Hey there knowladge base people, I’m H4 user. I’ve been tuning some EFHW`s and checking various UHF/VHF aerials for handhelds for a while now. HF’ I’ve build 49:1 un un 20m wire for 7,14,21,28 mhz frequencies. Usually display set 6-29Mhz and calibrate VNA. During the tuning proces I usually make the wire little longer and than shorten it by 15-20cm and than watch the SWR and resonance on freq. I intend to use. Here is the question: Why does the resonant frequency and SWR are not same? From previous discussions here, I’ve gained awareness that all measurements are more accurate when choosing smaller Span between the stimulus say insted 6-29mhz choosing 6-8mhz (40m band) - 20-22mhz for (15m band). I’ve tried to measure smaller section with similar results those being: when Recall from calibrated memory say 6-8mhz for tuning on morse portion of 7mhz band, the SWR will be say 7.030 yet the resonance displayed on thel left will be @ 6.870 Why is this happening ? Am I missing some technical or physical understanding ? J. OK4SU 73

Anyone tried to connect their NanoVNA directly to their TinySA... Very interesting. See pics below. The VNA is set to sweep from 125MHz to 175MHz. The SA is wide open from 0 to 800MHz. I was surprised to see signals all over the band though most are concentrated in the sweep limits. Notice LOGMAG is flat and the Smith chart shows no change across any range.. NOTE: There is 30dB external attenuation between these two... Just to be safe. Pic 1 AVG 4 Pic 2 MAX HOLD Pic 3 random shot no calc on trace

Just for fun, I tried connecting the rubber flex antenna from my Yaesu FT-70D handheld directly to the SMA connector on my NanoVNA (after calibration) and seeing what the characteristics were. I was pleasantly surprised on 2m. I figured that holding the VNA as shown would pretty closely simulate the same effect as holding the HT, and that seems to be the case. The resonant frequency did vary with the position of my hand, but it stayed pretty well within the 2m band. In the photo, the marker is at 146.0 MHz, SWR is less than 1.167 at minimum, impedance is approximately 55 ohms. On 70 cm, though, I found it to be much less cooperative. at 445.2MHz, SWR was about 2.8:1. Impedance reads 51.6 ohms net, but very capacitive (32.7 -j39.9 ohms) I'm not sure here whether being mounted to the HT would make a difference, and it is difficult to measure with any sense of accuracy.

Is there a link to anything (PDF, YouTube, etc) that covers what the top lines on the NanoVNA can report and how to interpret them (I have the H4)? I know there's a lot that can go on up there... I've searched the forum but not found any comprehensive reference.. thanks...

A new Technician Class Operator has limitations on putting a 10m antenna anyplace but as a dipole over a paved surface. I do not have any practical experience there and googled around and found nothing specific to this. I'm ready to say no real problem but would like other opinions. I only found on-line that a lossy earth on lower bands has a negative effect. The op does not have a tuner at the moment and by practical application a 10m center fed at .5wl should provide approx 72ohm and 1.4:1 SWR. The radiation pattern appears to be exclusively lobes at a 30degree elevation. Would the asphalt have a great impact here? Anyone? 73, Andy

What happens when you compare different calibration stubs—the 50 ohm load. The NanoVNA comes with 1 50 ohm calibration stub, but you need 2 (and 2 F-F barrel connectors if using the supplied cables) to do a proper ISOLATION calibration for S21 type tests. So I bought for about $15 another stub kit with an identical looking 50 ohm load and F-F barrel connector (a bonus was an M-M barrel connector the original kit didn’t have). Then, also for about $15 I saw a pair of different looking 50 ohm load stubs. I bought those too, wondering what would happen if I compared 50 ohm stubs? What if I CALIBRATED with one type of load stub and then TESTED (S11) the other? The three pics below tell the story. The two stub types match (50ohm, no reactance) only at the low end of my test frequency (1MHz–800MHz) range. They progressively diverge as frequency goes up, and as might be expected, the divergence is inverted. (A) becomes capacitative, and resistance goes down compared to (B), while (B) becomes inductive, and resistance goes up compared to (A)! Is there a difference in real measurements? I tested a J pole antenna across my calibrated range (1-800 MHz). Between 750-800 MHz the frequencies reported for the lowest SWRs varied by 4+ MHz depending on which calibration was used. At 100-150 MHz the measured difference was only 50 kHz. The device can only be as good as its calibration. Professional calibration kits cost THOUSANDS of dollars—I looked. Regarding absolute measurements the NanoVNA using the supplied or other inexpensive calibration stubs is “very close” at lower frequencies and progressively less reliable as the frequency goes up. Users who are doing measurements in the upper parts of the NanoVNA’s frequency range must keep this in mind. —---------- Picture 1: Load stubs (A/Top) supplied with the NanoVNA. (B/Bottom) a second set of 50 ohm loads purchased (cheap) from Amazon. Picture 2. 1MHz - 800MHz calibrate using the (B) stub from picture 1 but testing the (A) stub. Trace 1 is Resistance. Trace 2 the Smith chart. The A (DUT) stub is more capacitative and resistance goes down with increasing frequency. Picture 3. 1MHz - 800MHz calibrate using the (A) stub from picture 1 but testing the (B) stub. Trace 1 is Resistance. Trace 2 the Smith chart. The B (DUT) stub is more inductive, and resistance increases with increasing frequency.

I saw in a previous post that it was possible to modify the device to have a real time clock by adding a 32 KHz crystal which I tried to do. I ended up bridging some pins luckily with the battery disconnected but after I attempted to attach the crystal to the correct pins, connected the battery and flipped the power switch it starts up and looks ok but no sweeping and no response from touching the display. This modification appears to be very high risk and not too much of a reward other than the device knowing what the date and time is along with time stamping files correctly.

Ok I have a NanoVNA-H4 I have three coils I want to measure their inductance. I tried what I saw a few you tube videos of where, I simply calibrate it and put the coil across. well yeah it works maybe. Two of the coils of known value both I tested at 3 to 4 Mhz freq wise. The small one was supposed to be 8.5uh but measures as only 3.7 the bigger one i supposd to be 200uh but measures at 170uh. Now BOTH of them on the smith trace onlu make very small segment of a circle up in the capacitor land like around 1 and 2 o clock. Looking for suggestions. Joe

Hallo, ich habe das Problem das mein NanoVNA als USB Gerät erkannt wird und ich habe kein zugewiesenen COM Port. Somit kann ich mit der App auch nicht drauf zugreifen. Welchen Treiber muss ich für Windows 10 Installieren ?