[RFI] Fwd: Re: [TenTec] RE 28.634
jim at audiosystemsgroup.com
Thu Jan 6 10:38:55 EST 2005
The following post from the TenTec reflector is interesting because it
illustrates the obvious need for a list of common "birdie" frequencies and the
equipment that produces them. I've edited this post down a LOT, and it went on
for three days while hams around the world triangulated, gyrated, prognosticated
about signals from outer space (how could it be everywhere and triangulate
everywhere?), and talked about calling Riley. All of us have been in the position
of wanting to chase these things but not knowing where to start. Of course we can
DF them, but there are literally hundreds of them within the ham bands I use. It
would be a lot faster if you knew what you were looking for.
Would someone volunteer to collect the data for such a list if we contribute to
it? I would volunteer space on my website for it. As a general procedure, I
suggest that known frequencies of unknown sources be posted to the list, so that
those who have tracked them down can identify them.
To start the ball rolling, here are some frequencies I've found that I'm sure are
produced by 10BaseT Ethernet. 3511 kHz, 10106 kHz, 10122 kHz, 14030 kHz, and
Jim Brown K9YC
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What Uses Color Decoders
Every TV monitor and TV receiver (or projector) that displays video from
composite video or S-video sources has a color decoder.
VCR's and laserdisk players do not have color decoders because, although they
may isolate the luminance and chrominance from composite video, they do not
decode the chrominance signal.
The NTSC color decoder takes the chrominance (color) signal modulated on a
subcarrier and demodulates it to obtain two color difference signals such as Pb
and Pr. Then it recreates red, green, and blue content signals (RGB) from the
color difference signals and the luminance signal using mixtures of the latter
three signals or by performing a matrix transformation. Although this discussion
is for NTSC, PAL uses a similar color decoder.
A comb filter or (less expensively) a bandpass filter is used to isolate the
chrominance content from the total content of composite video. For S-video, the
chrominance signal is already separate from the luminance.
To reduce artifacts in the picture, the 3.58 Mhz (actually 3,579,545.4 Hz)
subcarrier is suppressed as much as possible from the chrominance signal.
In order to decode the color signal, a pure 3.58 Mhz subcarrier signal in the
proper phase is needed. It is generated locally by the color decoder. At the end
of every scan line, in a part of the waveform called the back porch, there are
about eight cycles of the subcarrier used for synchronizing. So long as the
local oscillator does not gain or lose more than a quarter of a cycle in 63.5
microseconds (one scan line time) these "color bursts" will keep the local
oscillator in sync. and in phase
Quoting George <w2yj at highstream.net>:
> I thought there was a reply earlier today or yesterday explaining that this
> was probably a color burst crystal frequency? The note indicated that the
> power was turned off in the house and the signal disappeared???
> Can anyone verify that the signal is not internally generated by our modern
> electronic "things"?
> Help me understand.
> ----- Original Message -----
> From: "David S.McCallum" <w7sac2 at cox.net>
> > From: "Dave Edwards" <kd2e at comcast.net>
> > So how 'bout some beam headings?
> > Let's see if it can be triangulated (sp?)
> > at all!!
> > I'll check myself when I get home.
> > ...Dave
> > ----- Original Message -----
> > From: "Tommy Bennwik" <bennwiktv at hotmail.com>
> > To: <tentec at contesting.com>
> > Sent: Wednesday, January 05, 2005 4:30 AM
> > Subject: [TenTec] RE 28.634
> >> 28.364 & 14.317 abt S-2 in Stockholm. Hiding under my bed!
> >> SM0PCA /Tommy
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