[amsat-bb] Odd TH-D74 behavior

Brent Taylor vy2hf.radio at gmail.com
Fri Dec 15 18:13:55 UTC 2017

Hi everyone,

Yesterday (Thursday), while on my whirlwind FN87/77 grid activation trip, I
ran into a frustrating thing with my TH-D74.

Wanting to use (Bose QC15) noise cancelling headphones for my downlink
audio, I used a 2.5mm male to 3.5mm female adapter pigtail to take the "SP"
audio off the side of the radio and feed it into the headphones, while
using my VX-8GR for full duplex transmit (for AO-91).

The problem: every time I plugged the pigtail into the side of the D74, its
frequency would change and the ability to QSY back to the intended downlink
frequency would be severely limited or even prevented altogether. I wanted
to be in VFO mode, for instance, and plugging the pigtail into the speaker
jack immediately took me to memory channel recall mode, on an apparently
random channel, and then prevent the selection of another memory or a
return to VFO mode.

So I thought I'd fix that problem by locking the radio with the long press
on the "F" key. No change in behaviour. The frequency change still happened
every time I plugged in to the speaker jack. The problem sometimes occurred
immediately upon plugging in, but sometimes it would work fine on VFO mode
for a few seconds before the changeover.

I will continue to fiddle with it to set put exact behaviors in varying
circumstances. I'm just wondering if anyone else has experienced a similar

What I ended up doing was going without headphones altogether and just
listening to the D74 out of its own speaker, in the wind, with feedback on
the uplink when I transmitted. Sorry about that mess!


Brent Taylor, VY2HF / W1PJ
Stratford, PEI, Canada

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