On Wed, Aug 5, 2020 at 12:05 AM, Erik Kaashoek wrote:
On Tue, Aug 4, 2020 at 05:20 PM, hwalker wrote:
Prior to the version 1.0-49 FW update a level calibration on my v0.3 tinySA would set leveloffset low to '0' which gave me a measurement error of < 1dB across the board measured against an external signal source.? With v1.0-49 a level calibration is now setting leveloffset low to '1.7' and my measurements against an external signal source are off by about that amount.? I have to manually set 'leveloff low 0' to regain my <1dB accuracy.? This using the new correction table.
Herb,
Can you check if the same is happening when you manually calibrate using the 30MHz cal output, center = 30MHz and span=10MHz and then an ACTUAL POWER set to -25?
If that gives a good result can you manually calibrate using? the 30MHz cal output, center = 30MHz and span=60MHz and then an ACTUAL POWER set to -25?
I'm most interested in the difference in calibrating powerlevel using ACTUAL POWER using a span of 10MHz versus a span of 60MHz.
Erik,
? ?My calibrator signal level (-26.7dBm)?is low by 1.7dB? which explains the leveloffset low issue. If I enter CONFIG->EXPERT CONFIG->ACTUAL POWER: -26.7 ?then my leveloffset low value is '0' as expected.? I did not experience this issue prior to v1.0-49, at least not that I can recall.? I changed inter-connecting cables to verify that my cable was not at fault by 1.7dB.
30MHz@10MHz?Span.? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 30MHz@60MHz?Span.
? ??
In any event, manually entering the actual powered measured at 30MHz, using a 10MHz span, is a satisfactory alternative level calibration procedure -? if the 30MHz calibrator level differs from -25dBm by more than a dB or so.
- Herb
