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Reception problems during heavy rain?



 
 
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  #1  
Old September 21st 18, 05:12 AM posted to uk.tech.digital-tv
Bill Wright[_3_]
external usenet poster
 
Posts: 3,601
Default Reception problems during heavy rain?

My aerial has a clear sight of Emley Moor and my distribution system
normally delivers a perfect signal to all the TV sets and recorders.
However, during the freakishly heavy rain in the early hours of today
our reception suffered a long series of brief break-ups. This
observation is based on my recording of Horizon HD on BBC4 (com 7).
I've never seen evidence of heavy rain affecting terrestrial UHF
reception, though of course that doesn't mean it can't happen. I'm
musing about the mechanism.
1. Something wrong at the transmitter; weather-related or otherwise
2. The link between playout and the transmitter; weather-related or
otherwise
3. My aerial being effectively submerged; the raindrops merging enough
to behave almost like continuous water
4. Path loss caused by the raindrops merging enough to behave almost
like continuous water.

If anyone else recorded Horizon I'd be interested to know if they had
reception problems. COM7 is on much lower power from Emley than the
'main' muxes', but even so we normally receive a signal with an
unmeasurably good s/n ratio.

Horizon was about black holes and quantum mechanics. My understanding
was superficial at best.

Bill
  #2  
Old September 21st 18, 09:18 AM posted to uk.tech.digital-tv
Woody[_4_]
external usenet poster
 
Posts: 2,088
Default Reception problems during heavy rain?

On Fri 21/09/2018 04:12, Bill Wright wrote:
My aerial has a clear sight of Emley Moor and my distribution system
normally delivers a perfect signal to all the TV sets and recorders.
However, during the freakishly heavy rain in the early hours of today
our reception suffered a long series of brief break-ups. This
observation is based on my recording of Horizon HD on BBC4 (com 7).
I've never seen evidence of heavy rain affecting terrestrial UHF
reception, though of course that doesn't mean it can't happen. I'm
musing about the mechanism.
1. Something wrong at the transmitter; weather-related or otherwise
2. The link between playout and the transmitter; weather-related or
otherwise
3. My aerial being effectively submerged; the raindrops merging enough
to behave almost like continuous water
4. Path loss caused by the raindrops merging enough to behave almost
like continuous water.

If anyone else recorded Horizon I'd be interested to know if they had
reception problems. COM7 is on much lower power from Emley than the
'main' muxes', but even so we normally receive a signal with an
unmeasurably good s/n ratio.

Horizon was about black holes and quantum mechanics. My understanding
was superficial at best.


For a start, don't believe that any transmitter that in theory is omni
is actually that. Despite you being LoS it does not follow that you are
not in one of the many small reductions ('nulls') of the coverage pattern.
Are you still using a group B or have you upgraded to a log periodic
yet? I'm about 26 miles away and the change from a (supposedly) wideband
multibeam to a LP has made a world of change in signal stability on
32/34 and 56.

It is possibly that the standby aerial was put into use for some reason
- indeed it may have been put into service longer term for the 700MHz
clearance and your signal has not been affected. However put into the
path such horrendously heavy rain as was around last night and it could
have serious effects. In my limited experience of rain effects IMO it is
likely to affect the quality rather than the signal strength, and as we
all know with DTV it is the quality that matters.


--
Woody

harrogate three at ntlworld dot com
  #3  
Old September 21st 18, 10:01 AM posted to uk.tech.digital-tv
Ian Jackson[_7_]
external usenet poster
 
Posts: 273
Default Reception problems during heavy rain?

In message , Woody
writes
On Fri 21/09/2018 04:12, Bill Wright wrote:
My aerial has a clear sight of Emley Moor and my distribution system
normally delivers a perfect signal to all the TV sets and recorders.
However, during the freakishly heavy rain in the early hours of today
our reception suffered a long series of brief break-ups. This
observation is based on my recording of Horizon HD on BBC4 (com 7).
I've never seen evidence of heavy rain affecting terrestrial UHF
reception, though of course that doesn't mean it can't happen. I'm
musing about the mechanism.
1. Something wrong at the transmitter; weather-related or otherwise
2. The link between playout and the transmitter; weather-related or
otherwise
3. My aerial being effectively submerged; the raindrops merging
enough to behave almost like continuous water
4. Path loss caused by the raindrops merging enough to behave almost
like continuous water.
If anyone else recorded Horizon I'd be interested to know if they
had reception problems. COM7 is on much lower power from Emley than
the 'main' muxes', but even so we normally receive a signal with an
unmeasurably good s/n ratio.
Horizon was about black holes and quantum mechanics. My
understanding was superficial at best.


For a start, don't believe that any transmitter that in theory is omni
is actually that. Despite you being LoS it does not follow that you are
not in one of the many small reductions ('nulls') of the coverage
pattern.
Are you still using a group B or have you upgraded to a log periodic
yet? I'm about 26 miles away and the change from a (supposedly)
wideband multibeam to a LP has made a world of change in signal
stability on 32/34 and 56.

It is possibly that the standby aerial was put into use for some reason
- indeed it may have been put into service longer term for the 700MHz
clearance and your signal has not been affected. However put into the
path such horrendously heavy rain as was around last night and it could
have serious effects. In my limited experience of rain effects IMO it
is likely to affect the quality rather than the signal strength, and as
we all know with DTV it is the quality that matters.

Maybe the situation is not quite the same, but Chatton (north
Northumberland) is (or, at least, was when it came into service) a
high-power off-air relay off Pontop Pike (about 50 miles to the south).
It's about 8 miles inland from Seahouses, full LOS.

In Seahouses, while watching (analogue) TV one warm evening, a bank of
dense fog rolled in off the sea. It became increasingly apparent that
there was a growing amount of multipath ghosting on the picture. It
steadily got worse and worse, until the picture was barely viewable -
then after a momentary break, it suddenly became OK again.

The explanation given to me was that there were two receiving aerials -
one half way up the mast, and one near the top. It was the top one that
was normally in use - and the lower one was a standby (and they had
switched to it).

What had happened was that the fog had caused a sudden change in the
temperature of the air and on its density, and this had led to an
unstable ducting effect, which in turn had severely affected the
'high-up' path of propagation. Lower down had been less disturbed.

So if fog can cause this sort of effect, can rain do the same -
especially if it is sudden and torrential?
--
Ian
  #4  
Old September 21st 18, 03:44 PM posted to uk.tech.digital-tv
Bill Wright[_3_]
external usenet poster
 
Posts: 3,601
Default Reception problems during heavy rain?

On 21/09/2018 09:01, Ian Jackson wrote:

In Seahouses, while watching (analogue) TV one warm evening, a bank of
dense fog rolled in off the sea. It became increasingly apparent that
there was a growing amount of multipath ghosting on the picture. It
steadily got worse and worse, until the picture was barely viewable -
then after a momentary break, it suddenly became OK again.

The explanation given to me was that there were two receiving aerials -
one half way up the mast, and one near the top. It was the top one that
was normally in use - and the lower one was a standby (and they had
switched to it).

What had happened was that the fog had caused a sudden change in the
temperature of the air and on its density, and this had led to an
unstable ducting effect, which in turn had severely affected the
'high-up' path of propagation. Lower down had been less disturbed.


Interesting.

Bill
  #5  
Old September 22nd 18, 05:17 PM posted to uk.tech.digital-tv
Mark Carver[_2_]
external usenet poster
 
Posts: 612
Default Reception problems during heavy rain?

On 21/09/2018 09:01, Ian Jackson wrote:
In Seahouses, while watching (analogue) TV one warm evening, a bank of
dense fog rolled in off the sea. It became increasingly apparent that
there was a growing amount of multipath ghosting on the picture. It
steadily got worse and worse, until the picture was barely viewable -
then after a momentary break, it suddenly became OK again.

The explanation given to me was that there were two receiving aerials -
one half way up the mast, and one near the top. It was the top one that
was normally in use - and the lower one was a standby (and they had
switched to it).

What had happened was that the fog had caused a sudden change in the
temperature of the air and on its density, and this had led to an
unstable ducting effect, which in turn had severely affected the
'high-up' path of propagation. Lower down had been less disturbed.

So if fog can cause this sort of effect, can rain do the same -
especially if it is sudden and torrential?


There were indeed two Tx trough aerials at Chatton, you can see them
here (in a picture taken by Bill)

http://tx.mb21.co.uk/gallery/gallerypage.php?txid=1082&pageid=915

Chatton had no alternative RBS standby feed transmitter, so it made
sense to have a diversity system looking at Pontop I presume ?

I've seen the same from Hannington when thunderstorms used to approach
from the south. The Rowridge feed signal would similarly go all
'ghosty', before the RBS feed from Crystal P would cut in.

--
Mark
Please replace invalid and invalid with gmx and net to reply.
  #6  
Old September 22nd 18, 05:20 PM posted to uk.tech.digital-tv
Mark Carver[_2_]
external usenet poster
 
Posts: 612
Default Reception problems during heavy rain?

On 22/09/2018 16:17, Mark Carver wrote:

There were indeed two Tx trough aerials at Chatton

^^^^

Doh ! Rx, not Tx of course, as you were........

--
Mark
Please replace invalid and invalid with gmx and net to reply.
  #7  
Old September 22nd 18, 07:24 PM posted to uk.tech.digital-tv
Bill Wright[_3_]
external usenet poster
 
Posts: 3,601
Default Reception problems during heavy rain?

On 22/09/2018 16:20, Mark Carver wrote:
On 22/09/2018 16:17, Mark Carver wrote:

There were indeed two Tx trough aerials at Chatton

********************** ^^^^

Doh !* Rx, not Tx of course, as you were........

Now we'll have to have a Tribunal of Inquiry to decide whether it was a
typo or not.

Bill
  #8  
Old September 22nd 18, 06:30 PM posted to uk.tech.digital-tv
Ian Jackson[_7_]
external usenet poster
 
Posts: 273
Default Reception problems during heavy rain?

In message , Mark Carver
writes
On 21/09/2018 09:01, Ian Jackson wrote:
In Seahouses, while watching (analogue) TV one warm evening, a bank
of dense fog rolled in off the sea. It became increasingly apparent
that there was a growing amount of multipath ghosting on the picture.
It steadily got worse and worse, until the picture was barely
viewable - then after a momentary break, it suddenly became OK again.
The explanation given to me was that there were two receiving
aerials - one half way up the mast, and one near the top. It was the
top one that was normally in use - and the lower one was a standby
(and they had switched to it).
What had happened was that the fog had caused a sudden change in the
temperature of the air and on its density, and this had led to an
unstable ducting effect, which in turn had severely affected the
'high-up' path of propagation. Lower down had been less disturbed.
So if fog can cause this sort of effect, can rain do the same -
especially if it is sudden and torrential?


There were indeed two Tx trough aerials at Chatton, you can see them
here (in a picture taken by Bill)

http://tx.mb21.co.uk/gallery/gallerypage.php?txid=1082&pageid=915


I see them!

I've also recalled that I was told that the changeover was not
automatic. The Chatton signal was actually monitored back at Pontop Pike
(which I presume was manned), and someone there threw a big switch to
swap the aerial feed.

Chatton had no alternative RBS standby feed transmitter, so it made
sense to have a diversity system looking at Pontop I presume ?


PP is indeed the only other main English station in the area (and a long
way south at that). Selkirk is over-the-hills-and-far-away, and carries
the Scottish service.

I've seen the same from Hannington when thunderstorms used to approach
from the south. The Rowridge feed signal would similarly go all
'ghosty', before the RBS feed from Crystal P would cut in.


--
Ian
  #9  
Old September 22nd 18, 07:16 PM posted to uk.tech.digital-tv
charles[_2_]
external usenet poster
 
Posts: 936
Default Reception problems during heavy rain?

In article ,
Ian Jackson wrote:
In message , Mark Carver
writes
On 21/09/2018 09:01, Ian Jackson wrote:
In Seahouses, while watching (analogue) TV one warm evening, a bank
of dense fog rolled in off the sea. It became increasingly apparent
that there was a growing amount of multipath ghosting on the picture.
It steadily got worse and worse, until the picture was barely
viewable - then after a momentary break, it suddenly became OK again.
The explanation given to me was that there were two receiving
aerials - one half way up the mast, and one near the top. It was the
top one that was normally in use - and the lower one was a standby
(and they had switched to it).
What had happened was that the fog had caused a sudden change in the
temperature of the air and on its density, and this had led to an
unstable ducting effect, which in turn had severely affected the
'high-up' path of propagation. Lower down had been less disturbed.
So if fog can cause this sort of effect, can rain do the same -
especially if it is sudden and torrential?


There were indeed two Tx trough aerials at Chatton, you can see them
here (in a picture taken by Bill)

http://tx.mb21.co.uk/gallery/gallerypage.php?txid=1082&pageid=915


I see them!


I've also recalled that I was told that the changeover was not
automatic. The Chatton signal was actually monitored back at Pontop Pike
(which I presume was manned), and someone there threw a big switch to
swap the aerial feed.


No, Pontop Pike was not manned, although it was a maintenance team base.


Chatton had no alternative RBS standby feed transmitter, so it made
sense to have a diversity system looking at Pontop I presume ?


PP is indeed the only other main English station in the area (and a long
way south at that). Selkirk is over-the-hills-and-far-away, and carries
the Scottish service.


I think there was a reasonable signal from Bilsdale around.

I've seen the same from Hannington when thunderstorms used to approach
from the south. The Rowridge feed signal would similarly go all
'ghosty', before the RBS feed from Crystal P would cut in.


--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle
  #10  
Old September 21st 18, 02:27 PM posted to uk.tech.digital-tv
Terry Casey[_2_]
external usenet poster
 
Posts: 965
Default Reception problems during heavy rain?

In article , harrogate3
@ntlworld.com says...

Are you still using a group B or have you upgraded to a log
periodic yet? I'm about 26 miles away and the change from a
(supposedly) wideband multibeam to a LP has made a world of
change in signal stability on 32/34 and 56.


You must be a very brave man to doubt the aerial installation
quality of such an accomplished expert in the field as Bill!

--

Terry

---
This email has been checked for viruses by AVG.
https://www.avg.com

 




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