Re: Open HPSDR Hermes (14 bit ADC, EP3C25) Transceiver Card
My measurements are from a K3S and TS-890S, with a 2 tone signal at 0dBm from the transverter port. The difference between the 2 fundamental tones is better than 50dB down at the 3rd orders, I will measure it again tonight and post it to you.
Where do you get the idea that a class A RF stage is incapable of such performance? Your -40dBc for Class A is typical for RF power amplifiers running at tens of watts.
Look here at figure 3a, this is a Class A RF amplifier with no pre-distortion running at 2W per tone. The IM3 is -51.48dBc, this is at 950 MHz.
When testing the 32S-3 Rob is testing the audio chain IMD as well as the finals. To properly measure an amplifier IMD you should use 2 isolated sources.
This is not a bad read.
I am not saying that I can achieve his level of performance at my final tetrode PA, just at the transverter input and the transverter itself.
From: main@SDR-Radio.groups.io <main@SDR-Radio.groups.io>
On Behalf Of oldjackbob via groups.io
On Fri, Feb 25, 2022 at 04:03 AM, Conrad, PA5Y wrote: