I finally got my hands on the
SG Laboratory Ltd amplifier for Es'Hail 2 satellite uplink and did some basic measurements. First I measured its frequency response with Siglent SSA 3032X generator/analyzer combo at 0 dBm input power (limit of the internal generator). I'm attaching the result below, it has 30 dB gain (1 W output power) in the target band. But it has much wider bandwidth than advertised, it employs
NXP MMG30271B as pre-amplifier and
Ampleon BLP9G0722-20G LDMOS as the power stage. However, I was mostly interested in how it behaves at 2.45 GHz and higher power levels. I used Agilent N9310A and R&S FSL18 for that, although I have less confidence in these measurements, because the analyzer was partially damaged a few years back (somebody put too much power to the input). At full 28 V supply voltage, the gain is:
0 dBm input => 1.3 W output, 31 dB gain
+11.1 dBm input => 10.2 W output, 29 dB gain
+13.3 dBm input => 13.5 W output, 28 dB gain
+17.0 dBm input => 20 W output, 26 dB gain
I actually missed 1 dB compression point, because I didn't expect it would lie below 10 W. That's mostly irrelevant for my application, however. I was more interested in how bad harmonics the amplifier produces at the extremes of the operational parameters - as I mentioned earlier, my plan is to control the output power via supply voltage. But my worries were unfounded, I couldn't find any 2nd or 3rd order hamonics during my experiments - the amplifier has an output microstrip filter which apparently does a great job. I'm attaching FSL18 screenshots which I took at 28 V supply/20 W power and 8.2 V/2.5 W power.
Overally, the amplifier is nicely made, the aluminium cooling base plate is 7 mm thick. It uses semiconductors from "respectable" producers, 78M05 regulator is from ONSemi and vox and PTT circuits employ Microchip MCP6001 opamps. Trimmer for vox hold time is from Bourns. It also has two identical directional couplers with detector diodes and RC filters at the output. They're denoted FWD and REF (forward and reflected?), I presume they're used to tune the amplifier during production. In the future, I may use them to detect and automatically shut down the amplifier when someone runs it without proper load. There is 7 mm headroom between components and lid, so I'll have no problem fitting my 2.45 GHz generator board inside. I plan to mount in on the lid above the vox circuits (upper left corner), to minimize the chance it would upset the PA circuits.