Rebroadcast from TV IF?

[Steve DeGroof]

Someone recently asked me if it was possible to rebroadcast whatever
program a TV was tuned to. The first thing I thought of was to have
a receiver that picked up the TV's IF signal and converted it to a
broadcast frequency (e.g. channel 8). What I wasn't sure of was:
1. How well shielded is a TV's IF section?
2. Are there existing devices that will convert the IF signal to
a broadcast channel?

Any ideas?

 

[Jim Thompson]

On 8 May 2004 08:37:25 -0700, degroof@mindspring.com (Steve DeGroof)
wrote:

Someone recently asked me if it was possible to rebroadcast whatever
program a TV was tuned to. The first thing I thought of was to have
a receiver that picked up the TV's IF signal and converted it to a
broadcast frequency (e.g. channel 8). What I wasn't sure of was:
1. How well shielded is a TV's IF section?
2. Are there existing devices that will convert the IF signal to
a broadcast channel?

Any ideas?

Better to use the Video/Audio Outputs and use a 2GHz link set, such as
that made by MATCO, Inc., ASK-2008-TR Wireless System (8 selectable
operating frequencies).

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[Joerg]

Hi Steve,

The A/V outputs are indeed much easier to use, as Jim said. However,
there are cheaper alternatives if the goal is to reintroduce on an
otherwise unoccupied channel into a house cable network. We do that with
a Radio Shack TV modulator. It was under $50, has a PLL and can be
programmed to most cable and terrestrial channels.

Regards, Joerg
http://www.analogconsultants.com

 

[Tam/WB2TT]

"Jim Thompson" <thegreatone@example.com> wrote in message
newsd0q90pe5u1t6pibm77p3et1ereg0hmmf9@4ax.com...

On 8 May 2004 08:37:25 -0700, degroof@mindspring.com (Steve DeGroof)
wrote:

Someone recently asked me if it was possible to rebroadcast whatever
program a TV was tuned to. The first thing I thought of was to have
a receiver that picked up the TV's IF signal and converted it to a
broadcast frequency (e.g. channel 8). What I wasn't sure of was:
1. How well shielded is a TV's IF section?
2. Are there existing devices that will convert the IF signal to
a broadcast channel?

Any ideas?

Better to use the Video/Audio Outputs and use a 2GHz link set, such as
that made by MATCO, Inc., ASK-2008-TR Wireless System (8 selectable
operating frequencies).

...Jim Thompson

You can still buy the cheapie RF modulators (Think Atari and Pong) with
CH3/4 output. Don't know if the amplitude works out. There used to be at
least one version that output UHF.These things are also sold as accessories
for digital cameras; don't know if those have sound.

Steve: if your TV doesn't have baseband output, I bet your VCR does.

Tam

--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[Paul Burridge]

On 8 May 2004 08:37:25 -0700, degroof@mindspring.com (Steve DeGroof)
wrote:

Someone recently asked me if it was possible to rebroadcast whatever
program a TV was tuned to. The first thing I thought of was to have
a receiver that picked up the TV's IF signal and converted it to a
broadcast frequency (e.g. channel 8). What I wasn't sure of was:
1. How well shielded is a TV's IF section?
2. Are there existing devices that will convert the IF signal to
a broadcast channel?

I know absolutely nuthin' about TVs, but are they only single
conversion? And is/are the IF(s) a common standard around the world?
Broadcast signals here in the UK vary, but are typically around
700-800Mhz at some huge power or other I can't recall off hand.
--

"What is now proved was once only imagin'd." - William Blake, 1793.

 

[John Larkin]

On Sat, 08 May 2004 19:25:32 +0100, Paul Burridge
<pb@notthisbit.osiris1.co.uk> wrote:

I know absolutely nuthin' about TVs, but are they only single
conversion? And is/are the IF(s) a common standard around the world?
Broadcast signals here in the UK vary, but are typically around
700-800Mhz at some huge power or other I can't recall off hand.

Thank you. That was very helpful.

John

writ ironic

 

[Joerg]

Hi Tam,

The cheapie ch 3/4 versions often drift a lot, and sometimes these channels are
occupied by high powered stations that are so strong that it even gets into
cable.

Since TVs don't have good IF filters it is best to stay one channel away from
any strong signal. But those Radio Shack programmable modulators or others of
this kind do a nice job here. Many of them are UHF only but there are usually
free channels there.

Regards, Joerg
http://www.analogconsultants.com

 

[Jim Thompson]

On Sat, 08 May 2004 18:04:48 GMT, Joerg
<notthisjoergsch@removethispacbell.net> wrote:

Hi Steve,

The A/V outputs are indeed much easier to use, as Jim said. However,
there are cheaper alternatives if the goal is to reintroduce on an
otherwise unoccupied channel into a house cable network. We do that with
a Radio Shack TV modulator. It was under $50, has a PLL and can be
programmed to most cable and terrestrial channels.

Regards, Joerg
http://www.analogconsultants.com

Personally I use a ChannelsPlus central modulator, but it's not
inexpensive.

Last time I played around with RS modulators they were hypersensitive
to video level, producing beat-note bars and crappy sound.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[Joerg]

Hi Jim,

Well, our first one croaked. But it always got kind of hot, forgot its
channel setting after a power outage and so on. They took it back and gave us
a replacement. Since then no problems. Excellent video and sound, eventhough
I use it as high as it goes on Ch69. Its RF level is a bit wimpy but heck,
for $40 or $50 I won't complain if I had to spring another $20 for a 10dB
amp.

I did look at the pro versions but figured that the difference would be
better invested in some fresh local brew. TV doesn't have a high ranking on
our entertainment scale and, therefore, we don't afford it much in terms of a
budget. No cable, no satellite. Good ol' antenna.

Regards, Joerg
http://www.analogconsultants.com

 

[Jan Panteltje]

On a sunny day (Sat, 08 May 2004 19:25:32 +0100) it happened Paul Burridge
<pb@notthisbit.osiris1.co.uk> wrote in
<po7q90dhefg2bcca7dd65emo8ialliih5m@4ax.com>:

On 8 May 2004 08:37:25 -0700, degroof@mindspring.com (Steve DeGroof)
wrote:

Someone recently asked me if it was possible to rebroadcast whatever
program a TV was tuned to. The first thing I thought of was to have
a receiver that picked up the TV's IF signal and converted it to a
broadcast frequency (e.g. channel 8). What I wasn't sure of was:
1. How well shielded is a TV's IF section?
2. Are there existing devices that will convert the IF signal to
a broadcast channel?

I know absolutely nuthin' about TVs, but are they only single
conversion?
Yes

In Europe, and US is different.
Sound is modulated different, bandwidth is different

And is/are the IF(s) a common standard around the world?

Broadcast signals here in the UK vary, but are typically around
700-800Mhz at some huge power or other I can't recall off hand.
UK has only UHF, while we have VHF, ch4-12whatever, plus UHF.

We have 5.5 MHz FM sound, plus a second carrier FM for stereo
or second language.
No idea if US has stereo and how?

You could indeed mix the IF up, but only if intercarrier sound.
Some TVs have a separate IF for the sound.
Why not use an old VCR UHF output?
VHS will be free soon, DVD taking over.
JP

 

[Paul Burridge]

On Sat, 08 May 2004 11:39:27 -0700, John Larkin
<jjlarkin@highlandSNIPtechTHISnologyPLEASE.com> wrote:

On Sat, 08 May 2004 19:25:32 +0100, Paul Burridge
pb@notthisbit.osiris1.co.uk> wrote:



I know absolutely nuthin' about TVs, but are they only single
conversion? And is/are the IF(s) a common standard around the world?
Broadcast signals here in the UK vary, but are typically around
700-800Mhz at some huge power or other I can't recall off hand.

Thank you. That was very helpful.

John

writ ironic

Don't mention it. I believe in sharing knowledge.

writ ironic

--

"What is now proved was once only imagin'd." - William Blake, 1793.

 

[Steve DeGroof]

"Tam/WB2TT" <t-tammaru@c0mca$t.net> wrote in message news:<84adne5hV_csvwDdRVn-ug@comcast.com>...

Steve: if your TV doesn't have baseband output, I bet your VCR does.

Sure, you can do it that way, and I do something like that myself. I've

got DVD, VCR and dish baseband signals feeding into a switch, then to my
TV and a modulator to feed to other rooms in the house.

But that's the easy way. I mean, off-the-shelf products? Where's the fun
in that? I was more interested in whether it was possible to do it the
hard way. It would seem doable, assuming the IF section was leaky enough.

 

[Bill Bailley]

"Steve DeGroof" <degroof@mindspring.com> wrote in message
news:a064d318.0405080737.3b37deed@posting.google.com...

Someone recently asked me if it was possible to rebroadcast whatever
program a TV was tuned to. The first thing I thought of was to have
a receiver that picked up the TV's IF signal and converted it to a
broadcast frequency (e.g. channel 8). What I wasn't sure of was:
1. How well shielded is a TV's IF section?
2. Are there existing devices that will convert the IF signal to
a broadcast channel?

20 years ago I built a small transmitter of the type I think you mean. It
was designed to take the TV IF and mix it with an overtone xtal oscillator
to place it in the regular FM band. It used one of those ceramic filters, an
IF amp and a mixer and was realized out of a Motorola integrated cct
designed for a an FM radio. The mixer output fed a short antenna without
amplification or preselection. (tut tut !)

The output has been quite sufficient to be heard well over a range of 50
feet or so, and the audio quality is fine but slightly underdeviated. The
tiny thing is now tucked inside and wired to the current TV we use, this
being it's third home. It has always been a comfort to me to have a radio on
the side table by my armchair, with the TV sound directed at my good ear
from about 18 inches. When things get noisy, I can just switch to a
headphone.

Bill.

 

[Andrew VK3BFA]

degroof@mindspring.com (Steve DeGroof) wrote in message news:<a064d318.0405080737.3b37deed@posting.google.com>...

Someone recently asked me if it was possible to rebroadcast whatever
program a TV was tuned to. The first thing I thought of was to have
a receiver that picked up the TV's IF signal and converted it to a
broadcast frequency (e.g. channel 8). What I wasn't sure of was:
1. How well shielded is a TV's IF section?
2. Are there existing devices that will convert the IF signal to
a broadcast channel?

Any ideas?

Excuse my ignorance in asking this, but why would you want to do it?.
Why bother to rebroadcast a signal from one TV channel to be picked up
on a set tuned to another channel?. Why not tune the 2nd set to the
same channel as the first one....

If you are trying to do this without hooking into the TV set IF chain
(no, I cant use the bloody apostrophe so wont try), then any set for
100 yards will QRM your new IF receiver. Same IF for all sets.

Possibly you friend is concerned about being sprung for watching
things he shouldnt be (ie he hasnt paid his subscription). The usual
method in this case is to hunt for the LO frequency of the front end
on the offending TV - this is fairly easily done.

Pure conjecture on my part, but please explain WHY you want to do
this.......

73 de VK3BFA Andrew

 

[Paul Burridge]

On 9 May 2004 06:51:21 -0700, ablight@alphalink.com.au (Andrew VK3BFA)
wrote:

Same IF for all sets.

And that is.....?

Possibly you friend is concerned about being sprung for watching
things he shouldnt be (ie he hasnt paid his subscription). The usual
method in this case is to hunt for the LO frequency of the front end
on the offending TV - this is fairly easily done.

By TV detector vans in the UK, certainly. But is there only the *one*
IF?
--

"What is now proved was once only imagin'd." - William Blake, 1793.

 

[Jan Panteltje]

On a sunny day (Sun, 09 May 2004 17:05:11 +0100) it happened Paul Burridge
<pb@notthisbit.osiris1.co.uk> wrote in
<h8ls90lkr759r2uagdq16mqskn7u6anaqu@4ax.com>:

On 9 May 2004 06:51:21 -0700, ablight@alphalink.com.au (Andrew VK3BFA)
wrote:

Same IF for all sets.

And that is.....?


Possibly you friend is concerned about being sprung for watching
things he shouldnt be (ie he hasnt paid his subscription). The usual
method in this case is to hunt for the LO frequency of the front end
on the offending TV - this is fairly easily done.

By TV detector vans in the UK, certainly. But is there only the *one*
IF?
Once I lived close to a ch 4 TV transmitter (that is around 67MHz), and

got good video from a xtal diode and one tuned circuit.
No need for any LO.
On the headphones it sounds like prrrrrrrrrrrr vertical sync.
A good antenna will help a lot too.
Finally, you can always build your own tuner (as I did), and make sure
LO does not radiate.

 

[Rich Grise]

"Paul Burridge" <pb@notthisbit.osiris1.co.uk> wrote in message
news:h8ls90lkr759r2uagdq16mqskn7u6anaqu@4ax.com...

On 9 May 2004 06:51:21 -0700, ablight@alphalink.com.au (Andrew VK3BFA)
wrote:

Same IF for all sets.

And that is.....?


Possibly you friend is concerned about being sprung for watching
things he shouldnt be (ie he hasnt paid his subscription). The usual
method in this case is to hunt for the LO frequency of the front end
on the offending TV - this is fairly easily done.

By TV detector vans in the UK, certainly. But is there only the *one*
IF?

Well, there's the video and the audio, but in the US they're fixed at
a difference of, I think, 4.5 MHz. But yes, I'm fairly sure every TV
in the country (probably true in other localities) are on the same
IF freq. I don't remember the exact number, but it's around 45 MHz,
I think. AM broadcast uses a 455KHz IF, and FM broadcast uses 10.7MHz,
so it's not really unusual that all the TVs use the same IF.

But why was it you can't just tune the TV into the same channel as
the other one?

Cheers!
Rich

 

[Andrew VK3BFA]

Paul Burridge <pb@notthisbit.osiris1.co.uk> wrote in message news:<h8ls90lkr759r2uagdq16mqskn7u6anaqu@4ax.com>...

On 9 May 2004 06:51:21 -0700, ablight@alphalink.com.au (Andrew VK3BFA)
wrote:

Same IF for all sets.

And that is.....?


In Australia its 38.something Mhz for vision with the sound IF 5.5Mhz

away - cant remember the actual frequencies as I have never had to
tune one up except as a school exercise years ago - and besides, its
now done in one SAW filter so it cant be touched.

Think the UK is the same except the sound if if 4.5Mhz different. They
are called "standards", and are generally followed as a matter of mass
production economy..

Possibly you friend is concerned about being sprung for watching
things he shouldnt be (ie he hasnt paid his subscription). The usual
method in this case is to hunt for the LO frequency of the front end
on the offending TV - this is fairly easily done.

By TV detector vans in the UK, certainly. But is there only the *one*
IF?

Who knows? - was recently involved in such an exercise to find
un-authorised/hacked pay tv satellite receivers, there were different
If's but it wasnt a practical problem to scan them all - and besides,
the signal leakage from the distribution system was so high it could
be seen on an IFR with a simple preamp!

 

[L. Fiar]

"Paul Burridge" <pb@notthisbit.osiris1.co.uk> wrote in message
newso7q90dhefg2bcca7dd65emo8ialliih5m@4ax.com...

I know absolutely nuthin' about TVs, but are they only single
conversion? And is/are the IF(s) a common standard around the world?

The sound IF for UK TV is 6MHz, other countries may use 4.5MHz,
5,5MHz and 6.5MHz.

On old sets, the sound IF could often be picked up with a
radio that covered the frequency. Europe has now put their
foot down with a firm hand, enforcing emission standards.
At one
time, you could hold a mains tester screwdriver by the blade,
near a TV... and the fecker would light up in your hand.

Broadcast signals here in the UK vary, but are typically around
700-800Mhz at some huge power or other I can't recall off hand.

Maplin did include a list of the transmitters, channels, antenna
polarization and power levels. Not sure if they still do, but I do have an
old one here somewhere.
I also have a list of the old VHF TV frequencies from the 405 line
standard days.

 

[L. Fiar]

"Paul Burridge" <pb@notthisbit.osiris1.co.uk> wrote in message
news:h8ls90lkr759r2uagdq16mqskn7u6anaqu@4ax.com...

On 9 May 2004 06:51:21 -0700, ablight@alphalink.com.au (Andrew VK3BFA)
wrote:

The usual method in this case is to hunt for the
LO frequency of the front end on the offending
TV - this is fairly easily done.

By TV detector vans in the UK, certainly.

I am not so sure if they can still easily do this.
Emission standards have been set higher, so new sets may not put out enough
to be easily detected.

But is there only the *one* IF?

For UK TV, there are sound, vision and chroma IFs.

The transmitter frequencies are between 471MHz and 853MHz.
From these, the TV uses two IFs:
Vision = 39.5MHz
Sound = 33.5MHz
The two create the final sound IF:
6MHz.

Chroma (colour) information uses a subcarrier:
Chroma = 4.43MHz

Vision is amplitude modulated, sound is frequency modulated, chroma uses
suppressed carrier sideband.