NOAA Weather radio design

[TJ Detweiler]

I need help in building a 162MHz NOAA radio from scratch. I have developed a schematic approaching in designing the circuit (see 1.jpg)

I also included components (2,3,4.jpg) that will be used in the radio but unsure which part goes where and the proper calculations that makes it work.

Could anyone give me some hint on how to proceed? thanks

 

[betwixt]

Before you go further, I think all the NOAA transmissions are now digital and encrypted. They used to be FM using simple audio tones, rather like a FAX signal but as far as I know they were all switched to digital a few years ago. You can still receive them but you need a license and key to decode them and of course some special software.

Brian.

 

[spudboy488]

I don't think that's completely true. There are digital aspects of the signal that are for alerts and specific area messaging but the standard 162MHz broadcasts are still clear FM. I'll have to check when I get home to see if the Chicago/Lake Michigan area broadcasts are still open but I'm pretty sure they are otherwise, thousands and thousands of marine radios would rendered useless.

 

[betwixt]

You could well be right although I thought most marine people use the HF version of the maps with superimposed isobars and direction arrows rather than the plain image from the satellite. I'm in Europe, perhaps the satellites covering the US are carrying different signals.

Say 'hello' to Chicagoland for me. I used to live and work in Illinois, just outside Chicago many years ago.

Brian.

 

[BradtheRad]

I have a weather alert radio from Radio Shack, purchased around 1990. It still picks up NOAA broadcasts.

At the back is a sliding switch with three positions, to select among these three frequencies. Usually two are silent or barely audible, while one is local and comes in clearly.
162.4 MHz
162.475
162.55

I also have a clock radio which picks up NOAA broadcasts. It has a knob to tune the frequency and find the best broadcast. It is tricky as the devil to adjust because it has a tendency to go off the frequency as soon as I pull my hand away from the knob.

 

[betwixt]

It seems you are right but the service is by terrestrial broadcasts in mainland US only. I don't know where the OP is located so they may be in luck. In Europe the NOAA signals are around 137.5MHZ but they come directly from the satellite rather than land based stations. It used to be possible to receive them and display them on a FAX machine or using a software equivalent but they have now all converted to a digital format. It is still possible to decode the data but a license from NOAA or Eumetsat is needed.

Link:

Brian.

 

[TJ Detweiler]

any one can give me actual help on the project?

 

[BradtheRad]

Nowadays they add more to the broadcasts than my old weather radio can pick up. Some of it is inaudible (as Betwixt describes).

I forgot to mention the broadcasts I get are a speaking voice only. Static (white noise) is constant on all 3 frequencies, except at times when reception is unusually good from the station closest to me. I'm pretty sure this means it is AM rather than FM.

If you want to hear only the speaking voice over the air, you'll need a good antenna and a tunable AM detector. At 162 MHz it may be more difficult to build than a 'crystal' radio receiver.

I'm afraid I don't know what will be involved in order for an amateur to extract the additional features (SAME-encoded alerts, etc.).

 

[ettabored]

NOAA Weather Radio Design (followups)

Just wanted to correct some items in a 2014 thread on this topic.

The NOAA weather radio information is NBFM (narrow band FM) on 7 frequencies centered around 162.4 Mhz. The NOAA weather satellite information (pictures) is on a completely different frequency around 137 Mhz.

The NOAA weather radio has a computer voice reading the forecast, along with digital information on specific alerts.

The weather radio signal uses FM modulation, which means is can be processed with an FM decoder chip used for older amateur radio equipment.
In 1998, the SAME (specific area message encoding) technology became available, it's better to use the baseband output from an FM decode to demodulate that.

In 2015, if you want the most flexibility, I'd recommend a software-defined radio approach.

Essentially you hook up an A/D converter with an appropriate RF front-end to your computer, and let it do the decoding of the radio signals / filtering work.
https://www.rtl-sdr.com/rtl-sdr-tutorial-receiving-noaa-weather-satellite-images/ (for older-style transmissions) or
https://www.rtl-sdr.com/rtl-sdr-tut...atellite-images-in-real-time-with-an-rtl-sdr/ (for the Meteor N2 images - newer modulation)

For the satellite signals, you will need a good outdoor antenna.

For the NOAA Weather Radio signals (found in the US and Canada), you may need a better antenna than the short "whip" antenna a typical weather radio comes with.

The NOAA web site has plans for a 162 Mhz antenna:

**broken link removed**