A Sky, cable and digital tv forum. Digital TV Banter

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » Digital TV Banter forum » Digital TV Newsgroups » uk.tech.digital-tv (Digital TV - General)
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

uk.tech.digital-tv (Digital TV - General) (uk.tech.digital-tv) Discussion of all matters technical in origin related to the reception of digital television transmissions, be they via satellite, terrestrial or cable. Advertising is forbidden, with no exceptions.

Recommended Makes Of Chimney Fixings for Terrestrial Aerial



 
 
Thread Tools Display Modes
  #1  
Old September 23rd 15, 10:08 AM posted to uk.tech.digital-tv
Java Jive[_2_]
external usenet poster
 
Posts: 1,774
Default Recommended Makes Of Chimney Fixings for Terrestrial Aerial

I understand the general principles of how to rig this, but I was
wondering if the riggers here would have any particular make they
swear by.

Note: Up here it can get VERY, VERY windy!
--
================================================== ======
Please always reply to ng as the email in this post's
header does not exist. Or use a contact address at:
http://www.macfh.co.uk/JavaJive/JavaJive.html
http://www.macfh.co.uk/Macfarlane/Macfarlane.html
Ads
  #2  
Old September 23rd 15, 02:36 PM posted to uk.tech.digital-tv
Bill Wright[_2_]
external usenet poster
 
Posts: 9,381
Default Recommended Makes Of Chimney Fixings for Terrestrial Aerial

Java Jive wrote:
I understand the general principles of how to rig this, but I was
wondering if the riggers here would have any particular make they
swear by.

Note: Up here it can get VERY, VERY windy!


Go for galvanised, welded stuff. Tell me what you're fixing (height,
loading) and the condition of the brickwork and size of chimbley and
I'll tell you what you need.

ATV Sheffield is a good source of info and place to buy.

Bill
  #3  
Old September 24th 15, 12:34 PM posted to uk.tech.digital-tv
Java Jive[_2_]
external usenet poster
 
Posts: 1,774
Default Recommended Makes Of Chimney Fixings for Terrestrial Aerial

Thanks Bill ...

On Wed, 23 Sep 2015 15:36:47 +0100, Bill Wright
wrote:

Java Jive wrote:
I understand the general principles of how to rig this, but I was
wondering if the riggers here would have any particular make they
swear by.

Note: Up here it can get VERY, VERY windy!


Go for galvanised, welded stuff. Tell me what you're fixing (height,
loading) and the condition of the brickwork and size of chimbley and
I'll tell you what you need.


To receive most probably from the local relay with a clear line of
sight just under 5 miles away, 2.6W ERP, Gp B Vertical, though first I
will probably investigate the very faint possibility of the main TX
over the hills and far away, 34 miles, 20kW, also Gp B but Horizontal,
but I'd be amazed if I were actually to get anything. Conveniently,
they're almost in the same direction.

The chimneys are currently being rebuilt, which is why I'd like to do
the job now.

ATV Sheffield is a good source of info and place to buy.


I'll probably investigate Inverness first, as my experience up here of
suppliers south of the border is that the moment you tell them you're
in the Highlands, they double the delivery charges.
--
================================================== ======
Please always reply to ng as the email in this post's
header does not exist. Or use a contact address at:
http://www.macfh.co.uk/JavaJive/JavaJive.html
http://www.macfh.co.uk/Macfarlane/Macfarlane.html
  #4  
Old September 24th 15, 12:40 PM posted to uk.tech.digital-tv
Java Jive[_2_]
external usenet poster
 
Posts: 1,774
Default Recommended Makes Of Chimney Fixings for Terrestrial Aerial

On Thu, 24 Sep 2015 13:34:17 +0100, Java Jive
wrote:

Thanks Bill ...


Oh, and about 10 - 15m above ground.
--
================================================== ======
Please always reply to ng as the email in this post's
header does not exist. Or use a contact address at:
http://www.macfh.co.uk/JavaJive/JavaJive.html
http://www.macfh.co.uk/Macfarlane/Macfarlane.html
  #5  
Old September 24th 15, 02:42 PM posted to uk.tech.digital-tv
Bill Wright[_2_]
external usenet poster
 
Posts: 9,381
Default Recommended Makes Of Chimney Fixings for Terrestrial Aerial

Java Jive wrote:
Thanks Bill ...


To receive most probably from the local relay with a clear line of
sight just under 5 miles away, 2.6W ERP, Gp B Vertical,


Some relays are very directional. The erp figure is the best you might
get! Really, a lot of relays should be specified as 0 to 2.6W erp!

A look at the relevant relay on MB21 might be interesting.

Anyway, you probably ought to go for a grouped 18 element aerial such as
this.

http://www.blake-uk.com/sr-yagi/404-...e-aerials.html

I have known reception of such low powered txs at 5 miles be problematic!

though first I
will probably investigate the very faint possibility of the main TX
over the hills and far away, 34 miles, 20kW, also Gp B but Horizontal,
but I'd be amazed if I were actually to get anything. Conveniently,
they're almost in the same direction.


Sounds like both would be good? But how to combine? Ah there's the rub!


The chimneys are currently being rebuilt, which is why I'd like to do
the job now.


Wait at least four days before fixing a lash kit to new mortar.

ATV Sheffield is a good source of info and place to buy.


I'll probably investigate Inverness first, as my experience up here of
suppliers south of the border is that the moment you tell them you're
in the Highlands, they double the delivery charges.


I don't think Blake charge extra. Have a look. In any case what matters
is how much you pay in total. A local outfit could mark up the goods a
lot more than the extra carriage might be.

Assuming a reasonable chimney with no big overhangs or excessively tall
pots a good fixing for the aerial above, in a very windy region, would
be a nine foot x 1.5" mast. A set of double chimney brackets and lashing
kits, bkts about 2ft apart. Trim the mast if it's too long; no point in
having the aerial too high. But it does need to be well above any smoke
or fumes from the chimney, and also well above interference from the
house (because the field strength will be low).

Low field strength means more risk of 'swamping' type interference
problems including TETRA and 4G, so a grouped ae would be my choice.

I'd seriously consider a low gain masthead amp.

If you do trim the mast save the offcuts for bonfire night. Good for
rocket launchers!

Bill

  #6  
Old September 24th 15, 02:44 PM posted to uk.tech.digital-tv
Bill Wright[_2_]
external usenet poster
 
Posts: 9,381
Default Recommended Makes Of Chimney Fixings for Terrestrial Aerial

Java Jive wrote:
On Thu, 24 Sep 2015 13:34:17 +0100, Java Jive
wrote:

Thanks Bill ...


Oh, and about 10 - 15m above ground.


The chimney? That sounds good. Hope the scaff is still up.
  #7  
Old October 9th 15, 01:24 PM posted to uk.tech.digital-tv
Java Jive[_2_]
external usenet poster
 
Posts: 1,774
Default Recommended Makes Of Chimney Fixings for Terrestrial Aerial

On Thu, 24 Sep 2015 15:42:53 +0100, Bill Wright
wrote:

Anyway, you probably ought to go for a grouped 18 element aerial such as
this.

http://www.blake-uk.com/sr-yagi/404-...e-aerials.html


That is way bigger than any of my neighbours' aerials, and up here
windage is a VERY significant factor. However ...

I have known reception of such low powered txs at 5 miles be problematic!


.... Yes, my own site confirms that the relay is possibly too weak to
give a usable signal at 5 miles.

though first I
will probably investigate the very faint possibility of the main TX
over the hills and far away, 34 miles, 20kW, also Gp B but Horizontal,
but I'd be amazed if I were actually to get anything. Conveniently,
they're almost in the same direction.


Sounds like both would be good? But how to combine? Ah there's the rub!


Well, I'll buy an aerial aimed at the relay, but before finally
mounting it, I'll see what happens when I try and receive the main.

ATV Sheffield is a good source of info and place to buy.


I'll probably investigate Inverness first, as my experience up here of
suppliers south of the border is that the moment you tell them you're
in the Highlands, they double the delivery charges.


I don't think Blake charge extra. Have a look. In any case what matters
is how much you pay in total. A local outfit could mark up the goods a
lot more than the extra carriage might be.

Assuming a reasonable chimney with no big overhangs or excessively tall
pots a good fixing for the aerial above, in a very windy region, would
be a nine foot x 1.5" mast. A set of double chimney brackets and lashing
kits, bkts about 2ft apart. Trim the mast if it's too long; no point in
having the aerial too high. But it does need to be well above any smoke
or fumes from the chimney, and also well above interference from the
house (because the field strength will be low).

[out of original order]

I'd seriously consider a low gain masthead amp.

If you do trim the mast save the offcuts for bonfire night. Good for
rocket launchers!


There are a number of properties very similar to mine in this area.
When first I came to mine, from the thickness of the walls I thought
it older than it actually is, that it dated from times when the cattle
were kept at one end of the building and the people in the other. Then
I realised that this couldn't be, because there was a chimney at
*each* end, and anyway the dwelling was unnecessarily high for this
style of dwelling. In fact, I've since discovered that this reasoning
was correct, and these houses are all much more recent and date from
immediately after WW1 - local land was parceled up into crofts and
the houses built on them to provide livings for returning, newly
demobbed, soldiers. Thus they were built in a hurry, using whatever
was to hand, and completely re-harling the wall the other end from the
proposed aerial siting has shown that the build of the walls and the
mortar in them is not of the first grade of work - for example,
there is no point in completely removing the rendering to expose the
underlying stone, because the original stone work wasn't anywhere near
good enough to justify such expense.

Although the tops of the chimneys have been rebuilt, the rest of them
are as was, so frankly the thought of a 9' mast in the sort of gales
we had last January would be just unthinkable. So many dwellings old
and new were damaged in those gales that local builders are still
repairing them, which is why they've only just come to mine. Many
lost parts of their roofs, many were damaged by falling trees which
often, bitterest of ironies, were planted originally as shelter belts!

Here's a pic, pre-harling, of the rebuilt chimney on the gable end
facing the transmitters, which are over the left shoulder from the
vantage point, around 7 o'clock on a ground plan with 12 o'clock being
the direction in which the shot was taken. For scale, the part of the
chimney pot above the coping will be about 68cm high:

www.macfh.co.uk/Temp/HouseWork.jpg (2MB)

In summary, most of the aerials around here are just large enough and
no more, and hunkered down on very short masts, sometimes even well
below the apex of the roof, so as to be shielded from the wind.

Low field strength means more risk of 'swamping' type interference
problems including TETRA and 4G, so a grouped ae would be my choice.


TETRA is unlikely to be a problem here, it's too remote, and we still
haven't got decent 3G, let alone 4G (nor FTTC come to that)! Although
I was careful to preserve the functionality of the downstairs
chimneys, both fireplaces are walled up, while the upstairs fireplaces
are exposed, but I've allowed the chimneys to be blocked off, because
I can't see anyone ever wanting actually to light a fire in them.
Consequently, chimney smoke is not likely to be a problem for the
present, and if and when I do have open fires, the aerial will be
windward of the prevailing wind direction.

Is an 8" chimney bracket one where the two cables around the chimney
are 8" apart?

Given that there's a 2" coping overhang, I reckon from the ATV site:
8" Mitre Chimney Bracket, possibly 2 and aerial between them
3' Mast thickest guage practically obtainable (I have a section of
scaffolding pole about that length, that was originally used to mount
a satellite dish, but whether a chimney bracket fastening could mount
anything of that diameter, I don't know)

Aerial still to choose. Can you suggest one with less
wind-resistance?
--
================================================== ======
Please always reply to ng as the email in this post's
header does not exist. Or use a contact address at:
http://www.macfh.co.uk/JavaJive/JavaJive.html
http://www.macfh.co.uk/Macfarlane/Macfarlane.html
  #8  
Old October 9th 15, 10:52 PM posted to uk.tech.digital-tv
Bill Wright[_2_]
external usenet poster
 
Posts: 9,381
Default Recommended Makes Of Chimney Fixings for Terrestrial Aerial

Java Jive wrote:

http://www.blake-uk.com/sr-yagi/404-...e-aerials.html


That is way bigger than any of my neighbours' aerials, and up here
windage is a VERY significant factor. However ...


Whether or not an aerial is blown down by the wind is not related to the
size of the aerial. It is dependent on whether or not it's been properly
installed. If you see an aerial that's been damaged by the wind, either
it's very old indeed or it wasn't properly installed.

Sounds like both would be good? But how to combine? Ah there's the rub!


Well, I'll buy an aerial aimed at the relay, but before finally
mounting it, I'll see what happens when I try and receive the main.


Yes, but both would be good. Except you can't combine them.

There are a number of properties very similar to mine in this area.
When first I came to mine, from the thickness of the walls I thought
it older than it actually is, that it dated from times when the cattle
were kept at one end of the building and the people in the other. Then
I realised that this couldn't be, because there was a chimney at
*each* end, and anyway the dwelling was unnecessarily high for this
style of dwelling. In fact, I've since discovered that this reasoning
was correct, and these houses are all much more recent and date from
immediately after WW1 - local land was parceled up into crofts and
the houses built on them to provide livings for returning, newly
demobbed, soldiers. Thus they were built in a hurry, using whatever
was to hand, and completely re-harling the wall the other end from the
proposed aerial siting has shown that the build of the walls and the
mortar in them is not of the first grade of work - for example,
there is no point in completely removing the rendering to expose the
underlying stone, because the original stone work wasn't anywhere near
good enough to justify such expense.

Although the tops of the chimneys have been rebuilt, the rest of them
are as was, so frankly the thought of a 9' mast in the sort of gales
we had last January would be just unthinkable. So many dwellings old
and new were damaged in those gales that local builders are still
repairing them, which is why they've only just come to mine. Many
lost parts of their roofs, many were damaged by falling trees which
often, bitterest of ironies, were planted originally as shelter belts!

Here's a pic, pre-harling, of the rebuilt chimney on the gable end
facing the transmitters, which are over the left shoulder from the
vantage point, around 7 o'clock on a ground plan with 12 o'clock being
the direction in which the shot was taken. For scale, the part of the
chimney pot above the coping will be about 68cm high:

www.macfh.co.uk/Temp/HouseWork.jpg (2MB)

In summary, most of the aerials around here are just large enough and
no more, and hunkered down on very short masts, sometimes even well
below the apex of the roof, so as to be shielded from the wind.


Re-read what I said. Use a 9ft mast because that's the shortest length
you can buy heavy gauge 1.5" masting. Use a set of double chimney
brackets and lashing kits, bkts about 2ft apart. This enormously reduces
the strain on the stack. Trim the mast if it's too long; no point in
having the aerial too high. Remember there's only 7ft above the top

bracket, and you shorten it even more. But it does need to be well above
any smoke or fumes from the chimney. It's corrosion from smoke and fumes
that brings aerials down. If no smoke, you can mount the aerial just
above the stack. But not really close to a pot because it will affect it.

Is an 8" chimney bracket one where the two cables around the chimney
are 8" apart?


No it's a single bracket 8" high. You need a pair of 'double chimney
brackets' mounted 2ft apart.

Given that there's a 2" coping overhang, I reckon from the ATV site:
8" Mitre Chimney Bracket,


No no no. One lashing wire will stress the stack. You must use a double
lashing kit and double bracket pair.

3' Mast thickest guage practically obtainable (I have a section of
scaffolding pole about that length, that was originally used to mount
a satellite dish, but whether a chimney bracket fastening could mount
anything of that diameter, I don't know)


The thickness of the mast is only one factor. The tube wall (gauge) is
important.

The double bracket sets all take scaffold tubes. Scaff tubes are a good
idea, but steel ones are so heavy they bring their own problems. Use
alloy ones.

Regarding the idea of mounting the aerial just above the roof: By far
the strongest winds occur when the wind is blowing onto a pitched roof
and it goes up the roof and at the apex and just above it is like a
hurricane. But three feet higher you are out of that stream and the wind
is much the same as it is at ground level. Mounting an aerial in that
danger zone is asking for trouble.


Aerial still to choose. Can you suggest one with less
wind-resistance?


No. The aerial I recommend is centre mounted. Anything smaller will be
end mounted and thus far more vulnerable. The aerial I recommend was
chosen because it combines good gain and directivity combined with small
windage. Please don't go and buy one of those end mounted 'high gain'
wideband pieces of **** as sold by the DIY shops. If you do I will come
round and rip it down and ram it up your arse. Just accept that I've
been fixing aerials in very windy places for the last 45 years and my
advice is good. Your location is not so exceptional. Try standing on top
of a 20 floor block of flats when it's windy.

Bill


  #9  
Old October 13th 15, 10:06 PM posted to uk.tech.digital-tv
Paul Ratcliffe
external usenet poster
 
Posts: 2,486
Default Recommended Makes Of Chimney Fixings for Terrestrial Aerial

On Fri, 09 Oct 2015 23:52:09 +0100, Bill Wright wrote:

Please don't go and buy one of those end mounted 'high gain'
wideband pieces of **** as sold by the DIY shops. If you do I will come
round and rip it down and ram it up your arse.


If this happens, please can you let me know and sell me a ticket for
the spectacle?
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT. The time now is 11:46 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.SEO by vBSEO 2.4.0
Copyright 2004-2018 Digital TV Banter.
The comments are property of their posters.