3
$\begingroup$

I decided to check the linearity of my Yaesu FT-891 signal using an RF sampler and an oscilloscope. To generate two-tone (1550 Hz, 2150 Hz) signal I used Audacity. To connect the transceiver to the PC (MacBook Pro 2018) I used SignaLink.

Surprisingly turned out that the signal is not quite linear:

enter image description here

No matter how I change to output volume this is the best I can get. For a comparison, here is the exact same signal when another (DIY) digital interface is used:

enter image description here

Thus I'm quite sure that the problem is with SignaLink. However I have little idea what exactly is causing it or even where to start from. I wonder whether this is a known problem and maybe someone already described a mod to fix it (I didn't manage to find one). If there is no known solution a little piece of advice on how to debug the issue would be much appreciated.

$\endgroup$
2
$\begingroup$

It might be the transformers frequency response is not flat. Try replacing them with reputable units that have a published frequency response such as here. See more signalink tweaks here.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for?Browse other questions tagged or ask your own question.