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With the QMX+ being a kit, any published value of MDS would have to be a range of fluid values since receiver characteristics will depend, not only on component tolerance deviations, but of builder's methods in soldering and the winding of toroids & transformers.
I decided to compare my QMX+ receiver sensitivity with the KX2 and FT-891, using a TinySA Ultra and appropriate attenuation.
As can be seen in the video below, the QMX+ does quite well.
After the video, I "measured" (by ear) the point at which a signal becomes too weak to copy on the other bands. The CP1 directional coupler does not cover 6 meters but I measured -113 dBm on that band, which is probably inaccurate. I will sweep the coupler on 6m with my VNA and post a corrected value soon.
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In actual use, I'm very pleased with the sensitivity of my home-built High Band QMX. And these results give me more confidence about my subjective sense of its sensitivity. THANKS John!
ReplyDeleteI should have done this right after building the rig (or any kit). But it validates what on-the-air experience tells me.
Delete73,
John
John - have you used the QMX+ on 6M? I'm wondering how well it works up there, as this would be my main motivation for getting one.
ReplyDeleteDave
AA7EE
No, Dave, sorry to say that I haven't used it on 6m at all. I rarely hear anyone mention using these radios on that band. 6m is the band for a patient ham and I'm not that (yet)!
Delete73,
John
Thanks John - appreciate the response. Hope you're doing well!
DeleteDave
AA7EE
Had you equalized the RF Gain by band, or is this with it set as per default? Seems like that might be needed on upper bands?
ReplyDeleteHans discussed it here: https://www.google.com/url?sa=t&source=web&rct=j&opi=89978449&url=https://groups.io/g/QRPLabs/topic/qmx_firmware_1_02_006/116049819&ved=2ahUKEwiQ2NTZqsiTAxWpz8kDHbBcGAoQFnoECCUQAQ&usg=AOvVaw3TJdKbzS94uVNQ5meXK3ue
Good point - it is at the defaults, I will revisit this. Thanks for the link.
DeleteSure thing! It used to be called "Audio Gain" but sounds more like RF Gain is the correct term for this function. I ask as I'm curious about my QDXs and their actual sensitivity.... And considering a QMX+ to replace them in my remote shack, too.
Delete