One of the things I’ve had issues with ever since purchasing the Yaesu FTDX10 transceiver is control of the audio chain via the USB connection on the rear of the radio.
The output from the radio into my Macbook Pro is just too high, WSJT-X is constantly pushed beyond the green zone and often into the red zone when monitoring FT8 signals with the AGC off. The only way to cure this is to keep the AGC on Auto which sometimes results in not hearing the very weak DX stations due to the AGC not reacting fast enough. Putting the AGC on fast causes the red line to be hit far too often once more.
Sadly, the USB Audio Codec doesn’t provide any volume adjustment on audio coming from the radio into the MacBook Pro thus, it’s just full volume all the way. This is a flaw in the codec design and really does need to be resolved long term.
Looking at the audio going the other way, that is from the MacBook Pro into the radio via the USB port fortunately there are gain controls available both on the MacBook Pro and on the radio itself.
Ever since venturing into the world of WSJT-X & FT8/4 I’ve had an issue with only being able to move the PWR slider in the WSJT-X up to the first marker at the bottom of the screen, anymore and the ALC on the radio goes off the scale instantly!
So yesterday I decided to investigate the audio chain into the radio more thoroughly and see what could be done about the levels.
Looking at the radio manual I found that there is an RPORT GAIN setting in the menu system that can be used to alter the amount of gain applied to the incoming audio signal on the USB port in the radio.
As detailed in the manual, the default setting for this is 50 in a range of 0 to 100. So that’s a 50% increase in gain applied to the incoming audio at the radio end, that’s quite a boost! (The gain is applied both in SSB and Data Modes)
I decided to experiment reducing this figure to see if it gave me greater control over the audio output from WSJT-X via the PWR control. This did indeed help however, there was still too much audio coming into the radio from the MacBook Pro and so I needed to look further along the audio chain.
Moving back onto the MacBook I opened the Midi App and took at look at the Output controls for the USB Audio Codec, sure enough this was set to max for both channels, not good.
Reducing the levels in the midi app started to make much more of a difference, I could now raise the audio level using the PWR control in WSJT-X without things immediately going wild and could now control the levels with a far greater level of granularity than ever before.
After much tinkering I eventually found the levels whereby I could drive the rig to the selected output power (20w) without the ALC going off the scale and the signal becoming horribly distorted, there was calm in my audio chain once more.
So what settings did I settle on?
On the radio itself I wound down the RPORT GAIN setting from 50 to 20, this reduced the amount of gain applied to the audio coming in on the USB port considerably and helped to tidy up the FT8 signal.
It’s great that there is the facility on the radio to reduce the gain on the inbound audio signal, if only Yaesu would do the same for the outbound audio level.
Next, on my MacBook Pro via the Midi app I reduced the output level on the USB Audio Codec from the default maximum down to 0.494 (-19). This stops the audio level from being too high going into the radio and removes all distortion from the resulting signal.
Once these small changes have been made it becomes necessary to raise the PWR level in the WSJT-X app to roughly the centre position. At this point the radio gets a clean, distortion free audio input whilst driving the radio to the full 20w output with no movement on the ALC whatsoever.
I found I could move anywhere on the frequency spectrum on FT8 without any of the levels changing and with the ALC not moving whilst the radio delivered the full 20w output.
I also checked FT4 mode as it is an MFSK mode to see if these settings worked for it too and I’m glad to say it worked perfectly! (I also found I really liked FT4!)
Altering the PWR level in WSJT-X doesn’t have the huge effect it had before and now it’s very easy to adjust the level without the ALC going off the scale in an instant.
It took me about an hour or so to get this just right but, it was well worth the time invested.
I hope this is of use to other Apple Mac computer users in the HAM community.
More soon …