nanoVNA-H v3.4 is out, and I don’t yet see significant problem reports.
When I compare the circuit with v3.3 (which I have), apart from new battery charger IC etc, the changes are in three areas:
- decoupling power to the mixers;
- increasing the drive to the mixers; and
- higher attenuation of input on the rx port. Continue reading nanoVNA-H – rework of v3.3 PCB to v3.4?
At The system wide conjugate match stuff crashes out again I discussed the failure of Walt Maxwell’s teachings on system wide simultaneous conjugate match using an example drawn from an online expert’s posting.
The replicated scenario with matching with an L network where the inductor has a Q of 100, no other loss elements is shown below. (Quality real capacitor losses are very small, and the behavior will not change much, the inductor loss dominates.)
Above is a model in Simsmith where I have adjusted the lossy L network for a near perfect match. I have used a facility in Simsmith to calculate the impedance looking back from L1, often known as the source impedance at a node but in Simsmith speak the calculated L1_revZ on the form, (ie back into the L network) from the equivalent load. Continue reading A thinking exercise on Jacobi Maximum Power Transfer
RFPM2 – current probe described a current probe for use with a power meter calibrated in dBm (eg RFPM1 and RFPM2).
RFPM2 – current probe – #2 exposed some of the build details.
This article reports the completed article.
Above the current probe with RFPM2, the display does not show well at this camera angle… it is actually a lot clearer when viewed from a higher angle.
The instrument noise floor is around -76dBA or 0.16mA. When coupled to a conductor the background noise level will raise that by some site dependent amount, at my home coupled to an antenna feed line it bounces between -75 and -65dBA. Continue reading RFPM2 – current probe – #3
At nanoVNA – measurement of two 920MHz LoRa antennas I mentioned my growing frustration with the USB interface on the nanovna, particularly the tendency to reset the nanoVNA with the slightest wiggle and the frustration in trying to use the resulting mess.
I have previously cleaned both plug and socket a couple of times, the last time was after some board modifications and flux residue was washed from the board keeping the USB socket dry, then the USB socket was flushed with clean solvent and blow dry.
The USB problems have become apparent only recently and rapidly got worse. Continue reading nanoVNA-H – v3.3 USB problems
I was recently revising the code for the Coax Relay Driver to use a PIC16F1827 chip, and thought a good improvement would be a board that held the prototype electronics and the pulse latching relay together as an assembly.
Above is the design from Fusion360 to be cut from 3mm clear PVC sheet on the CNC router.
Above is the cut piece with four M3 heat melt threaded inserts for the electronics.
Above is the completed prototype assembly. The white cable to the left is an ICSP connection for programming / in circuit debugging of the code.
Whilst I used a CNC router do cut the board out, it could easily be done with a jigsaw and drill.
The article IoT – exploration of LoRa – part 3 showed some components of a simple LoRa system.
This article reports measurements made on two antennas used in the prototype system.
Above is a view of the prototype system. Continue reading nanoVNA – measurement of two 920MHz LoRa antennas
One of the many nanoVNA cloners makes an interesting little inexpensive demo board with a selection of components, filters etc to develop familiarity with the nanovna.
Above is a pic of the demo board and the supplied jumper cables. The demo board may not include information relevant to using the cables and connectors supplied. Continue reading nanoVNA – that demo board and its U.FL connectors
Recent discussion with a correspondent about the design issue of the so-called Co-Co collinears, vertical collinears made with alternating sections of common coax ranged onto the conflict between the phase velocity of the wave on the inside of the coax and the wave on the outside of the coax, and the difficulty in aligning both the outside standing wave pattern for optimal pattern, and the internal phasing to feed those sections with optimal phase. Continue reading Coaxial Collinear – dielectric loading the outer conductor
The HRD-831 (AKA HDR-831) is a low power mini FM stereo transmitter out of China.
The device appears to have FCC approval under the model HRD-831, but is sold out of China in a configuration that may not have FCC approval. Continue reading HanRongDa HRD-831 FM transmitter – configuration and review
At https://groups.io/g/nanovna-users/message/9185 a user posted a measurement made with his nanoVNA of a length of coax with termination.
Above is his initial reported measurement of
an approximate 350′ length of coax with a known good dummy load on the opposite end. 350′ is 106.7m. Whilst this chart is less value than a Smith chart rendering, understanding the nature of things allows us to infer the Smith chart. Continue reading nanoVNA user post provides an interesting example for study #1