title:GNU Radio receive CW
keywords:sdr,airspy,gnuradio

#

Lets listen to CW/morse on HAM bands

## Frequencies

The easiest frequencies where CW tranmissions can be spotted are on 
HAM bands. There is option to search for military related ones but those
are dependent on schedule. 

| Bands, KHz Lower Limit| Upper Limit | 
| --- | --- |
| 3500   | 3560 | 
| 5258.5 | 5264.0 | 
| 7000   | 7040 |
| 10100  | 10130 |
| 28000  | 28070 |

## GNU radio blocks

Here is the blocks that monitors the CW on few HAM bands

![AirSpyHF](/img/sdr/airspyhf_cw_receiver_part1.png)

![AirSpyHF](/img/sdr/airspyhf_cw_receiver_part2.png)

This creates tunes to central frequency as channel0 and channel1
is offset from central frequency. To catch few CW transmissions if there is any
and allowe to switch between 2 of those with slider. 

## Links

https://en.wikipedia.org/wiki/Morse_code  
https://rsgb.org/main/operating/band-plans/hf/  
https://rsgb.org/main/operating/band-plans/hf/3-5mhz/  
https://rsgb.org/main/operating/band-plans/hf/5mhz/ 
https://rsgb.org/main/operating/band-plans/hf/7mhz/  
https://rsgb.org/main/operating/band-plans/hf/10mhz/  
https://rsgb.org/main/operating/band-plans/hf/28mhz/