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UHF home distribution and witchcraft



 
 
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  #41  
Old August 24th 19, 06:12 PM posted to uk.tech.digital-tv
Bob Latham
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Posts: 747
Default UHF home distribution and witchcraft

The author has marked this message not to be archived. This post will be deleted on September 7, 2019.

In article ,
NY wrote:

Given the description, I interpret the peaks (reading left to
right) as:


22
25
(large gap with very weak signals)
39/40
42/43
45/46
48
(small gap)
55/56
60
(small gap)


69: blue marker which corresponds to info below the graph which
says that the marker is monitoring strength of UHF 69 which is 858
MHz and assumes a channel bandwidth/spacing of 8 MHz and has a
power of 21 dBuV/m


So I presume the horizontal scale runs from UHF 21-69.


Spot on.

Bob.

--
Bob Latham
Stourbridge, West Midlands
  #42  
Old August 24th 19, 07:03 PM posted to uk.tech.digital-tv
charles[_2_]
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Posts: 936
Default UHF home distribution and witchcraft

In article ,
Bob Latham wrote:
In article ,
wrote:


Let us know how you get on!


I've just done a fundamental test I should have done before posting
at all.


I took the conditioned aerial signal at the point where the 24dB
attenuator plugs into the filter combiner (first point in the lounge)
and connected that directly through to the distribution amp. This
them removes everything between what comes down from the loft and the
distribution amp.


No change what so ever. C40 perfect going into distribution amp has
variable MER after the amp. On the back of the kitchen TV C39 is
awful quality according to the TV and yet both BER and MER are
perfect according my test meter.


I then added a 9dB attenuator just before the distribution amp.



Giving what level input?

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle
  #43  
Old August 24th 19, 11:28 PM posted to uk.tech.digital-tv
[email protected]
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Posts: 122
Default UHF home distribution and witchcraft



From memory, the OP is troubled by strong Brierley hill signals which are from Ch 29 to 37.

Not only that, he is also troubled by strong signals from the wrekin which includes signals broadcast at 41, 44 and 47.

Hence the notch filters at Ch 37 and 47.

Sutton Coldfield broadcasts muxes 7 and 8 and these are not available at the wrekin or Brierley hill, hence his preference for Sutton Coldfield..…..
  #44  
Old August 25th 19, 09:41 AM posted to uk.tech.digital-tv
Jim Lesurf[_2_]
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Posts: 4,567
Default UHF home distribution and witchcraft

In article , Bob Latham
wrote:

The display shows channels 21 to 69. The blue bar is the "reader" which
in the picture in on C69. the PWR and frequency of of where the blue bar
is, you can move it left and right to look at specific channels. It is
on 69 in the picture to move it out of the way as when it is over a
channel you cannot see the green bar value.


Hope that helps.


Yes: In that it explaines the blue bar, etc. But...

No: in that it doesn't tell me for certain how/if the device might detect,
say, an oscillation or transmission at 1GHz big enough to blow your hat
off! As shown it looks like the blue bar is the highest frequency it will
display, but for all I know, the 'empty space' to its right is showing the
spectrum above it is void of signals.

So I can't tell if it remains possible that something in your setup is
oscillating at a frequency your device ignores, but which upsets the TV.

Having a high gain amp and a complex set of wiring makes this possible in
my experience - albeit in other applications. However I also found that
some amps sold for UHF also did this in the past.

Do you have something like a simple wideband power 'meter'? I've tested a
couple of these in the past and the did respond out-of-band so might show
this up.

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics https://www.st-andrews.ac.uk/~www_pa...o/electron.htm
biog http://jcgl.orpheusweb.co.uk/history/ups_and_downs.html
Audio Misc http://www.audiomisc.co.uk/index.html

  #45  
Old August 25th 19, 10:49 AM posted to uk.tech.digital-tv
Bob Latham
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Posts: 747
Default UHF home distribution and witchcraft

The author has marked this message not to be archived. This post will be deleted on September 8, 2019.

In article ,
charles wrote:

Giving what level input?


Just done this again to get that info. This is the fully processed
aerial signal just after the 24dB attenuator being connected directly
into the input of the distribution amp.

C39
Level 68dBuV
CN 31.5dB
BER 99%
MER 99%


C40
Level 69dBuV
CN 28dB
BER 99%
MER 99%

Obviously 9dB lower with the extra attenuator added.

I've not got the experience to know if those figures are good, bad or
indifferent to be honest.


Bob.

--
Bob Latham
Stourbridge, West Midlands
  #46  
Old August 25th 19, 11:01 AM posted to uk.tech.digital-tv
Bob Latham
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Posts: 747
Default UHF home distribution and witchcraft

The author has marked this message not to be archived. This post will be deleted on September 8, 2019.

In article ,
Jim Lesurf wrote:

Yes: In that it explaines the blue bar, etc. But...


No: in that it doesn't tell me for certain how/if the device might
detect, say, an oscillation or transmission at 1GHz big enough to
blow your hat off! As shown it looks like the blue bar is the
highest frequency it will display, but for all I know, the 'empty
space' to its right is showing the spectrum above it is void of
signals.


I strongly suspect that the scan finishes after C69.

So I can't tell if it remains possible that something in your setup
is oscillating at a frequency your device ignores, but which upsets
the TV.


Having a high gain amp and a complex set of wiring makes this
possible in my experience - albeit in other applications. However I
also found that some amps sold for UHF also did this in the past.


Do you have something like a simple wideband power 'meter'?


Regrettably I do not.

I've tested a couple of these in the past and the did respond
out-of-band so might show this up.


Recommend? price?

Looking forward to the conversation me to wife: well yes I did buy
that fancy meter that cost quite a bit but it turns out I need ....

Bob.

--
Bob Latham
Stourbridge, West Midlands
  #47  
Old August 25th 19, 01:37 PM posted to uk.tech.digital-tv
Jim Lesurf[_2_]
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Posts: 4,567
Default UHF home distribution and witchcraft

In article , Bob Latham
wrote:

Do you have something like a simple wideband power 'meter'?


Regrettably I do not.


I've tested a couple of these in the past and the did respond
out-of-band so might show this up.


Recommend? price?


Difficult to do with any reliability for various reasons. However FWIW...

These show calibration measurements I did on the FUNCube (expensive and
needs specific software) and two cheap 'level meters'.

http://jcgl.orpheusweb.co.uk/funcube/FUNcalibrate.html
http://jcgl.orpheusweb.co.uk/DVB/FringeCal.html
http://jcgl.orpheusweb.co.uk/DVB/SLXmeter.html

The snags are that I did the measurements some years ago, and I suspect
that even if you can buy the same model of meter as one I checked, they'll
vary from one example to another! So all the above does is show they do
tend to respond 'out of band'. The drawback of 'cheap' is that the device
may be made without much in terms of quality control or consistency. That's
why I calibrated mine with a decent HP sig gen, etc, when I had easy access
to one. (No longer the case, alas). Similarly, the readings they show are
only 'bigger the better' rather than being able to take the stated values
seriously.

However a cheap meter may help if you can also try a filter. e.g. one of
the '4G' passive filters. If that drops the measured level a lot its a sign
of a some RF above the current DVB-T band. [1] I think you can still buy
both the meters and the filters from places like CPC. Bill may also be able
to suggest something better.

Looking forward to the conversation me to wife: well yes I did buy that
fancy meter that cost quite a bit but it turns out I need ....


The fancy meter will do some useful things and is probably a lot better
calibrated than the cheap meters. And so cheap you can probably get one
without her noticing... :-)

All the above said, I don't know this is the source of your problems. Only
that it is possible. So given the low cost worth a try perhaps.

Jim

[1] And if - as I assume - your system already filters off 4G that implies
an oscillation or a failed filter!

--
Please use the address on the audiomisc page if you wish to email me.
Electronics https://www.st-andrews.ac.uk/~www_pa...o/electron.htm
biog http://jcgl.orpheusweb.co.uk/history/ups_and_downs.html
Audio Misc http://www.audiomisc.co.uk/index.html

  #48  
Old August 25th 19, 01:46 PM posted to uk.tech.digital-tv
Bill Wright[_3_]
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Posts: 3,601
Default UHF home distribution and witchcraft

On 24/08/2019 18:08, Bob Latham wrote:
In article ,
wrote:

Let us know how you get on!


I've just done a fundamental test I should have done before posting
at all.

I took the conditioned aerial signal at the point where the 24dB
attenuator plugs into the filter combiner (first point in the lounge)
and connected that directly through to the distribution amp. This
them removes everything between what comes down from the loft and the
distribution amp.

No change what so ever. C40 perfect going into distribution amp has
variable MER after the amp. On the back of the kitchen TV C39 is
awful quality according to the TV and yet both BER and MER are
perfect according my test meter.

I then added a 9dB attenuator just before the distribution amp.

Again no difference to either fault.

To me this proves categorically that this problem is nothing to do
with Humax and Sony boxes, Sky boxes, Sky link+ boxes splitters and
combiners because none of them were in circuit.

As I said a couple of days ago - witchcraft.


Cheers,

Bob.

So now you bypass the amp.

Bill
  #50  
Old August 26th 19, 12:53 PM posted to uk.tech.digital-tv
Bill Wright[_3_]
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Posts: 3,601
Default UHF home distribution and witchcraft

On 26/08/2019 12:30, Terry Casey wrote:

We pulled the centr dielectric out of the old plug and found
that, when the cable was prepped, the last eight of an inch or
so of foil screen had been ripped off.

Very weird.


A similar one, and I've had it more than once: A microscopically thin
turning of brass, almost invisible to the eye, gets lodged between the
body and the inner. It's possible to look into the mouth of the plug and
not see this.

Bill
 




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