency instead means no more interference.

Using a Digibox to do this is unlikely to be helpful, when this
receiver only works one way.

This could also explain why other viewers do not report this problem,
when receivers can switch between the lower and upper L.Os at
different points. And 11,623 MHz is within the range when most
receivers would consider switching over.

In theory nothing should get into the TV system thanks to heavy screening,

Many earlier cable installations were far from ideal in terms of
screening, where of course that was also before these signals were
shared with the telecoms market.

I noticed interference myself on the same cable type as Sky's
recommended CT100 cable. My solution was to upgrade the cable to CT125
spec (more correctly FT125), when then the interference on this
frequency was greatly minimised.

Remember that the coaxial cable if the shielding is not good enough
will act like a giant aerial. On large early installations, then the
cable type could be far from ideal.

Anyone fitting coaxial cable these days of less than CT100 spec is
really asking for trouble.

but of course that's theory for you.

The professionals know far beyond simple theory.

I walked
right round the block with a screwdriver shoved into the analyser's input. The
spike peaked at one corner. Above my head was a hideously rigged point-to-point
microwave aerial -- one of those things that looks like a length of pipe. Dunno
whether that was the culprit or just a red herring.

You would have to check the frequency output, but at that frequency it
would have to be faulty.

Not to mention that by turning it off, then you can see if the problem
goes away. Should it be the problem, then quite rightly the owner has
to have it repaired, replaced or removed.

Has anyone any experience of this sort of problem?

Anyone who values their satellite reception and have encountered what
happens when the telecoms system shares this frequency range.

I noticed my interference problem during analogue reception, when
under digital you would simply have blackness. Still my problem was
not bad enough to take out digital reception, but I upgraded the cable
anyway.

Before that time there was no interference...

Cardman
http://www.cardman.com
http://www.cardman.co.uk

On 13 Jul 2004 23:27:31 GMT, o (Bill) wrote:

Some of you might remember me asking if anyone knew which Astra 28E
transponder NASN was on. The answer turned out to be D9S. The frequency is
11623MHz.

After being down-converted by the (Universal) LNB, then that would be
sent to the receiver at 1873 MHz. You should keep in mind that the
receiver does not receive the signal at the same frequency as is sent
by the satellite.

Today I investigated the complaint that started me on this trail. A
very nice US citizen living near here in a large apartment complex had
intermittent reception of NASN. No-one else in the block had a problem, but
there again no-one else is American, and the other channels in the mux would
only be of interest to lunatics. When I asked the analyser to analyse D9S it
said that the channel power was just fine, but it refused to even consider
decoding the datastream. I turned the line power off, thus disabling the
polarity switch at the repeater. Exactly where D9S had been there was a large
spike, only a few dB below the transponder power. The IF frequency is 1873MHz.
I suspect a local cellphone mast.

That is highly likely, when 11623 subject to the 9750 L.O would be
downlinked to the receiver at exactly 1873 Mhz.

However, there is one thing that you can do to get around this
problem, provided that you have control over the 22 KHz tone signal in
your receiver of course.

As the second L.O in the LNB is 10600 Mhz. This means that this 11623
MHz signal can also be downlinked at 1023 Mhz. And watching it at this
frequency instead means no more interference.

Using a Digibox to do this is unlikely to be helpful, when this
receiver only works one way.

This could also explain why other viewers do not report this problem,
when receivers can switch between the lower and upper L.Os at
different points. And 11,623 MHz is within the range when most
receivers would consider switching over.

In theory nothing should get into the TV system thanks to heavy screening,

Many earlier cable installations were far from ideal in terms of
screening, where of course that was also before these signals were
shared with the telecoms market.

I noticed interference myself on the same cable type as Sky's
recommended CT100 cable. My solution was to upgrade the cable to CT125
spec (more correctly FT125), when then the interference on this
frequency was greatly minimised.

Remember that the coaxial cable if the shielding is not good enough
will act like a giant aerial. On large early installations, then the
cable type could be far from ideal.

Anyone fitting coaxial cable these days of less than CT100 spec is
really asking for trouble.

but of course that's theory for you.

The professionals know far beyond simple theory.

I walked
right round the block with a screwdriver shoved into the analyser's input. The
spike peaked at one corner. Above my head was a hideously rigged point-to-point
microwave aerial -- one of those things that looks like a length of pipe. Dunno
whether that was the culprit or just a red herring.

You would have to check the frequency output, but at that frequency it
would have to be faulty.

Not to mention that by turning it off, then you can see if the problem
goes away. Should it be the problem, then quite rightly the owner has
to have it repaired, replaced or removed.

Has anyone any experience of this sort of problem?

Anyone who values their satellite reception and have encountered what
happens when the telecoms system shares this frequency range.

I noticed my interference problem during analogue reception, when
under digital you would simply have blackness. Still my problem was
not bad enough to take out digital reception, but I upgraded the cable
anyway.

Before that time there was no interference...

Cardman
http://www.cardman.com
http://www.cardman.co.uk

On Wed, 14 Jul 2004 13:19:13 GMT, "Alan"
wrote:

Yes Bill, exactly the same thing here in coventry (bedworth to be precise),
and more interestingly it started at 5pm on a friday and finished between
9-10am on the following monday morning every week,

Sounds like they upped the power to deal with the weekend demand
increase. I am not too sure the theory behind that idea, but this is
clearly weekend times for the telecoms market.

across about 5 transponders, in a very small area, covering about 5 houses
(outside this the Sky boxes worked fine)

The telecoms market works in mysterious ways. ;-]

ended up resiting the dishes at ground level (etc.)after an unsuccsefull
visit from the RA investigation team who refused to attend when it was
actually doing it!!

Resetting the dish is unlikely to help. THIS IS THE CABLE!!!

So it would only help if you moved the cable.

Upgrade your coaxial cable to a specification with better shielding,
when then this problem could well vanish.

Cardman
http://www.cardman.com
http://www.cardman.co.uk

On Wed, 14 Jul 2004 13:19:13 GMT, "Alan"
wrote:

Yes Bill, exactly the same thing here in coventry (bedworth to be precise),
and more interestingly it started at 5pm on a friday and finished between
9-10am on the following monday morning every week,

Sounds like they upped the power to deal with the weekend demand
increase. I am not too sure the theory behind that idea, but this is
clearly weekend times for the telecoms market.

across about 5 transponders, in a very small area, covering about 5 houses
(outside this the Sky boxes worked fine)

The telecoms market works in mysterious ways. ;-]

ended up resiting the dishes at ground level (etc.)after an unsuccsefull
visit from the RA investigation team who refused to attend when it was
actually doing it!!

Resetting the dish is unlikely to help. THIS IS THE CABLE!!!

So it would only help if you moved the cable.

Upgrade your coaxial cable to a specification with better shielding,
when then this problem could well vanish.

Cardman
http://www.cardman.com
http://www.cardman.co.uk

On 14 Jul 2004 15:40:11 GMT, o (Bill) wrote:

So what goes on at weekends that might cause it? How odd.

More users. I am thinking about a bandwidth issue, when extra power
equals a greater data rate.

Cardman
http://www.cardman.com
http://www.cardman.co.uk