Re: My first measurements with relay daughterboard

iz oos
 

Now you have the proof you actually did an excellent job. I followed the easier (not so easy btw... ) route of replacing the relays with the Axicom but I believe you really made a better use of the LPFs.


Il 19/giu/2019 03:56, "Gordon Gibby" <ggibby@...> ha scritto:

I finally sat down to do some more work on my uBitx -- with the external relay daughterboard -- wired with just regular, unshielded wire.   I recall that I damaged and lost one section of one of the low pass filters (I think on 20 meters).


Here attached is the first plot I got attempting to look at the CW harmonics on 80/40/30 meters, using a 12V supply.   I had 67 dB of pads in line with the Siglent spectrum analyzer, and that entered as a correction factor.   Video and RBW were 30 kHz.   Frequencies are from 3-63 MHz so each major division is 6 MHz.   using "traces" with an averaging of 2, I was able to capture and hold traces of 80, 40 and 30 meter CW signals.   You can figure them out from the frequencies, but 

80 meters = purple

40 meters = yellow

30 meters = blue 


The blue horizontal line is my attempt to mark the FCC limit requirement for harmonics, 43 dB below an observed output of about 37 dBm.     


If I should make this measurement differently, I'm quite willing to hear improvements!  This was my first crack at it, and I've only had the spectrum analyzer for 2 months.   It has been used on MANY projects already.    


I believe you can see that the harmonics are WELL below the limit for these items tested.


I'll work at this some more and hopefully made more and better measurements.




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