I was looking at a receiver catalog, and some of the receivers were
advertised as containing a "DSP comb filter" which could be turned on
when needed.

Can anyone tell me what a comb filter does and when it would be used?

www.devilfinder.com DSP Comb Filters

I looked it up because I didn't know myself.
cuhulin

"Carl" wrote in message
...
I was looking at a receiver catalog, and some of the receivers were
advertised as containing a "DSP comb filter" which could be turned on
when needed.

Can anyone tell me what a comb filter does and when it would be used?

It's supposed to clean up the signal. Basically, the frequency response has
many peaks and valleys that together resemble a hair comb.

The color difference channels are modulated in quadrature, but this has
nothing to do with the comb filter.

The comb filter works exactly as explained in my other post. Look at
this diagram:
http://www-ccrma.stanford.edu/~jos/p...b_Filters.html
The Z raised to the minus M is a generic delay of M samples. Basically
you sum the real time signal with a delayed signal. It's that simple.




matt weber wrote:
On Sat, 03 Dec 2005 18:20:58 GMT, "FDR"
wrote:


"Carl" wrote in message
...
I was looking at a receiver catalog, and some of the receivers were
advertised as containing a "DSP comb filter" which could be turned on
when needed.

Can anyone tell me what a comb filter does and when it would be used?

It's supposed to clean up the signal. Basically, the frequency response has
many peaks and valleys that together resemble a hair comb.

The Comb filter was developed for Television. The colour information
in NTSC is transmitted in 3 parts. A B&W receiver only decodes one
part. The other two called Chromiance and Luminance are not entirely
seperated in the frequency domain, but are in the time domain. In
lower cost Color TV's, there is simply a 'hard' filter and the
chromiance and lumiance signals are processed as though they were
fully seperated in the frequency domain, resulting in loss of colour
detail and resolution. A comb filter performs the decoding effectively
in the time domain, where full seperation is possible, resulting in
higher detail and resolution.

An example of such of a system is AM stereo, and some Modems (Milgo
4800 baud comes to mind). It is possible to generate independent
sidebands, so a Double Sideband, Supressed Carrier, or Un-Suppressed
carrier (AM stereo) overlap in the frequency domain, but the carriers
used to produce them in the balanced modulator are at quadrature
(i.e. one sideband was built with Sin (wt) and the other with
Cos(wt)), the sidebands will also be a quadrature. This is in fact
how the Telephone company used to transmit long distance calls.

If you use an envelope detector with AM stereo you get L+R, however
if you use two product detectors that use phase locked, and 90
degrees out of phase carriers, it is possible to get for example only
Left Channel out of one, and only Right Channel out of the other
detector.

The Intergral over time (power in this case) of sin(wt)cos(wt) dt will
always be zero.

A comb filter generally involves some sort of phase locked, synhronous
detection even if carried out digitally.

My RCA 27 inch screen tv set I bought in October 15,1999 has a comb
filter.That's what it said on the box it came in and also in my owners
manual booklet thingy.I paid about $276.00 for the tv set,that same
model tv set now sells for about $174.00 at the local Wal Mart stores
around here.Next tv set I buy will be a flat screen tv set.
cuhulin

In article . com,
wrote:
In a TV, the comb filter is made by summing adjacent lines using a
delay element. The phase of the color subcarier alters between lines,
so summing adjacent lines cancels the chroma. You can invert the signal
and cancel the luminance.

Another way to say this is that the Comb filter works with NTSC because
both the lumiance and chroma have their high frequency (fine detail)
information in harmonics of the horizontal scan rate. But the color
subcarrrier frequency was deliberatly picked to have an offset of 1/2
the horizontal frequency so that the frequency spectrums of the two
signals occupy the gaps in each other's signal. By having a filter
response with a notch for every harmonic of the horizontal scan rate,
you can get the chroma information without the lumiance interfering.

Mark Zenier
Googleproofaddress(account:mzenier provider:eskimo domain:com)

Carl wrote:
I was looking at a receiver catalog, and some of the receivers were
advertised as containing a "DSP comb filter" which could be turned on
when needed.

Can anyone tell me what a comb filter does and when it would be used?
------------------------------------
As others have mentioned, Comb Filtes are often used in video
applications.
This link dose a pretty good job of explaining what they are and why
they are used.

http://members.aol.com/ajaynejr/vidcomb.htm

Terry

"Chris" wrote in message
...
On 23 Oct 2006 04:25:01 -0700, an_old_friend wrote:

Chris wrote:

why do you play these usenet game fool

Bwa HAHAHAHAHAHAHA!!!! Sigged.

(And I'm not the one who was just banned by qrz.com.)


----
In message . com,
Mark Morgan autolamed himself when he asked "why do you need yet
another sock puppet"

.....

Poor shunned Mark. No more QRZ, eh? I dare say he deserved same.

Now he's trying to hijack the thread.

On Mon, 23 Oct 2006 11:19:29 +0000 (UTC), "Chris"
wrote:

QRZ.COM will no longer allow Mark Morgan to post in their forums.

Now we will see even more of him here. Aren't we lucky?

nope my time here will depend on how drivel people like post
http://kb9rqz.blogspot.com/

--
Posted via a free Usenet account from http://www.teranews.com

Mark in the Dark' wrote in
:

On Mon, 23 Oct 2006 18:36:16 -0500, "Not Lloyd" anon@anon wrote:


anagin you don't even bother with a a point



Mark in the Dark has a point. It's on top of his head.


Learn CW Mark in the Dark, Don't get banned from more sites.


SC