What's the IF frequency in a Freeview box?
 

It can't be the long established 39.5 MHz for vision and 33.5 MHz for sound
as there's only one carrier. If everything else remained the same as an
analogue TV tuner, then the IF for a Freeview mulitplex would be 36.75 MHz.
But that doesn't sound like a very convenient frequency. Doesn't it need to
be a multiple of the symbol rate or something like that?

Does anyone know what the IF frequency of a Freeview tuner is?

What's the IF frequency in a Sky Digital box (not the LNB oscillator or the
LNB output, but the frequency inside the box when the signal from the LNB
gets down-converted again to tune in one particular transponder and decode
the QPSK modulation)?

What's the IF frequency in a Freeview box?
 

On 21/11/2007 20:57, Stephen wrote:

It can't be the long established 39.5 MHz for vision and 33.5 MHz for sound
as there's only one carrier.

Aren't there 1705 (2k) or 6817 (8k) carriers on DVB-T?

What's the IF frequency in a Freeview box?
 

"Stephen" wrote in message
...
It can't be the long established 39.5 MHz for vision and 33.5 MHz for
sound as there's only one carrier. If everything else remained the same as
an analogue TV tuner, then the IF for a Freeview mulitplex would be 36.75
MHz. But that doesn't sound like a very convenient frequency. Doesn't it
need to be a multiple of the symbol rate or something like that?

Does anyone know what the IF frequency of a Freeview tuner is?

What's the IF frequency in a Sky Digital box (not the LNB oscillator or
the LNB output, but the frequency inside the box when the signal from the
LNB gets down-converted again to tune in one particular transponder and
decode the QPSK modulation)?

See:

http://www.digitalradiotech.co.uk/ar...r-Freeview.php

What's the IF frequency in a Freeview box?
 

"Stephen" wrote:

Does anyone know what the IF frequency of a Freeview tuner is?

I believe that Freeview tuners have a superhet front-end with a single
stage of IF that feeds straight into an ADC for a software-defined radio,
and all of it inside a chip with no external tuning coils. So the IF
frequency would probably be proprietary to the chip maker and they
wouldn't have to mention it in the chip's functional definition. For all
I know, each Freeview chip maker might use a different IF frequency.

http://en.wikipedia.org/wiki/Software_defined_radio

--
Dave Farrance

What's the IF frequency in a Freeview box?
 

In article , Paul Martin
writes
In article ,
Stephen wrote:

It can't be the long established 39.5 MHz for vision and 33.5 MHz for
sound as there's only one carrier. If everything else remained the
same as an analogue TV tuner, then the IF for a Freeview mulitplex
would be 36.75 MHz. But that doesn't sound like a very convenient
frequency. Doesn't it need to be a multiple of the symbol rate or
something like that?

Good question. I think some DSP tricks are used instead (undersampling,
possibly).

Is the implication of this that there's no IF to be detected by a
detector van?

Just wondering... impishly.

Regards,

Simonm (struggling to keep up at the back).

--
simonm|at|muircom|dot|demon|.|c|oh|dot|u|kay
SIMON MUIR, BRISTOL UK
EUROPEANS AGAINST THE EU http://www.eurofaq.freeuk.com/
GT250A'76 R80/RT'86 110CSW TDi'88 www.kc3ltd.co.uk/profile/eurofollie/

What's the IF frequency in a Freeview box?
 

Paul Martin wrote:

Is the implication of this that there's no IF to be detected by a
detector van?

Even if there is an IF, it'll be far harder to detect, due to the
pseudo-random nature of the signal. Tuners are also very well screened
nowadays. With LCD TVs there's no scan coil radiation, as there are no
scan coils.

If TV detector vans ever worked (other than psychologically) they'll be
less effective come Analogue Switch Off.

Although that said there have been a couple of cases of the coastguard being
called out to a carrier on the international distress frequency, 121.5 MHz (9
x 13.5 MHz luminance sampling freq )

--
Mark
Please replace invalid and invalid with gmx and net to reply.

What's the IF frequency in a Freeview box?
 

"Paul Martin" wrote in message
...

If TV detector vans ever worked (other than psychologically) they'll be
less effective come Analogue Switch Off.


Oh I am sure they worked. As a lowly student I received a letter for the TV
license people stating "There is a television set located in the upper left
back room of this house" so unless they had x-ray specs they must have
detected it.

But I agree, it will be much, much more difficult with LCD and flatscreens
with no large radiations of IF.

//Clive.

What's the IF frequency in a Freeview box?
 

Stephen wrote:

Does anyone know what the IF frequency of a Freeview tuner is?

Typically 36-and-a-bit MHz channel centre frequency, at least in
traditional discrete superhet tuners. Some receivers do A/D conversion
at this 1st IF, others downconvert to a 2nd IF around 4 MHz first.

What's the IF frequency in a Sky Digital box (not the LNB oscillator or the
LNB output, but the frequency inside the box when the signal from the LNB
gets down-converted again to tune in one particular transponder and decode
the QPSK modulation)?

Standard 2nd IFs in the analogue satellite days were around 480 MHz and
130-ish MHz. But don't most digital boxes use 'zero-IF silicon tuners'
these days?

--
Andy

What's the IF frequency in a Freeview box?
 

"Clive" wrote in message
...

"Paul Martin" wrote in message
...

If TV detector vans ever worked (other than psychologically) they'll be
less effective come Analogue Switch Off.


Oh I am sure they worked. As a lowly student I received a letter for the
TV
license people stating "There is a television set located in the upper
left
back room of this house" so unless they had x-ray specs they must have
detected it.

But I agree, it will be much, much more difficult with LCD and flatscreens
with no large radiations of IF.

//Clive.

Picking up computer monitor screens used to be a far more lucrative gig, if
you were of the criminal or intelligence communities. I once worked at a
plant in the US that had sensitive stuff inside (well away from me!) and
they had a camper van outside with various equipment permanently monitoring
what they could pick up from inside via the big aerial on the roof.

And the way to make the PC "US DOD secure" was to enclose it in a Faraday
cage, disconnect the floppy drive (pre-USB but I imagine they have be
disabled too), no network etc. I did wonder about leakage via the power
lead but I believe that was sufficiently small to be secure. It was also
interesting to consider what exactly they could do with such a secured PC!

Paul DS.

What's the IF frequency in a Freeview box?
 

Well, back in the 80s, I had a look inside a detector van, as has been
mentioned, there were several ways to detect tvs. Local oscillators of
tuners radiating via the aerial, and laf output at the IF frequency, and
detection at vlf of scan signatures.

None were that accurate so it became a problem in blocks of flats!

I'd have thought the local oscillator could still be detected, but most of
the rest is probably obscured these days by radiation from switch mode psus
and computer equipment.

Brian

--
Brian Gaff....Note, this account does not accept Bcc: email.
graphics are great, but the blind can't hear them
Email:
__________________________________________________ __________________________________________________ __________


"Paul Martin" wrote in message
...
In article ,
SpamTrapSeeSig wrote:
In article , Paul Martin
writes
In article ,
Stephen wrote:

It can't be the long established 39.5 MHz for vision and 33.5 MHz for
sound as there's only one carrier. If everything else remained the
same as an analogue TV tuner, then the IF for a Freeview mulitplex
would be 36.75 MHz. But that doesn't sound like a very convenient
frequency. Doesn't it need to be a multiple of the symbol rate or
something like that?

Good question. I think some DSP tricks are used instead (undersampling,
possibly).

Is the implication of this that there's no IF to be detected by a
detector van?

Even if there is an IF, it'll be far harder to detect, due to the
pseudo-random nature of the signal. Tuners are also very well screened
nowadays. With LCD TVs there's no scan coil radiation, as there are no
scan coils.

If TV detector vans ever worked (other than psychologically) they'll be
less effective come Analogue Switch Off.

--
Paul Martin