Does anyone know where I can buy a twin RF modulator - i.e. two a/v
inputs, with RF pass-through and preferably wideband channel choice?

I want to use it for a pair of CCTV cameras which I want to be able to
view on various TV's around the house. I was originally thinking of
daisy-chaining a pair of modulators together, but my existing AV setup
is very extensive (Tivo, Sky Plus, VCR, distribution around the
house...) so I'm concerned about the signal loss. I've already had
problems with signal loss after introducing new RF equipment into the
loop.

TIA for any tips.

"ITM" wrote in message
news
Does anyone know where I can buy a twin RF modulator - i.e. two a/v
inputs, with RF pass-through and preferably wideband channel choice?

I want to use it for a pair of CCTV cameras which I want to be able to
view on various TV's around the house. I was originally thinking of
daisy-chaining a pair of modulators together, but my existing AV setup
is very extensive (Tivo, Sky Plus, VCR, distribution around the
house...) so I'm concerned about the signal loss. I've already had
problems with signal loss after introducing new RF equipment into the
loop.

TIA for any tips.

I think you'll find it difficult to get an RF modulator to send out two
different station signals from the one box, but you might be able to find a
modulator with two camera inputs and one RF output, which will then switch
between the two cameras or show both in a "picture in picture" format, but
these will be slightly more expensive.


---
http://www.basecuritysystems.no-ip.com

Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.673 / Virus Database: 435 - Release Date: 01/05/04

"ITM" wrote
| Does anyone know where I can buy a twin RF modulator - i.e. two a/v
| inputs, with RF pass-through and preferably wideband channel choice?

try uk.tech.digital-tv and wait for Bill to come around; also see his
website:
http://www.wrightsaerials.tv/
http://www.wrightsaerials.tv/Resourc...annel%20TV.pdf

and ebay.co.uk under tvaerialguy

http://cgi6.ebay.co.uk/ws/eBayISAPI....include=0&user
id=tvaerialguy&sort=2&rows=25&since=-1&rd=1

item no 3093791615 sounds like what you want for the modulator (shame he
hasn't got two of 3093791602) and maybe 3093791617 for the filter-leveller.

| I've already had problems with signal loss after introducing new
| RF equipment into the loop.

You don't need to daisy-chain them, just adjust the signals to the correct
level on each channel and then combine them eg


UHF Broadcast TV --------------- notch filters
| if needed to remove
| clashes with in-house
V channels
UHF in to Sky and Tivo |
|
-----|
|
Sky Box UHF out - channel pass filter |
and level adjust -----------|
|
Tivo UHF out - channel pass filter |
and level adjust --------------|
|
CCTV UHF out - channel pass filter |
and level adjust --------------|
|
CCTV UHF out - channel pass filter |
and level adjust --------------|
|
COMBINER ---- TVs

(or somethign like that anyway)

Owain

ITM wrote:
Does anyone know where I can buy a twin RF modulator - i.e. two a/v
inputs, with RF pass-through and preferably wideband channel choice?

I want to use it for a pair of CCTV cameras which I want to be able to
view on various TV's around the house. I was originally thinking of
daisy-chaining a pair of modulators together, but my existing AV setup
is very extensive (Tivo, Sky Plus, VCR, distribution around the
house...) so I'm concerned about the signal loss. I've already had
problems with signal loss after introducing new RF equipment into the
loop.

It's probably simpler to get a signal combiner, and simply plug both
modulators into it, before feeding to the rest of the house.

"Owain" wrote
| You don't need to daisy-chain them, just adjust the signals to the correct
| level on each channel and then combine them eg
|
|
| UHF Broadcast
| |
| V
| UHF in to Sky and Tivo

Well, duh. Sky doesn't need a UHF in, I was thinking of a Freeview box.

Owain

"BigWallop" wrote in message
...

"ITM" wrote in message
news
Does anyone know where I can buy a twin RF modulator - i.e. two a/v
inputs, with RF pass-through and preferably wideband channel choice?

I want to use it for a pair of CCTV cameras which I want to be able to
view on various TV's around the house. I was originally thinking of
daisy-chaining a pair of modulators together, but my existing AV setup
is very extensive (Tivo, Sky Plus, VCR, distribution around the
house...) so I'm concerned about the signal loss. I've already had
problems with signal loss after introducing new RF equipment into the
loop.

TIA for any tips.

I think you'll find it difficult to get an RF modulator to send out two
different station signals from the one box, but you might be able to find
a
modulator with two camera inputs and one RF output, which will then switch
between the two cameras or show both in a "picture in picture" format, but
these will be slightly more expensive.



Might be worth a visit to the Antiference web site:

http://www.antiference.co.uk/da.htm

They have quite a good range of products that might be of help or give some
ideas.


---
http://www.basecuritysystems.no-ip.com

Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.673 / Virus Database: 435 - Release Date: 01/05/04

On Mon, 3 May 2004 15:32:59 +0100, "Owain"
wrote:

You don't need to daisy-chain them, just adjust the signals to the correct
level on each channel and then combine them eg


UHF Broadcast TV --------------- notch filters
| if needed to remove
| clashes with in-house
V channels
UHF in to Sky and Tivo |
|
-----|
|
Sky Box UHF out - channel pass filter |
and level adjust -----------|
|
Tivo UHF out - channel pass filter |
and level adjust --------------|
|
CCTV UHF out - channel pass filter |
and level adjust --------------|
|
CCTV UHF out - channel pass filter |
and level adjust --------------|
|
COMBINER ---- TVs

(or somethign like that anyway)

Owain

Uh-oh...this is looking a little more complicated than I thought...!

I hadn't anticipated the need for channel pass filters and level
adjusters...could someone please explain this?

I've just come across this, which looks like what I thought I needed:

http://custom1.farnell.com/cpc/produ...%5 Fid=251767

It looks a little expensive, but from what you're all saying, will I
also need something in addition to this??

Thanks for all the help.

On Mon, 03 May 2004 14:40:02 GMT, Ian Stirling
wrote:

ITM wrote:
Does anyone know where I can buy a twin RF modulator - i.e. two a/v
inputs, with RF pass-through and preferably wideband channel choice?

I want to use it for a pair of CCTV cameras which I want to be able to
view on various TV's around the house. I was originally thinking of
daisy-chaining a pair of modulators together, but my existing AV setup
is very extensive (Tivo, Sky Plus, VCR, distribution around the
house...) so I'm concerned about the signal loss. I've already had
problems with signal loss after introducing new RF equipment into the
loop.

It's probably simpler to get a signal combiner, and simply plug both
modulators into it, before feeding to the rest of the house.


Although the channels need to be chosen carefully to avoid
interference of the modulator harmonics with the TV signals.

This involves checking the channels in use and avoiding those that are
3,5,7 and 9 channels away from any terrestrial signal.


..andy

To email, substitute .nospam with .gl

On Mon, 03 May 2004 18:02:12 +0100, Andy Hall
wrote:

Although the channels need to be chosen carefully to avoid
interference of the modulator harmonics with the TV signals.

This involves checking the channels in use and avoiding those that are
3,5,7 and 9 channels away from any terrestrial signal.


.andy

To email, substitute .nospam with .gl

All of my existing channels are in the range 23-50. If I use the twin
RF modulator from CPC, and put the cameras on channels 53 and 56 then
in theory there should be no problems, right?

In this case, would I have any need for channel pass filters or level
adjusters??

On Mon, 03 May 2004 17:15:07 GMT, ITM wrote:

On Mon, 03 May 2004 18:02:12 +0100, Andy Hall
wrote:

Although the channels need to be chosen carefully to avoid
interference of the modulator harmonics with the TV signals.

This involves checking the channels in use and avoiding those that are
3,5,7 and 9 channels away from any terrestrial signal.


.andy

To email, substitute .nospam with .gl

All of my existing channels are in the range 23-50. If I use the twin
RF modulator from CPC, and put the cameras on channels 53 and 56 then
in theory there should be no problems, right?

Sorry, but it isn't as easy as that.

Apart from avoiding being on the TV channels, you also need to avoid
being on (N + 5) and (N + 9) away from them as well or you will get
interference.

This means looking up the exact channels in use by the terrestrial
transmitter(s) and avoiding those that are 5 and 9 channels away, as
well as any that are adjacent.

http://www.wrightsaerials.tv/Resourc...hannel%205.pdf


In this case, would I have any need for channel pass filters or level
adjusters??

Channelising filters will help with adjusting everything to equal
level.

www.teldis.com



..andy

To email, substitute .nospam with .gl

On Mon, 03 May 2004 18:51:13 +0100, Andy Hall
wrote:
Channelising filters will help with adjusting everything to equal
level.

Sorry I've never come across a channelising filter...presumably this
would need to fitted in line with the output RF from the twin
modulator? A Google search didn't find any such beast - could you
possibly direct me to a URL for one of these?
What would happen if I didn't use a filter?

On Mon, 03 May 2004 18:00:12 GMT, ITM wrote:

On Mon, 03 May 2004 18:51:13 +0100, Andy Hall
wrote:
Channelising filters will help with adjusting everything to equal
level.

Sorry I've never come across a channelising filter...presumably this
would need to fitted in line with the output RF from the twin
modulator?

Yes.

Normally you use a single input levelling filter on the signals coming
from the antenna and a multiple input one on the inputs from the local
modulators. Then you combine the two outputs together through a
splitter and amplify the result via a distribution amplifier to feed
the TV sets.

A Google search didn't find any such beast - could you
possibly direct me to a URL for one of these?

http://www.teldis.com/CP-SCLSCC.htm


What would happen if I didn't use a filter?

You will see a variation in picture quality across the different
signal sources and may see interference.

..andy

To email, substitute .nospam with .gl

"ITM" wrote
| You don't need to daisy-chain them, just adjust the signals to the
| correct level on each channel and then combine them eg
| (or somethign like that anyway)
| Uh-oh...this is looking a little more complicated than I thought...!
| I hadn't anticipated the need for channel pass filters and level
| adjusters...could someone please explain this?

As Andy said, you need to avoid 3/5/7/9 channels to existing channels. As
well as the 5 'normal' terrestrial channels, you will probably also have
digital multiplexes (making 10 or 11 channels in use) and possibly also
fainter 'copies' of the normal terrestrial channels from more distant
transmitters. Once the 3/5/7/9 channel spacing is taken into account there
end up being a shortage of spare channels.

You also want to avoid having multiple sources of the same channel being
passed through different devices, and wildly differing levels between
channels.

So you put channel pass filters to kill anything unwanted at source and
adjust the levels of the wanted channels, if needed, before distributing
round.

| I've just come across this, which looks like what I thought I needed:
|
http://custom1.farnell.com/cpc/produ...Catalogue&prod
uct%5Fid=251767
| It looks a little expensive,

Especially when you could get item no 3094296967 for a tenner at the moment
(3 modulators) accompanied by excellent technical support :-) or you might
just as well buy two of these

http://custom1.farnell.com/cpc/produ...Catalogue&prod
uct%5Fid=251765

| but from what you're all saying, will I
| also need something in addition to this??

That depends on the channels allocated and their signal levels, in your area
(and just how good a job you want to do).

Owain