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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.

How to identify a good (low-loss) aerial lead



 
 
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  #1  
Old January 27th 18, 09:00 PM posted to uk.tech.digital-tv
NY
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Posts: 1,260
Default How to identify a good (low-loss) aerial lead

My wife wanted me to move the telly to a new position further away from the
aerial socket. I happened to have a 10m aerial lead (with moulded-on Belling
Lee plugs) but I found that reception was very poor: the signal strength
gauge on the TV's tuning menu was noticeably lower and the signal quality
(how ever that is calculated!) was also lower, and almost non-existent for
COM7 and COM8. Reception of channels on the affected multiplexes had more
break-ups and some channels could not be received at all.

Obviously that cable is a load of crap. But how do you identify a good
low-loss cable that doesn't attenuate the signal anywhere across the UHF
spectrum? The duff one was only about 5 mm diameter and was very flexible,
whereas the much shorter cable that the TV already had was about 10 mm
diameter and was very stiff. Is diameter a good indicator? Are there any
brand names that are good or bad?

Assuming that a single TV has good reception, if splitting the signal it
three ways should happen to cause poor reception, is an aerial amplifier
before the splitter likely to help? Again, are there any good and bad
brands?

  #2  
Old January 28th 18, 12:26 AM posted to uk.tech.digital-tv
Bill Wright[_3_]
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Posts: 2,304
Default How to identify a good (low-loss) aerial lead

On 27/01/2018 21:00, NY wrote:
My wife wanted me to move the telly to a new position further away from
the aerial socket. I happened to have a 10m aerial lead (with moulded-on
Belling Lee plugs) but I found that reception was very poor: the signal
strength gauge on the TV's tuning menu was noticeably lower and the
signal quality (how ever that is calculated!) was also lower, and almost
non-existent for COM7 and COM8. Reception of channels on the affected
multiplexes had more break-ups and some channels could not be received
at all.


Those leads lose between 5 and 10dB. Over the years I've made a fortune
because of them.


Obviously that cable is a load of crap. But how do you identify a good
low-loss cable that doesn't attenuate the signal anywhere across the UHF
spectrum? The duff one was only about 5 mm diameter and was very
flexible, whereas the much shorter cable that the TV already had was
about 10 mm diameter and was very stiff.


No, it will be 6 to 7mm.

Is diameter a good indicator?


If you're having a prostate biopsy or a cystoscopy the diameter will be
of great interest to you.

Are there any brand names that are good or bad?


The spec is what matters. In view of your request I've sat up all night
writing an article for you. Total blood sweat and tears it was. Here it is.
http://www.wrightsaerials.tv/article...-quality.shtml



Assuming that a single TV has good reception, if splitting the signal it
three ways should happen to cause poor reception, is an aerial amplifier
before the splitter likely to help?


Yes.

Again, are there any good and bad
brands?


Labgear, Proception, Antiference, Vision, Triax, Televes, Hirshmann,
Fracarro. Basically anything except the ****e sold on eBay and in the
DIY sheds. Have a look at CPC.

Bill
  #4  
Old January 28th 18, 08:32 AM posted to uk.tech.digital-tv
Jeff Layman[_2_]
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Posts: 697
Default How to identify a good (low-loss) aerial lead

On 28/01/18 00:26, Bill Wright wrote:

The spec is what matters. In view of your request I've sat up all night
writing an article for you. Total blood sweat and tears it was. Here it is.
http://www.wrightsaerials.tv/article...-quality.shtml


Very informative article, Bill.

One question - how did you get that strange picture artefact just below
the centre of the Type D cable in Fig2?!

--

Jeff
  #5  
Old January 28th 18, 08:50 AM posted to uk.tech.digital-tv
Brian Gaff
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Posts: 7,100
Default How to identify a good (low-loss) aerial lead

To be honest if there is a rule of thumb here, I've not found one. Some of
the cheapo thin ones can be very good, though often the mechanical strength
is not up to much.

I'm beginning to think that they just buy in any old bits and if it works
well its more luck than good judgment. I had one of those little set top
aerials that looked like little yagis back in the analogue days and thought
it awful, as the lead position was very critical. One day, finding it in the
junk pile, I put a decent bit of coax on it and it was surprisingly good, so
it does make you wonder where the companies get their supplies from.

If somebody could crack the low loss good rejection and good matching for a
flexible cable problem I reckon they would clean up.
Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"NY" wrote in message
o.uk...
My wife wanted me to move the telly to a new position further away from
the aerial socket. I happened to have a 10m aerial lead (with moulded-on
Belling Lee plugs) but I found that reception was very poor: the signal
strength gauge on the TV's tuning menu was noticeably lower and the signal
quality (how ever that is calculated!) was also lower, and almost
non-existent for COM7 and COM8. Reception of channels on the affected
multiplexes had more break-ups and some channels could not be received at
all.

Obviously that cable is a load of crap. But how do you identify a good
low-loss cable that doesn't attenuate the signal anywhere across the UHF
spectrum? The duff one was only about 5 mm diameter and was very flexible,
whereas the much shorter cable that the TV already had was about 10 mm
diameter and was very stiff. Is diameter a good indicator? Are there any
brand names that are good or bad?

Assuming that a single TV has good reception, if splitting the signal it
three ways should happen to cause poor reception, is an aerial amplifier
before the splitter likely to help? Again, are there any good and bad
brands?



  #7  
Old January 28th 18, 02:08 PM posted to uk.tech.digital-tv
Bill Wright[_3_]
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Posts: 2,304
Default How to identify a good (low-loss) aerial lead

On 28/01/2018 13:42, Woody wrote:

Or if you want flexibility - proper RG59.

--



I would argue with you there. We have just got a new caravan and all
the aerial cabling is in RG59. It is so stiff it will even pull the
SMB connector of the back of the radio when the radio is pushed home
in its mount.

WF100 or similar would do just as good or a better job (slightly less
lossy than RG59) and is much more user friendly.



Agreed, although I suppose the expression 'RG59' is interpreted
differently by different manufacturers. There could be super flexible stuff.

Bill
  #8  
Old January 28th 18, 02:10 PM posted to uk.tech.digital-tv
Bill Wright[_3_]
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Posts: 2,304
Default How to identify a good (low-loss) aerial lead

On 28/01/2018 08:32, Jeff Layman wrote:
On 28/01/18 00:26, Bill Wright wrote:

The spec is what matters. In view of your request I've sat up all night
writing an article for you. Total blood sweat and tears it was. Here
it is.
http://www.wrightsaerials.tv/article...-quality.shtml


Very informative article, Bill.

One question - how did you get that strange picture artefact just below
the centre of the Type D cable in Fig2?!


No idea! It was, as they say, 'All right when it left here'!

Bill
  #9  
Old January 28th 18, 02:18 PM posted to uk.tech.digital-tv
Bill Wright[_3_]
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Posts: 2,304
Default How to identify a good (low-loss) aerial lead

On 28/01/2018 08:50, Brian Gaff wrote:
To be honest if there is a rule of thumb here, I've not found one. Some of
the cheapo thin ones can be very good, though often the mechanical strength
is not up to much.


I've seen samples of the thin white flyleads that radiate or receive
like crazy. The problem, I discovered, was that the screen was a piece
of plastic coated with some sort of conductive paint. This is not
tubular, it is a strip, wrapped round to make a tube shape. The
non-conductive side overlaps the conductive side at the join. Obviously
there is no conduction across the join. Although the gap in the screen
is only the thickness of the non-conductive material (probably 0.2mm) it
seems that this is enough for the cable to act as 'leaky feeder'. I
first encountered this stuff in the analogue days. I had complaints that
the picture was reasonable when the flylead was unplugged from the
wallplate, but when it was plugged in the picture was double. The
transmitter was visible from street level, and the fault was of course
pre-echo.

Bill
  #10  
Old January 28th 18, 02:48 PM posted to uk.tech.digital-tv
charles[_2_]
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Posts: 659
Default How to identify a good (low-loss) aerial lead

In article ,
Bill Wright wrote:
On 28/01/2018 08:50, Brian Gaff wrote:
To be honest if there is a rule of thumb here, I've not found one. Some of
the cheapo thin ones can be very good, though often the mechanical strength
is not up to much.


I've seen samples of the thin white flyleads that radiate or receive
like crazy. The problem, I discovered, was that the screen was a piece
of plastic coated with some sort of conductive paint. This is not
tubular, it is a strip, wrapped round to make a tube shape. The
non-conductive side overlaps the conductive side at the join. Obviously
there is no conduction across the join. Although the gap in the screen
is only the thickness of the non-conductive material (probably 0.2mm) it
seems that this is enough for the cable to act as 'leaky feeder'. I
first encountered this stuff in the analogue days. I had complaints that
the picture was reasonable when the flylead was unplugged from the
wallplate, but when it was plugged in the picture was double. The
transmitter was visible from street level, and the fault was of course
pre-echo.


my favourite "unscreened" lead was at a house in Daventry quite close to
what was then the BBC short wave transmitter site. The householder was
suffering serious interfeence to her picture at certain times of the day.
Crownded into her tiny room was myself, someone from the BBC transmitter
site, the local cable system (operated by RR) manager and someone from RR
Head Office . We had seen the interference earlier and it was going to be
5th harmonic of one transmitter or 7th harmonic of another. The tramitter
would be tripped to identify which it was. I'd just connected my spectrum
analyser to the flylead that fed the set, found the signal rather low and
put my lead straight into the wall socket. I then exclaimed out loud "This
lead is losing 25dB!" "Can't be."said the RR local manager. "Why not?" said
his head office boss "Because we only send at +10". At this point the Head
Office man said "Thank you, BBC. we don't need you any more" and we left.

--
from KT24 in Surrey, England
 




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