After some time playing with SDR I decided to finally get a decent dedicated shortwave radio.
In this image the Sangean ATS-909X2 is set to receive at 14.074 MHz in USB mode to capture some FT8 signals.
The phone is running the FT8CN app and it captures the audio to decode the messages via the microphone.
7.074 MHz and 28.074 MHz also work great for this.
I still haven’t memorized the wavelength mappings so I always think in frequency
When I first got my Tech, I was restricted mostly to 10m on HF, or ~28Mhz, so that was the first one I got down. Then I noticed each band deeper into HF was basically twice the wavelength (or half the frequency), so 20m is ~14Mhz, and 40m is ~7Mhz and so on. The exact placement within that band gets pulled up on an allocation chart, but that’s how I was able to wrap my head around it.
That’s a good method, it makes sense! I will remember these now: 3.5,7,14,28 = 80,40,20,10, and use them to anchor the others.
As I played with the radio I would compute 300,000 m/s / 40 m -> 30/4 is 7.5 so somewhere close to 7 MHz… But this method was a bit cumbersome so I have just been ignoring the wavelengh so far, hehe.
We all come to it in different ways.
Are you only an SWL (shortwave listener) or do you also have an amateur license?
I don’t have a license yet, or any SW transmitters. I have been thinking of maybe getting a license. I started playing with GSM/LTE modules, then LoRa, then got into identifying signals all over the place using SDR.
This past week I decided to buy a dedicated shortwave radio to see if it gives me something that the SDR doesn’t, and it actually does, it has different ergonomics and I find it a lot smoother for exploring the 100 KHz - 30 MHz region. With my SDR I think it is a bit cumbersome to explore this region as someone who doesn’t know what to look for. The radio is more constrained and set up to move through the spectrum in ways that make sense.
That’s a wonderful way to begin. To add to your tools, there’s also a free web SDR offered by a group of volunteers: https://www.sdrutah.org/. There’s also KiwiSDR: http://kiwisdr.com/public/. I’m partial to SDRUtah because they have really good labels and it’s easy to understand what one is looking at. LoRa is neat and I’ve also been interested in getting into Meshtastic.
I encourage you to pursue your license, most jurisdictions now do not require Morse code, so it’s never been easier. Welcome to the hobby!
Thanks a lot for your kind words and recommendations!
As for Morse code, actually yesterday I watched a video that blew my mind, this one: https://www.youtube.com/watch?v=GvQ_UnePS7w
It is so cool. Even if no longer necessary, the way this operator communicates over Morse code is fascinating and I would really like to be able to do that some day. So, if I do get a license I am for sure going to at least try to learn the bare minimum to identify myself and say hello with this nice gadget 😄
Morse code is amazing in its capacity to be intelligible much much farther under the same power as phone (voice) because the modulation requirements are orders of magnitude smaller than needed for phone; another way of looking at it is CW (“Morse”) requires far less power to be intelligible the same distance as phone. Phone bandwidths are 1500-3000hz where CW is like 100hz. I grabbed a screenie of an SDR during a worldwide amateur radio competition a few years ago which illustrates what I mean:
Each narrow streak on the left are CW operators making CQs (contacts), while on the right, the broad strokes are voice operators doing the same.
If you pursue learning Morse, I implore you use the CWops method which is not to use graphics, or other mnemonics commonly found on the internet. You don’t have to join CWops–just use their recommendation of listening and sending: https://morsecode.world/international/trainer/trainer.html. The reason here is that graphics and such will form a bottleneck in learning.
You’ve got me started on talking Amateur radio, so I mildly apologize. One of the absolute strengths of CW is being able to take a very small, compact transceiver (about the size of an adult hand) with limited power (10W) and a resonant length of wire backpacking, then string up the wire on a tree and make worldwide contacts. On 10W.
One of the greatest things about CW operators is that they will respond to your CQ or call at your speed, so even if you’re a very slow sender, most folks are quite patient to complete the CQ.
I was just now looking through a few resources to learn morse code so this is very helpful! It is fortunately simpler than I thought - I was under the impression that the code mapped to full words, not individual letters/numbers, and so that it was essentially a different language. Memorizing the alphabet seems relatively straight forward to me now, but it probably takes a lot of time and effort to become proficient. I’ll give it a try.
It is indeed magical when one considers the minimum resources needed to transmit and receive CW over long distances. Of course digital modes are quite efficient and accessible now, but I don’t think most people can turn millisecond arrays of 0’s and 1’s into actual words without the help of some fancy device.