Re: How To Do A SWR Sweep on 2 Meter HT Antenna ?
On 10/20/22 11:45 AM, Frank wrote: How To Do A SWR Sweep on 2 Meter HT Antenna ?
Whats better: Should I connect the 2 meter HT antenna directly to the VNA or should I connect the 2M HT antenna to the end of a SMA cable then to the VNA ?
The VNA is sort of like an HT and you're holding it in your hand, so I'd say that's closer. The other approach is to make a test fixture, use coax with a LOT of appropriately chosen ferrite beads (probably not 31 for 140 MHz) to decouple it and put the VNA 10-20 feet away (so the operator is not in the near field of the antenna. Test fixture should then replicate the operator's effect. i.e. that you've got a lossy arm holding the HT next to a lossy body. For what it's worth human muscle, bone, and vessel tissues are about 1.5 S/m and epsilon 40. So a bag of salt water with the right conductivity with some polyester fiber or flakes (fake snow, pillow stuffing)that is about half the volume (to bring epsilon down from 80 for water)) Sea water is about 3 S/m and about 3.5% salt. So that will get you started. (ProTip, add a preservative so mold doesn't grow in your RF simulant - it's really, really gross) Or, test in a fixture that replicates "free space" - accept that it's not what the thing looks like in real life, but does provide something to compare against.
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Re: SWR measurements too high and HIGHLY unstable
If you have strong RF sources - broadcasters or public service - transmitters - closeby, these can cause erratic and unstable readings when connected to antennas. After all the cal's are completed, try measuring known loads without the antennas. These should measure true to the known loads. Dave - W?LEV On Thu, Oct 20, 2022 at 6:56 PM Myroslav Mykhalchuk <samuray7@...> wrote: Hello all,
I¡¯m very new to Nano VNA, so my apologies if my question is stupid or is
answered elsewhere. I just bought a new device (the smaller version) from
nanovna.com<> with the main purpose of measuring SWR. I
did follow the instructions for setting the range (stimulus) and
calibrating before the use. I tried the procedure and measurements in
shortwave as well as VHF bands. At all bands the SWR curve is highly
unstable, changing constantly and jumping greatly if I just approach the
device with my hand. On several of my antennas with proven and workable SWR
which should be between 1 and 2, I¡®m getting MUCH higher SWR values,
roughly averaging 10 and sometimes approaching 40! or so. However, SWR
reduces sharply if I approach the antenna with my hang.
Does it mean that I¡®ve got a defect or fake NanoVNA-H? If so, is it worth
it to try and exchange the device through nanovna.com<>?
I don¡®t even see any support contacts there. If exchange is not possible,
would anyone suggest what I can try and fix myself - maybe some HF
shielding?
Many thanks ahead for your thoughts! Cheers,
Myro
-- *Dave - W?LEV* *Just Let Darwin Work* -- Dave - W?LEV
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SWR measurements too high and HIGHLY unstable
Hello all,
I¡¯m very new to Nano VNA, so my apologies if my question is stupid or is answered elsewhere. I just bought a new device (the smaller version) from nanovna.com<> with the main purpose of measuring SWR. I did follow the instructions for setting the range (stimulus) and calibrating before the use. I tried the procedure and measurements in shortwave as well as VHF bands. At all bands the SWR curve is highly unstable, changing constantly and jumping greatly if I just approach the device with my hand. On several of my antennas with proven and workable SWR which should be between 1 and 2, I¡®m getting MUCH higher SWR values, roughly averaging 10 and sometimes approaching 40! or so. However, SWR reduces sharply if I approach the antenna with my hang.
Does it mean that I¡®ve got a defect or fake NanoVNA-H? If so, is it worth it to try and exchange the device through nanovna.com<>? I don¡®t even see any support contacts there. If exchange is not possible, would anyone suggest what I can try and fix myself - maybe some HF shielding?
Many thanks ahead for your thoughts! Cheers,
Myro
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Re: How To Do A SWR Sweep on 2 Meter HT Antenna ?
Hi, use a cable and calibrate at the end of the cable first. This way you can use any length cable you like as youve calibrated out any differences.
regards Pete
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Re: How To Do A SWR Sweep on 2 Meter HT Antenna ?
A monopole like an HT antenna requires an image plane. In use, this is a
combination of the HT body and your own body. So, to correctly measure an
HT antenna, this image plane must be replicated. Without that, the data is
somewhat meaningless. I have used a large copper plane with a BNC in the
center to measure these antennas. Not truly the way they are used in
practice, but at least its somewhat rigorous to antenna theory.
Dave - W?LEV
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On Thu, Oct 20, 2022 at 6:45 PM Frank <rftech@...> wrote: How To Do A SWR Sweep on 2 Meter HT Antenna ?
Whats better: Should I connect the 2 meter HT antenna directly to the VNA
or should I connect the 2M HT antenna to the end of a SMA cable then to the
VNA ?
-- *Dave - W?LEV* *Just Let Darwin Work*
--
Dave - W?LEV
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Re: How To Do A SWR Sweep on 2 Meter HT Antenna ?
Either way will not help much. An HT antenna is expecting a ground through the radio and your hand. To get anything even remotely effective you would need a piece of metal like a pie pan or pizza pan with the antenna mounted in the middle. Otherwise you will see poor readings
Sent by me
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On Oct 20, 2022, at 14:45, Frank <rftech@...> wrote:
?How To Do A SWR Sweep on 2 Meter HT Antenna ?
Whats better: Should I connect the 2 meter HT antenna directly to the VNA or should I connect the 2M HT antenna to the end of a SMA cable then to the VNA ?
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How To Do A SWR Sweep on 2 Meter HT Antenna ?
How To Do A SWR Sweep on 2 Meter HT Antenna ?
Whats better: Should I connect the 2 meter HT antenna directly to the VNA or should I connect the 2M HT antenna to the end of a SMA cable then to the VNA ?
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hello,
The latest menu map I have seen is for FW 1.2
The FW keeps changes so fast that, so far, no one has taken the time to try and update the menu maps. As soon as one is presented, it's obsolite.
The latest FW is 1.2.16 for the H and H4.
Clyde KC7BJE
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Oh yeah. Like the venerable MRF454 with 1 ohm impedances.
But the NanoVNA isn't much worse than any other VNA. And typically, you're looking to optimize a narrow band matching circuit, right?
So you can rig up a jig to measure the matching networks, then put them in the calculation (dembedding). You measure the input to the input network which is connected to the transistor, and from that, you can calculate what the transistor is doing.
This is where a tool like scikit-rf which can import and manipulate all the matrices is nice.
(or ADS)
Careful on spurious oscillations which will blow up port 2 on your VNA - BTDT. The NanoVNA is MUCH cheaper to fix than an 8510.
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Re: Need NanoVNA-H4 Manual
Thanks PE0CWK, appreciate your help.
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Hi Tim,
I have tried both.? With my HW version 4.3_MS NanoVNA the MS file works fine, but with my HW version 4.2 neither the SI hex or binary files will work.? They download fine but the NanoVNA just comes up with a blank, dark screen.
Tom
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On 10/20/2022 10:44 AM, Tim Dawson wrote: I have loaded the, iirc, .14 with Cube just fine, but have used the .bin as opposed to .hex images . . . . Have you tried those by chance?
On October 20, 2022 11:35:24 AM CDT, Tom Thompson <w0ivj@...> wrote:
Using STM32CubeProgrammer I can get both NanoVNA-H-SI_v1.2.08.00 hex and NanoVNA-H-SI_v1.2.14 hex to download to the NanoVNA-H4 but only NanoVNA-H-SI_v1.2.08.00 hex will run. DfuSe Demo (v3.0.6) will down load NanoVNA-H-SI_v1.2.14 dfu and the NanoVNA-H4 will run. I prefer the cube programmer, so can anyone resolve this?
Tom W0IVJ
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I have loaded the, iirc, .14 with Cube just fine, but have used the .bin as opposed to .hex images . . . . Have you tried those by chance?
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On October 20, 2022 11:35:24 AM CDT, Tom Thompson <w0ivj@...> wrote: Using STM32CubeProgrammer I can get both NanoVNA-H-SI_v1.2.08.00 hex and NanoVNA-H-SI_v1.2.14 hex to download to the NanoVNA-H4 but only NanoVNA-H-SI_v1.2.08.00 hex will run. DfuSe Demo (v3.0.6) will down load NanoVNA-H-SI_v1.2.14 dfu and the NanoVNA-H4 will run. I prefer the cube programmer, so can anyone resolve this?
Tom W0IVJ
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.
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Re: NanoVNA-saver crashes on calibration
On Thu, Oct 20, 2022 at 04:46 PM, N2MS wrote:
Isn't DiSlord's latest version 1.2.16?
DiSlord posted version 1.2.16 in message # 4004 on September 30, 2022.
Mike N2MS
At least in his GitHub repo the version is still at 1.2.15 (I get the version info by grepping for this line): #define VERSION "1.2.15" Martin
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Using STM32CubeProgrammer I can get both NanoVNA-H-SI_v1.2.08.00 hex and NanoVNA-H-SI_v1.2.14 hex to download to the NanoVNA-H4 but only NanoVNA-H-SI_v1.2.08.00 hex will run. DfuSe Demo (v3.0.6) will down load NanoVNA-H-SI_v1.2.14 dfu and the NanoVNA-H4 will run. I prefer the cube programmer, so can anyone resolve this?
Tom W0IVJ
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In case it may be of interest, I also measured one of the triode sections in a 12AU7 dual triode tube recently in grounded grid. I biased it at 0Vgk and 90V HT at 11mA anode current and extracted an S2p model using the VNA. I used bias tees and made direct connections to the pins of the tube (no tube base was used). Therefore, the model should be quite realistic for the raw tube before it is fitted to a base. The base will add capacitance between the pins and some inductance, so I made the measurements without the base.
The result for GMAX and K is given below. This shows that the tube can go unstable and oscillate up at about 500MHz as K is still below 1 here. This was quite a surprise for this basic little triode tube. I think the reason K fluctuates a lot up at UHF is because of the transit time in the tube. Presumably this causes reflections and this is probably why the fluctuations in GMAX and K are present up at UHF.
I've also included a classic Ft plot for the MMBTH10 BJT in common emitter at 10Vce and 5mA Ic. Ft is a fairly consistent 900MHz at each marker point. At unity current gain the Ft is 854MHz. In all cases, I always make sure the VNA source power is at a low level to prevent non-linear effects and I use an N4431B-60006 4 port Ecal and I exploit the fixture simulator option in the VNA to calibrate the (18GHz) test fixture such that the reference plane is right at the pins of the device under test as in the image below. All biasing and DC blocking is done outside the calibration plane.
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To Donald S Brant Jr and Jim Lux, I want to match an old transmitting transistor. The coil nearest the base is about 6 ohms, that is about 1-3cm wire. Calibration and measuring those is hard.
It is too easy with fets.
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Re: NanoVNA-saver crashes on calibration
Isn't DiSlord's latest version 1.2.16?
DiSlord posted version 1.2.16 in message # 4004 on September 30, 2022.
Mike N2MS
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On 10/19/2022 11:36 AM Ho-Ro <homuth-rosemann@...> wrote:
I provide unmodified bin and hex binaries of DiSlord's latest version in a branch of my clone, for version info just check the commit message - currently version 1.2.15:
These are the download links:
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Re: Need NanoVNA-H4 Manual
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Hi All. I am a newbie here and I need a manual for my new NanoVNA-H4 and also step by step instructions on how to calibrate and save the cal data.
Frank
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Hi All. I am a newbie here and I need a manual for my new NanoVNA-H4 and also step by step instructions on how to calibrate and save the cal data.
Frank
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Nice results.
I did the same experiment with a Hugen 2.3 and had to move to S21 measurements for accurate results on 1-30 MHz.
Maybe, if I get around to it, I? will try these low/high resistance S11 measurements on an H4.2.
Thanks.
Arie PA3A
Op 20-10-2022 om 01:33 schreef jmr via groups.io:
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Across the 5MHz to 50MHz frequency range, it's still possible for a basic nanovna to make fairly accurate resistance measurements across a wide range of resistances using a basic s11 measurement. In the plot below I measured a suite of test resistors from 0.167? through to 330k? from 2MHz to 30MHz. You can see in the chart below that my little nanovnaH did quite well in these tests. It failed to measure the 330k? resistor but did OK across 0.167? through to about 100k?. At higher test frequencies the performance of the nanovna will degrade but I think the performance of the nanovnaH is quite impressive in the plot below. This was all done with a single s11 calibration.
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Clyde Lambert
Ho-Ro
Arie Kleingeld PA3A