Re: Some basic load measurements
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The nanoVNA begins using the second harmonic as soon as the sweep crosses the 300 MHz threshold and, at the same time, boosts the output level of the Si5351. It does this again at the 600 MHz threshold where it begins to use the third harmonic with yet another boost in 5351 output. I suspect the power boost parameters are saved along with the bin correction factors when a calibration is done for a specific range.
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Pretty clever stuff actually. WA8TOD On Aug 8, 2019, at 12:05 PM, Warren Allgyer via Groups.Io <allgyer@...> wrote:
The Si5351 is rated to 200 MHz but most work to well over 300 MHz on the fundamental. There are other products out there, notably among them RFzero , that are based on the 5351 and produce usable output to well beyond the 23 cm band. I run my Si5351 based beacon on the RFzero at 1296 MHz WSPR flawlessly using the fifth harmonic. WA8TOD On Aug 8, 2019, at 11:55 AM, tuckvk3cca <tuckvk3cca@...> wrote: How does the nano do that when the Si5351 can only generate a square wave up to 200MHz? The schematic shows these signals just come straight out? Digital Alias signals or something?Sent from my Samsung Galaxy smartphone. -------- Original message --------From: Warren Allgyer <allgyer@...> Date: 08/08/2019 16:17 (GMT+01:00) To: [email protected] Subject: Re: [nanovna-users] Some basic load measurements Attached is a spectrum analyzer plot of the nanoVNA with CW output set for 300 MHz. The second harmonic at 600 MHz is -19 dBc as is the third harmonic at 900 MHz.Warren AllgyerWA8TOD |
Warren Allgyer