2nd run of the spectrum test on the V5 #ubitx

Jim Sheldon

I wasn't totally happy with the screen captures I got yesterday when I posted the initial spectrum test with the new SSA 3021x spectrum analyzer so I re-ran them this morning and paid a lot more attention to detail.  I set the fundamental carrier as close to 0db as I could get it (20 meters is the only one that wouldn't quite get there by about 2dB so you'll have to do the math on that one but it is not really pretty.

My 2nd V5 board should be here tomorrow (latest Wednesday) as it's left DHL Leipzig, Germany enroute their Cincinnati customs inspection point before continuing to Wichita, KS and as soon as I get it, I'll put it in the test fixture so I can run the same tests on it before building it into a new case.  Someone mentioned open frame coupling to the spectrum analyzer so I covered everything with a metal cooking pan and used short clip leads to ground the pan to the rig.  I did not notice any difference in readings with the shield over the rig vs removed so I left it in place just to be sure.

This time I ran through all the bands the stock uBITX covers - 80/60/40/30/20/17/15/12 and 10 meters.  Each plot is labeled by band in the screen shots attached.  None of the pictures are edited and I tried to make sure the markers were close to the right frequency peak with marker 1 as fundamental, 2 as 2nd harmonic, 3 as third and 4 as fourth.  Only have the luxury of 4 on screen markers so the 5th harmonic and beyond if even present in the display will have to be taken for granted.

As stated before in yesterday's thread, I do not have a two-tone test oscillator (yet) so no SSB spur pix until I get one.  If someone else with a decent spectrum analyzer wants to do them in my stead, please do so as it will probably be a couple weeks before Pacific Antenna ships me the kit and a couple hours after that to build it.

Here are the pix from today's spectrum tests - SSA 3021X Spectrum Analyzer, 50 ohm RF sampler with variable attenuator and terminated by a Microwave Associates 50 ohm, 20 watt dummy load.  No actual power measurements were taken at this time, only checking for harmonic levels related to the fundamental carrier level in dB.

Jim Sheldon, W0EB
TSW Project Coordinator

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