No microphone audio to the radio

Erik B · December 20

I have recently set up my 6600 remotely. Everything works fine, except I can't get the mic audio to the radio from my computer. The computer in question is my dedicated radio computer, on which I have logging software etc. It's a fairly new PC running Windows 11, 64 bits.
I get the microphone audio into SmartSDR, in the P/CW window I have a the level bar moving when speaking in the microphone. But when I push MOX there is no output modulation from the radio.
CW transmits just fine, FM gives a carrier, tune also gives output power.

When trying from a second computer it all works out of the box, using identical settings. These two computers are on the same network, both behind the same router and network switch.

I have tried switching off firewall without any luck. I have also tried uninstalling SmartSDR, deleting all appdata and starting from scratch. I tried another network card (WIFI instead of ethernet). I tried another soundcard. I tried to uninstall and re-install drivers for both sound cards. I tried winsock reset. I tried to shut off IPv6. I tried to shut off QoS packet scheduler.
I also tried other input selections in SmartSDR (of course PC is the correct one, but just for the sake of testing). Only the PC with DAX off is showing audio on the level bar in the P/CW window (just as expected - this should be the correct setting).

I would be very grateful for some tips on what to try next!

VE7ATJ_Don · December 20

So, based on your symptoms, it would seem to be 'something' with that first computer (since you say it all works fine on the 2nd one).

What's different about the first one? That would be where I would start. Look at the 'Settings' on each of the boxes and see if/where there are differences. Are you sure there's no functional problems with the first one? Can you just leave the 2nd one in the circuit for now and leave it running while we figure out what's going on with the first?

Erik B · December 21

Thanks Don for the reply!
As for the settings, they are identical in both computers for SmartSDR. But as for the rest (Windows settings), there are obviously differences running different hardware etc. I think it would help me to better understand how microphone audio works in Smartlink. My understanding is that audio firsr gets in to SmartSDR, and is then streamed via UDP to the radio over internet. If this is correct, I would rather think that the issue lies on the network side... (since at least the level bar in SmartSDR is moving, I would assume that the soundcard configuration is OK).

Both computers I tried are desktop PC´s, the one working being a bit away from the operating position. I guess I could run a cable to the second one for mic audio only, and run CAT on the first computer to be able to control mode and frequency via my logging software. But it`s certainly not a permanent solution 😅

Erik B · December 21

Having tested all options I could think of, I uninstalled everything from the computer and did a clean install of Windows 11 (deleted all partitions). With a totally new and clean Windows I installed only SmartSDR. It gives the exact same problem as before. I can't understand what could be causing this. The computer is under one year old, running an Intel i5 processor and plenty of RAM.

Here is a summary of troubleshooting already performed:

- Verified that the same Flex radio works perfectly on another PC using the same SmartSDR version, same LAN, same router, same switch for both PCs

SmartSDR / Radio side:

- TX profiles reset
- MIC source verified correct
- DAX TX confirmed OFF
- PC Audio used (not DAX)
- CW works normally
- TUNE produces normal RF output
- Mic level meter move normally in SmartSDR
- SSB/FM produces no TX audio / no RF modulation (carrier only on FM)
- TX via MOX and PTT tested

SmartSDR / Flex drivers (problem PC):
- Multiple uninstall/reinstall attempts
- Full clean install of SmartSDR:
- SmartSDR, DAX, CAT, FlexVSP uninstalled
- All FlexRadio folders manually removed
- All hidden Flex drivers removed from Device Manager
- Reinstalled SmartSDR as Administrator

Windows / OS level:
- Tested with a brand new local Windows user account
- Disabled all non-Microsoft services (msconfig)
- Windows Defender Firewall disabled
- No third-party antivirus, VPN, or EDR software installed
- Winsock reset
- TCP/IP stack reset
- IPv6 disabled
- QoS Packet Scheduler disabled
- NIC offload features disabled (LSO, checksum offload, RSS, EEE, etc.)
- Verified no third-party NDIS filters present (PowerShell Get-NetAdapterBinding)

Network / hardware tests:
- Tested with Ethernet
- Tested with Wi-Fi
- Same behavior on both network interfaces

Final verification:
- Performed a completely clean Windows installation:
- Disk fully wiped (all partitions deleted)
- Fresh Windows 11 install from USB media
- Only SmartSDR installed (nothing else)
- No additional drivers installed (only what Windows installed automatically)
- Result: exact same symptom persists

Hardware / platform details (problem PC):

CPU: Intel 13th Gen Core i5-13400 (10 cores / 16 threads)
Motherboard: ASUS PRIME B660M-A WIFI D4 (Rev 1.xx)
BIOS: American Megatrends Inc. v3601 (2024-10-12), UEFI mode
Chipset: Intel B660
RAM: 32 GB DDR4
Graphics: Intel UHD Graphics 730 (integrated)
Storage: NVMe SSD (Windows installed on NVMe)
Wired NIC: Intel Ethernet Connection I219-V
Wireless NIC: Intel Wi-Fi 6 AX201 (160 MHz)
Audio devices:
Onboard HD Audio (Realtek-based, Microsoft driver)
USB Audio devices (generic USB audio)
TPM: TPM 2.0 present
Secure Boot: Enabled
Virtualization: Hypervisor detected / VBS enabled by Windows
OS: Windows 11 Pro (fresh clean install from USB)
Installation type: Full disk wipe, no in-place upgrade
Software installed: SmartSDR only (no other applications except for Windows default)

Mike-VA3MW · December 21

I get the microphone audio into SmartSDR, in the P/CW window I have a the level bar moving when speaking in the microphone. But when I push MOX there is no output modulation from the radio.
CW transmits just fine, FM gives a carrier, tune also gives output power.

I have this happen every few months. Usually rebooting the radio resolves it.

Erik B · December 22

Thanks Mike.
In my case unfortunatly there seems to be another issue. At least 20 reboots and the problem persists. It's working fine from another computer, so I don't think the issue is at the radio side.

What harware-related issue could possibly cause Smartlink TX UDP to fail? I believe the hardware/firmware/BIOS are the only things left since a totally clean re-install of Windows didn't resolve the issue.

Prior to installing the radio at the remote QTH, I tested it with the same computer on LAN which worked fine. So the problem seems to be with Smartlink related to my specific hardware.

No microphone audio to the radio

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