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uk.tech.digital-tv (Digital TV - General) (uk.tech.digital-tv) Discussion of all matters technical in origin related to the reception of digital television transmissions, be they via satellite, terrestrial or cable. Advertising is forbidden, with no exceptions.

Somebody down my way...



 
 
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  #11  
Old October 28th 16, 02:50 AM posted to uk.tech.digital-tv
Graham.[_12_]
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Posts: 413
Default Somebody down my way...

On Thu, 27 Oct 2016 19:13:33 +0100, "Brian Gaff"
wrote:

Buzzing sound just like everybody else would and indeed used to from
scanning radios. Come on its obvious surely? It was great fun when the
Europeans used band 1 and 3 for tv as you could hear the buzz and knew that
sporadic E or F2 was around. Indeed from here on band 1 you could nearly
always hear Lille 819 line tv buzz in the low end of band one with a three
element beam up high enough and horizontal.
Brian


There used to be an unoffical beacon in the 2m band in these parts on
144.750. It was the 3rd harmonic of the Holme Moss sound carrier.

Annother Holme Moss fact, The mast is suprisingly close to the road,
but you can often drive past it in clouds and not see it at all.





--

Graham.

%Profound_observation%
  #12  
Old October 28th 16, 03:33 PM posted to uk.tech.digital-tv
Graham.[_12_]
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Posts: 413
Default Somebody down my way...

"Benderthe.evilrobot" Wrote
in message:

"Brian Gaff" wrote in message
...
Has one of those old analogue Video sender devices, as up in the 800Mhz
area I can often hear some sound from various sources, sometimes its
foreign sounding tv, sometimes one of the Sky channels or a movie.
I would assume whe this is illegal and may be interfered with by digital
transmissions at some time in the fuuture.
I wonder if they realise others can hear it. Not heard any video though so
maybe that is too low a level.


With the old analogue TVs, it was possible for the sound IF to pick up SW
radio if it wasn't adequately shielded. Since there probably isn't much FM
at 6MHz, it hinted at less than perfect AM rejection. The vision IF is
somewhere around 39.5MHz, breakthrough would indicate faulty traps/filtering
at the final IF stage/detector.

You can also get heterodyning of perfectly legitimate transmissins that
shift a weak image of it into a band they shouldn't be.

TV sound is FM, usually its easier to demodulate FM with an AM detector than
the other way round - the Bush/Rank A823 chassis early revisions used a
slope-tuned AM detector. OTOH: some band II radios will just about bring in
the bottom edge of the VHF airband - it depends on the AM rejection (or lack
of) of each individual receiver.



That RBM chassis was very badly designed and was the main culprit
for picking up Moscow and Piking on the 49meter-band. I used to
make braid -breakers out of co-ax and PVC tape to deal with it.

I discovered amateur radio when a tap fell off the ferrite rod
aerial of my pocket radio and it started to receive signals above
as well as below the LO. I used to hear G3UKZ chatting to G2DBV
on Sunday mornings on topband, and those gentlemen became my
mentors in the hobby.
--

%Profound_observation%


----Android NewsGroup Reader----
http://usenet.sinaapp.com/
  #13  
Old October 28th 16, 06:49 PM posted to uk.tech.digital-tv
Benderthe.evilrobot
external usenet poster
 
Posts: 148
Default Somebody down my way...


"Graham." wrote in message
...
"Benderthe.evilrobot" Wrote
in message:

"Brian Gaff" wrote in message
...
Has one of those old analogue Video sender devices, as up in the 800Mhz
area I can often hear some sound from various sources, sometimes its
foreign sounding tv, sometimes one of the Sky channels or a movie.
I would assume whe this is illegal and may be interfered with by digital
transmissions at some time in the fuuture.
I wonder if they realise others can hear it. Not heard any video though
so
maybe that is too low a level.


With the old analogue TVs, it was possible for the sound IF to pick up SW
radio if it wasn't adequately shielded. Since there probably isn't much
FM
at 6MHz, it hinted at less than perfect AM rejection. The vision IF is
somewhere around 39.5MHz, breakthrough would indicate faulty
traps/filtering
at the final IF stage/detector.

You can also get heterodyning of perfectly legitimate transmissins that
shift a weak image of it into a band they shouldn't be.

TV sound is FM, usually its easier to demodulate FM with an AM detector
than
the other way round - the Bush/Rank A823 chassis early revisions used a
slope-tuned AM detector. OTOH: some band II radios will just about bring
in
the bottom edge of the VHF airband - it depends on the AM rejection (or
lack
of) of each individual receiver.



That RBM chassis was very badly designed and was the main culprit
for picking up Moscow and Piking on the 49meter-band.


When Television magazine was in its prime, I used to read about other
engineers complaining what a nasty piece of work the colour decoder was. The
were pretty much 2 versions - a 2 chip and the earlier 1 chip + many
discretes. It was more often than not one of the chips, and easy to diagnose
once you learned the ropes.

It was usually the vertical output that gave me the worse struggles.

One colour fault that could've been tricky was a SC emitter follower in the
signal path. The customer wanted to wait, so I rolled my sleeves up and got
stuck in. I noticed a heat stain rising from a BC148 near the edge of the
PCB. After a bit of searching, I couldn't find a culprit, so I replaced the
220mW BC148 with a 300mA BC108.

At least the early marks had the same stacked pair of horizontal output
transistors as the Philips G8. Setting up the balancing inductor was lots of
fun.

  #17  
Old October 30th 16, 06:26 PM posted to uk.tech.digital-tv
Adrian Caspersz
external usenet poster
 
Posts: 273
Default Somebody down my way...

On 28/10/16 18:49, Benderthe.evilrobot wrote:

That RBM chassis was very badly designed and was the main culprit
for picking up Moscow and Piking on the 49meter-band.


When Television magazine was in its prime


(Interesting stuff snipped)

Hello "Benderthe.evilrobot" (Ian?)

We occasionally have juvenille posters here troll with that kind of
identity.

Does this really fit you, and make others take you seriously?

--
Adrian C
  #18  
Old October 30th 16, 06:48 PM posted to uk.tech.digital-tv
Benderthe.evilrobot
external usenet poster
 
Posts: 148
Default Somebody down my way...


"Terry Casey" wrote in message
...
In article ,
says...

"Terry Casey" wrote in message
...

You are comparing the dissipation of the BC148 with the
collector current of the BC108!

In practice, the specifications of both types are identical
(although I would back the BC108 as having a longer life as
it doesn't suffer from the problems caused by the plastic
encapsulation of the BC148).


The difference is the dissipation; 220mW for the 148 and 300mW for the
108.

I'm kinda wondering how you could miss 300mA was a
typo.............................................. ......


Sorry but you still got it wrong! The maximum collector
current for both types is 200mA whereas the maximum
dissipation of the BC148, at 350mW, is actually higher that
the 300mW specified for the BC108 ...

See:

https://dl.dropboxusercontent.com/u/24301298/BC108%20-%
20BC148.png

or http://tinyurl.com/bc108-bc148


The values I remember are from an early Mullard pocket databook maybe late
60s/early 70s - since then; dozens of companies have produced second source
devices, and a few had their own interpretation of the specifications.

AFAIK: Both devices have identical silicon die, the main difference is
higher power dissipation for the metal TO18 can than the plastic lockfit
package.

  #19  
Old October 30th 16, 08:14 PM posted to uk.tech.digital-tv
Bill Wright[_3_]
external usenet poster
 
Posts: 1,973
Default Somebody down my way...

On 30/10/2016 18:26, Adrian Caspersz wrote:

Hello "Benderthe.evilrobot" (Ian?)

We occasionally have juvenille posters here troll with that kind of
identity.

Does this really fit you, and make others take you seriously?


But he's of robot heritage. That makes you a racist.

Bill
  #20  
Old October 30th 16, 09:03 PM posted to uk.tech.digital-tv
Benderthe.evilrobot
external usenet poster
 
Posts: 148
Default Somebody down my way...


"Bill Wright" wrote in message
...
On 30/10/2016 18:26, Adrian Caspersz wrote:

Hello "Benderthe.evilrobot" (Ian?)

We occasionally have juvenille posters here troll with that kind of
identity.

Does this really fit you, and make others take you seriously?


But he's of robot heritage. That makes you a racist.


IOW: - "bite my shiny metal ass".

 




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