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FT8 power drop during transmit

f.r.harris Member ✭✭
edited June 2021 in SmartSDR for Mac
I have the following issue for the app SmartSDR for Mac-macOS--1 V1.9.5, D3.9.32 fw:1.0 running on x86_64 on macOS Version 11.4 (Build 20F71)

After updating to this version Smart SDR Mac and Flex firmware , when using FT8, the transmit activates, indicators turn red, and the power level comes up to selected value.

But instead of remaining at that power level for the entire transmit duration (13 sec), the transmit power level drops to zero after 4-7 sec, but all the transmit indicators remain red for the entire period.

This is a new phenomenon since upgrading.

Any ideas?


  • Mike-VA3MW
    Mike-VA3MW Administrator, FlexRadio Employee, Community Manager, Super Elmer, Moderator admin
    edited June 2021


    Would you be able to record a video of it and post it here?



  • f.r.harris
    f.r.harris Member ✭✭


    Ok, i think this is sniffed out. Been working with Marcus at SmartSDR for Mac. Man is a genius.

    I was having power drop offs during FT8 transmission cycles. 

    First step was to turn on "transmit on waterfall" and it showed horizontal lines across the transmit stream. Also by turning up the volume, I could hear the volume wavering like it was getting repeatedly interrupted. Not good.

    Took my MacBook to a friends house who runs a 6600. His setup was working perfectly. My problem came with me, so it is in my MacBook.

    To verify, I brought my friends Maestro with me and added it to my system in parallel. My waterfall showed numerous horizontal lines and the Maestro was clean, so not the Flex 6400 and not my network.

    Next, added a usb to lan adapter to my MacBook and connected to Flex by ethernet cable. Worked fine once i remembered to turn off the wifi on the MacBook, and force connection to the lan adapter. So, not the software in the MacBook.

    So we have narrowed it down tho the wifi circuitry in the MacBook. Not a result i was hoping for. I can find no other answer.

    So my options are use the existing MacBook (2015 vintage) on lan cable (kinda defeats the purpose of a flex, don't it?), or i can get a new MacBook. I was gonna try the software on my wife's iMac, but its too old for the SmartSDR software. Too bad.

    When this setup works, it's magic. But there is a fertile area for gremlins. Might just have too much computer in my radio.

    AND OF COURSE, this happened right before ARRL Field Day. Just my luck.

  • Mike-VA3MW
    Mike-VA3MW Administrator, FlexRadio Employee, Community Manager, Super Elmer, Moderator admin

    Marcus is a very smart person! Glad he was able to help.

  • John KB4DU
    John KB4DU Member ✭✭✭✭

    WiFi is often the culprit. Since is is a shared (with all the neighbors) resource. Switching to an a/c (5ghz) WiFi access point helped a lot here.