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Re: Some basic load measurements
Yes, the chips can be programmed directly at 300 MHz and actually beyond. When the chip runs out of range it will actually just sit on the previous called for frequency and ignore the command. The fundamental shows up at 300 MHz. At 301 MHz it drops back to 150.5 on the fundamental, boosts the output power about 6 dB, and outputs a 301 MHz second harmonic. None of this is inherent to the chip necessarily but is programmed in the VNA software.
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How the software distinguishes between the fundamental and the desired second or third harmonic is a mystery to me as well. I only know what I see on the spectrum analyzer. Clearly the fundamental is not attenuated so I have no idea how response to it is managed. WA8TOD On Aug 8, 2019, at 7:24 PM, tuckvk3cca <tuckvk3cca@...> wrote:
That is interesting. I have not played with SiLab chips for quite a while being more familiar with the Analog Devices AD98xx families. I couldn't find in the data sheet if it can be programed directly for 300MHz fundamental which is beyond the 200MHz max specs. Is that actually possible or the chip is really programmed internally for 150MHz to yield an output at 300MHz? Normally harmonics are a nuisance and they can degrade the bridge measurements without adequate filtering. How does the software avoid these errors?Sent from my Samsung Galaxy smartphone. -------- Original message --------From: Warren Allgyer <allgyer@...> Date: 08/08/2019 18:13 (GMT+01:00) To: [email protected] Subject: Re: [nanovna-users] Some basic load measurements 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. Pretty clever stuff actually.WA8TODOn 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.WA8TODOn 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 |
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Re: Some basic load measurements
Is that actually possible or the chip is really programmed internally for 150MHz to yield an output at 300MHz?Just because the Si5351 is not specified for 300MHz does not mean that most cannot be overclocked to generate 300MHz fundamentals. Normally harmonics are a nuisance and they can degrade the bridge measurements without adequate filtering.Michael Knitter uses the same Si5351 with a weaker processor in his FA-VA5. Some relevant DSP magic is described around 11:30/30:01 here: |
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Re: Some basic load measurements
That is interesting. I have not played with SiLab chips for quite a while being more familiar with the Analog Devices AD98xx families. I couldn't? find in the data sheet if it can be programed directly for 300MHz fundamental which is beyond the 200MHz max specs. Is that actually possible or the chip is really programmed internally for 150MHz to yield an output at 300MHz? Normally harmonics are a nuisance and they can degrade the bridge measurements without adequate filtering. How does the software avoid these errors?Sent from my Samsung Galaxy smartphone.
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-------- Original message --------From: Warren Allgyer <allgyer@...> Date: 08/08/2019 18:13 (GMT+01:00) To: [email protected] Subject: Re: [nanovna-users] Some basic load measurements 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. Pretty clever stuff actually.WA8TODOn 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.WA8TODOn 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
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Re: Some basic load measurements
What is the scale of this plot? Is the 900MHz end 40dB RL. It can't? be less than 70dB anywhere if each y grid is 10dB.Sent from my Samsung Galaxy smartphone.
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-------- Original message --------From: Peter Gottlieb <hpnpilot@...> Date: 08/08/2019 16:20 (GMT+01:00) To: [email protected] Subject: Re: [nanovna-users] Some basic load measurements I did actually do that and was seeing about the same return loss.? The plot is somewhat noisy and there is a periodic spike at perhaps 300 MHz as captured in the attached photo. Peter> On Aug 8, 2019, at 10:09 AM, tuckvk3cca <tuckvk3cca@...> wrote:> > Would you be able to use your OSL load to calibrate the nano and then run a scan with it on the supplied dummy? A comparison of the plots ftom the nano vs the 8753 should be interesting. I note that you can get quite decent sma dummy loads with guaranteed swr <1.06 or 30.7dB for under $15. These are less fragile than the ones supplied. Sent from my Samsung Galaxy smartphone.> -------- Original message --------From: Peter Gottlieb <hpnpilot@...> Date: 08/08/2019? 03:52? (GMT+01:00) To: [email protected] Subject: Re: [nanovna-users] Some basic load measurements I made some further measurements using the 8753 setup.I did the OSL cal on one port and looked at both the Smith chart as well as S11.I didn't bother with the cheap BNC load.? I used averaging (16) to get more stable measurements.The Smith chart was of little use as each load showed up as a tiny one pixel dot almost exactly in the middle.? However, it does display reactance values.All the values here are from the 8753.Load??????? R??????????????? Z contrib ohms???? value S11 @ 900 MHzOSL???????? 50.000????????? 0.0000???????????????? 0.0000 H -76 dB (noisy)Nano????? 49.184????????? 0.4255???????????????? 76.942 pH -40.673 dBNarda???? 50.438??????? -33.203 m???????????? 5.3205 nF -47.356 dBTiny??????? 49.389????????? 0.5977????????????????? 105.58 pH -40.678 dBNote the resistance values on the 8753 differ from the DC resistance somewhat, even normalizing to the OSL value.? You can clearly see the OSL becomes the definition of 50 ohms and the S11 is at the analyzer noise floor.tuckvk3cca pointed out how the 1.02 SWR corresponded to a 40 dB return loss and he is spot on.? The Narda shows the best return loss at 900 MHz of better than 47 dB.What would be considered a high quality load?? The one that comes with the NanoVNA is not terrible considering the other tiny one I have, which has a NSN number on it, is very similar.? Not that having a NSN number infers anything spec particular, but at least it will have a minimum set of specs so somebody thought about it.I note that the very small SMA terminations are slightly capacitive while the 1.5" long Narda termination (it probably has some power rating) is slightly inductive.? These variations are too small to see on the Smith chart at regular scale.PeterOn 8/6/2019 10:43 PM, Peter Gottlieb via Groups.Io wrote:> Resending from website as it didn't seem to go through as a message.? Also my pasted table from Excel lost formatting so I tried to fix it to be more readable.>>> I just did some very simple resistance and SWR measurements using a HP 8753ES with 85046A, resistance was measured using a calibrated Agilent 34401A in 4 wire mode.>> I did a very basic one port 3 point cal using a Anritsu OSL which is specified to over 3 GHz.>> I took measurements at 900 MHz.>> Load????????????????????? R ohms????? SWR????????? SWR notes> OSL??????????????????????? 50.052?????? 1.001???????? Flat> Cheap BNC??????????? 51.104?????? 1.908???????? Sloping up with freq> Nano load?????????????? 49.044?????? 1.019???????? Flat> Narda 12.4 GHz????? 49.536?????? 1.018????????? Flat> Tiny SMA???????????????? 50.787????? 1.009????????? Flat>>> I am guessing there is some significant reactive component in the BNC terminator.? All three of the SMA loads showed a flat SWR with frequency so I'm thinking they all have a minimal reactive component.>> The difference in resistances while keeping SWR low was a bit of a surprise to me.? The load that came with the Nano is over an ohm off of the load I used to calibrate yet the SWR remains at a low 1.019. Why is this?? I did the math and surprisingly this is indeed correct, per calculation the SWR should be 1.021 vs my measured 1.019.? I'd say this is darn close seeing one measurement is DC resistance and the other is at 900 MHz.>> So my conclusion is that SWR is not a sensitive number to see resistance differences.>> Once I read some of the references cited I can do some more advanced measurements.>> Peter>> >> >
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300 MHz spike...
What causes the spike to show at 300 MHz when it switches and what has been done in the later software to get rid of the spike?
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Burt, K6OQK On August 8, 2019 9:13:15 AM PDT, Warren Allgyer <allgyer@...> wrote:
The nanoVNA begins using the second harmonic as soon as the sweep --
Sent from my Android thingamabob with K-9 Mail. Please pardon the spelling errors as the dog can't spell so good. |
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Re: Some basic load measurements
What causes the spike to show at 300 MHz when it switches and what has been done in the later software to get rid of the spike?
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Burt, K6OQK On August 8, 2019 9:13:15 AM PDT, Warren Allgyer <allgyer@...> wrote:
The nanoVNA begins using the second harmonic as soon as the sweep --
Sent from my Android thingamabob with K-9 Mail. Please pardon the spelling errors as the dog can't spell so good. |
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Re: Some basic load measurements
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 |
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Re: Some basic load measurements
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.
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Show quoted text
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 |
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Re: Some basic load measurements
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.
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Show quoted text
-------- 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
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Re: Some basic load measurements
Attached spectrum analyzer plot shows the output of the nanoVNA at three different CW stimulus settings:
Red trace shows 250 MHz setting - Fundamental is used. Green trace shows 350 MHz setting - Fundamental is output at 175 MHz and second harmonic at 350 MHz is used. Blue trace shows 650 MHz setting - Fundamental is output at 216.67 MHz and third harmonic at 650 MHz is used. Warren Allgyer WA8TOD |
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Re: Possible bug?
Hi Mike -
Set sweep range:Based on my experiments, firmware uses (only) last selected marker to set START, STOP, CENTER, or CW. SPAN seemingly uses 2 markers... |
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Re: Some basic load measurements
I did actually do that and was seeing about the same return loss. The plot is somewhat noisy and there is a periodic spike at perhaps 300 MHz as captured in the attached photo.
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Peter On Aug 8, 2019, at 10:09 AM, tuckvk3cca <tuckvk3cca@...> wrote: |
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Re: Some basic load measurements
Would you be able to use your OSL load to calibrate the nano and then run a scan with it on the supplied dummy? A comparison of the plots ftom the nano vs the 8753 should be interesting. I note that you can get quite decent sma dummy loads with guaranteed swr <1.06 or 30.7dB for under $15. These are less fragile than the ones supplied.?Sent from my Samsung Galaxy smartphone.
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-------- Original message --------From: Peter Gottlieb <hpnpilot@...> Date: 08/08/2019 03:52 (GMT+01:00) To: [email protected] Subject: Re: [nanovna-users] Some basic load measurements I made some further measurements using the 8753 setup.I did the OSL cal on one port and looked at both the Smith chart as well as S11.I didn't bother with the cheap BNC load.? I used averaging (16) to get more stable measurements.The Smith chart was of little use as each load showed up as a tiny one pixel dot almost exactly in the middle.? However, it does display reactance values.All the values here are from the 8753.Load??????? R??????????????? Z contrib ohms???? value S11 @ 900 MHzOSL???????? 50.000????????? 0.0000???????????????? 0.0000 H -76 dB (noisy)Nano????? 49.184????????? 0.4255???????????????? 76.942 pH -40.673 dBNarda???? 50.438 ? ? ?? -33.203 m? ?????????? 5.3205 nF -47.356 dBTiny??????? 49.389 ???????? 0.5977 ???????????????? 105.58 pH -40.678 dBNote the resistance values on the 8753 differ from the DC resistance somewhat, even normalizing to the OSL value.? You can clearly see the OSL becomes the definition of 50 ohms and the S11 is at the analyzer noise floor.tuckvk3cca pointed out how the 1.02 SWR corresponded to a 40 dB return loss and he is spot on.? The Narda shows the best return loss at 900 MHz of better than 47 dB.What would be considered a high quality load?? The one that comes with the NanoVNA is not terrible considering the other tiny one I have, which has a NSN number on it, is very similar.? Not that having a NSN number infers anything spec particular, but at least it will have a minimum set of specs so somebody thought about it.I note that the very small SMA terminations are slightly capacitive while the 1.5" long Narda termination (it probably has some power rating) is slightly inductive.? These variations are too small to see on the Smith chart at regular scale.PeterOn 8/6/2019 10:43 PM, Peter Gottlieb via Groups.Io wrote:> Resending from website as it didn't seem to go through as a message.? Also my pasted table from Excel lost formatting so I tried to fix it to be more readable.>>> I just did some very simple resistance and SWR measurements using a HP 8753ES with 85046A, resistance was measured using a calibrated Agilent 34401A in 4 wire mode.>> I did a very basic one port 3 point cal using a Anritsu OSL which is specified to over 3 GHz.>> I took measurements at 900 MHz.>> Load????????????????????? R ohms????? SWR????????? SWR notes> OSL??????????????????????? 50.052?????? 1.001???????? Flat> Cheap BNC??????????? 51.104?????? 1.908???????? Sloping up with freq> Nano load?????????????? 49.044?????? 1.019???????? Flat> Narda 12.4 GHz????? 49.536?????? 1.018????????? Flat> Tiny SMA???????????????? 50.787????? 1.009????????? Flat>>> I am guessing there is some significant reactive component in the BNC terminator.? All three of the SMA loads showed a flat SWR with frequency so I'm thinking they all have a minimal reactive component.>> The difference in resistances while keeping SWR low was a bit of a surprise to me.? The load that came with the Nano is over an ohm off of the load I used to calibrate yet the SWR remains at a low 1.019. Why is this?? I did the math and surprisingly this is indeed correct, per calculation the SWR should be 1.021 vs my measured 1.019.? I'd say this is darn close seeing one measurement is DC resistance and the other is at 900 MHz.>> So my conclusion is that SWR is not a sensitive number to see resistance differences.>> Once I read some of the references cited I can do some more advanced measurements.>> Peter>> >
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Warren Allgyer
Oristo
F4WCV
Burt K6OQK
