Listen to the Music

Listen to the music, but not on SSB with a 3kHz bandwidth. What I mean is, listen to the Amateur Radio Bands, and you will quickly understand what I'm talking about. Some of the audio signals on our bands are appalling. Even worse are some of the reports that people are relaying back to these poor operators.

It's worth noting that many amateur radio operators strive to have a clean and pleasant signal. However, both the amateur radio community and society, in general, have become non-constructive regarding any form of insights or criticism. Therefore, the information below may help some operators check their transmission quality.

A little bit of research on the internet reveals that the human voice contains frequencies ranging from about 100Hz to 8000Hz. However, only the energy between about 300Hz and 3800Hz contributes to the intelligibility of speech. Vocal content below 400Hz provides "body" to the voice, which is great for singers and radio announcers. Speech content above 3000Hz provides presence and can aid communication, to some extent. However, the added bandwidth can introduce noise and other complications.

In my opinion, in a Single Side Band (SSB) communication system, it's crucial to achieve the highest Signal-to-Noise Ratio (SNR) at the receiving station under strenuous propagation conditions to get the message across. To achieve this goal, we should transmit the portion of the human speech that affects articulation the most, which research has shown to be the spectrum between 300Hz and 3300Hz.

These bandwidth limits have been established in the days of long distance telephone systems and have served the telecom industry of our world quite well.

The standard SSB TX filter in most SSB transceivers is 2.7kHz wide, and a well-adjusted SSB transceiver has this filter aligned so that it will pass audio between 300Hz and 3000Hz. Since SSB transmitters are peak power-limited, transmitted energy below approximately 250 Hz will show power on the power meter but will not contribute to the articulation at the receiving station. However, these days we often see signals with a "power-grab" dominating the bands. Many operators focus solely on increasing their power output, resulting in signals that are difficult to copy and interfering with other spectrum users on either side of the selected channel. These bass-heavy signals can swamp the AGC in a receiver, creating a low-frequency rumble that is unintelligible and potentially causing issues for other spectrum users.

Fortunately, with the availability of publicly accessible Web-SDR systems, it's now possible to monitor one's own transmissions quite easily. 

The way I do this is however, slightly different as described below. 

To set up a transmission check, I first record a test transmission and play it back through the transceiver which is connected to a dummy load/antenna. While transmitting the recording, I listen to the signal using a second receiver (in my case, an SDR-IQ) to adjust the TX-audio profile, including the TX Bass and TX Treble on the ICOM, MIC gain, and compression.

When adjusting compression, I make sure to adjust the MIC gain so as to avoid the compressor pumping up background noise during speech breaks. By listening to my own transmission, I can tailor the audio characteristics to ensure that all transmitted power remains inside the available SSB channel. This is particularly important for QRP stations or foundation license holders, as losing just 3dB to either side of the channel means that only a quarter of the peak power is transmitted inside the wanted SSB channel, potentially making it difficult for the receiving station to copy the signal.

Below is a display of a test I conducted to get a more balanced audio profile. The LSB signal within the top of the waterfall in the below picture is showing emphasis on the low end of the audio spectrum. Visible on the bright red right hand area. Below this signal we can clearly see that I have selected/created a more balanced audio profile.

Analysing those signals, we can see that the first signal has quite a lot of emphasis on the lows, at around 100-400Hz (on the right the big red line). This makes the signal sound rather bassy, and although it shows a lot of power on the power meter, it is not overdriven (like most of the signals on the bands today). 

Operators who prefer to use wide-open audio filter might find this sounds okay. But for longer distances, were the receiving station only has a bit better than marginal reception, say S5, it would be difficult to copy.
The second signal shows much better-balanced audio and I would classify this as very good communication audio. However, the bandwidth of both signals is approximately 2.9kHz (100-3000Hz) which is still in the 3kHz channel bandwidth. I believe that the bottom signal would still sound rather nice at a 2.6, 2.4kHz bandwidth even in 2.1kHz with a lot less noise bandwidth this signal would still sound Q5.

Oh and ESSB enthusiast find my view of the use of narrow band audio for SSB harrowing. However, it would be nice if these OM's would find a space in our limited spectrum were they would NOT interfere with low power stations that they might not hear.

I've been seeing quite a few ESSB operators on 40m clobbering small signals due to their inability to hear those stations and make it difficult for others to make the contact with those stations. 

Also, I don't believe that ESSB should be used during a contest where bandwidth is limited, not even by a contest station.