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Wired TV RF distribution question

T

TheMekon

Jan 1, 1970
0
Not sure if this is the right forum but here goes....


I need to distribute off-air TV round a client's premises to about 20
outlets as RF
Easy, I get my friendly aerial man to do a distribution amplifier etc.

(I am in the UK and we are talking about PAL system I)

But...

Client also needs 6 channels of locally sourced video mixed in with the
distribution.
If it was 1 or 2 channels I would just get cheap modulators, choose a
couple of blank channels and mix it in with the off-air feed.
But doing 6 channels worries me.
Do I need to worry about the performance of cheap modulators?
Do I need to worry about intermodulation problems?
What else do I need to worry about?

Thanks!
 
M

Marky P

Jan 1, 1970
0
Not sure if this is the right forum but here goes....


I need to distribute off-air TV round a client's premises to about 20
outlets as RF
Easy, I get my friendly aerial man to do a distribution amplifier etc.

(I am in the UK and we are talking about PAL system I)

But...

Client also needs 6 channels of locally sourced video mixed in with the
distribution.
If it was 1 or 2 channels I would just get cheap modulators, choose a
couple of blank channels and mix it in with the off-air feed.
But doing 6 channels worries me.
Do I need to worry about the performance of cheap modulators?
Do I need to worry about intermodulation problems?
What else do I need to worry about?

Thanks!

Hmmm. I'm not THE expert on here, but let's see... Where abouts in
the country will this installation be? You need to find out all the
frequencies used for analogue & digital TV that cover your clients
area THEN find out if there a six spare ones. It's possible, but
sounds like a bit of a sod.

Marky P.
 
D

Dave Plowman (News)

Jan 1, 1970
0
Not sure if this is the right forum but here goes....

I need to distribute off-air TV round a client's premises to about 20
outlets as RF
Easy, I get my friendly aerial man to do a distribution amplifier etc.
(I am in the UK and we are talking about PAL system I)

Client also needs 6 channels of locally sourced video mixed in with the
distribution.
If it was 1 or 2 channels I would just get cheap modulators, choose a
couple of blank channels and mix it in with the off-air feed.
But doing 6 channels worries me.
Do I need to worry about the performance of cheap modulators?
Do I need to worry about intermodulation problems?
What else do I need to worry about?

You Haven't a chance in hell of getting that number of channels to work
well. They'll work after a fashion, though.
 
T

tony sayer

Jan 1, 1970
0
Dave Plowman (News) said:
You Haven't a chance in hell of getting that number of channels to work
well. They'll work after a fashion, though.

Yes it will work, you just need the right equipment.

Look up Taylor transmitters in Oldham they do this sort of stuff and
sell it everyday!. A combination of modulators and channel filters is
what's required.

Bill W could no doubt give you chapter and verse on this subject...
 
C

charles

Jan 1, 1970
0
You Haven't a chance in hell of getting that number of channels to work
well. They'll work after a fashion, though.

I think you'll have to keep out all stray ones. That means using
channelised filters on the input. Then you should have reasonably clear
space to add your 6 new ones. Remember to avoid n+5 and n+9, although the
latter doesn't affect modern sets. ('n' being wanted channels)
 
I

Ivor Jones

Jan 1, 1970
0
[snip]

: : Yes it will work, you just need the right equipment.
: :
: : Look up Taylor transmitters in Oldham they do this
: : sort of stuff and sell it everyday!. A combination of
: : modulators and channel filters is what's required.
: :
: : Bill W could no doubt give you chapter and verse on
: : this subject... --
: : Tony Sayer

I have 6 "extra" channels distributed around the house (2 x DVD recorders,
2 x VHS recorders, 2 Freeview boxes) and it works, but there's not a lot
of space between some of them..!

I'm in the Midlands and receive from Sutton Coldfield (Lichfield for Ch.5)
and the channel numbers used are as follows:

22 - Freeview 1
26 - Freeview 2
31 - VCR 1

37 - Ch 5
40 - BBC2
43 - ITV1
46 - BBC1
50 - Ch 4

60 - DVD 1
65 - DVD 2
68 - VCR 2


Ivor
 
D

Dave Plowman (News)

Jan 1, 1970
0
Yes it will work, you just need the right equipment.
Look up Taylor transmitters in Oldham they do this sort of stuff and
sell it everyday!. A combination of modulators and channel filters is
what's required.
Bill W could no doubt give you chapter and verse on this subject...

I've yet to see one work what I'd consider perfectly. And I've seen plenty
of RF distribution systems in studio complexes. Where I assume cost
doesn't matter.
 
B

Bill Wright

Jan 1, 1970
0
TheMekon said:
Not sure if this is the right forum but here goes....


I need to distribute off-air TV round a client's premises to about 20
outlets as RF
Easy, I get my friendly aerial man to do a distribution amplifier etc.

(I am in the UK and we are talking about PAL system I)

But...

Client also needs 6 channels of locally sourced video mixed in with the
distribution.
If it was 1 or 2 channels I would just get cheap modulators, choose a
couple of blank channels and mix it in with the off-air feed.
But doing 6 channels worries me.
Do I need to worry about the performance of cheap modulators?
Do I need to worry about intermodulation problems?
What else do I need to worry about?


This is what we do. It's our mainstream business.

See:

http://www.wrightsaerials.tv/SystemPlan.htm

http://www.wrightsaerials.tv/Main Services/System Planning/example of working drawing 2.pdf

http://www.wrightsaerials.tv/410boxesthreeandfour.htm

Contact me via the website if you think we can do business.

Bill
 
C

charles

Jan 1, 1970
0
I've yet to see one work what I'd consider perfectly. And I've seen plenty
of RF distribution systems in studio complexes. Where I assume cost
doesn't matter.

but, if you've seen them in BBC studio complexes, consider how many Studio
Capital Projects people knew anything about RF. Mike Lyons did - in the
end.
 
B

Bill Wright

Jan 1, 1970
0
charles said:
but, if you've seen them in BBC studio complexes, consider how many Studio
Capital Projects people knew anything about RF. Mike Lyons did - in the
end.

Some of the worst RF botchery I've ever seen was in studios and news centres
and such like places.

Bill
 
B

Bill Wright

Jan 1, 1970
0
Dave Plowman (News) said:
I've yet to see one work what I'd consider perfectly. And I've seen plenty
of RF distribution systems in studio complexes. Where I assume cost
doesn't matter.

Well, I'm sorry, but you're wrong. There's no great difficulty in getting
excellent results from multichannel RF systems if you know what you're
doing. We do it every day. It isn't magic and it isn't rocket science.

We have customers who demand perfection, and they get it.

My own household/workshop system carries ten in-house channels, seven
off-air analogue and six off-air muxes and believe me I won't tolerate
anything less than perfect reception.

I know what's made you believe that it can't be done. You just never seen it
done properly so you've quite reasonably reached a (specious) general
conclusion.

Some of the worst systems I've seen have been in studio complexes. I could
name names . . .

Bill
 
C

charles

Jan 1, 1970
0
Some of the worst RF botchery I've ever seen was in studios and news
centres and such like places.

It doesn't surprise me at all. In Manchester you could watch the output of
the continuity studio in the road outside on a tv set. Talk about 'leaky
feeders'.
 
M

Mike J

Jan 1, 1970
0
charles said:
but, if you've seen them in BBC studio complexes, consider how many Studio
Capital Projects people knew anything about RF. Mike Lyons did - in the
end.

Ah a name to remember - re-built London Switching Centre as well!!

Mike
 
G

Graham.

Jan 1, 1970
0
charles said:
It doesn't surprise me at all. In Manchester you could watch the output
of
the continuity studio in the road outside on a tv set. Talk about 'leaky
feeders'.

The MDS was reasonably well engineered when it was first installed
(in-house) in the mid 80s

Before that there was a Top Rank twisted-pair system (vision carrier
a little higher than Redifusion IIRC) feeding 22in Doric monitors.
 
A

Alan White

Jan 1, 1970
0
Ah a name to remember - re-built London Switching Centre as well!!

Mike was the Project Engineer for the video installation assisted by
Mike Turner and Keith Sudel. I was the Project Engineer for the audio,
comms and switching installation assisted by Dave Daborn and Graham (?).

I think it was the second time that we'd used a
modular system of desk construction, the first being in Belfast CTA in
the late 60s. Prior to that, every desk panel was custom made for its
application. This was expensive and inefficient in terms of
Engineer/Draughtsman time and effort. Another Engineer, Denis Noble,
who worked for me on the Belfast CTA project, and I decided to go for
a set of standard modules which could be fitted into a desk to fulfil
the operational requirement. We used ISEP frames and modules, decided
that BBC ED24 grey was not a good colour in subdued lighting so went
for a dark green (068 in BS2660?) with yellow engraving, round push
buttons for executive functions, square buttons for non-executive and
the cabling to every panel had to be long enough to allow that panel
to be positioned anywhere in the desk. Roger Jephcott, who was the
Ops. Manager(?) requested a rearrangement one week before the service
date which was very easily accomplished. That would have been
impossible using the old construction method.

I can't remember what we used for the audio matrix but it was probably
Type 25 miniature relays which were in widespread use by then and had
replaced the PO 3000 in most applications. The video matrix would have
been a DD effort. One anomaly, which we had to overcome everywhere
with a married audio/video matrix, was that DD, in their wisdom had
wired the control inputs to the video matrix in terms of the
destinations and our audio matrix was wired in terms of the sources.
This was sorted out on PO tag blocks with the control cables from the
audio matrix being wired to the column tags and the control wires to
the video matrix being wired to the row tags (or the other way round).

Dave Daborn did a brilliant job on this desk. I think it was the most
successful desk that we'd installed up to that time and, probably,
since. Certainly there was a great deal of discussion about the layout
and the fact that it was built virtually in situ helped a lot.
 
M

Mike J

Jan 1, 1970
0
Alan said:
Mike was the Project Engineer for the video installation assisted by
Mike Turner and Keith Sudel. I was the Project Engineer for the audio,
comms and switching installation assisted by Dave Daborn and Graham (?).

I think it was the second time that we'd used a
modular system of desk construction, the first being in Belfast CTA in
the late 60s. Prior to that, every desk panel was custom made for its
application. This was expensive and inefficient in terms of
Engineer/Draughtsman time and effort. Another Engineer, Denis Noble,
who worked for me on the Belfast CTA project, and I decided to go for
a set of standard modules which could be fitted into a desk to fulfil
the operational requirement. We used ISEP frames and modules, decided
that BBC ED24 grey was not a good colour in subdued lighting so went
for a dark green (068 in BS2660?) with yellow engraving, round push
buttons for executive functions, square buttons for non-executive and
the cabling to every panel had to be long enough to allow that panel
to be positioned anywhere in the desk. Roger Jephcott, who was the
Ops. Manager(?) requested a rearrangement one week before the service
date which was very easily accomplished. That would have been
impossible using the old construction method.

I can't remember what we used for the audio matrix but it was probably
Type 25 miniature relays which were in widespread use by then and had
replaced the PO 3000 in most applications. The video matrix would have
been a DD effort. One anomaly, which we had to overcome everywhere
with a married audio/video matrix, was that DD, in their wisdom had
wired the control inputs to the video matrix in terms of the
destinations and our audio matrix was wired in terms of the sources.
This was sorted out on PO tag blocks with the control cables from the
audio matrix being wired to the column tags and the control wires to
the video matrix being wired to the row tags (or the other way round).

Dave Daborn did a brilliant job on this desk. I think it was the most
successful desk that we'd installed up to that time and, probably,
since. Certainly there was a great deal of discussion about the layout
and the fact that it was built virtually in situ helped a lot.

You mean like this Alan?

http://www.bostonmanor.plus.com/SWC_Main_Desk.jpg

and stories like this:-

http://www.bostonmanor.plus.com/ExBHComms/SWC.html

The previous re-build was after the first DD solid state matrix came in.
Controlled by 24way yaxley switches with a centre extra concentric
switch to select 1-24 + 25 (P&B) as no-one made 25way break before make
switches!!
That was after the first matrix install which was controlled from the
25way Ledex switches via the old video switching level as the other
levels were still in use for audio and 'marking'

Mike
(SWC 1969ish and sometime supervisor)
 
B

Bill Wright

Jan 1, 1970
0
charles said:
It doesn't surprise me at all. In Manchester you could watch the output
of
the continuity studio in the road outside on a tv set. Talk about 'leaky
feeders'.

I've told the story on here before of the housing estate that got satellite
telly from their aerials, thanks to the news facility over the road.

Bill
 
A

Alan White

Jan 1, 1970
0
You mean like this Alan?

http://www.bostonmanor.plus.com/SWC_Main_Desk.jpg

and stories like this:-

http://www.bostonmanor.plus.com/ExBHComms/SWC.html

The previous re-build was after the first DD solid state matrix came in.
Controlled by 24way yaxley switches with a centre extra concentric
switch to select 1-24 + 25 (P&B) as no-one made 25way break before make
switches!!
That was after the first matrix install which was controlled from the
25way Ledex switches via the old video switching level as the other
levels were still in use for audio and 'marking'

I remember the Ledex switches, which always struck me as being
incredibly crude. Didn't they come four to a box (or am I thinking of
something else) and were very noisy?

Andy Hame posted this link about eighteen months ago when this topic
came up,
www.acdale.plus.com/PeteT/LO_SWC_Desk.html which shows the desk in all
its glory.

Thanks very much indeed for your link. It all seems so long ago now but
then I suppose it was.

Mike Lyons and I did a lot together including rebuilding Cardiff
Broadway Switching Centre, my first 'big' job, Belfast Central Technical
Area, London SWC, and Glasgow Switching Centre. Happy days!

Thanks again, that was good.
 
T

tony sayer

Jan 1, 1970
0
charles said:
but, if you've seen them in BBC studio complexes, consider how many Studio
Capital Projects people knew anything about RF. Mike Lyons did - in the
end.

Suppose they were either SCPD or TCPD ;)...


There wasn't a RCPD was there?...
 
J

James Edwards hacksaw.com

Jan 1, 1970
0
tony said:
Suppose they were either SCPD or TCPD ;)...


There wasn't a RCPD was there?...


Not as I recall.


SCPD = Studio capital projects department, possibly now part of Siemens.

TCPD = Transmitter capital projects department is now a division in
the Warwick based company called National Grid Wireless, was at Henry
Wood house.

RD = Research Department at Kingswood Warren.
DD = Designs Department at Western House
ED = Equipment Department in Chiswick.

These three merged to form BBC R&D based at Kingswood Warren in Surrey.


There were other sections such as Transmitter group, Engineering
information Department, Communications Department ect.

Much of it merged, such as TCPD and Transmitter group merged to form
BBC Transmission.

Jim
 
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