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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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  #21  
Old January 30th 18, 01:34 PM posted to uk.tech.digital-tv
Woody[_5_]
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Posts: 1,830
Default How to identify a good (low-loss) aerial lead


"Bill Wright" wrote in message
news
On 29/01/2018 21:04, Vir Campestris wrote:
On 28/01/2018 21:48, NY wrote:
And I'll get a good 3-way splitter so I can feed my PC's two
tuners as well as the TV; that's a much better solution that
buying a second 2-way splitter and cascading them


Bill will comment on this, but it sounds to me as if an amp would
help here. A decent splitter-amp at the socket driving the long
cable and the two PC tuners.


Well yes, but in the absence of information re the incoming signal
levels, we* have to advise that a passive splitter is tried first.
If problems arise, a one-in one-out 12dB amp before the splitter is
likely to provide a healing balm.

This leads me to philosophise or at least mumble incoherently into
my beard (thus disturbing my badger) as I sit in the lavatory. From
time to time people appear here requesting help or information about
their terrestrial TV reception. Leaving aside the fact that they
should by rights put themselves in the hands of their local aerial
installer (all members of this esteemed profession being as honest
as the day is long and enormously knowledgeable) this does give us a
problem. Why I approach a dwelling with a TV reception problem I am
clocking the local topography, and I have knowledge of the relevant
transmitters. At the house I squint at the aerial, if it is visible.
In the house I look at the signal presented to the main TV set,
using an analyser. I am then likely to clamber laboriously on the
roof ("Are you sure you're all right [at your age] Mr Wright?" in
order to measure the field strength. The I sometimes have to heave
my moribund corpus into the loft. Finally I have some sort of idea
of what's up (apart from my blood pressure).

But these requests for help on this newsgroup! Glory be! The range
of feasible local field strength is something like 60dB. The aerial
could be anything at all; the cable likewise. All we can do is make
a stab in the dark. I really don't like to join in these highly
speculative guessing games.

Bill

*Royal we



For the record a good quality 9dB ProCeption amp (loved by William, on
the bog or not) intended for external use is readily available from
Toolstation.

(Dons flameproof suit for using the full-length name - and I'm not his
mother!)


--
Woody

harrogate3 at ntlworld dot com


  #22  
Old January 30th 18, 07:33 PM posted to uk.tech.digital-tv
Bill Wright[_3_]
external usenet poster
 
Posts: 2,304
Default How to identify a good (low-loss) aerial lead

On 30/01/2018 13:34, Woody wrote:

For the record a good quality 9dB ProCeption amp (loved by William, on
the bog or not) intended for external use is readily available from
Toolstation.

(Dons flameproof suit for using the full-length name - and I'm not his
mother!)



Get used to being called Andy Pandy from now on.
Bill
  #23  
Old January 30th 18, 08:45 PM posted to uk.tech.digital-tv
Woody[_5_]
external usenet poster
 
Posts: 1,830
Default How to identify a good (low-loss) aerial lead


"Bill Wright" wrote in message
news
On 30/01/2018 13:34, Woody wrote:

For the record a good quality 9dB ProCeption amp (loved by William,
on
the bog or not) intended for external use is readily available from
Toolstation.

(Dons flameproof suit for using the full-length name - and I'm not
his
mother!)



Get used to being called Andy Pandy from now on.



Begger, I missed that one.

Any chance of a truce?



--
Woody

harrogate3 at ntlworld dot com


  #24  
Old January 30th 18, 11:52 PM posted to uk.tech.digital-tv
Bill Wright[_3_]
external usenet poster
 
Posts: 2,304
Default How to identify a good (low-loss) aerial lead

On 30/01/2018 20:45, Woody wrote:

Any chance of a truce?


OK I'll agree to a truce.
Bill
  #25  
Old January 31st 18, 11:04 AM posted to uk.tech.digital-tv
NY
external usenet poster
 
Posts: 1,260
Default How to identify a good (low-loss) aerial lead

"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?



Another thing occurs to me. A lot of consumer equipment (TVs, set top boxes,
DVB USB decoders) has tuning menus which quote "signal strength" and "signal
quality" - sometimes as a crude unlabelled bar from which you can infer an
approximate percentage, sometimes with actual figures though no units.

I presume that you cannot compare corresponding readings from two different
brands of device (and maybe not even between different models of the same
brand). However if you use the *same* device in different situations (eg
with different flyleads, with/without aerial splitter and/or amplifier) you
can get a *rough* estimate of how these affect the strength and quality of
the signal, as long as you don't infer that twice the figure is twice as
good.

What is "signal quality" a measure of? Is it essentially the amount of
error-correction that is necessary to overcome multi-path, interference from
neighbouring transmitters and interference from devices that shouldn't even
be producing transmissions in the UHF band?

As will all things digital, I imagine that providing the signal quality is
above some threshold level, any increase beyond that will have no
perceivable benefit - so statements like "I've increased the signal quality
from 67% to 73% so you'll get a better picture" is a load of ******** if the
device's digital cliff is at 30%.

Since I only have consumer equipment, and not professional meters, I can
only go by the figures that my DVB-T USB device gives, and I've established
the sort of level that produces a good, glitch-free picture at my present
house for the various multiplexes (bearing in mind that different muxes have
different powers and that attenuation will vary with UHF channel), so I can
compare these with readings at the new house with various setups (eg device
plugged directly into wall socket, device into wall socket via 2-way
splitter, device connected directly or via splitter on the end of a flylead
of the required length).

I'm approaching it on a semi-scientific basis: change one variable at a time
and see how the results change, both numerically and qualitatively (ie do I
start getting glitches).

I will be highly amused to see what the effect of my dreaded "10m of white
string" cable is :-) I will *not* be using it again - except for tying up
the raspberry canes in the garden. I'll be buying a proper air-gap
dielectric cable, the shortest that will do the job, on a sale/return basis,
from my local TV shop (who originally upgraded the ancient group K aerial
for analogue to a wideband aerial for digital): maybe I'll get them to make
up a cable to their professional high standards.

I like to *try* to solve technical problems myself, but I'm not too proud to
ask for professional help - preferably from a reputable local trader rather
than a large chain store staffed by patronising but clueless morons :-) And
anything that involves going up ladders is definitely something I won't
touch.

  #26  
Old January 31st 18, 11:47 AM posted to uk.tech.digital-tv
Peter Duncanson
external usenet poster
 
Posts: 4,244
Default How to identify a good (low-loss) aerial lead

On Wed, 31 Jan 2018 11:04:17 -0000, "NY" wrote:

"NY" wrote in message
news:[email protected] co.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?



Another thing occurs to me. A lot of consumer equipment (TVs, set top boxes,
DVB USB decoders) has tuning menus which quote "signal strength" and "signal
quality" - sometimes as a crude unlabelled bar from which you can infer an
approximate percentage, sometimes with actual figures though no units.


My Samsung TVs display "Bit error level" rather than "Quality".

I assume that "Bit error level" is the same as, or related to, "Bit
Error Rate":
https://en.wikipedia.org/wiki/Bit_error_rate

"Quality" will be the inverse of "error rate(or level)", i.e. max
quality = zero errors

I presume that you cannot compare corresponding readings from two different
brands of device (and maybe not even between different models of the same
brand). However if you use the *same* device in different situations (eg
with different flyleads, with/without aerial splitter and/or amplifier) you
can get a *rough* estimate of how these affect the strength and quality of
the signal, as long as you don't infer that twice the figure is twice as
good.

What is "signal quality" a measure of? Is it essentially the amount of
error-correction that is necessary to overcome multi-path, interference from
neighbouring transmitters and interference from devices that shouldn't even
be producing transmissions in the UHF band?

As will all things digital, I imagine that providing the signal quality is
above some threshold level, any increase beyond that will have no
perceivable benefit - so statements like "I've increased the signal quality
from 67% to 73% so you'll get a better picture" is a load of ******** if the
device's digital cliff is at 30%.

Since I only have consumer equipment, and not professional meters, I can
only go by the figures that my DVB-T USB device gives, and I've established
the sort of level that produces a good, glitch-free picture at my present
house for the various multiplexes (bearing in mind that different muxes have
different powers and that attenuation will vary with UHF channel), so I can
compare these with readings at the new house with various setups (eg device
plugged directly into wall socket, device into wall socket via 2-way
splitter, device connected directly or via splitter on the end of a flylead
of the required length).

I'm approaching it on a semi-scientific basis: change one variable at a time
and see how the results change, both numerically and qualitatively (ie do I
start getting glitches).

I will be highly amused to see what the effect of my dreaded "10m of white
string" cable is :-) I will *not* be using it again - except for tying up
the raspberry canes in the garden. I'll be buying a proper air-gap
dielectric cable, the shortest that will do the job, on a sale/return basis,
from my local TV shop (who originally upgraded the ancient group K aerial
for analogue to a wideband aerial for digital): maybe I'll get them to make
up a cable to their professional high standards.

I like to *try* to solve technical problems myself, but I'm not too proud to
ask for professional help - preferably from a reputable local trader rather
than a large chain store staffed by patronising but clueless morons :-) And
anything that involves going up ladders is definitely something I won't
touch.


--
Peter Duncanson
(in uk.tech.digital-tv)
  #27  
Old January 31st 18, 12:32 PM posted to uk.tech.digital-tv
Bill Wright[_3_]
external usenet poster
 
Posts: 2,304
Default How to identify a good (low-loss) aerial lead

On 31/01/2018 11:04, NY wrote:

Another thing occurs to me. A lot of consumer equipment (TVs, set top
boxes,
DVB USB decoders) has tuning menus which quote "signal strength" and
"signal
quality" - sometimes as a crude unlabelled bar from which you can infer an
approximate percentage, sometimes with actual figures though no units.

I presume that you cannot compare corresponding readings from two different
brands of device (and maybe not even between different models of the same
brand). However if you use the *same* device in different situations (eg
with different flyleads, with/without aerial splitter and/or amplifier) you
can get a *rough* estimate of how these affect the strength and quality
of the signal, as long as you don't infer that twice the figure is twice
as good.


Well, not even with that proviso. Some of these signal strength and
quality gauges have a scale that is very heavily compressed at one end
or the other, sometimes even to the extent that anything above a reading
derived from a signal that could only sensibly be classed as mediocre
will be at the end stop, so improvement of the signal will not show any
improvement. It is very interesting to observe the signal indicators on
a domestic receiver and gradually vary the strength of the incoming
signal by means of a variable attenuator. It is even more interesting to
hold the signal steady and gradually vary the signal/noise ratio (and
thus BER) by means of a noise generator. The readings from the receiver
are likely to be nonsensical.

These comments do not apply universally; some receivers give quite
useful readings.

As we discovered recently, receivers confronted with a signal they don't
understand due to the manufacturer or the transmission people not
sticking to the DVB spec, might have the quality bar shooting up and
down like a whore's drawers.


As will all things digital, I imagine that providing the signal quality is
above some threshold level, any increase beyond that will have no
perceivable benefit - so statements like "I've increased the signal quality
from 67% to 73% so you'll get a better picture" is a load of ******** if
the
device's digital cliff is at 30%.


No but it's always good to improve the signal quality if there is little
cost, even if it's above threshold, in case of occasional CCI or whatever.

Bill
  #28  
Old January 31st 18, 03:12 PM posted to uk.tech.digital-tv
Woody[_5_]
external usenet poster
 
Posts: 1,830
Default How to identify a good (low-loss) aerial lead


"NY" wrote in message
o.uk...
"Bill Wright" wrote in message
news
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.


Ha ha

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


Many thanks for taking the trouble to write that very useful and
informative article.

The short length of cable that the TV installation people supplied
between wall socket and PVR is one that they made up: a length of
type A or D (it had semi-airspaced dialectric - couldn't see whether
there was any foil tape) which had been stripped at the ends and had
plugs that threaded onto the outer insulation. That cable,
admittedly only about 1 metre long, gives near perfect results on
all multiplexes. It is thick and stiff (oo, er).

My long 10 metre length of el-cheapo has moulded plugs (so I've no
idea what the dialectric is like) and it's much thinner. It gives
good reception on BBC channels (PSB1, UHF 26 on Bilsdale) but
frequent blockiness on ITV and CH4 (PSB2, UHF 29 on Bilsdale). Given
that both multiplexes are the same power and are very close in
frequency, it's odd that one is so much better than another. HD
channels (PSB3, UHF 23) are atrocious; is DVB-T2 more or less
tolerant of weak signal? COM7 and COM8 are non-existent, to the
extent that if I rescan with that cable in situ, those channels are
not even found. Like I said, that cable is 100% crap.

I'll certainly be buying a new length of cable - probably needs to
be about 5m with the TV in the new position that SWMBO has put it
(which *is* a better place). And I'll get a good 3-way splitter so I
can feed my PC's two tuners as well as the TV; that's a much better
solution that buying a second 2-way splitter and cascading them :-)
Admittedly that setup works fine at our present house (a 2-way
splitter fitted by the aerial fitter to feed two rooms and my own
dirt-cheap splitter to feed both tuners from the same downlead), but
where we'll be living from next week has a slightly weaker signal
(*).

When we find a house of our own (we've sold our house but the one we
were interested in fell through so we're staying at my parents'
holiday cottage to avoid losing our sale) it will probably be in
Knaresborough so we'll have a choice of Emley or Bilsdale, and
therefore Leeds or Newcastle local news.



(*) Present house is 21 miles and has 74 dBuV/m whereas new house is
25 miles and 61 dBuv/m - using Charles Macfarlane's JavaJive.
Present has a bit of land encroaching into the lower half of the 60%
Fresnel zone, whereas new place has no obstructions until the last
few hundred yards when a hill gets in the way and it looks as if we
only see the upper half of the Fresnel zone, with virtually no lower
half or line of sight :-(


You are going to have great fun in Knaresbro'. As it is on a selection
of hills and deep valleys you might get Bilsdale, Emley, both, or nowt
depending where you live - even Belmont or Hayshaw Head for that
matter. Unfortunately for much of the area if you are on high Bilsdale
is line of sight and almost exactly the opposite direction to Emley.
What is more Emley uses 32/34/41/44/47/48/51/52 and LTV on 55:
Bilsdale as you well know is 23/26/29/31/37/40/43/46 so automatic
tuning will have a field day with the interleaving! It might not work
properly even if your TV has regional selection capability. Manual
tuning of course overcomes the issue.

Never mind - we have good, very fast, and reliable VM cable round here
if you need an option!



--
Woody

harrogate3 at ntlworld dot com


  #29  
Old February 1st 18, 08:23 AM posted to uk.tech.digital-tv
Indy Jess John
external usenet poster
 
Posts: 1,283
Default How to identify a good (low-loss) aerial lead

On 31/01/2018 11:04, NY wrote:

Another thing occurs to me. A lot of consumer equipment (TVs, set top boxes,
DVB USB decoders) has tuning menus which quote "signal strength" and "signal
quality" - sometimes as a crude unlabelled bar from which you can infer an
approximate percentage, sometimes with actual figures though no units.

Some years ago, just prior to the Digital switch-over, I was given a
Maplin's voucher for Christmas. I had a CRT analogue TV at the time, so
I spent the voucher on a satellite dish and a set-top box.

Next door has a Sky dish, so I measured its angle relative to the house
wall, and mounted my dish at the same angle, then made an approximate
guess at the vertical angle (bearing in mind I was comparing next door's
oval dish with my round one).

I wasn't too far out though because when I connected the set-top box to
the dish and TV I got a picture on the box's default channel. I then
set the menu to display the signal quality and put a mirror in place so
I could adjust the dish and see the results on the TV screen through the
window. I then did tiny adjustments left-right and up-down until the
strength and quality bars gave the best lengths and tightened everything up.

It might not be perfect according to a professional satellite finder,
but it had proved to be good enough ever since.

Jim
  #30  
Old February 1st 18, 08:53 AM posted to uk.tech.digital-tv
Woody[_5_]
external usenet poster
 
Posts: 1,830
Default How to identify a good (low-loss) aerial lead


"Indy Jess John" wrote in message
...
On 31/01/2018 11:04, NY wrote:

Another thing occurs to me. A lot of consumer equipment (TVs, set
top boxes,
DVB USB decoders) has tuning menus which quote "signal strength"
and "signal
quality" - sometimes as a crude unlabelled bar from which you can
infer an
approximate percentage, sometimes with actual figures though no
units.

Some years ago, just prior to the Digital switch-over, I was given a
Maplin's voucher for Christmas. I had a CRT analogue TV at the
time, so I spent the voucher on a satellite dish and a set-top box.

Next door has a Sky dish, so I measured its angle relative to the
house wall, and mounted my dish at the same angle, then made an
approximate guess at the vertical angle (bearing in mind I was
comparing next door's oval dish with my round one).

I wasn't too far out though because when I connected the set-top box
to the dish and TV I got a picture on the box's default channel. I
then set the menu to display the signal quality and put a mirror in
place so I could adjust the dish and see the results on the TV
screen through the window. I then did tiny adjustments left-right
and up-down until the strength and quality bars gave the best
lengths and tightened everything up.

It might not be perfect according to a professional satellite
finder, but it had proved to be good enough ever since.



You wouldn't have been able to do that with a Sky box - they are
notoriously deaf and slow to respond!


--
Woody

harrogate3 at ntlworld dot com


 




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