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Re: OM3LZ version 3 power supply BOM needed
It looks like v 4? has a schematic with the part numbers. Since it is very similar to v 3. I may be able? to figure out which parts will actually fit on the board.
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I try? to source parts for several projects at once to lessen the impact of? postage costs.? The trick is? to order all the parts and not leave any off.. In carpentry there is a caution, measure twice and cut once :) I have to check the parts lists several times to avoid disappointment. Jim n2go On 2/26/21 12:21 AM, Kerry wrote:
I looked at his website; the third version is more complex than the one for which I kept data; I built my VNA in, I think, 2007 so the data that I have is for an earlier version. |
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Re: OM3LZ version 3 power supply BOM needed
I looked at his website; the third version is more complex than the one for which I kept data; I built my VNA in, I think, 2007 so the data that I have is for an earlier version.
It must be version two as it's different to version one.. I didn't build it; I just made a simple 5v & 12v linear supply with simple zener-based over-voltage protection. It has never failed. Kerry VK2TIL. |
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Re: BOM for revision 4.1 board needed
This thread reminded me that I have a pristine, unpopulated v4.1 board and a pair of bridge boards available for a reasonable offer. I built the original N2PK, upgraded it once with the faster detector and had plans to upgrade again when I bought the board. The death of a spouse and the march of time interfered.
I also have an unused Valpey-Fisher VFAC570BH 148.344 MHz clock oscillator I'd like to get $40 for, which is what I paid for it 20 years ago. Wes N7WS |
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Re: BOM for revision 4.1 board needed
Hi Kerry
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Someone had the 4.1 stuff. Thanks. There are a lot of similarities. Now to dig for the remaining parts.... Jim n2go On 2/24/21 3:09 PM, Kerry wrote:
G'day Jim. |
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Re: help getting started with myVNA
G'day Brian.
Glad you got it sorted and recorded it here for future reference. I didn't reply earlier because I've never tried to use myVNA without the "magic number" so had nothing to contribute. myVNA is a wonderful program and a pleasure to use; thanks yet again to Dave. It's good to see some activity here; I hoped that the N2PK Group wouldn't just "fizzle-out". It's still a remarkable instrument; Paul was one of the pioneers of this kind of VNA. Kerry VK2TIL. |
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Re: help getting started with myVNA
Follow up on my posts.
Getting activation resolves the issue with nothing happening on the sweep and calibration buttons, thanks Dave for fast reply 1)Win 10 64 bit works great with myVNA 2)Parallel port control using the Startech parallel adapter card (PEX1P) works great. Only three steps. Load Startech supplied driver (CD), Run Dave's "InstallDriver.exe" program, Read out LPTx Resource settings from device manager (BFF8 in my case) and put this in myVNA, then all works great. 3)Having two simultaneous receive capability without a bridge enables closed loop analysis from low frequency on up 4) myVNA program offers unbelievable flexibility for this type of network analyzer solutions measurement. I will try to follow up on my results for modifying the internal transformers to obtain lower frequency performance. If anyone else decides to do this type of measurements in the future I would love to hear about there successes and issues. Having used a profressional Ridley box (AP300) the only difference I see is his ability to adjust the injection amplitude at different level across the frequency band. Of course you can do the same here , but just use several sweeps and merge the data. Brian |
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Re: help getting started with myVNA
I¡¯m thinking that this was a really stupid question. I forgot to mention that I have not received the product codes yet. For some reason I was assuming that the program would work, but would time out like windows does after a month. But now I realize that the sweeps were most likely disabled until I get the codes.
Is this correct? I had just sent my request to Dave yesterday, so if my assumption is correct I should be fine with win10 64 bit and a star tech parallel port card. Note: another nice feature of myVNA is Dave allows you to set a nonstandard address for the addon parallel card. Brian |
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help getting started with myVNA
After years of using exiter, I am trying myVNA for the first time. The installation went well and I followed the configuration setup without any issues. My setup is a win10 64bit machine, however at this time I have not completed assembling my USB to parallel port adapter board. I decided to purchase a Startech PCIe parallel card and use this in the meantime. (since my N2PK has a parallel port).
The config went well and I am able to set and verify the frequency of the LO DDS. In addition when I run the vector volt meter, initial the ADC is blank, however after checking the "DDS Phase Init Test" box the numeric displays come to life and the readings makes sense for a non-calibrated VNA. However this issue I am having is that the buttons at the top to start a sweep do nothing. The expected scan time is reported at the bottom, but no progress on the scan and the DDS LOs do not get programmed to the starting frequency. They stay at the last frequency used in the vector volt meter test. So my conclusion is either there is an issue with win 10 64bit combined with parallel port, or there is some other issue with my setup that is preventing a sweep from starting. Since I have not used this before I'm not sure what to expect, however the calibration window that I think should popup when I hit calibration does not open. This leads me to think its a parallel port/win10/64 bit issue. Has any one used this combination with myVNA successfully? Is there something I need to do to start the calibration window besides hitting the button? Do other users find that the ADC readings in vector volt meter do not start without pushing the "DDS Phase Init check box? Sorry for the basic questions about this and any experience with myVNA is helpful in my debugging. My investigation of the archieved messages didn't help. Brian |
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Re: simultaneous s11 and S21 mewasurements
Ron Skelton
That's good to know Brian
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On 2021-02-19 14:02, Brian k wrote:
Ron, which software to use was my original question. I concluded the same as you that the myVNA is the most flexible. Brian |
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Re: simultaneous s11 and S21 mewasurements
Ron Skelton
Hi Brian thank you for the details. I'm puzzled about the software
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you are using . The MyVNA program and user guide from G8KBB is quite exceptional. 73 Ron W6WO On 2021-02-19 00:21, Brian k wrote:
Ron, |
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Re: simultaneous s11 and S21 mewasurements
Ron,
My original request for dual measurements is due to my limitation of using the exciter software. It can only do one detector at a time. While this works for many measurements it does not work for a in loop active monitoring. This isn¡¯t actually a s11 or s21 measurement, but using a nice feature of the n2pk to have an external bridge. This proves two channels ( like a scope) and a synchronous source that is used for monitoring feedback systems. The best explanation is in this app note. I want to add that vnas like the low cost series of nanoVNAs have been designed to be very convenient for s21 and s11, but they can¡¯t as easily be adopted for these measurements . I hope the attachment helps explain this better than I have Brian |
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Re: simultaneous s11 and S21 mewasurements
Ron Skelton
Hi Gary I note that you are engaged in this topic so please to
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explain to me in a few words how it relates to the subject of dual S11 S21 measurements. Isn' t this just a feature of the dual detector architecture ,very useful in tuning a filter and such PS I have virtually dropted out of Ham Radio but will remain interested in VNA discussions 73 Ron On 2021-02-15 12:35,e Gary Johnson wrote:
On Mon, Feb 15, 2021 at 09:12 AM, Brian k wrote:Has anyone previously implemented (using myVNA) an active loop injectionYes, during development of an audio amplifier. |
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Re: simultaneous s11 and S21 mewasurements
Toni, yes I noticed the difference after I sent the reply. Your right this definitely needs to be accounted for. I am thinking that the lo output from the dds is a little easier to deal with. The current source from the dds is flexible and in the worst case I could ac couple without a transformer. I would lose 3db of output power, but I think that would be worth the bandwidth extension. Thanks for following up on my mistake
Brian |
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Re: simultaneous s11 and S21 mewasurements
On DDS side you have different transformer T4-6T (1:4 ration), but on detectors are 1:1 as mentioned. On DDS side (ad9851) you should
check for impedance mismatch. Since I am lack of time I am not able to check this mods, but I will be grateful for any test results. |
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Re: simultaneous s11 and S21 mewasurements
I looked into the ltc2440 and being a sigma delta, the alias requirements are simplified. It appears over the range of OSR (over sample rate) I can achieve a 60db rejection between 28k for the fastest rate and 55hz for the slowest rate. This should easily handle the lo leakage and image rejection associated with running the lowest frequency of 4kHz thought the TT1-6 transformers. The myVNA allows selection of OSR down to 6.8Hz, for the bandwidth.
So before I start hacking up my VNA I want to summarize my plan to see if anyone can find additional issues. I don¡¯t expect the dynamic range to be great, I am looking to an easy way to verify the loop responses of switching power supplies, ALC loops and PID control of anything between 5kHz and 1MHz. Replace T1_6T with TT1-6 transformers on mc1496 and ad9851. Replace parallel interface with wb6dhw usb interface Load myVNA Configure myVNA for dual slow detector and remove bridge Add injection transformer in place of the bridge. Thanks the plan, any suggestions Brian |
Wes Stewart
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