Re: Part Number for the Demokit Cable
On Tue, Jan 7, 2020 at 01:47 PM, Phil Royce wrote:
" looks like 23 more cables to order and fix them permanently on to sma patch panel, I don't want to take on and off these, knowing in the past these connectors are not continuous use parts."
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I bought a couple of demo boards for classroom teaching and they didn't even last out the day with my students. A lifted trace on one board and intermittent cable connections on both boards after use by my better students. For a teaching environment, I would suggest something sturdier like the SDR-Kits Testboard Kit, or as you suggested permanently attached and fixed in place demo board cables.
- Herb
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Re: errors of "error" models
Gary, just a guess (I'm not a VNA designer) but it might be because it's
easier to design and characterize an "absolute" (open or short) with
nominally infinite impedance than something that needs to match some
arbitrary value. And how would you choose the arbitrary values?
Different users have different requirements.
I think, but am not sure, that using arbitrary values also would prevent
any pretense at corrected measurements beyond those arbitrary values.
When your limits are infinity, nothing stands in your way. :-)
73,
John
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On 1/7/20 2:48 PM, Gary O'Neil wrote: Hi again Jeff;
I believe I now sufficiently understand the technical aspects of the discussions in this thread to forego the wizardry behind the pursuit of high accuracy. it appears sufficiently sound.
On that happy note¡ I will state my one remaining question succinctly. Why the obsession over accuracy at the the two most unstable phase regions of highest Q and unreachable limits of infinity and zero?
A reasonable and credible answer will be a bounded tolerance of impedance or phase in those regions, and an estimate of the consequence of exceeding the tolerance boundaries.
I will reiterate¡ There is nothing wrong with how this is treated what is being done or the rationale behind the obsession. The only question is simply... Why?
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Re: Part Number for the Demokit Cable
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Re: errors of "error" models
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Re: Part Number for the Demokit Cable
Found a better price here for bulk. I'm use to lab prices so these are pretty cheap but not going to use constantly just for demo and test theories.
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Re: Part Number for the Demokit Cable
looks like 23 more cables to order and fix them permanently on to sma patch panel, I don't want to take on and off these, knowing in the past these connectors are not continuous use parts. Thanks for the part number.
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Measuring resonance from coax far end.
Hi folks,
This is more a generic VNA question, but thought i'd ask.
I've seen a trick to "eliminate" the coax by calibrating via the OSL on the
far end of the coax, rather than having OSL connected directly to the VNA.
Essentially it's re-calibrated with the coax factored into the equation,
virtually moving the feedpoint to inside the shack for accurate antenna
feedpoint measurement.
If i calibrate the far end, take resonance readings, then recalibrate with
the OSL connected directly to the VNA, re-take resonance readings, would it
be safe to assume if there is common-mode current interference on the coax
it would account for differing results (if there are any)?
If there's no common-mode currents, the coax-length should be invisible.
Just want to make sure i've got my theory correct. :)
Thanks & 73s,
Chris.
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Re: Part Number for the Demokit Cable
30 mating cycles ?? That gets you through the Demo Board only twice !! Where can one get extra cables, I think I may need them if I am to use the Demo Board to show off what the NanoVNA can do. 73, Dick, W1KSZ ________________________________ From: [email protected] < [email protected]> on behalf of reuterr@... <reuterr@...> Sent: Tuesday, January 7, 2020 12:42 PM To: [email protected] < [email protected]> Subject: Re: [nanovna-users] Part Number for the Demokit Cable ebay.com, eBay item number: 352840116109, $2.29 free shipping Please see my documentation at: /g/nanovna-users/wiki/RF-Demo-Kit-use73, Rudi DL5FA
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Re: errors of "error" models
Hi again Jeff;
I believe I now sufficiently understand the technical aspects of the discussions in this thread to forego the wizardry behind the pursuit of high accuracy. it appears sufficiently sound.
On that happy note¡ I will state my one remaining question succinctly. Why the obsession over accuracy at the the two most unstable phase regions of highest Q and unreachable limits of infinity and zero?
A reasonable and credible answer will be a bounded tolerance of impedance or phase in those regions, and an estimate of the consequence of exceeding the tolerance boundaries.
I will reiterate¡ There is nothing wrong with how this is treated what is being done or the rationale behind the obsession. The only question is simply... Why?
--
73
Gary, N3GO
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Re: Cancelling out coax feeder length?
As luck would have it, Times Microwave website has a coax calculator that includes the delay! My feeder is 26cm of RG316, which comes out as 1.3nS. Was also pleased to find the nanovna allows delay to be entered in pS or nS!
The resulting traces for this antenna are very complex, but it does show the VSWR is good. The complexity I think is likely to be due to the multi-element groundplane arrangement of the antenna! but I will do more testing later.
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Re: Cancelling out coax feeder length?
How long is your feeder and what kind of, I assume, coax? It's really quite easy. Give me those parameters, and I'll show you. Dave - W?LEV On Tue, Jan 7, 2020 at 7:19 PM Martin Barfield G7MRV <marting7mrv@...> wrote: That makes sense, thanks,
however the problem I have is that I cannot do it this way, due to the
antenna being fixed and not being able to access the feeder connection, so
it will need the maths!
So, its the electrical delay parameter thats needed, and this is in
picoseconds... I also know the length and the type of feeder, so should be
able to find the necessary parameters now to calculate the delay,
It would have been so much easier of course if i'd bought two of the same
patch leads, like I usually do!
Cheers
Martin
-- *Dave - W?LEV* *Just Let Darwin Work* *Just Think*
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Re: Part Number for the Demokit Cable
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Re: Cancelling out coax feeder length?
That makes sense, thanks,
however the problem I have is that I cannot do it this way, due to the antenna being fixed and not being able to access the feeder connection, so it will need the maths!
So, its the electrical delay parameter thats needed, and this is in picoseconds... I also know the length and the type of feeder, so should be able to find the necessary parameters now to calculate the delay,
It would have been so much easier of course if i'd bought two of the same patch leads, like I usually do!
Cheers
Martin
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Re: Nanovna Saver Q issue
On Tue, Jan 7, 2020 at 09:40 AM, vincent coppola wrote:
" ..The problem appears to be in determining the correct 3db points. Please note the band stop filter is the only filter that I have tried to measure Q .."
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Vince,
You might include a screen capture of showing the analysis data and the bandpass filter. If your filter is not flat in the bandpass, has large ripple in the bandpass, or there are not enough measurement points then an accurate automated determination of the 3 dB points may not be possible.
The program asks the user to place a marker in the flat area of the bandpass and then computes the lower and upper 3 dB frequency points from that marker value. The computed points may not correspond to any of your actual measurement points and the program will choose the closest point. For better accuracy, choose a higher number of sweep segments which will give more measurement points over the frequency range.
- Herb
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Part Number for the Demokit Cable
Anyone have a part number on the Demokit Cable, I want to have more than just two cables for the kit?
Thanks,
73 de ke4pwe
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Re: What Series/Parallel RLC are used for?
Again, read the tutorials associated with the NANOVNA sites. Series and parallel RLC circuits represent resonant circuits. The R represents the lumped loss in these circuit configurations. They may be used in impedance matching and filters of most kinds. Read up on resonance and you will become enlightened as to their universal uses in all things RF. Dave - W?LEV On Tue, Jan 7, 2020 at 5:50 PM aa_talaat via Groups.Io <aa_talaat= [email protected]> wrote: Hi,
For the NanoVNA Mod 3 software, what is the use of Series and Parallel RLC
measurement? I guess in case of S11 measurement it would give me the series
and parallel impedance of the passive part under test in the form or RLC.
Is this the case?
What about S21 measurement, what would be their uses?
-- *Dave - W?LEV* *Just Let Darwin Work* *Just Think*
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What Series/Parallel RLC are used for?
Hi,
For the NanoVNA Mod 3 software, what is the use of Series and Parallel RLC measurement? I guess in case of S11 measurement it would give me the series and parallel impedance of the passive part under test in the form or RLC. Is this the case?
What about S21 measurement, what would be their uses?
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Ver 0.2.1. A very nice, usefull piece of software. The only problem I can see is when measuring Q in the band stop filter analysis mode, the value is incorrect and too low. The problem appears to be in determining the correct 3db points. Please note the band stop filter is the only filter that I have tried to measure Q. Thanks Vince
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I believe this is the referenced book (attached photo and syllabus for the class below) - pulled from the parent directory of the handout directory.
Randy
NC8U
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On Jan 6, 2020, at 4:59 AM, Adrian Scripc? <benishor@...> wrote:
Hey Allison,
Thanks for the hints. Any idea on the referenced books?
Thanks,
Adrian
On Sun, Jan 5, 2020 at 4:19 PM aparent1/kb1gmx <kb1gmx@... <mailto:kb1gmx@...>> wrote:
KV5R,
They are the handout for the courses on antenna and feedlines.
As such they are often read this, evaluate this question.
If your going to suck those files up, then get the books that go with them
as many
do reference them for reading. If not you are just wasting disk space.
Allison
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No direct email, it goes to bit bucket due address harvesting in groups.IO
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Lithium chemistry battery charges have a setting called "Storage Charge". Why? Because storing batteries with a full charge contributes to the swelling that you see. All my RC plane batteries are stored with a charge level of "Storage Charge" usually about half capacity. They keep a long time that way. Yes, I have to charge them before I use them.
I would advise that you put your nanoVNA away after using it without topping the battery. You'll have enough energy to make a quick test or two. If you anticipate needing to use it for a period of time, charge it up or leave it connected to your PC while you measure. But, then put it away with less than full charge.
If you suspect your unit has a drain current while it's on the shelf, charge it once in a while. Not fully. Just enough to bring it back to storage charge level. Don't forget, if you discharge a lithium battery down to about 3 volts per cell, you will likely ruin the battery.
Oh, and NEVER short them. They make GREAT fires.
BruceN / K4TQL
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*"To invent, you need a good imagination and a pile of junk"* -- Thomas Alva Edison (1847-1931)
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Phil Royce
Dick
