Re: Shootout of Substitute SG504 heads = a better head.


The Stable CW was from an HP8753D VNA, not the SG504. It had about a +/-1dB over the range, but the Boonton allowed me to match peaks and null out errors. Took a while. But I could digitally dial in precise frequencies pretty quick on the VNA as well as scroll thru or auto sweep at slow rates like over a minute....while watching the SA match sweep with a peak tracking marker and pick out any odd wobbles in the levels after each pass of entering cal constants. After several passes I did narrow, slow sweeps and optimized the SA cal constants to reflect the Boonton levels. It took about 30 manual constant entries and a couple hours tweaking to get it right; could have been worse.

I went thru the trouble of calibrating the SA manually with the Boonton so I could dial in relatively precise frequencies on the SA from the SG504, also I could see harmonics. I could record the traces and export the evaluations to a PC as well If need be. Also, it's good to have an SA with decent Cal. for any other purpose.

I am looking at a project to nearly double the SA range so I can use it up to 2.5Ghz (Wifi /bluetooth). Just ordered a good VCO chip and mixer chip that seem to have the specs to do it. Looks like I'll have to do two mixes. One up for the TG and one down for the rcvr. I have a couple mini circuits 2Ghz mixers on hand for the basic tests. Once I can get some confidence in the results I'll buy another mixer chip and build out the system. I can use the VNA for a LO signal and my TPI synthesizer for the RF as it goes to 4.4 Ghz. Test out the concept and then do some RF design to do it at the chip level for a standalone device. The Boonton can validate the results being a 12.4Ghz capable unit. No doubt I'll have some more manual cal. constant fun to make that a useful result.
I can sync all the devices to a 10Mhz source including the VCO chip. My OCXO Trimble isn't here yet though.

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