Receiver with analog output

[mitosan]

Hi,

Is there any device or board that will let me set the frequency/band from my own digital controller using something such as with I2C or SPI (or from a PC/USB if its the only way), that can output the signal from that frequency in an analog form that I can feed to my own ADC for processing with my own controller.

I am ultimately interested in building hardware to try to decode and interpret a wide range of things such as GPS signals and weather satellite info but figure I will start with something simple such as trying to get the date/time info from the radio time signals. So a device that can tune to a wide range of frequencies would be ideal but if I have to pick one then so be it.

I am coming at this from a hardware design project for the fun of it, it probably wouldn't make sense to do this for a commercial project which might be why I am struggling to find such a device. I do not need something to give me the pretty spectrum outputs and listen to anything more than one specific frequency at once.

Thanks in advance.

 

[ka3aaa]

since you didnt say what freqs you want to listen to there are plenty of recievers available to do just that. shortwave radios or scanners for one,

 

[mitosan]

Thank you,

In my country (UK) the time signals are on 60 KHz.

I'm also interested to try and get GPS signals which I think are on ~1170-1570 MHz.

Also, weather satellites, which I think are in the range of 137 MHz and FM.

 

[613scanner]

If you are just looking to get the time to sync up this hypothetical device and you are already going to decode GPS, GPS can be used to sync a clock. this will probably make things simpler if you are not trying to do anything else low freq.

 

[mitosan]

Thats a good point but I was thinking it will be easier to decode the time signals and get some experience doing that before doing something with GPS which feels a bit more advanced, though if you are saying it will be harder to acquire the time signals to begin with then it might offset that

 

[Dirk_SDR]

1. E.g. every SDR Software is able to pipe the audio output to any external device.
2. You're talking about ADC and hardware to decode signals. What do you mean? If you have the audio (at least for simple signal types) you can use software to decode the signals.
There are already some programs that are able to decode DCF77, MSF, ... from audio files or live audio output.
So I ask myself: what do YOU want to do?

 

[mitosan]

Hi Dirk, thank you for your reply

I am interested in creating my own hardware that can decode some of the various signals that are out there, for some of the more complex ones this will likely also need a microcontroller and some software which I will also have to write. I know that there are existing 'off the shelf' solutions for this but my interest is in creating my own at the hardware level. I am comfortable doing this from the point of taking a signal, putting it through the ADC and doing my own processing.

Where I lack any experience is actually acquiring the signals in the first place.

Because they are all on different frequencies (and maybe changing frequencies due to doppler on GPS), it would be helpful if there was a device or board out there where I could set the frequency via some basic protocol over I2C / SPI / UART and it would give the raw signal on some analog output. I am trying to find if such a device exists but from what I have seen the answer is no. It would be nice if the device did not require a PC to configure it.

 

[Dirk_SDR]

1. Hardware to decode signals (from audio):
Ok, the ADC you want to use is a piece of hardware. But what else will you do? Use some logic ICs as decoder?
You also mention a microcontroller. I wrote a software decoder for DCF77 on an AtMega years ogo. Worked well. Do you mean that?
2. Receiver with analog output and a kind of serial port to set frequency:
Similar is used for HF transceivers: they often have a CAT interface to remote the transceiver. Do you mean sth. like that?

You see: Perhaps it would be good to describe in more detail what you plan to do.

 

[mitosan]

Hi Dirk,

1) Yes, after the ADC will come some logic ICs or some microcontroller depending exactly on what project, I will do separate projects for each of the types of signal I would like to decode, some simple ones might be done entirely with logic gates, more complex requiring a microcontroller, it is TBD. Also, it will depend how it goes, perhaps I will try one approach and find it is difficult and so try another. I don't understand how what comes after the ADC should have a big impact on the type of receiver that is feeding into it, but concede I am out of my depth and willing to be educated!

2) Receiver with analog output and a kind of serial port to set frequency - This sounds exactly like what I am looking for assuming that whatever commands are required on the serial port are well documented.

When you were working on your project with the ATmega, what reciever were you using?

Thank you.

 

[Dirk_SDR]

1) I think you should first take a let's say "simple" project like decoding Morse, MSF or DCF77, because "coded signals" of very many kinds are used. Partly they are so complex, that a typical uC wouldn't be able to decode them and you would have to use too many logic ICs to fit into an appartment. In addition many coded signals cannot be simply derived from a receiver's audio! So you'll need a receiver and probably additional hardware to realize a part of the decoding and prepare the signals in a way, that your uC or PC is able to use for decoding or simply showing the result.
2) Over the last years I wrote e.g. DCF77 decoders in Bascom and assembler (old example, perhaps use Google translate):
DCF77-Decoder als Bascom-Library – RN-Wissen.de
... in GCC for ATmega or in a graphical programming language for fischertechnik Robotics TXT.
I made other decoders e.g. for Morse code.
For DCF77 I used a normal DCF77 receiver module like this one:

https://www.amazon.de/Milageto-DCF77-Empfangsmodul-elektronische-Singalkomponenten-DCF-3850M-800/dp/B0BBB45R6Z

For Morse code I used a normal HF receiver's audio with a front end as described here:

Morse Code Decoder Circuit: Using a PIC Microcontroller Magazine

Amateur Radio site including Curcuit Diagrams, Antenna Construction, Radio Repairs

www.hamradio.cc

 

[k9wkj]

2 - RTL_SDRs
1 - Hamitup upconverter or similar
that should cover 100Khz - 1.7Ghz
there is a plethora of control software and one can pipe the audio out to whatever hardware you wish
or decode things in the software

 

[mitosan]

Hi all,

> In addition many coded signals cannot be simply derived from a receiver's audio!

I didn't know that!

Ok it sounds like there are a few things I need to look into and that perhaps the whole thing is not as simple as I was expecting. I will go and do a bit more research and probably come back with some more questions at a later date

Thank you

 

[popnokick]

Not only a plethora of control software but there is also a plethora of signal modulation types, only some of which can be demodulated from the audio output. Look here - Signal Identification Wiki
This site takes a VERY long time to load due to the audio and video samples.... be patient.

 

[krokus]

Hi all,

> In addition many coded signals cannot be simply derived from a receiver's audio!

I didn't know that!

Ok it sounds like there are a few things I need to look into and that perhaps the whole thing is not as simple as I was expecting. I will go and do a bit more research and probably come back with some more questions at a later date

Thank you

That is why the discrimator taps are required, the "normal" audio outputs have been filtered/shaped in ways that prohibit data decoding.

 

[Carter911]

Wow, big projects!

Spark Fun Electronics used to sell a GPS developers board that output the raw signals.
I don't know if they still have it or not.
They might still have the info for it, so you might be able to find it elsewhere.

IIRC, one about needs a PHD in math to process the raw GPS data.

You might start with a (MicroChip) AVR micro, or whatever you are comfortable with, and just decode the NMEA data outputs from a GPS receiver, (The Date, Time, Lat, Long, Signal Strength, # Sats in View, # of sats used for the decoding, etc.; NOT the pure, raw, signals).

Banggood Electronics, (and others), sells a number of small PBC modules that include RF amps, mixers, local osc, etc., so that you can essentially build your own receiver, and feed the raw signal into your own demodulator (microcontroller).

You might also go to the RTL-SDR website and have a look at all of the software they list, several of which allow one to tune a $25 - $50 RTL-SDR wide band receiver and output the raw data, via USB, to a PC / RPi. That is probably the easiest, (reasonably priced), way to receive the signals and get the raw data, (GPS, ADSB (Aircraft), Sat Weather, etc.).

For the < 1 MHz-ish time signals one typically buys the RF receiver, from Banggood Electronics, or Alibaba, etc, and then feeds the signal into a micro.

Good luck with your projects!

JC

 

[dickie757]

ADALM-Pluto from Analog Devices sounds like a perfect fit. It has a ARM processor, RF channel, onboard memory, and tons of online support.

I have one, but I barely know what to do with it. While working on a different project, I realized I can SSH into the Pluto from my smartphone! You can load and run software directly on the device. It needs a power supply, of course.

ADALM-PLUTO Detailed Specifications [Analog Devices Wiki]

wiki.analog.com

Happy hunting!

 

[mitosan]

Wow, everyone, thank you!

A lot for me to be reading about over the holidays!