can digital get picture if analog TV is weak? - Page 2

Do you have a question? Post it now! No Registration Necessary

Translate This Thread From English to

Threaded View
Re: can digital get picture if analog TV is weak?



Quoted text here. Click to load it

It's all about syntax - of course there is no such thing as a digital
antenna or a digital microphone for that matter but it is human nature,
especially in Australia to shorthand the language even if it's technically
wrong. Personally I like this charming Australian characteristic.

A so called "digital antenna"  is one that has been designed to receive
those frequencies that are used in Australia for DTV.ie nothing below Ch6
(analog). Mine is a Fraccaro log periodic
http://www.laceys.tv/secure/index.php as is my friend who has absolutely no
analog reception regardless of antenna design array, well not unless he was
willing to put up a 200 foot pole! The Fracarro pulls in 96% signal strength
with similar quality on his Topfield 5000. And here I am a few suburbs away
with perfect line of site with 100%. So this antenna must be doing something
the others don't, all tried by a antenna specialist engineer (not Hills!
etc) who did extensive measurements of signal strength and quality using a
range of antenna designs. So as far as my friend is concerned he is not the
least bit interested in the technical analysis just the excellent results he
has achieved for a $50 antenna that is quite tiny, even the birds don't sit
on it and another $150 for installation and new quad cable etc..




Re: can digital get picture if analog TV is weak?



Quoted text here. Click to load it

Thanks  Stu,  your  a  lone  voice in the  wilderness.  People  are  gulable
when it  comes to this  sort of thing,  Just  say  "digital"  and the  price
goes  up,  The  intrest  intensifies,  and  people  cue up to  be  ripped
off.

The  link that  Phil  posted  [Hi  Phil]  is a  typicial example  of the
rip-off  machine in action.  About  the only thing  you  might  need  is a
better  cableing  system ,  In other words  swap the  cable  for a length of
RG 6,  thats  worth 30 cents a  meter  and  people  like  Dick Smith  sell
for  $3   a meter.  Cos  it's  digital  cable.   and  your away.
                                                                    bassett



Re: can digital get picture if analog TV is weak?



"bassett"
 "Stuart"
Quoted text here. Click to load it



** The link I posted was for the  EXACT   SAME   ANTENNA

-    you   bloody  half- wit !!


http://www.australiandigitaltv.com/accessories/digitalantenna.htm



........  Phil





Re: can digital get picture if analog TV is weak?


Quoted text here. Click to load it

Lone voice?
I said that earlier in the thread:
http://groups.google.com.au/group/aus.electronics/browse_frm/thread/77397d5268a10553/b39e6f3e6c5b435e?hl=en#b39e6f3e6c5b435e

Quoted text here. Click to load it


The link Phil posted (which was my original link in an old thread) is
the exact "digital band" antenna being talked about!
It is *not* an example of "the rip-off  machine in action", it is a
log-periodic digital band antenna, designed just for the digital
channels.

Let me know your PayPal address so I can send you a dollar so you can
buy yourself a clue.

Dave.


Re: can digital get picture if analog TV is weak?



Quoted text here. Click to load it

Save your dollar, he wouldn't know where to buy one.

MrT.



Re: can digital get picture if analog TV is weak?



Quoted text here. Click to load it

Although as Bassett has said, there are a lot of rip-offs out there and
certainly a lot of misinformation about digital antennae systems, there is
some info which is correct.  For example - Anyone from the good old analogue
days (circa 1980's) will recall the Hill's Telray series VHF antennae.  When
I went across to digital very early in the piece my antenna system consisted
of a Telray TL4, a Hills Band 4 UHF antenna (20 or more elements - can't
recall the model number) and a diplexer hooking the two together, fed by
double shielded coax similar but not the same as the current RG6.  The
combination worked quite well for analogue not withstanding the unfixable
ghosting problems in my reception area.

On purchasing a STB I noticed reception of ABC digital (VHF ch 12) was very
flaky and the signal level almost down in the "red" compared to the other
digital channels which were way up the other end of the scale.  It turned
out that after pulling up the specs on the TL4 that it performs very well to
Ch11, where thereafter the gain of the antenna takes a steep dive.  This
along with the original diplexer really knocked the crap out of the signal
level at those frequencies.  Replacing the TL4 with a Hill's DY10 and
upgrading the diplexer totally solved the problem.

There is however a bit more to the story.  Replacing the diplexer also meant
replacing the short lengths of cable between the antennae and the diplexer
with F connectors (replacing saddle clamp connections) and of course fitting
the downlead with an F connector too.

It is recognised within the industry that albeit the digital signal is
relatively robust it isn't completely immune to interference.  Whereas with
analogue we put up with the odd bit of noise on the picture, digital can be
affected to the point of significant pixilation and muting of the audio.
This can be subjectively more annoying than watching a noisy analogue
picture.  Antenna downfeeds and distribution cables installed in close
proximity to power cables, fluoro lighting and some other electrically
"noisy" equipment can degrade the quality of the received digital signal
leading to pixilation and in some cases muting of the audio.  Using a good
quality tri or quad shielded coax and sensible placement of the cable(s) in
relationship to other electrical services can make all the difference to the
quality of the signal the TV or STB receives.

Unfortunately there are a lot of legacy analogue antenna systems out there.
Some suitable for digital, some not.  Blocks of flats with amplified
distribution systems designed purely for analogue are typically a nightmare
for digital as only the designated analogue channels are amplified and
equalised, leaving the intervening digital channels with level and
equalisation problems.  Likewise there are some houses out there with a good
old ch2, 7, 9 antenna with a 300 ohm balance ribbon feed.  With the
exception of SBS they are probably getting by with adequate analogue
reception but lets face it, the antenna has probably seen 30+ years of life
and is well and truly overdue for replacement.  The sad part is the owner
will be quite prepared to fork out $4k on a new plasma or LCD TV but won't
spend a couple of hundred bucks getting the antenna system replaced.

Cheers,
Alan

 



Re: can digital get picture if analog TV is weak?


On Aug 7, 1:33 pm, "Alan Rutlidge"
Quoted text here. Click to load it

Unfortunately I'm still having issues with interference after trying
all the usual recommendations:
- replaced all my cabling to quad shield RG6 and F connectors, even
from the wall outlet to the TV.
- switched to a new higher gain antenna to get better signal strength
- checked my mains earthing
- connected the antenna to its own earth stake.
- made sure the cabling was not near any other cables
- and finally switched antenna's yet again to a log-periodic type
(that reduced the number of drop-out's very significantly)

But alas I still get the occasional drop-out due to some external
influence (not local appliance switching in my house, although that
does it too), and of course due to MrMurphy it's always right at a key
point in a show. Losing the picture for a second is ok, but the audio
pop is really annoying.

But at least it's down to a very manageable level now.

Dave.


Re: can digital get picture if analog TV is weak?



"David L. Jones"


Quoted text here. Click to load it



**  Some STBs produce occasional huge audio pops ( like the TEAC DVB-300)
while others are near silent when a burst interference causes the pic to
freeze.

However, an audio pop could be nothing to do with the STB but rather a
result of the same RF burst getting into the audio earth wiring due to the
existence of ground loops.

Try installing an antenna isolator before the STB.




.......  Phil
















Re: can digital get picture if analog TV is weak?


Quoted text here. Click to load it

I've tried 3 different STB's and all are pretty much the same with the
interference and the popping. Guess I didn't get lucky.

Quoted text here. Click to load it

Will do, thanks Phil.
A quick search doesn't turn up much though, know where I can get one?

Thanks
Dave.


Re: can digital get picture if analog TV is weak?



"David L. Jones"
 Phil Allison
Quoted text here. Click to load it


 **  K-Mart used to sell 'em.

   Not impossible to wind your own iso-balun.




.......   Phil



Re: can digital get picture if analog TV is weak?



Quoted text here. Click to load it

Albeit I think I've just about solved all my digital TV reception issues, it
is still far from perfect. :-(
AFAIK in Perth the digital transmitters are not running at full power
(apparently to reduce interference) to older analogue sets and analogue VCRs
with less than perfect tuners.  When and if the analogue services are shut
down the digital transmitters will be allowed to run at full power.  This
should improve the signal to noise ratio and hopefully resolve some
reception problems.  Having said that, too much signal level can be a
problem as well.  Attenuating the signal at the wall outlet will not only
reduce the signal level to an acceptable one, but reduce the interfering
noise by the same amount.

The problem with RF is it isn't a totally predictable science.  Take mobile
phone coverage as an example.  There are too many variables which influence
the propagation of the signal to be totally sure of the outcome.  Add
external interferences (natural and man made) and you have a cocktail of
situations which can lead to problems.  And of course there are the
variations in tuners from very good to bloody woeful.  No wonder Joe Average
is confused.  If you haven't already visited the DTV forum it might be worth
your while for advice (both good and bad).  http://www.dtvforum.info/ It
isn't the definitive answer to all your questions, but at least it's a start
and there are some knowledgeable bods there who are willing to share there
expertise.

Cheers,
Alan



Re: can digital get picture if analog TV is weak?



Quoted text here. Click to load it

Try raising or lowering the antenna by 300mm or so. Multipath reflections
might be causing some of your problems.


Re: can digital get picture if analog TV is weak?


Quoted text here. Click to load it

Tried that, no joy.

Thanks
Dave.


Re: can digital get picture if analog TV is weak?



Quoted text here. Click to load it

Crappo. I consider no drop-outs/pixelation to be "good" and *lots* of
drop-outs/pixelation to be "bad".
No signal/picture at all would be "really bad" of course. :-)

Quoted text here. Click to load it

One designed specifically for reception of digital transmission frequencies,
in your area. One with a suitable feed co-ax and also suitable connections
etc.

Quoted text here. Click to load it

Sure they do, as defined.

Quoted text here. Click to load it

So you can view Ch31/community access TV? :-(

MrT.




Re: can digital get picture if analog TV is weak?



Quoted text here. Click to load it

  I  don't think  you have idea,  just  how  digital  works.  With  digital
you  get a picture or  you  don't. it's that  simple.  No  snow,  no noise,
etc.  also  there is  no  need  for   a mast head  amp,  EVER.  regardless
of  what  your  installer  might tell you.
  Digital   works  with a  multi-layer of  signals,  once the  signal is
transmitted , it's  picked  up  by the   forward error  correction, [FEC]
in the receiver  and the  best  signals are  selected  and  sent to the
tuner   Most  common   configuration  is  3/4.  From the  four  signals
sent  it  selects  three,  If it  can't  find  three  it  simply  shuts
down .  You  might  get  some  pixallation  in heavy  rain,  this  happens
simply  because  for a  few  millie-seconds  it  can't   access  the  signal
requirements,  If  it  continues  it  simply  shuts  down, until  it  can
work as  it  should.
Quoted text here. Click to load it

  There is  no  differance between  antenna  types,  they  work or  they
don't. it;'s as  simple as that.   In  some  situations plan old  "rabbit"
ears will  work, or a  coat hanger,  and there's  nothing  digital about
them,

Quoted text here. Click to load it

 examples  please

Quoted text here. Click to load it
  Not  in   country  area's  mate.
                                                          bassett



Re: can digital get picture if analog TV is weak?


Quoted text here. Click to load it

You really don't get it do you "Basset"?

I agree with MrT. How often you get drop-out's effectively determines
how good or bad a digital TV reception you've got. Lots of drop-outs
is certainly "worse" than no drop-outs. Yes it's still digital, but
that's not the point.

Quoted text here. Click to load it

*yawn*

Quoted text here. Click to load it

You really don't get it do you "Basset"?
A "digital" antenna designed just for the digital TV bands of interest
is certainly a different "type" of antenna than say an analog Yagi or
rabbit ears.

Quoted text here. Click to load it

*yawn*
Give up dude.

Dave.


Re: can digital get picture if analog TV is weak?



"bassett"

Quoted text here. Click to load it


** This next bit is hysterical .......


Quoted text here. Click to load it


**  Wow  -  not even with 200 metres of co-ax after the antenna ....


Quoted text here. Click to load it


**   Hmmmmm  -   just like the TV ad says :

Its the BITS  that John West rejects that make the TUNA  work best  ....


Quoted text here. Click to load it


**  ROTFL   !!!..

Everyone knows that  2 out of  3 ain't bad   !!!


Quoted text here. Click to load it


**  The connection with " pixies "  here is getting very strong.

  " bassett " is chasing them all over the damn place   !!!!!




.......   Phil



Re: can digital get picture if analog TV is weak?



Quoted text here. Click to load it
digital

Funny then that I have a digital STB and a digital PVR that both give
picture drop-outs on occasion.
And I am in a good signal area. My friend who also has a STB and PVR suffers
*far* worse problems.

I suggest it is YOU who has no idea!

Quoted text here. Click to load it

Or you are! :-)

Quoted text here. Click to load it

Pity you can't read the definition given, or simply can't understand it.
But I am indeed envious if you live in a rural area and *never* get any
signal problems, especially with an "old coat hanger"! :-)

Quoted text here. Click to load it

Others have already posted examples. Have you looked at those yet?

MrT.



Re: can digital get picture if analog TV is weak?



Quoted text here. Click to load it

This much is correct.

Quoted text here. Click to load it

Total rubbish. In a marginal area a GOOD low noise amplifier at the
Antenna
will give better reception as with any other form of transmission
system.
It must have a very low noise figure and enough gain to make up for
any
feedline loss and splitter losses between the antenna and the
receiver.
Lots of gain is not better but an amplifier can make an otherwise
unreceivable
signal watchable. There is a requirement that there be a carrier to
noise
ratio of at least 19+ dB at the antenna to receive DVB COFDM
transmissions
with a 23Mb/s data rate.

bassett also wrote....

Quoted text here. Click to load it

This is the most hysterically funny explanation of how digital works
that I
have ever seen. It just proves how clueless bassett is about things
digital.

Firstly there are not 4 layers of anything transmitted. The
transmitted
signal used for terrestrial transmission in Australian standard
digital
consists of either 2K (some 1700 carriers) or 8K (some 6000 carriers)
in quadrature each modulated with 64 QAM (Quadrature Amplitude
Modulation) giving a stream data rate of 23.052768 Mbits/S with our
normal FEC and guard interval.
The use of FEC is a method of transmitting extra bits with the wanted
stream MPEG data to make it more rugged.
The FEC is not in the receiver it's transmitted as extra data bits in
the
stream that allow reconstruction of damaged packets in the receiver.
What 3/4 FEC means is that for every 3 actual bits of data an extra
bit
is transmitted as FEC. In other words for every wanted 3 bits of
information
4 are transmitted. NOT 4 signals only one with extra information.

Small corruptions of the stream data will not cause pixellation as
the
FEC allows the damage to the data to be corrected and no visible
degradation is seen. If the data is corrupted more than the FEC being
transmitted is capable of correcting then either pixellation will
occur
or the decoding will fail.

If high values of FEC are transmitted such as 1/2 where every bit in
the stream is transmitted twice there is obviously more correction
available but at the penalty of loss of wanted data rate.

In particular on satellite transmissions FEC values of 1/2, 2/3 or 3/4
are
usually used especially 1/2 or 2/3 where small dishes are being
used for reception.

The more robust forms of FEC are not generally used in terrestrial
digital transmissions as there is a need for the highest possible
data rate to be able to transmit HD and SD at once in the same stream.


Re: can digital get picture if analog TV is weak?



Quoted text here. Click to load it

Whatever,,
 But it  strange  that all the experts  are  having  trouble  and all  the
dickheads  have  perfect  reception.
                                                                         bassett


Site Timeline