[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Discuss-gnuradio] Over the Air Signal Capture

From: Martin Dvh
Subject: Re: [Discuss-gnuradio] Over the Air Signal Capture
Date: Sun, 16 Jan 2005 18:49:49 +0100
User-agent: Mozilla Thunderbird 0.9 (X11/20041124)

address@hidden wrote:
If anyone needs some more sample data captured, please let me know. I should have my USRP board today. I'm in the Phoenix, AZ metro area and would be happy to capture signal that may help in development of processing blocks.

Provide frequency, bandwidth, and sample length information. I'll try to help out. I have antennas for DC - 3GHz. Right now I'm thinking of a GPS snapshot, 2m (144-148MHz), 70cm (440-450MHz) ham bands, and maybe a public service band (455-465MHz) has a lot of narrow band FM activity.
If you are at it. A NTSC television channel would be nice. (I found a NTSC capture at http://comsec.com/data/ but it seems to have a high power interference signal at about 1 MHz)

RF Frequency: don't know what is in your area, just pick one.
bandwith:     6 Mhz
sample length: 0.15 seconds is enough for a few video-frames. a few second 
would be nice for audio.

Make sure you have at least 6 Mhz bandwidth to get the whole television 
channel. (Including audio)

Also know that The frequency of a  Television channels is most of the time said 
to be the frequency
 of the Video carrier which is NOT at the centre of the channel.
You can check with a fft graph.
The high peak is the video carrier. The whole channel is from 1.25 Mhz below 
that and  3.75 Mhz above.
So if you set the centre freq at:
rf_centrefreq = video_carrier_freq + 1.75 Mhz
and have a bandwith of at least
bandwidth =  6 MHz
you will be fine.

See the chart below for specifications of NTSC channels:

BROADCAST-channel#     MHz        VIDEO-carrier    SOUND-carrier
21                     512-518    513.25           517.75

Also nice would be air-traffic control samples.
These are narrow AM-modulated in the 120-130 Mhz band.
I think a bandwidth of 10 or 20 kHz should do (didn't check for exact specs yet)
length: if there is a transmission 10 seconds would be enough.

I think the following should be receivable in your region:
Phoenix Sky Harbor Airport:
Automated Traffic Information Service
121.2 MHz (current airport conditions)

Approach Control
North - 119.2 and 120.7 MHz
South - 123.7 and 124.1 MHz

Control Tower
North runway - 118.7 MHz
South runway - 120.9 MHz

Ground Control (controls aircraft on the taxiways and ramps)
North - 119.75 MHz
South - 132.55 MHz

Clearance Delivery (gives airlines their final routings and clearances)
118.1 MHz

thanks and greetings,

reply via email to

[Prev in Thread] Current Thread [Next in Thread]