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.

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. 

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

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



## 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/