distibution amps (proception?)
Stephen
My in laws have replaced their analogue TV with a digital one. There
is good reception on all channels except ITV1 which freezes or goes
blocky from time to time.
I think this could be one of three things:
1. the aerial: it's on the roof, and I don't want to go up there!
2. the cable. It's old so it's likely to be the brown stuff and as it
runs down the side of the house, it may have been attacked by the sun
and rain over the years.
3. three sockets are fed from the one lead. Could too many joins in
the cable be causing loss.
I don't know which is the culprit, so I guess it is a matter of trying
them one by one until the problem is fixed.
As I understand it, the lead goes from the aerial into the loft, where
the first split occurs and then outside, down the walls.
If I upgrade the cable from the loft down would that help?
What is the correct way to have several sockets off one aerial? Should
each socket have its own feed from a distribution amp? I know
amplification is not the answer to poor reception because you are
amplifying the noise as well as the signal but is it that a
distribution amp only amplifies the signal enough to overcome the
losses of splitting it into several outputs?
I was wondering whether it would be a good idea to connect the three
sockets into a 4-way amp, rather than just daisy chaining them?
There's no power in the loft, so I think the easiest way round this
would be to use one of those amps which has a separate supply that
goes up the lead. I've looked on the internet and see that a company
called "proception" make some of these.
Is proception a good brand?
Or should I not do any of this and get a man to climb on the roof with
a meter and check the aerial is pointing the right way? The fact that
the other channels are good makes me think the aerial is ok.
Thanks,
Stephen.
Paul D Smith
> Or should I not do any of this and get a man to climb on the roof with
> a meter and check the aerial is pointing the right way? The fact that
> the other channels are good makes me think the aerial is ok.
>
> Thanks,
> Stephen.
It's normally helpful if you give the first part of your postcode as that
tells us where approximately you are and, for example, whether the digital
multiplexes might be outside the frequency response of your old analogue
aerial. Where I am in London, we're fine but I know that where my mother
lives, only some digital channels work unless the aerial is changed.
Paul DS
Bill Wright
> Hello,
>
> My in laws have replaced their analogue TV with a digital one. There
> is good reception on all channels except ITV1 which freezes or goes
> blocky from time to time.
I'll leave it to others to suggest various 'short cuts', but my instant
reaction to your tale is that you should replace the whole thing with a
new aerial, distribution amp in the loft, and cables to each point.
Bill
Rick
"Stephen" <ste...@nowhere.com.invalid> wrote in message
news:g5r9f6lejs203a9ch...@4ax.com...
Before you become too involved, it may be something as simple as dodgy fly
lead, Belling Lee connector or outlet plate (if one's fitted) also when is
dso due?. if it hasn't already happened, then when it does the power of the
PSB channels will dramatically improve .
Woody
news:g5r9f6lejs203a9ch...@4ax.com...
There is no harm in using an aerial amp provided it doesn't give
too much gain. Amplified signal noise (provided there is not too
much) will most likely not cause a problem but distortion (for
instance anything that will cause a ghost in analogue) will
destroy digital.
There will be lighting wiring in the loft which (preferably
through a fused spur or similar) is perfectly capable of powering
an amp.
Screwfix do a 4-way distribution amp that can be powered up any
cable.
http://www.screwfix.com/prods/51891/Electrical-Supplies/TV-Range/Amplifiers-Distribution/Labgear-PUM141-S-Screened-Masthead-Amp-4-Way-10dB
You will need a PSU - noted on the page.
Be aware that DTTV is very sensitive to interference. If old-type
brown downlead is in use it will pick up things like passing
traffic ignition interference which will cause freezing and/or
pixelation, what exactly happens depends upon the TV software -
we have a Sharp and rather than show pixelation it blanks the
screen for a second or two. Replacing the cable with PF100 or
similar with its internal foil screen will help enormously.
Also don't be misled by 'a good picture' on all channels. DTTV
works or it doesn't - there is no halfway house. If the TV has an
analogue tuner have a look at that, it will give you a better
idea of the signal strength/quality, and note it is the quality
not so much the strength that matters with digital.
Finally, make sure your serving transmitter has in-band channels.
Some sites transmit one or more muxes out of band so a wideband
aerial rather than a banded one (as with analogue) may be
necessary. Post DSO most sites will transmit in-band as they will
take over existing channels as used by analogue. Look at the
aerial (with bins if necessary) and see if the caps in the end of
the boom are coloured. Black usually indicates wideband, any
other colour may indicate a banded aerial. www.wolfbane.com is a
good site to check which transmitter sites are available and
which should be used and thus which aerial will be needed.
As Bill says, it looks like your best solution would be to
replace the lot - at least you will then be certain.
--
Woody
harrogate three at ntlworld dot com
tony sayer
<ste...@nowhere.com.invalid> scribeth thus
Yes Andy Wade who posts here sometimes designs these:)..
>
>Or should I not do any of this and get a man to climb on the roof with
>a meter and check the aerial is pointing the right way? The fact that
>the other channels are good makes me think the aerial is ok.
>
>Thanks,
>Stephen.
--
Tony Sayer
Stephen
>Before you become too involved, it may be something as simple as dodgy fly
>lead, Belling Lee connector or outlet plate (if one's fitted) also when is
>dso due
I think they have tried a couple of leads, so that rules those out but
I suppose the socket could be at fault, I will have a look, thanks.
Switchover is 2011, central region.
Thanks,
Stephen.
Stephen
<paul_d...@hotmail.com> wrote:
>It's normally helpful if you give the first part of your postcode as that
>tells us where approximately you are and, for example, whether the digital
>multiplexes might be outside the frequency response of your old analogue
>aerial.
Sorry, I didn't know that. They live in DE13, Burton. They have two
analogue aerials. They tried the TV on the other aerial and it was
fine. I realise the two analogue aerials could be different makes and
models so perhaps that proves nothing but the second aerial is not
shared between sockets, so that might be a factor. I didn't realise
that multiplexes could be outside the response of an analogue aerial.
thanks, I am learning something new today.
Thanks,
Stephen.
Stephen
<harro...@ntlworld.spam.com> wrote:
>There will be lighting wiring in the loft which (preferably
>through a fused spur or similar) is perfectly capable of powering
>an amp.
Thanks for the detailed reply. I did consider that but I didn't want
to confuse them any more!
>Screwfix do a 4-way distribution amp that can be powered up any
>cable.
>
>You will need a PSU - noted on the page.
That's the kind of thing I was thinking of, thanks.
>Be aware that DTTV is very sensitive to interference. If old-type
>brown downlead is in use it will pick up things like passing
>traffic ignition interference
Are you saying it picks up interference from spark plugs firing as
they go down the street? I never knew that!
>Replacing the cable with PF100 or
>similar with its internal foil screen will help enormously.
Thanks, I was thinking of doing this.
>Also don't be misled by 'a good picture' on all channels. DTTV
>works or it doesn't - there is no halfway house. If the TV has an
>analogue tuner have a look at that, it will give you a better
>idea of the signal strength/quality, and note it is the quality
>not so much the strength that matters with digital.
The analogue looks fine, in fact they use the analogue to watch ITV
because it is unwatchable on digital.
Thanks for all the help,
Stephen.
Bill Wright
> As Bill says, it looks like your best solution would be to
> replace the lot - at least you will then be certain.
After all, if the cable is perished the aerial must be ready for
replacement.
Bill
Bill Wright
You can see Sutton C from most of the rooftops of Burton, and Lichfield
as well. The ch55 mux is outside Group B but if the aerial and cable,
etc, are otherwise OK it shouldn't matter. If the aerial and cables are
OK I doubt if you'd need an amp; just a passive splitter.
A mate of mine put his own aerial up last summer. He lives in Burton. He
wanted to use an amp because he wanted to combine the satellite box
output, and the aerial had to have a 12dB attenuator on it to cut the
signal down.
Of course you might be in a screened location, in which case forget the
above.
Bill
Peter
Stephen,
Your parents have 2 aerials, they do not have 2 analogue aerials.
I only point this out in case they do go for a new distribution system
- steer clear of aerial installers/firms that advertise/try to sell
Digital Aerials - there ain't no such animal.
--
Cheers
Peter
(Reply to address is a spam trap - pse reply to the group)
Paul Ratcliffe
wrote:
> 3. three sockets are fed from the one lead. Could too many joins in
> the cable be causing loss.
Possibly. More to the point is how are you feeding three sockets from one
lead?
> What is the correct way to have several sockets off one aerial? Should
> each socket have its own feed from a distribution amp? I know
> amplification is not the answer to poor reception because you are
> amplifying the noise as well as the signal but is it that a
> distribution amp only amplifies the signal enough to overcome the
> losses of splitting it into several outputs?
>
> I was wondering whether it would be a good idea to connect the three
> sockets into a 4-way amp, rather than just daisy chaining them?
Daisy chaining is a complete and utter bodge. It will never work properly.
> There's no power in the loft, so I think the easiest way round this
> would be to use one of those amps which has a separate supply that
> goes up the lead. I've looked on the internet and see that a company
> called "proception" make some of these.
>
> Is proception a good brand?
Yes. That would be the cheapest starting point.
> Or should I not do any of this and get a man to climb on the roof with
> a meter and check the aerial is pointing the right way? The fact that
> the other channels are good makes me think the aerial is ok.
Do as Bill said, if the above fails.
Paul D Smith
news:mgraf6tqc1lcbqb3j...@4ax.com...
Below is a "brain dump" of the little I know. I imagine there are a few
mistakes but it will get you started along the right route. Bill Wright has
a good site about this stuff and there are a few others around. if you're a
nerd, this will be interesting and if you're considering a new aerial, it
might stop you getting stung.
TV uses "channels" 21-69. Now a radio signal is a radio signal and doesn't
know whether it's carrying analogue TV (one TV station on the channel) or
digital TV (multiple stations multiplexed (merged together and sharing...) a
channel). So there's no such thing as a "digital" TV aerial - but that
doesn't stop cowboys trying to sell you one!
Now in most areas, only a small "group" of these channels are used so in
London, we use a "group A" aerial which handles approx. 21-35. Then you get
B, C, D and (I may be wrong here) E. A group aerial is a "specialist" and
often preferred but.... There are also W (wideband) which tries to do all
channels (jack of all trade, master of none, avoid unless you need it) and
"Log periodic" which is a totally different design of aerial to the ones you
commonly see but is actually very good at being a wideband, if you have a
strong enough signal.
But there's a slight snag. In London we can squeeze all the analogue and TV
channels into the same group. In most of the country they couldn't so you
have three situations...
1. Watch analogue only using your current aerial
2. Watch analogue and digital now using an aerial which MIGHT work or where
you might need an aerial which also handles the channels CURRENTLY being
used by digital. This is sometimes where those widebands mentioned above
come in, or sometimes TWO group aerials (let's say A & D) might be used,
carefully wired together to provide the channel coverage required without
resorting to a wideband.
3. After analogue switch off in your area, the digital channels are
typically moving to where the analogue channels were so an "old" aerial
might then get all the digital channels - so perhaps you could wait a little
and skip getting a new aerial for part 2!
There are plenty of tables on the web which tell you what channels are
currently, and post digital switchover (DSO) will be used.
Then there's "aerial gain" i.e. how good the aerial is at transferring the
signal from "the ether" into the cable. High gain can sometimes be good
(you live miles from the transmitter, nothing else around) or bad (too close
to the transmitter, or pulling in other more remote transmitters too).
Remember that wideband "master of none"? Well cowboys often compensate for
the poor performance of a wideband (where it's really not needed) by using a
"high gain wideband" - great because they're big monsters and they can
charge the sucker more for the wrong sort of aerial!
So if you get a new aerial, you want to do a little digging to get a rough
idea of what you need (see Bill's e-mail for one) and typically avoid the
"high gain, digital (aka wideband)" aerials (sometimes they're even gold
coloured!) which the cowboys sell to unsuspecting punters.
A little knowledge is a dangerous thing but at least you'll have a chance of
getting a decent picture and not having a monster piece of crap on your
roof.
P.S. CT100/PF100 cable throughout - it's got both a good braided covering
AND solid copper wrap to ensure best quality signal gets from the aerial to
the TV. And avoid joints and use F-connectors (the sort used on satellite
cables) everywhere except where the cable enters the TV (which normally has
to be the "normal TV connector" aka Belling-Lee).
Doctor D
The OP is most likely using Sutton Coldfield (are you receiving West
Midlands regional TV?) on which I still install group B aerials with no
noticeable problems on the C55 multiplex. The problem is unlikely to be
wrong aerial group, more likely aerial fault or deterioration.
The OP may be using Waltham (East Midlands regional TV - aerial points
eastish) in which case to get all muxes he needs to replace his group C/D
aerial with a wideband as even after DSO mux A is on C29 and now they're all
over the place.
Put your address here http://www.dtg.org.uk/industry/coverage.html and click
on "trade view" at the top right.
Java Jive
<ste...@nowhere.com.invalid> wrote:
>
> is good reception on all channels except ITV1 which freezes or goes
> blocky from time to time.
>
> I think this could be one of three things:
>
> 1. the aerial: it's on the roof, and I don't want to go up there!
Then if push comes to shove, you or they'll have to pay someone else
to do so!
It's quite possible that if it is a very old aerial it may not have a
balun - unless the aerial is a log-periodic design, it is desirable
that it should have one.
> 2. the cable. It's old so it's likely to be the brown stuff and as it
> runs down the side of the house, it may have been attacked by the sun
> and rain over the years.
Yes, and as I think someone else pointed out it will be only
single-insulated (outer consisting only of braid), whereas
double-insulated (outer consisting of braid within solid) is
considered desirable as it is held to do a better job of rejecting
electro-magnetic interference.
> 3. three sockets are fed from the one lead. Could too many joins in
> the cable be causing loss.
Not good.
> I don't know which is the culprit, so I guess it is a matter of trying
> them one by one until the problem is fixed.
Or saying that maybe it's time the complete system was given a
complete overhaul, presumably by a pro if no-one wants to venture up
on the roof.
> As I understand it, the lead goes from the aerial into the loft, where
> the first split occurs and then outside, down the walls.
>
> If I upgrade the cable from the loft down would that help?
It may do so, but see below.
> What is the correct way to have several sockets off one aerial? Should
> each socket have its own feed from a distribution amp? I know
> amplification is not the answer to poor reception because you are
> amplifying the noise as well as the signal but is it that a
> distribution amp only amplifies the signal enough to overcome the
> losses of splitting it into several outputs?
Yes, that seems to be the accepted view.
> I was wondering whether it would be a good idea to connect the three
> sockets into a 4-way amp, rather than just daisy chaining them?
Almost certainly that will effect some improvement.
> There's no power in the loft, so I think the easiest way round this
> would be to use one of those amps which has a separate supply that
> goes up the lead. I've looked on the internet and see that a company
> called "proception" make some of these.
>
> Is proception a good brand?
I can't comment on those, but others have already.
I note that others have also suggested taking a fused spur of the
lighting main for the bedrooms, which will almost certainly be
accessible in the loft. Certainly this can be done, but note that if
there is a source of electrical spikes in the house (for example dirty
central-heating switching can cause massive spikes), with a fused spur
you can't put spike-protection between the mains supply and the
distribution amp, as spike-protectors generally plug into a socket.
I would recommend taking a spur off the ring-main that serves the 13A
sockets in the bedroom up into the loft. It's more expensive, but you
can then plug the amp into a spike-protector.
Note, however, that you should also try and fix the source of the
spikes, as inherently they threaten all the other A-V and
microprocessor controlled equipment in the house.
> Or should I not do any of this and get a man to climb on the roof with
> a meter and check the aerial is pointing the right way? The fact that
> the other channels are good makes me think the aerial is ok.
The fact that the other channels are good suggests to me that the
signals are at least marginal to good-ish, but I would suggest they
should be better.
Doctor D has suggested using the trade view of the official postcode
checker at Digital UK, and I would certainly support that suggestion.
You may also like a more visual second opinion, in which case you can
put your full postcode into my checker and for the transmitter option
choose Find The Likeliest:
http://www.macfh.co.uk/JavaJive/AudioVisualTV/TerrestrialTV/TerrestrialCalculator.php
As Doctor D has suggested the results from this suggests Sutton
Coldfield as the transmitter to use, the signal path being virtually
completely unobstructed (unless any local obstructions such as nearby
high-rise buildings or trees are visible out of the window - AFAIAA,
none of the checkers can work to that level of detail).
Again as DD suggests, Waltham is the next most likely (Lichfield
carries only Ch 5 for Analogue and the HD channels for pre-DSO
digital).
The fact that you are getting only marginal signals from what seems on
the face of it to be a good location for reception suggests that
something is wrong. I would be inclined to start at the aerial and
work down, checking out and if necessary replacing anything that is
not up to scratch, but of course I understand that from the DIY
amateur point of view* that it's easiest and therefore tempting to do
those things that are easily accessible and hope for the best with the
rest!
As you admit to have been lurking and learning, a good thing to do,
you may also care to read the preceding page on my site, which is a
General Introduction to Terrestrial TV (click one of the links in the
top or bottom left-hand corner of the calculator page linked above).
You may find that useful for filling in gaps your knowledge,
understanding jargon, etc.
* I should stress that the amateur DIY approach is also my own, and
my web pages are specifically aimed at such people - my own field of
expertise lies elsewhere.
--
=========================================================
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
Stephen
<peter.th...@googlemail.com> wrote:
>Your parents have 2 aerials, they do not have 2 analogue aerials.
>
>I only point this out in case they do go for a new distribution system
>- steer clear of aerial installers/firms that advertise/try to sell
>Digital Aerials - there ain't no such animal.
Thanks. The silly thing is that I already knew there is no such thing
as a "digital aerial"; in fact, when my F-I-L asked "do you think we
need a digital aerial", I told him the same thing you told me.
I think what confused me was Paul's reply in which he said: "whether
the digital multiplexes might be outside the frequency response of
your old analogue aerial." and because he used the term "analogue
aerial", I repeated it in my reply.
I think what Paul was trying to say was that may be the digital
channels are transmitted on a different group of frequencies to the
analogue channels, so I might need to swap a group A aerial for a
group B. Bill's reply says that one multiplex is out of the group but
otherwise it should be ok.
I'm not criticising Paul because his other post shows he knows what
he's talking about; it was me that got the wrong end of the stick.
Sorry.
Thanks,
Stephen.
Stephen
wrote:
>You can see Sutton C from most of the rooftops of Burton, and Lichfield
>as well. The ch55 mux is outside Group B but if the aerial and cable,
>etc, are otherwise OK it shouldn't matter. If the aerial and cables are
>OK I doubt if you'd need an amp; just a passive splitter.
Thanks. You must be local-ish ;)
I'm not sure what ch55 mux is, I'll have to look it up, would that be
the ITV one? If so, that would explain the problem.
I'm pretty sure the cable will be old brown low-loss coax, so I will
replace as much as possible with ct100.
I haven't seen the how the cable is shared between outlets. I think
there is a "Y" connector that splits it into two leads which go to two
rooms and one of those sockets is daisy chained to a third.
I need to add a new cable to take the third socket directly to the
loft. I suppose a passive splitter has the advantage it doesn't need
power but then if there's a power cut and the amp doesn't work, it
won't matter because the TV won't be working either! Do you recommend
any particular passive splitter?
Thanks,
Stephen.
Bill Wright
> On Tue, 30 Nov 2010 21:37:44 +0000, Peter
> <peter.th...@googlemail.com> wrote:
>
>> Your parents have 2 aerials, they do not have 2 analogue aerials.
>>
>> I only point this out in case they do go for a new distribution system
>> - steer clear of aerial installers/firms that advertise/try to sell
>> Digital Aerials - there ain't no such animal.
>
> Thanks. The silly thing is that I already knew there is no such thing
> as a "digital aerial"; in fact, when my F-I-L asked "do you think we
> need a digital aerial", I told him the same thing you told me.
When you deal with the public day in day out it gets a bit tedious
explaining all this. As far as I'm concerned if they ring up wanting 'a
digital aerial' I merely ask 'Have you got a problem with digital
reception on the existing aerial?'. If they say yes they can have a new
'digital' aerial with pleasure (once the snow's off the roofs).
Bill
Stephen
wrote:
>The OP is most likely using Sutton Coldfield (are you receiving West
>Midlands regional TV?) on which I still install group B aerials with no
>noticeable problems on the C55 multiplex. The problem is unlikely to be
>wrong aerial group, more likely aerial fault or deterioration.
Yes, it's West Midlands TV or "BBC Birmingham and Coventry" as I like
to call it ;) I wish I could tune into East Midlands today instead of
Nick Owen, after this, I'll have to look into how to turn my own
aerial around ;)
Thanks,
Stephen
Stephen
<paul_d...@hotmail.com> wrote:
>Below is a "brain dump" of the little I know.
Thanks. I wouldn't say you know a little, you seem to know a lot. I'm
sure it was my fault that I misunderstood your earlier post.
Stephen
wrote:
>The problem is unlikely to be
>wrong aerial group, more likely aerial fault or deterioration.
Sorry, I forgot to ask: does an aerial deteriorate? I can imagine it
might get knocked out of alignment by winds and birds or do they rust
or something else all together? Thanks.
Bill Wright
> On Tue, 30 Nov 2010 20:33:36 +0000, Bill Wright <bi...@invalid.com>
> wrote:
>
>> You can see Sutton C from most of the rooftops of Burton, and Lichfield
>> as well. The ch55 mux is outside Group B but if the aerial and cable,
>> etc, are otherwise OK it shouldn't matter. If the aerial and cables are
>> OK I doubt if you'd need an amp; just a passive splitter.
>
> Thanks. You must be local-ish ;)
No I'm not but I know a few people in Burton and I work nearby occasionally.
>
> I'm not sure what ch55 mux is, I'll have to look it up, would that be
> the ITV one? If so, that would explain the problem.
No, it's mux D, and contains only shite.
>
> I'm pretty sure the cable will be old brown low-loss coax, so I will
> replace as much as possible
All of it! All of it!
with ct100.
>
> I haven't seen the how the cable is shared between outlets. I think
> there is a "Y" connector that splits it into two leads which go to two
> rooms and one of those sockets is daisy chained to a third.
Oh God you can't go on with that. Get it all ripped out man!
>
> I need to add a new cable to take the third socket directly to the
> loft. I suppose a passive splitter has the advantage it doesn't need
> power but then if there's a power cut and the amp doesn't work, it
> won't matter because the TV won't be working either!
Good planning eh?
Do you recommend
> any particular passive splitter?
Have a look at the ones in the CPC book. This sort of thing:
http://cpc.farnell.com/_/344004/splitter-4-way-5-2400mhz/dp/AP01023
Bill
Stephen
wrote:
>>Is proception a good brand?
>
>Yes Andy Wade who posts here sometimes designs these:)..
He of uk.diy fame? What a small world!
I thought you said he sometimes designs them; I was about to ask who
designs them at other times but then I re-read the sentence!
I had heard of labgear and antiference but never proception before.
Thanks,
Stephen.
charles
they won't 'rust' since they are made of aluminium alloy, but they will
corrode. This corrosion may well happen inside the terminal box. That's
where the cable is connected. Then you will proably get avery 'lossy'
connection between the aerial and the downlead.
Yes, you can get bird or wind damage, but that's usually obvious from the
ground. (bent or missing elements)
--
From KT24
Using a RISC OS computer running v5.16
J G Miller
>
> I merely ask 'Have you got a problem with digital
> reception on the existing aerial?'.
Have you started getting any calls about problems with HD reception on
an existing aerial, requiring an upgrade to an HD aerial?
After all, the Freeview HD multiplex from Emley Moor is only low power,
and those nice people who watch "Look Hull: The Peter Levy Show"
do not even get a Freeview HD signal from Belmont.
tony sayer
<ste...@nowhere.com.invalid> scribeth thus
I might be Wrong but I believe Proception came out of the demise of
Labgear somewhere!...
--
Tony Sayer
Woody
So if it is SC then DSO is 21st September 2011.
Bill Wright
bust (not his fault I'm sure...)
Bill
Bill Wright
> In <id5up7$j8e$1...@speranza.aioe.org>, Bill Wright <bi...@invalid.com> wrote:
>
>> Stephen wrote:
>>> I'm not sure what ch55 mux is, I'll have to look it up, would that be
>>> the ITV one? If so, that would explain the problem.
>> No, it's mux D, and contains only shite.
>
> ITV4 which is showing daily highlights of The Ashes at the moment.
>
> Stephen, have a look at
> http://www.unsatisfactorysoftware.co.uk/dtt/dtt.cgi?reg=UK.E.CEN.SUT&by=mux&type=&col=LNMT&disp=2&prt=1
> for the breakdown.
>
> HTH
Oh yes, sorry, I generalised too wildly.
Bill
Woody
>>Be aware that DTTV is very sensitive to interference. If
>>old-type
>>brown downlead is in use it will pick up things like passing
>>traffic ignition interference
>
> Are you saying it picks up interference from spark plugs firing
> as
> they go down the street? I never knew that!
>
Analogue TV is one signal (or carrier) amplitude modulated with a
picture signal - that is the signal amplitude varies with the
picture content. There are two additional carriers injected into
the composite, one carrying analogue mono sound and one carrying
NICAM stereo sound. The whole thing occupies something less than
7MHz of bandwidth in the 8MHz channel spacing. Pulse interference
will be decoded as either peak white or peak black and so will
result in white or black interference on screen but it will not
destroy the picture.
Digital (terrestrial) TV (DTTV) has a number of program stations
mixed or multiplexed together into one digital data stream.
Unlike analogue which has one (three?) carriers, the digital
carriers are 1KHz or thereabouts apart which in theory means 8000
carriers in one 8MHz slot, but if memory serves me correctly (and
no doubt someone will correct me) it is actually a bit less than
that in practice - 7804 rings a bell. The whole stream carries
both sound and vision information. Each carrier can be thought of
as representing bits of data so will be on or off (again a great
simplification) to form a data stream which your TV - or rather
computer that thinks it is a TV - can decode and present you with
multiple program stations.
As a result if there is pulse interference - such as that caused
by spark ignition, and even fridge/washing machine switches - in
relative terms the duration can take a goodly chunk out of the
data stream. Like a CD the data stream does carry heavy and very
clever error correction, but sometimes the error is too great and
it cannot be corrected. The result is a picture freeze,
pixelation, or picture blanking, defined by the TV 'computer'
software. Using PF100 or similar cable with a foil screen will
tend to reduce pick-up of such interference and result in a
stable picture.
In terms of amps, even if the user is in Burton, a good quality
masthead or loft amp with low gain (say 9-12dB) followed by a
screened passive splitter (look at Screwfix again) will be better
than just splitting the signal. Most aerial amp/splitters would
probably give too much gain and insufficient headroom to
accommodate the (considerable) transmitter power increase that
will accompany DSO.
Note the above is a <considerable> simplification so you may
understand a bit more about what we contributors to this group
take as 'normal' (ha!)
I think generally - but especially in this group - we will need
to start referring to channels being those of the radio frequency
kind and stations being the programs. At present with analogue
they are essentially one and the same, but in DTTV they are most
definitely not.
[Ducks down behind flameproof screen.]
Bill Wright
There's been quite a few who've bought an HD set and then found that
they can't get a signal. So many people round here are on Belmont,
Crosspool, or whatever. I usually suggest Freesat, unless there's a
reasonable Emley signal available.
A few weeks ago there was a short-lived mystery when several Emley
viewers rung to say that HD wouldn't work. Before we went out to them
they all reported that it had come back by itself.
Bill
Andy Wade
> [...] unless the aerial is a log-periodic design, it is desirable
> that it should have [a balun].
The log-periodic also needs a balun to connect it correctly to a coax
feeder - it's made up of centre-fed dipoles, after all. Usually the
balun is formed 'for free' by feeding the coax from the back though one
of the boom / transmission line members and connecting it to the
feedpoint at the front. The balun is there alright, it's just not
apparent as a separate component.
Compare a properly-fed log-periodic with set-top and caravan 'logs'
which tend just to have a dangling coax attached at the front. On the
former the coax is pretty RF-dead on its outside and moving it around,
within reason, doesn't affect reception much. On the latter type the
feeder is quite 'hot' - common experience with set-top products is that
the cable positioning can be quite critical. The value of proper feeder
termination is clear.
> Yes, and as I think someone else pointed out it will be only
> single-insulated (outer consisting only of braid), whereas
> double-insulated [...]
Single- and double-*screened* (*shielded* for left-pondians) are the
terms you're looking for, not 'insulated'!
> I note that others have also suggested taking a fused spur of the
> lighting main for the bedrooms, which will almost certainly be
> accessible in the loft.
Yes, and that's fine for those confident to do it (or to pay an
electrician), but the Proception remote-powerable multi-way amps
(proAMP104X, '108U and '310X were introduced to give the installer
another option. The RF performance of these products is not inferior to
locally mains-powered types and the smaller size and reduced heat
dissipation can give more location options.
> Certainly this can be done, but note that if there is a source of
> electrical spikes in the house (for example dirty central-heating
> switching can cause massive spikes), with a fused spur you can't put
> spike-protection between the mains supply and the distribution amp,
> as spike-protectors generally plug into a socket.
Spike protectors (whether plug-in or hard wired) might help protect the
amplifier's PSU if you have unusually dirty mains, but are unlikely to
do much to reduce the effect of mains-borne impulsive interference on
DTT. Attention to aerial siting (and balun) and coax screening,
including removal of old unscreened/isolated outlets and poor flyleads,
are what is needed.
> I would recommend taking a spur off the ring-main that serves the 13A
> sockets in the bedroom up into the loft. It's more expensive, but you
> can then plug the amp into a spike-protector.
That's completely unnecessary in 99.9% of cases, I'd suggest.
> Note, however, that you should also try and fix the source of the
> spikes, as inherently they threaten all the other A-V and
> microprocessor controlled equipment in the house.
That's easier said than done in reality and you certainly mustn't do
things like connecting capacitors across gas boiler thermostats (in case
they fail s/c).
> [...] - AFAIAA, none of the checkers can work to that level of
> detail).
The 'official' JPP/DUK predictor does have some knowledge of ground
clutter, and of the TX antenna radiation patterns (both wanted and
interferers), which I doubt that yours does. I do like yours for the
mapping and path profiles though :-).
> The fact that you are getting only marginal signals from what seems on
> the face of it to be a good location for reception suggests that
> something is wrong.
I get the feelings (a) that the existing installation is knackered and
(b) that after DSO a decent aerial and a passive splitter might be all
that is required.
--
Andy
Bill Wright
> I get the feelings (a) that the existing installation is knackered and
> (b) that after DSO a decent aerial and a passive splitter might be all
> that is required.
I'd even go further and suggest that the latter option might be adequate
pre-DSO.
Bill
Java Jive
<spamb...@maxwell.myzen.co.uk> wrote:
> On 01/12/2010 14:40, Java Jive wrote:
>
> > [...] unless the aerial is a log-periodic design, it is desirable
> > that it should have [a balun].
>
> The log-periodic also needs a balun
Yes, yes, this conversation has occurred here before, but at the OP's
level of knowledge such detail is an overload of unnecessary
information. What a DIY-er needs to know is that a 'conventional'
aerial needs to have a balun, while a log-periodic does not. The fact
that the latter is because one is formed by the way the aerial is
wired/connected in - it was previously agreed here - all domestic
types available in the UK doesn't alter this basic, easily remembered
rule.
> > Yes, and as I think someone else pointed out it will be only
> > single-insulated (outer consisting only of braid), whereas
> > double-insulated [...]
>
> Single- and double-*screened* (*shielded* for left-pondians) are the
> terms you're looking for, not 'insulated'!
Yes, a slip. It's a fair cop.
> > I note that others have also suggested taking a fused spur of the
> > lighting main for the bedrooms, which will almost certainly be
> > accessible in the loft.
>
> Yes, and that's fine for those confident to do it (or to pay an
> electrician), but the Proception remote-powerable multi-way amps
> (proAMP104X, '108U and '310X were introduced to give the installer
> another option. The RF performance of these products is not inferior to
> locally mains-powered types and the smaller size and reduced heat
> dissipation can give more location options.
>
> > Certainly this can be done, but note that if there is a source of
> > electrical spikes in the house (for example dirty central-heating
> > switching can cause massive spikes), with a fused spur you can't put
> > spike-protection between the mains supply and the distribution amp,
> > as spike-protectors generally plug into a socket.
>
> Spike protectors (whether plug-in or hard wired) might help protect the
> amplifier's PSU if you have unusually dirty mains, but are unlikely to
> do much to reduce the effect of mains-borne impulsive interference on
> DTT. Attention to aerial siting (and balun) and coax screening,
> including removal of old unscreened/isolated outlets and poor flyleads,
> are what is needed.
>
> > I would recommend taking a spur off the ring-main that serves the 13A
> > sockets in the bedroom up into the loft. It's more expensive, but you
> > can then plug the amp into a spike-protector.
>
> That's completely unnecessary in 99.9% of cases, I'd suggest.
It seemed to make a huge difference on my own system.
> > Note, however, that you should also try and fix the source of the
> > spikes, as inherently they threaten all the other A-V and
> > microprocessor controlled equipment in the house.
>
> That's easier said than done in reality and you certainly mustn't do
> things like connecting capacitors across gas boiler thermostats (in case
> they fail s/c).
I never suggested such a thing, nor ever would. I was implying to get
the boiler serviced and maybe the room thermostat replaced.
> > [...] - AFAIAA, none of the checkers can work to that level of
> > detail).
>
> The 'official' JPP/DUK predictor does have some knowledge of ground
> clutter
So does mine, although at a lower resolution than the official one,
but none of them have knowledge of individual high-rise buildings,
stadia, etc. As clutter near the site is the most likely to obstruct,
looking out of the window is still the best way to spot it.
> and of the TX antenna radiation patterns (both wanted and
> interferers), which I doubt that yours does. I do like yours for the
> mapping and path profiles though :-).
>
> > The fact that you are getting only marginal signals from what seems on
> > the face of it to be a good location for reception suggests that
> > something is wrong.
>
> I get the feelings (a) that the existing installation is knackered and
Yes.
> (b) that after DSO a decent aerial and a passive splitter might be all
> that is required.
I yield to your greater experience.
Bill Wright
>>> [...] - AFAIAA, none of the checkers can work to that level of
>>> detail).
>> The 'official' JPP/DUK predictor does have some knowledge of ground
>> clutter
>
> So does mine, although at a lower resolution than the official one,
> but none of them have knowledge of individual high-rise buildings,
> stadia, etc. As clutter near the site is the most likely to obstruct,
> looking out of the window is still the best way to spot it.
At a recent job the customer had taken his aerial from the top of the
rear gable because he was building an extension. He re-erected the
aerial on the side gable, but found that reception was terrible. He was
baffled as to why this should be, since the aerial was at the same
height. There was a dormer window near the near aerial location and I
was able to show him that the aerial was now 'looking' through next
door's roof. The difference in reception was a bit extreme though, and
more than could be explained by just one roof being in the way. However
the house that was in the way was actually the customer's son's house,
and the customer told me that the steep roof had a large games room
inside it. At each side of the games room was a void, and the vertical
walls of the games room were made from foil-backed plasterboard.
Raising the aerial six feet increased signal levels by a rather
staggering 16dB!
Bill
J G Miller
>
> At each side of the games room was a void, and the vertical
> walls of the games room were made from foil-backed plasterboard.
So he had no need to wear a tin foil hat whilst playing games on the Internet?
Bill Wright
the manufacturers have though of the extra sales potential?
Bill
Stephen
<harro...@ntlworld.spam.com> wrote:
>a good quality
>masthead or loft amp with low gain (say 9-12dB) followed by a
>screened passive splitter (look at Screwfix again)
Thanks for all the posts. I have had a quick skim of them but will go
back and re-read and digest them.
I just wanted to let you know I have been round tonight to have a look
at the wiring. It seems I got the description wrong. I thought that
the aerial split using a Y connector like this:
http://www.screwfix.com/prods/11650/Electrical-Supplies/TV-Range/Leads-Connectors/Coaxial-Y-Splitter
and that the two outputs went to two sockets, with a third socket
being chained from the second.
Actually the splitters in use are not Y splitters but something
looking like this:
http://www.diy.com/diy/jsp/bq/nav.jsp?action=detail&fh_secondid=9686567
But I imagine they are the same thing in a different shaped box; are
they?
My instinct is that these splitters are not good but I don't know why.
Am I right to think that?
The good news is that all three sockets have their own leads up to the
loft. The bad news is that two are in brown coax and the third is in a
very, very thin black coax. I've never seen anything like it before
but then again, I'm not a pro.
Replacing two of the cables will not be a problem; they can be dropped
down the outside wall. The third room will be a problem as it does not
have an external wall. If the cable was in conduit it would be ok but
I suspect it is plastered in. If they don't want to redecorate, they
may have to settle for trunking, I suppose?
I've got some ct100 with copper foil in anticipation. Is copper foil
better than aluminium or is foil foil?
I think the problem is that they are trying to feed three rooms but
the splitters only have two outputs so there is something like this:
aerial to splitter 1
splitter 1 to room 1 and splitter 2
splitter 2 to room 2 and room 3
Only it's actually worse than that because somehow, I forget now (I
should have drawn it whilst I was there) they have managed to use
three splitters!
If each split causes a loss, then rooms 2 and 3 after three splits are
going to have lost a lot.
I think the first thing to do is to rip these out. I was puzzled by
the comments that labgear had gone bust because screwfix seems full of
their stuff, or is it that this is a new company using an old
company's name?
At first I saw this 4-way splitter:
http://www.screwfix.com/prods/69265/Electrical-Supplies/TV-Range/Amplifiers-Distribution/4-Way-Splitter-with-Powerpass-All-Ports
but the eight way is only a pound more:
http://www.screwfix.com/prods/29730/Electrical-Supplies/TV-Range/Amplifiers-Distribution/Labgear-8-Way-Splitter-with-Powerpass-All-Ports
I wonder whether to get the 8-way as this would allow for expansion if
they wanted tvs everywhere in the future? Or does more outputs mean
more loss?
I'm guessing these are more sophisticated than the other types of
splitter above?
This has the advantage of not needing power but if an amp does prove
necessary, I think I will go with the remote powered version.
Has anyone spotted any flaws in my plans so far?
I figure even if other things have to be done, this is a good start as
the cables need tidying and simplifying and even a new installation
will need to use a splitter.
Thanks,
Stephen.
PS it is Sutton Coldfield.
Java Jive
<ste...@nowhere.com.invalid> wrote:
>
> My instinct is that these splitters are not good but I don't know why.
> Am I right to think that?
I confess that those are my instincts too, but at least some of the
pros here seem to think that they'd be ok if the signal was good
enough, and I'm not qualified to argue against them.
> Replacing two of the cables will not be a problem; they can be dropped
> down the outside wall. The third room will be a problem as it does not
> have an external wall. If the cable was in conduit it would be ok but
> I suspect it is plastered in. If they don't want to redecorate, they
> may have to settle for trunking, I suppose?
Depending on the build of your house, you may be able to replace all
three *relatively* easily (when is anything involving building work
actually 'easy'?).
Generally, the easiest way to replace cable is to use the old cable to
pull through the new length. You really need two people. You start
by taking the coil or drum of new cable up into the loft, but do not
cut it to length yet. Trim the end of both the old and the new cable,
the new one at a slant so that it tapers. Using electrical tape, tape
the new cable to the old cable about 15 to 30cm in from the end of the
old so that the join tapers away from the old cable, which will help
it get past obstructions. Using the stretchiness of the tape to bind
the two together very tightly, start taping a little way down from the
'front' end of the new cable (you can leave the tail of the old cable
hanging loose in most circumstances), and work up towards the taper so
that each new layer of tape covers the front edge of the previous
layer, thus again helping to prevent anything that might catch,
finishing by covering what will be the 'front' tapering end of the
join to make it smooth (like this, only at a greater angle than is
possible to illustrate with ASCII art):
<--- \\\\\\\\\\\\\\\\\\\\\\\\\\\\\
\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
Then one person gradually pulls from the socket end while the other
feeds the cable from the top by rotating the whole coil or drum, not
by uncoiling it as you would a vacuum cleaner lead before using it,
which would put twists into the cable that would make it hard to
control when, inevitably, it comes up against an obstruction. There
will probably have to be much shaking and other manipulations
accompanied by loud cursing before it gets all the way through, but,
with luck, it'll make it. When you've got it all the way, leaving
some slack at each end, you can cut it to length.
Whatever else you do, DON'T DROP THE CUT END OF THE NEW CABLE DOWN
THE HOLE FROM ABOVE! Tie it or tape it to something until you are
ready to connect up in the loft.
Further, if, like my 80s cowboy house, the walls are predominantly
plasterboard on slats with a void behind them, you may be able to take
the two cables that currently go outside down the void, thus avoiding
their being vulnerable to UV and other forms of weathering. The most
difficult part of the process will be getting them past the upstairs
flooring, which tends to jut out into the void. In my case, I already
had an aerial socket in the bedroom just above that point, so I could
use that to gain access to the problem area and generally chivvy the
cable join about until it went through.
HEALTH WARNING: The dust from rockwool insulation commonly used in
lofts is not good for your lungs. Use a mask.
> I think the problem is that they are trying to feed three rooms but
> the splitters only have two outputs so there is something like this:
Yes, I'd agree.
> At first I saw this 4-way splitter:
I would call that a distribution amp - to me a splitter means a
passive device.
> I'm guessing these are more sophisticated than the other types of
> splitter above?
Yes, as their fuller name implies, they are active devices that
amplify the signal before splitting it, so compensating for the losses
that would otherwise be incurred, whereas the other types currently in
place are just passive devices, which do incur loss.
Bill Wright
> Thanks for all the posts. I have had a quick skim of them but will go
> back and re-read and digest them.
Best print them on rice paper then.
> http://www.diy.com/diy/jsp/bq/nav.jsp?action=detail&fh_secondid=9686567
>
> But I imagine they are the same thing in a different shaped box; are
> they?
Yes
>
> My instinct is that these splitters are not good but I don't know why.
> Am I right to think that?
Yes
>
> The good news is that all three sockets have their own leads up to the
> loft. The bad news is that two are in brown coax and the third is in a
> very, very thin black coax. I've never seen anything like it before
> but then again, I'm not a pro.
How thin is thin? But anyway, it won't be any good.
>
> Replacing two of the cables will not be a problem; they can be dropped
> down the outside wall. The third room will be a problem as it does not
> have an external wall.
A room without a view? No-one to worry you? No-one to hurry you?
If the cable was in conduit it would be ok but
> I suspect it is plastered in. If they don't want to redecorate, they
> may have to settle for trunking, I suppose?
Oh just run some white coax down the corner behind the door. They'll
never even notice it.
>
> I've got some ct100 with copper foil in anticipation. Is copper foil
> better than aluminium or is foil foil?
Well, the answer lies in the foil.
But if you've already bought the cable why do you care about this? I
suppose if you'd paid extra for copper and I said aluminium was OK you
would have said "Drat! Foiled again!"
>
> I think the problem is that they are trying to feed three rooms but
> the splitters only have two outputs so there is something like this:
>
> aerial to splitter 1
> splitter 1 to room 1 and splitter 2
> splitter 2 to room 2 and room 3
And splitter shalt begat splitter and splitter shalt begat splitter and
so it shall continue until the farthest corner of the House, when there
shalt be no signal left. And those that dwell in the farthest corner of
the house shalt rent their garments and gnash their teeth for they shalt
have a plaugue of pixellation, and probably locusts as well. Thus spake
the Lord. (Jeremiah Ch6, v45)
>
> Only it's actually worse than that because somehow, I forget now (I
> should have drawn it whilst I was there) they have managed to use
> three splitters!
>
> If each split causes a loss, then rooms 2 and 3 after three splits are
> going to have lost a lot.
It's a laugh really, this. It's the sort of thing that brightens my day.
>
> I think the first thing to do is to rip these out.
Yes.
I was puzzled by
> the comments that labgear had gone bust because screwfix seems full of
> their stuff, or is it that this is a new company using an old
> company's name?
Phoenix syndrome.
>
> At first I saw this 4-way splitter:
> http://www.screwfix.com/prods/69265/Electrical-Supplies/TV-Range/Amplifiers-Distribution/4-Way-Splitter-with-Powerpass-All-Ports
>
> but the eight way is only a pound more:
> http://www.screwfix.com/prods/29730/Electrical-Supplies/TV-Range/Amplifiers-Distribution/Labgear-8-Way-Splitter-with-Powerpass-All-Ports
>
> I wonder whether to get the 8-way as this would allow for expansion if
> they wanted tvs everywhere in the future? Or does more outputs mean
> more loss?
Yes. Stick with the four way. You could always buy a two way and another
four way later.
>
> I'm guessing these are more sophisticated than the other types of
> splitter above?
Yes, they're quite casual, but sophisticated. No really, they are much
better.
>
> This has the advantage of not needing power but if an amp does prove
> necessary, I think I will go with the remote powered version.
Mr Wade has cunningly spotted a market and exploited it. It's good
stuff, but plug it into the mains somewhere where some cleaner won't
want to connect her vacuum. It's no good labelling the plug "Do not
unplug" or "Do not disconnect" or whatever. At one place (a country
hotel) the proprietor promised to provide a power source in the loft,
but failed so to do. My notices escalated from "Do not unplug" though
"TV system: do not unplug", "Do not unplug as this plug makes all the
tellys work", "Please please please do not unplug as this makes all they
tellys work" through to "Do not touch this you daft foreign bint or I
will kill you." It was all in vein. I should have tried "Por favor não
desconecte, você mulher estúpida."
>
> Has anyone spotted any flaws in my plans so far?
You must change every inch of cable, especially the one from the aerial
to the splitter.
Bill
Bill Wright
> HEALTH WARNING: The dust from rockwool insulation commonly used in
> lofts is not good for your lungs. Use a mask.
Yes, it's best to remain anonymous if you're going to start with
pneumoconiosis.
Bill
Stephen
wrote:
>Oh just run some white coax down the corner behind the door. They'll
>never even notice it.
It's easy when you know how! I hadn't thought of white cable; I was
thinking of the brown that was already there and the black that I
have.
>Well, the answer lies in the foil.
>But if you've already bought the cable why do you care about this? I
>suppose if you'd paid extra for copper and I said aluminium was OK you
>would have said "Drat! Foiled again!"
Well, I could take it back for an exchange ;) But you are quite right,
I should have asked before I bought. I'm sure that I read copper was
better but I can't remember why.
>And splitter shalt begat splitter and splitter shalt begat splitter and
>so it shall continue until the farthest corner of the House, when there
>shalt be no signal left.
And that's the room with the problem. It's all becoming clear now: the
problem, not the picture!
>It's a laugh really, this.
Just to make you laugh more, I think I have remembered a bit more how
the wiring goes. I think the first splitter box is wired "backwards".
The box has two "output" sockets and a hard-wired input.
Splitter 1:
output 1: aerial
output 2: room 1
input: to splitter 2
As you can tell, I don't know the technical details. If there is
nothing inside these boxes then it wouldn't matter but assuming there
is something, to balance impedances or something, having the aerial
connected to an output must be doing something wrong surely?
I still can't remember how they've managed to include a third splitter
though.
I guess the system has been expanded over the years and each time
they've just added another box to split and add a new cable. They must
get a strong analogue signal as they haven't noticed any problems
until going digital, but as it's already been said digital either
works or it doesn't and is less forgiving in that way.
>Phoenix syndrome.
Is the new labgear as good as the old labgear equipment?
> Stick with the four way. You could always buy a two way and another
>four way later.
If they added a two way to two four ways, wouldn't this be the branch
of a branch situation that they already have? Or is it that because
these are better splitters they can cope with that?
I'll go with the 4-way model as it is more than what they need at the
moment and to be fair, expansion is unlikely. I presume that the more
outputs, the more signal loss, so the 4w unit might be better (SF web
site didn't give specs). Do I need to do something with the unused
output?
Thanks,
Stephen.
Bill Wright
>
>> It's a laugh really, this.
>
> Just to make you laugh more, I think I have remembered a bit more how
> the wiring goes. I think the first splitter box is wired "backwards".
> The box has two "output" sockets and a hard-wired input.
>
> Splitter 1:
> output 1: aerial
> output 2: room 1
> input: to splitter 2
>
> As you can tell, I don't know the technical details. If there is
> nothing inside these boxes then it wouldn't matter but assuming there
> is something, to balance impedances or something, having the aerial
> connected to an output must be doing something wrong surely?
Variations found in surface-mount 'splitters':
Resistive split, input/output irrelevant
Inductive split, input is input, outputs are output (unless used as a
combiner)
One rear saddle clamp input feeds both front sockets (both types above)
One rear saddle clamp input feeds single front socket and second saddle
clamp on rear (both types above)
Two rear saddle clamp inputs feed two front sockets separately (not a
splitter).
But it's all irrelevant. Rip it all out!
> Is the new labgear as good as the old labgear equipment?
Not even remotely.
>
>> Stick with the four way. You could always buy a two way and another
>> four way later.
>
> If they added a two way to two four ways, wouldn't this be the branch
> of a branch situation that they already have? Or is it that because
> these are better splitters they can cope with that?
Yes, and because you are going to replace all the cable. Every inch of it.
>
> I'll go with the 4-way model as it is more than what they need at the
> moment and to be fair, expansion is unlikely. I presume that the more
> outputs, the more signal loss, so the 4w unit might be better (SF web
> site didn't give specs). Do I need to do something with the unused
> output?
No. The effect of leaving it unterminated is slight.
Bill
Andy Wade
>>> I would recommend taking a spur off the ring-main that serves the 13A
>>> sockets in the bedroom up into the loft. It's more expensive, but you
>>> can then plug the amp into a spike-protector.
>>
>> That's completely unnecessary in 99.9% of cases, I'd suggest.
>
> It seemed to make a huge difference on my own system.
Interesting - what sort of amplifier and what sort of spike protector?
>> The 'official' JPP/DUK predictor does have some knowledge of ground
>> clutter
>
> So does mine, although at a lower resolution than the official one,
What clutter database are you using? I assumed you only had terrain
height data.
> but none of them have knowledge of individual high-rise buildings,
> stadia, etc.
Wrong - the 'official' predictor has exactly that. It's not perfect
because, AIUI, there's no data about the RF transparency of the
obstacles, but it's much better than nothing. Information on incoming
interference (co- and adjacent-channel) is another important requirement
for valid prediction.
--
Andy
Andy Wade
> It's no good labelling the plug "Do not unplug" or "Do not
> desconecte, você mulher estúpida."
<g> Couldn't you get a fused connection unit installed?
On our remote-powered multi-way amps and multi-o/p mastheads (and
probably most of the competition) there's always the option to use more
than one power unit. Then if one is temporarily unplugged the system
stays up. I know of some installations in small blocks of flats where
there's a PSU in each flat all connected to one amplifier. Yes it's
wasteful of materials and energy, but only on a fairly small scale and
it does provide a pragmatic solution.
--
Andy
tony sayer
ell.myzen.co.uk> scribeth thus
>On 02/12/2010 02:52, Java Jive wrote:
>
>>>> I would recommend taking a spur off the ring-main that serves the 13A
>>>> sockets in the bedroom up into the loft. It's more expensive, but you
>>>> can then plug the amp into a spike-protector.
>>>
>>> That's completely unnecessary in 99.9% of cases, I'd suggest.
>>
>> It seemed to make a huge difference on my own system.
>
>Interesting - what sort of amplifier and what sort of spike protector?
>
>>> The 'official' JPP/DUK predictor does have some knowledge of ground
>>> clutter
>>
>> So does mine, although at a lower resolution than the official one,
>
>What clutter database are you using? I assumed you only had terrain
>height data.
Clutter databases, well good ones, are quite expensive;!...
>
>> but none of them have knowledge of individual high-rise buildings,
>> stadia, etc.
>
>Wrong - the 'official' predictor has exactly that. It's not perfect
>because, AIUI, there's no data about the RF transparency of the
>obstacles, but it's much better than nothing. Information on incoming
>interference (co- and adjacent-channel) is another important requirement
>for valid prediction.
>
--
Tony Sayer
Bill Wright
Bill
Java Jive
<spamb...@maxwell.myzen.co.uk> wrote:
> On 02/12/2010 02:52, Java Jive wrote:
>
> >>> I would recommend taking a spur off the ring-main that serves the 13A
> >>> sockets in the bedroom up into the loft. It's more expensive, but you
> >>> can then plug the amp into a spike-protector.
> >>
> >> That's completely unnecessary in 99.9% of cases, I'd suggest.
> >
> > It seemed to make a huge difference on my own system.
>
> Interesting - what sort of amplifier and what sort of spike protector?
It's a LabGear MSA241 that also provides DC to a masthead. I don't
have the make/model of the spike protector or masthead to hand. I'd
need to clamber up into the attic to establish the latter - something
I only do when compelled*. It was bought about 15-20 years ago to
protect my PC, and was used for that until I purchased one of the
spike protected 4-ways just after moving in here. It's the plug block
type that plugs directly into the wall socket and has a socket on the
other side into which the PC or whatever is plugged.
* I probably ought to though - my recollection is that when I first
set it up analogue was virtually as good as DTT. Now analogue is
looking decided second rate, I suspect that the masthead amp may have
given out. I really ought to test things out, but as I no longer have
a working DTT receiver, I have little motivation.
> >> The 'official' JPP/DUK predictor does have some knowledge of ground
> >> clutter
> >
> > So does mine, although at a lower resolution than the official one,
>
> What clutter database are you using? I assumed you only had terrain
> height data.
UMD, there's a link to the source material in the acknowledgements
section at the bottom of the calculator page. Unfortunately, it only
has 1km resolution, but even that's a lot better than nothing. The
clutter is the brown shaded area in the profiles. There was a
discussion about it and about how I was applying the data in a
previous thread, most relevant was this post:
http://groups.google.com/group/uk.tech.digital-tv/msg/c908aa3911a9f8e7
> > but none of them have knowledge of individual high-rise buildings,
> > stadia, etc.
>
> Wrong - the 'official' predictor has exactly that. It's not perfect
> because, AIUI, there's no data about the RF transparency of the
> obstacles, but it's much better than nothing. Information on incoming
> interference (co- and adjacent-channel) is another important requirement
> for valid prediction.
I think right, actually, though I should add two caveats:
1) I am assuming that the official postcode checker is based on the
UK Planning Model (UKPM), which ISTR is the case.
2) I have been unable to establish the date of this doc - it's
possible it may have been updated or even superseded:
http://www.broadcastpapers.com/whitepapers/IBCNTLUKPlanningDTTVC.pdf
However, assuming the above is reliable, the UKPM uses a clutter
database of 25m resolution, obviously a far superior resolution to
mine, but apart from that the data appears to be applied in exactly
the same manner as is mine. Clutter is classified according to a
number of different ground cover types each of which adds a particular
height on top of that from the terrain and earth's curvature. Thus
for any particular 25m2 cell there is only knowledge of its clutter
class and the height associated with that, not the particular height
of the particular clutter in that particular cell.
Thus I don't believe the UKPM knows about even a stadium next door any
more than mine does, it's up to the person installing an aerial on the
basis of either to use their common sense when looking out over the
direction whence the signal arrives at the site.
tony sayer
>However, assuming the above is reliable, the UKPM uses a clutter
>database of 25m resolution, obviously a far superior resolution to
>mine, but apart from that the data appears to be applied in exactly
>the same manner as is mine. Clutter is classified according to a
>number of different ground cover types each of which adds a particular
>height on top of that from the terrain and earth's curvature. Thus
>for any particular 25m2 cell there is only knowledge of its clutter
>class and the height associated with that, not the particular height
>of the particular clutter in that particular cell.
JOOI have you been using Radio Mobile and SRTM data at all?..
Rather interesting as for some locations it shows heights a bit above
the ordnance datum thus presuming that their radar distance sounder was
receiving reflections off the roofs of buildings in urban areas which is
all rather well but doesn't show what the clutter losses are for say
internal in-building levels..
And for that info you it seems have to pay a lorra dosh;!...
>
>Thus I don't believe the UKPM knows about even a stadium next door any
>more than mine does, it's up to the person installing an aerial on the
>basis of either to use their common sense when looking out over the
>direction whence the signal arrives at the site.
Indeed!..
--
Tony Sayer
Stephen
<spamb...@maxwell.myzen.co.uk> wrote:
>On our remote-powered multi-way amps and multi-o/p mastheads (and
>probably most of the competition) there's always the option to use more
>than one power unit.
Whilst not applicable to me, that's interesting to know. Is there a
theoretical limit or could everyone in a block of flats have a psu to
feed one amp without problem?
Following the advice here, I'm going to try and use a passive splitter
(once the loft has warmed up!) and see if that is enough before going
to any powered alternative.
I was looking at remote-powered amps and see there are two types: mast
head amps and "indoor" (distribution?) amps. Are they the same
circuitry inside different boxes or is it important I get a particular
type for a particular job?
It's just that remote powered mast head amps seem very easy to find
(for obvious reasons), whereas the "indoor" type are harder to find,
probably because there is less demand. Would it hurt if I used a mast
head one not at the mast head? I'm sure it wouldn't but it's best to
ask the experts first.
Thanks,
Stephen.
Stephen
wrote:
>Generally, the easiest way to replace cable is to use the old cable to
>pull through the new length. You really need two people. You start
>by taking the coil or drum of new cable up into the loft, but do not
>cut it to length yet. Trim the end of both the old and the new cable,
>the new one at a slant so that it tapers. Using electrical tape, tape
>the new cable to the old cable about 15 to 30cm in from the end of the
>old so that the join tapers away from the old cable, which will help
>it get past obstructions. Using the stretchiness of the tape to bind
>the two together very tightly, start taping a little way down from the
>'front' end of the new cable (you can leave the tail of the old cable
>hanging loose in most circumstances), and work up towards the taper so
>that each new layer of tape covers the front edge of the previous
>layer, thus again helping to prevent anything that might catch,
>finishing by covering what will be the 'front' tapering end of the
>join to make it smooth (like this, only at a greater angle than is
>possible to illustrate with ASCII art):
><--- \\\\\\\\\\\\\\\\\\\\\\\\\\\\\
> \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
>
>Then one person gradually pulls from the socket end while the other
>feeds the cable from the top by rotating the whole coil or drum, not
>by uncoiling it as you would a vacuum cleaner lead before using it,
>which would put twists into the cable that would make it hard to
>control when, inevitably, it comes up against an obstruction.
Thanks. I have tried taping two (non-coax) wires together before but
with varying success. I don't think I've overlapped them as much as
you, nor tapered them, so perhaps these factors account for my 50:50
success rate.
I will certainly give it a go, but my worry is that the wire may have
been clipped to the wall and plastered over. I think it's a solid
block wall, rather than studs and plasterboard. Only one way to find
out though!
I know what you mean about cable twisting if it comes off "sideways".
I've seen it happen with twin and earth. I didn't know it happened
with coax so I'll be careful. I'd like to buy a reel holder but they
seem to cost more than the cable!
Thanks,
Stephen.
Java Jive
wrote:
>
The attributions at the bottom of the calculator and the earlier
thread I linked in reply to Andy explain this.
The terrain data is pure SRTM. All the data files covering the
Lon/Lats of the BI - 49-60N, 11W-3E which includes IoM, NI, and CI -
are on my server. SRTM data has a resolution of about 90m.
The clutter data is from the University of Maryland (UMD). I wrote a
python script to extract the data from their rather large worldwide
file into a smaller one covering the same range of Lon/Lats as the
SRTM data. This has a resolution of 1km.
As you know, both these sources are also used by Radio Mobile.
There is a python script which reads this data and returns an array of
results as JSON, which you can see for yourself by adding a debug
parameter, causing the results to be returned as human readable HTML.
For example, the following path, from Clettraval transmitter in the
Outer Hebrides to St Kilda (it's always a good idea if some testing is
unrealistically awkward), by chance has a void in the SRTM data, which
the script successfully interpolates over. Note that the parameters
are case sensitive. The data columns returned are Long, Lat, Height
Of Earth's Curvature, SRTM Terrain Height, Clutter Delta Height,
Fresnel Radius.
PLEASE NOTE:
URL munged to prevent search engines finding it. Remove the spaces
and linefeeds to use. Please do not reproduce this URL elsewhere,
particularly not without preserving the munging. I don't mind people
using the script to do the odd investigation, particularly if it's to
check out my calculator and report back anything that looks like an
error, but if I begin to suspect systematic use or abuse, I reserve
the right to prevent such without warning.:
h t t p : / / w w w . macfh.co.uk / cgi-bin/UKTV.py
?x1=-7.443638&y1=57.616888
&x2=-8.580112&y2=57.813941&cb=test&db=True
For the future:
1) Change the way the SRTM and UMD data is read so that all the
points on a path are read, rather than sampling them in steps, but
this might have big implications for server loading, and I'm not sure
it will be feasible.
2) Try and get reliable radiation patterns for all the UK
transmitters and apply them to the calculations as well as display
them on one or other or both maps. As I've said here before, Ofcom
are making them very difficult to acquire, particularly for the legacy
analogue and pre-DSO digital transmissions.
3) Do the entire calculation on the server, which will allow
something like a proper Longley-Rice, rather than the simplified
calculation which is all that is realistic in the client's browser.
> Rather interesting as for some locations it shows heights a bit above
> the ordnance datum thus presuming that their radar distance sounder was
> receiving reflections off the roofs of buildings in urban areas which is
> all rather well but doesn't show what the clutter losses are for say
> internal in-building levels..
No, that would be a tall order!
> And for that info you it seems have to pay a lorra dosh;!...
And as my site is completely free and doesn't earn me any money, I am
only prepared to spend on it a reasonable minimum for hosting. I
recently moved it to a new provider, actually, but as the lifetimes of
both sites overlapped, I hope and believe the swap took place without
any appreciable interruption of service.
We seem to be well away from distribution amps now, so I've changed
the subject. Apologies to the OP for the unintentional hi-jacking of
the original thread.
Andy Wade
> On Fri, 03 Dec 2010 17:25:53 +0000, Andy Wade
> <spamb...@maxwell.myzen.co.uk> wrote:
>
>> On our remote-powered multi-way amps and multi-o/p mastheads (and
>> probably most of the competition) there's always the option to use more
>> than one power unit.
>
> Whilst not applicable to me, that's interesting to know. Is there a
> theoretical limit or could everyone in a block of flats have a psu to
> feed one amp without problem?
The limit is number of outputs on the amplifier, so no more than about
eight or ten PSUs, usually. If you passively split the outputs to feed
more points, stick to one PSU per amplifier output unless using
splitters with directional power pass from all legs. Larger blocks of
flats will use a single o/p MATV amp and passive distribution network,
or satellite multiswitches, so the multi-PSU technique ceases to be
relevant (although each output section in a multiswitch is often powered
by the corresponding satellite receiver).
> I was looking at remote-powered amps and see there are two types: mast
> head amps and "indoor" (distribution?) amps. Are they the same
> circuitry inside different boxes or is it important I get a particular
> type for a particular job?
Originally mastheads were single-output preamplifiers used in weak
signal areas so were optimised for low noise figure. Multi-way amps
were indoor mains-powered units with good signal handling capability.
Now that we have multi-o/p mastheads and remote-powered indoor amps the
boundaries are much less distinct.
So far as the Proception range is concerned the proMHD14R and proAMP104X
are very similar designs, differing mainly in the housing, LED indicator
and maximum supply voltage. These are both dual-mode products that can
do return-path (for controlling a Sky box from one or more remote IR
'eyes'. The forward gains are relatively low (so the max. i/p signal
handling is good) and the masthead version should be though of as an
'active splitter' rather than a low noise preamp. If you were
struggling in a weak signal area one of the higher (or the variable)
gain products would be more appropriate. If you need more than four
outputs and/or multi-band inputs along with remote powering then the
proAMP310X is the product of choice.
> Would it hurt if I used a mast head one not at the mast head?
Not in principle, but check the output capability if the incoming
signals are strong. You might need an attenuator on the input. And
don't make the mistake of thinking that the higher the gain the better...
--
Andy
Terry Casey
>
> I'd like to buy a reel holder but they
> seem to cost more than the cable!
>
Broom handle or similar and a couple of boxes or other support.
Nail, screw, tape or tie broomhandle in place to stop it rolling off ...
--
Terry
Stephen
<spamb...@maxwell.myzen.co.uk> wrote:
>The limit is number of outputs on the amplifier, so no more than about
>eight or ten PSUs, usually.
Sorry, my brain was only half in gear. It's obvious now you say that
you can't have more psus than the amp has outputs!
>Not in principle, but check the output capability if the incoming
>signals are strong. You might need an attenuator on the input. And
>don't make the mistake of thinking that the higher the gain the better...
because it amplifies noise as well as signal?
Thanks,
Stephen.
Bill Wright
>
>> Not in principle, but check the output capability if the incoming
>> signals are strong. You might need an attenuator on the input. And
>> don't make the mistake of thinking that the higher the gain the better...
>
> because it amplifies noise as well as signal?
Because you might exceed the amp's max output capability, then you would
just get a load of interference.
Bill