Many thanks to SWLing Post contributor, Jake Brodsky (AB3A), who shares the following guest post:
How I Listen to Encore on Radio Tumbril
Listening to Classical music on shortwave is a challenge. It has loud and soft parts to the music. There may be selective fading. It isn’t a simple thing.
Also, configuring a software defined radio such as the highly configurable SDR# is not trivial. Note to readers: SDR# has been updated a lot recently and the noise reduction features are vastly improved. Kudos to Youssef Touil for all the hard work on this software. He continues to impress me with every update.
So I have some suggestions for those who are interested in listening:
First, get a decent set of over-the-ear headphones. Don’t rely on laptop speakers. They’re usually not designed for audio fidelity.
Set the radio for DSB reception with Lock Carrier and Anti-Fading checked. I also set the bandwidth to cover about 11 kHz or thereabouts.
On the Audio tab I uncheck the Filter Audio option. I’m going to rely on IF filtering to do my work for me.
Next, find an empty channel on the band where you will be listening to the program. Enable the IF Noise Reduction feature, set it to HiFi, and then set the threshold so that the noise floor is reasonably low. If you set the threshold too high, you’ll lose the higher frequency audio and there will be artifacts from the noise floor that I find unpleasant. A little bit of noise reduction is good, but more is not better.
I also enable the IF Filter/notch processing window to handle any stray birdies from switching mode power supplies. However, if not needed, I turn that feature off.
I turn off the AGC. And then I set the volume level to something reasonable, not too loud, not too soft, but just barely able to hear the noise floor.
Then I tune in the program. I was listening to the Sunday Evening (Monday 0200 UTC) broadcast from WRMI on 5950 kHz. There was some fading going back and forth. However, I took the atmospherics in stride, as if it were part of the experience. The broadcast from this evening
ended with the Pastoral Symphony from Beethoven. There were a few fades and there were a few swells, all due to atmospherics as the signal faded to the noise floor and emerged from it. But there was very little distortion. (thanks to the excellent engineers at WRMI).
The experience was actually sublime.
This is why I listen to shortwave broadcasts.
73,
Jake Brodsky, Amateur Radio Station AB3A
Good tips here, and they inspired me to try again catching some short wave radio via an RTL-SDR in SDR#. I had never managed it before.
One step missing from the above – and it may be because it was too obvious/fundamental to include! – is to change the ‘sampling mode’ in the settings panel. I had to set it to either I or Q branch before I could use those lower frequencies. But once I did, the shortwave bands came alive! And the above tips from Jake helped massively, particularly Lock Carrier and Anti fading. I had a wire antenna attached to the SDR’s own telescopic aerial, but found that shortwave reception was fine with or without it attached.
I tuned around the bands for a bit, just to reassure myself it was working adequately. Next time I will try and track down a specific, scheduled broadcast of a music show.
I have found SDR# very complex to use so I am grateful to people for giving specific tips on certain listening modes.
Going a step or few along, I recommed StereoTool if wiling to learn about audio processing. The free features should suffice for casual shortwave listening.
https://www.thimeo.com/stereo-tool/
This software is aimed at broadcasters, and there is quite a bit of competition in this market, which has been going on for a long time.
The software is designed to optimise the signal prior to feeding the transmitter. For example, FM in the USA boosts the high frequencies up by a huge 18 dB. (15 dB elsewhere. This means that loud high pitched sound for example from cymbals have to be reduced otherwise the transmitter will overmodulate causing interference to other broadcasters. It also causes distortion due to clipping. So they will be made to sound dull.
NRSC curve is the above but in AM and is for transmitters. The receiver need the reverse.
Low level boost is audio compression which requires a clean signal, in HF receivers this is often not the case, and it will amplify the noise when the program is quiet.
The other functions are to clean up signals which are digital. The only way a receiver in the HF band can receive digital signals is to use Digital Radio Mondiale instead of AM, and it will not need processing because it is quiet, stereo and has the missing high frequency sound.
Actually it is aimed at anyone wanting to process whatever audio. 😉 The broadcast side pays the bills for development. I recommended it for a reason.
I have been using ST for many years to clean up analog and digital audio on the receiving side, including AM music and even SSB voice comms. Works great for its intended purposes, and again, if willing to spend the time and effort to learn its numerous features. Just a few useful highlights include multi-band noise gate, multi-band AGC, highs reconstruction, bass harmonics, etc.
For example, regarding the comment on clipping. ST features an impressive declipping algorithm, and yes, it works fine for analog audio. Declipping is a paid feature, though.
Hei Jake,
The filter audio option in SDR# is actually doing more than a low pass filter; it adds in a high pass filter to remove carrier wave rumbling (especially noticeable in some situations using strong NR). In newer versions it’s also a de-emphasis system mening that it has enhanced bass and reduced / not harsh highs compared to “raw” unfiltered audio.
With the noise reduction, have a play with my hard and soft pressets and tell me what you think 🙂
I enjoy the program and thanks for the SDR# tips!
Jake,
What is the bandwidth of the filter used at WRMI? Considering that HF channels are in increments of 5 kHz. If they limit audio bandwidth of 5 kHz prior to transmission to minimise interference to other signals, then the RF bandwidth will be 10 kHz. If they transmit a wider bandwidth, a 5 kHz deep sharp notch filter is desirable. This is because the carrier will cause a 5 kHz whistle due to intermodulation distortion or an adjacent channel carrier. These are the techniques used for wideband MF AM, but with different values.
The AGC is measuring the power in the received AM signal. It is used to control the signal gain, so switching it off, will mean that if the signal fades, the sound will become weaker. If it is on, that will not occur but at very weak signal levels noise will increase as the signal becomes weaker.
It’s a pity they don’t transmit DRM, which is noise free free of phasing effects of multiple path signals , stereo capable and it reconstructs the high frequencies up to the limit of hearing.
I typically see sidebands extending out to about 5.5 kHz on either side of WRMI’s carrier. That’s where the 11 kHz wide filter number comes from.
I’m also not using a particularly extravagant antenna. A YouLoop is often what I have because it travels well with me. With an antenna like that, the atmospheric noise floor is usually just above the thermal noise floor of an HF+Discovery SDR.
On 5950, with a setup like this, I don’t usually hear adjacent stations. Also, there are new features for canceling out adjacent and co-channel AM transmissions. I haven’t used them extensively yet.
This is one thing I don’t miss about the earlier days of shortwave radio where stations were practically on top of each other.
As for DRM, well, maybe. I’ve listened to digital stations on MW AM broadcast (WWFD in Frederick, Maryland) from my car. When it works, it is great. However, it is not a resilient signal. DRM may be a bit better, but it still doesn’t handle selective fading as well as it could. In a situation such as I described last night, it would have failed me.
As much as I like to play with digital technologies, I like listening to analog signals. If you want to listen to music programs, there are literally hundreds, if not thousands of play-lists and podcasts online. What I like and enjoy with Shortwave is the spontaneity of discovery and ethereal quality of the sound.
Remember that DRM sounds terrible on music with lots of HF though and that’s something almost impossible to fix due to the low bitrate. Just give funklust a listen D:
Here is a direct comparison between xHE-AAC 24kbps (A realistic maximum sound quality for a strong signal over DRM HF) compared to an AM signal that was strong enough to hear the full sound range:
https://lea.rnei.org/sdrs/1897/
If only the HFCC allowed stations to broadcast in full 20KHz everything would sound like CRI who broadcast in 20KHz to Europe despite the rules and sounds like this:
https://lea.rnei.org/sdrs/SDRSharp_20220920_101525Z_6020000Hz_AF.wav
Jake,
I like your creative use of the SDR settings to get the most audio quality out of a shortwave broadcast.
Part of the charm of shortwave, for me, is that it sounds (often) like it comes from far away. But at the same time, part of the fun is tweaking the controls to get the best audio quality.
One of my very first as an adult shortwave listener was hearing the Dutch Royal Symphony direct from Holland (I might be wrong on the details). I remember thinking: that’s really, really cool.
Cheers, Jock
That is exactly what I expect when I listen to Shortwave. The combination of the ethereal, distant sound, as if you’re hearing messages or music from another era, is almost magical to me. In that respect, I think Brice Avery is really on to something with his eclectic mix of classical music. There are certain pieces of music that fit this venue very well. Bach’s Siciliano from Sonata BWV 1031 is another example of music that travels well across the distances of shortwave.
What I especially like about modern shortwave receiver technologies is that they’re getting really good at reducing distortion to the point where you’re hearing just the atmospheric contribution and not much else.
“The experience was actually sublime.” Yes, and this is why I listen to shortwave, too.
You bring up goods point in your settings suggestions. One, in particular, I hadn’t thought of is turning off the AGC with programming like classical music that has such a wide dynamic range.
Again, many thanks for sharing this, Jake!
Cheers,
Thomas