Re: tinySA : most accurate power level
|
If you read the specifications for any of the TINYSAs, Eric recommends measurements to remain faithful to the input signal (no compression or aliasing) stay less than -26 dBm.? I usually shoot for -30 dBm.? Yes, your measurement is likely in compression.
Dave - W?LEV
I'm building a 1kW+ HF power amplifier.? I've a 2kW homebrew dummy-load with a 60dB PAD (measured with a nanoVNA it's around 60db flat to 100MHz).? ?
?
With an IC7300 at 100% FM, 7.2MHz, the tinySA reads -10.5dBm? (As expected: 50dBm less 60db = -10dBm)? (Checking the linearity from from ICOM at 10% to 100% indicates all is working well).
?
So far, so good.
?
Inserting the AMP & LPF: there's a gain of around 12dB (after a 15dB protective PAD at the input of the AMP).? Aligned with the device specification.??
Input: 42.5dBm output 52.5dBm (i.e. -7.5dBm as measured by the tinySA)
?
When the input is increased to 50dBm, one would expect around 62dBm (1600W) at the output : assuming nothing has entered compression.
However, the tinySA reads -2.5dBm which equates to 57.5dBm at the dummy-load (560W).? The AMP is drawing 1,426W DC, the device's datasheet suggests an efficiency of around 80%.? So, one might expect the tinySA to read around 0dBm, indicating 60dBm at the dummy-load.? Checking with a thermal camera, nothing in the AMP (transformer cores) or the LPF cores appear to be getting overly hot (not 850W hot!).??
?
My question is:
Is it likely that the tinySA has become non-linear once above around -10dBm at its input?
Is there a sweet spot where the tinySA is most accurate???
?
I haven't manually configured the tinySA's input attenuator: i.e. it's in Auto mode.? Been using NanoVNA-APP with the tinySA.??
Yep, my next test is to insert a 10dB PAD between the tinySA & dummy-load (the AMP is currently off line for a completely different reason).??
?
Thanks in advance.
?
|
