How does the QMX behave with a 50 ohm dummy load?? If the QMX reads a low VSWR with a dummy load, the QMX is working properly. In your previous post showing the Putty screen, VSWR was shown as 1.94 to 1, not 4.9 to 1 shown on your QMX screen.? It may be that you have a bad coax cable. If that's not the problem,? depending on your antenna, you may have a high common mode current on the coax feedline causing erroneous and/or variable readings. I'm not sure what your "little antenna" is. If this is the problem, it can be helped with a common mode choke at the rig. If you still get a bad VSWR with a 50 ohm dummy load, there may be a problem with a bad coax cable or a problem? VSWR circuitry in the QMX - perhaps a bad or intermittent solder connection, but this is unlikely
-Steve K1RF
------ Original Message ------
Date 7/12/2024 2:11:22 PM
Subject Re: [QRPLabs] QMX (1_00_020) SWR - Issue?
On Fri, Jul 12, 2024 at 06:16 PM, Dave VE3GSO wrote:
Return Loss
Thank you for your suggestion.
So I followed these 2 videos
I calibrated my VNA and set the following parameters:
Freg Range - Start: 13.8Mhz
?????????????????? - End: 14.5 Mhz?
I set 2 markers. One at 14.024 and another at 14.075 750
As you can see from the picture I have a very low SWR. I believe that I also have a Return Loss of -26.77dB at 14.024 MHz and -20.76dB at 14.074 MHz which I think is within the acceptable limits.
I unplugged the antenna from the VNA and plugged it straight into the QMX and as you can see when I run the Hardware Test SWR Sweep I get nearly 5.0 on the 14.074 MHz frequency.
Am I doing something wrong?
