Which Satellite work in 135-140MHz??
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NOAA POES Weather Sats. They operate in the 137-138MHz. You can recieve realtime images from them with a computer and a modified scanner.
NOAA-15 137.500MHz
NOAA-17 137.625Mhz
NOAA-18 137.910MHz
NOAA-19 137.100Mhz
If you monitor these freqs and have tracking software you will hear the unmistakable tick tock tick toc of their signal. If you are interested in receiving the images they produce you can use WXtoming software (Freeware) to process into false color images of the earth and cloud cover during their passes overhead.
bglatour001
Member
Define "modified scanner"....
To receive APT transmissions from the NOAA weather satellites, you require a receiver. The satellites transmit their datastream in the 137 MHz band using frequency modulation (FM). Although you can listen to their 'tick-tock' signature using a fairly inexpensive scanner and whip antenna such a system will not enable the reception of good images.
The reason for this apparent anomaly is due to the bandwidth of the signal. Most scanning receivers have available FM bandwidths of either 150kHz, for FM broadcasts, or about 5kHz for amateur or mobile service transmissions. Weather satellite signals require a bandwidth of 40kHz - 50kHz to accommodate the signal itself plus the Doppler effect. The Doppler effect is identical with the familiar change in pitch of a police car siren as it approaches then recedes from you - initially high pitched, becoming lower as the satellite firstly approaches the listener, flies overhead, then recedes again, this variation is added or subtracted to the signal thus widening its bandwidth.
Therefore a specialised receiver or modified scanner is necessary.
The reason for this apparent anomaly is due to the bandwidth of the signal. Most scanning receivers have available FM bandwidths of either 150kHz, for FM broadcasts, or about 5kHz for amateur or mobile service transmissions. Weather satellite signals require a bandwidth of 40kHz - 50kHz to accommodate the signal itself plus the Doppler effect. The Doppler effect is identical with the familiar change in pitch of a police car siren as it approaches then recedes from you - initially high pitched, becoming lower as the satellite firstly approaches the listener, flies overhead, then recedes again, this variation is added or subtracted to the signal thus widening its bandwidth.
Therefore a specialised receiver or modified scanner is necessary.
CalebATC
Member
Are the tick-tocks continuous or spaced out? I am trying my UHF SATCOM antenna now, to see if that works, and then I will give a few of my other antennas a try.
Are they in circular polarization pattern? How hard should it be to pick the up? What antenna would be the best? How good of reception are they compared to the ISS or any other of the amsats?
Are they in circular polarization pattern? How hard should it be to pick the up? What antenna would be the best? How good of reception are they compared to the ISS or any other of the amsats?
Rover
Member
Here are a few great links for 136-138 mhz sats. Lots of interesting things up there too hear..
136 to 138 MHz band satellites
Satellite Radio Frequencies - 136-138 MHz band
Space Frequency Listing, 136-153 MHz, Downlink
Check out some of the links on these pages and other VHF/UHF frequencies.
73 Rover
136 to 138 MHz band satellites
Satellite Radio Frequencies - 136-138 MHz band
Space Frequency Listing, 136-153 MHz, Downlink
Check out some of the links on these pages and other VHF/UHF frequencies.
73 Rover
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The signals from the NOAA weather satellites are transmitted with right-hand circular polarisation. There are two common antenna for this, the crossed dipole (or turnstile) and the quadrifilar helix (QFH) antenna (in each case, designed and tuned specifically for the 137 MHz band).
The antenna should be positioned with a clear aspect to all horizons. If roof-mounted, make certain that no metal objects are likely to come between it and the satellites. Ideally, it should be the topmost structure on any antenna mast. If you cannot roof-mount your antenna, good results are still possible so long as there are no obstructions nearby. Good results have been reported with the antenna secured to a post just a metre above ground level.
The antenna should be positioned with a clear aspect to all horizons. If roof-mounted, make certain that no metal objects are likely to come between it and the satellites. Ideally, it should be the topmost structure on any antenna mast. If you cannot roof-mount your antenna, good results are still possible so long as there are no obstructions nearby. Good results have been reported with the antenna secured to a post just a metre above ground level.
CalebATC
Member
That helps a lot, thanks!
When I first started with APT, I was using a handheld Radio Shack
scanner. I modified it by removing the IF filter and putting in a .01
uF disk capacitor to give it a wider bandwith. The satellites have a
wide bandwith, and if you don't have the mod, it will still work, but
you'll see the whitest parts of the clouds will appear as a fuzzy,
noisy spot. I think the signal gets clipped there without the mod.
I started with a Diploe/turnstyle antenna which did work, but those
have a bunch of nulls which even if the satellite is directly
overhead, you'll get some weak spots in the signal causing dark bands
across the image. I made a QFH from PVC pipe and coax. It's been on
my roof for years working great!
Dude,
You forgot the most important one : LIVE REAL TIME SATELLITE AND SPACE SHUTTLE TRACKING AND PREDICTIONS
I purchased my multi-fax receiver years ago and built a home brew quadrifilar helix (QFH) antenna and loved it! It was a real big deal back then to be able to receive real time weather sat images on your computer back before the Internet became so popular. I still have images of hurricanes that came up the east coast back in the 90s.Not only did we have the NOAA birds back then but we also had the Russian Sat's as well. I have since got out of it but thinking of getting back into it again. I think NOAA-18 and 19 are the prime birds up now.
Anyone interested might want to look at the funcubedongle, its a SDR receiver with a usuable bandwidth of about 80KHz, I haven't tried receiving anything from NOAA sats with it yet but I will try sooner or later. I just hope my software will allow me to adjust the filter that wide
Please let us know if it works. I am kinda .... curious to see if you like the results
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