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.

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



 
 
Thread Tools Display Modes
  #11  
Old January 28th 18, 06:25 PM posted to uk.tech.digital-tv
Paul Ratcliffe
external usenet poster
 
Posts: 2,486
Default How to identify a good (low-loss) aerial lead

On Sun, 28 Jan 2018 00:26:35 +0000, Bill Wright wrote:

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


Which night though? Seeing as you're wittering on about channel 67 and
analogue TV...
Ads
  #12  
Old January 28th 18, 07:17 PM posted to uk.tech.digital-tv
Bill Wright[_3_]
external usenet poster
 
Posts: 2,448
Default How to identify a good (low-loss) aerial lead

On 28/01/2018 19:25, Paul Ratcliffe wrote:
On Sun, 28 Jan 2018 00:26:35 +0000, Bill Wright wrote:

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


Which night though? Seeing as you're wittering on about channel 67 and
analogue TV...

It was one night in 1987. I'm psychedelic of course, so I knew he'd be
asking the question in the future.

Bill
  #13  
Old January 28th 18, 08:45 PM posted to uk.tech.digital-tv
David Woolley[_2_]
external usenet poster
 
Posts: 550
Default How to identify a good (low-loss) aerial lead

On 27/01/18 21:00, NY wrote:
But how do you identify a good low-loss cable that doesn't attenuate the
signal anywhere across the UHF spectrum?


You don't, because there is no such beast! Even with the good cables
mentioned, 20m of cable will reduce the signal power by almost half on
the higher channel numbers.

(Higher diameters have lower losses. Cable with foamed insulation have
lower losses than ones with solid insulation. Shorter cables have lower
losses.)
  #14  
Old January 28th 18, 08:48 PM posted to uk.tech.digital-tv
NY
external usenet poster
 
Posts: 1,329
Default How to identify a good (low-loss) aerial lead

"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 :-(

  #15  
Old January 29th 18, 12:58 AM posted to uk.tech.digital-tv
Bill Wright[_3_]
external usenet poster
 
Posts: 2,448
Default How to identify a good (low-loss) aerial lead

On 28/01/2018 21:48, NY wrote:

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


Ha ha


After the camera up the arse job the guy said, "That wasn't too bad, was
it?"
I replied, "Let's just say I've decided against my career change. I was
thinking about going on the game."


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.


The digital cliff has much to answer for. In addition, these cheap
cables don't always impedance match the feeder cable so you can get some
very strange effects that vary with frequency. Also, if the flylead is
over-long and the surplus is coiled, the response can vary across the
frequency band as the coil is messed around with. I'm guessing there's
signal transfer out of and back into the cable, thus causing standing
waves or at least response dips.

Another oddity of these cables is that sometimes the molded plugs have
the screen connected at the plug by a single spike on the plug that
pushes into the screen. I don't know why but experimentally fitting
proper plugs can greatly reduce the 'anomalies'.

I had a whole lot of these 1.5m white flyleads bestowed upon me (long
story) so I put a few of them on a stall at the church fair labelled
'Dog leads (small dogs only) 10p'. They sold out.

Another thing. At an 'residential complex', years ago, I made a big
thing of telling them they had to have good quality flyleads, the reason
being that several of the in-house channels unavoidably used channels
also used by a distant but line-of-sight and high powered tx. Signal was
pouring in through the windows (unimpeded by the vertically polarised
metal objects about 6" apart in the window areas). They forgot my good
advice and purchased 1,000 flyleads from a well-known source for 210.
When the problems started the priority, of course, was that egg
shouldn't get on face, so we replaced the flyleads slowly, on demand.

Bill

  #16  
Old January 29th 18, 09:09 AM posted to uk.tech.digital-tv
Brian Gaff
external usenet poster
 
Posts: 7,250
Default How to identify a good (low-loss) aerial lead

Hmm, yes I've seen that stuff plus some kind of weird mesh made from a
mixture of plastic and copper, which is almost as bad. There were some
denser ones that worked well and were still flexible but eventually went at
the earth end of the moulded on plugs.

All very hit and miss.
I recall a respectable looking one with an old Philips VCR that was
completely useless, ie if you put your hand on it you could change the
signal levels going through it.
Brian

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

Blind user, so no pictures please!
"Bill Wright" wrote in message
news
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



  #17  
Old January 29th 18, 12:59 PM posted to uk.tech.digital-tv
Bill Wright[_3_]
external usenet poster
 
Posts: 2,448
Default How to identify a good (low-loss) aerial lead

On 29/01/2018 10:09, Brian Gaff wrote:

I recall a respectable looking one with an old Philips VCR that was
completely useless, ie if you put your hand on it you could change the
signal levels going through it.
Brian


In the early 80s I encountered some very expensive 'professional' UHF TV
modulators that drifted half a channel if you put your hand near them.

Bill
  #18  
Old January 29th 18, 08:04 PM posted to uk.tech.digital-tv
Vir Campestris
external usenet poster
 
Posts: 439
Default How to identify a good (low-loss) aerial lead

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.

Andy
  #19  
Old January 30th 18, 01:07 AM posted to uk.tech.digital-tv
Bill Wright[_3_]
external usenet poster
 
Posts: 2,448
Default How to identify a good (low-loss) aerial lead

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
  #20  
Old January 30th 18, 05:58 AM posted to uk.tech.digital-tv
Johnny B Good[_2_]
external usenet poster
 
Posts: 513
Default How to identify a good (low-loss) aerial lead

On Tue, 30 Jan 2018 02:07:02 +0000, Bill Wright wrote:

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.


In short, it seems to me that you're trying to state that trying to
answer such questions is akin to guessing the length of a piece of
string, sight unseen. :-)

--
Johnny B Good
 




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 11:51 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.