开云体育

The “Five County Digital Training Net” (Philadelphia region) is hosting a
series of Zoom Workshops on Monday evenings at 7-9 pm. The topic: Nano VNA
Fundamentals
All are welcome to join.
Link:


We have already held two sessions covering the fundamentals of what a VNA
is capable of measuring and the second session covered how to CALIBRATE the
VNA over a frequency range.

The 3rd Zoom session on November 14th will cover what a Nano VNA measures
and what it calculates: the forward and the reflected signals are compared
(S11) and the following are calculated:

1) Reflection Coefficient (rho) - a fraction from 0 to 1.0 representing
the ratio of returning signal to incident signal. In an antenna, you do not
want any reflected (return) signal, so the ideal reflection coefficient is
zero.

2) Return Loss (dB) - this is based on the reflection coefficient and
represents the loss of signal, but measured in decibels (dB) rather than as
a percent or fraction. Hams rarely use this measurement. Why?

3) SWR - standing wave ratio - We all use this term but what does it
mean? What is an “acceptable” SWR in terms of antenna performance.

I will tie these three measurements into what a Smith Chart reveals.

Come join the discussion.
I am not an RF Engineer - so I try to keep this at a moderate level of
mathematics.

De k3eui
Barry (k3euibarry - at - gmail.com)
Five County Digital Net manager
Philadelphia PA
November 13 2022







--

(you can see it also on Nano or Tiny LCD at right bottom)

*However*, the *H4* variant of the nanoVNA and the new tinySA *Ultra* use 4"
480×320 screens.

# The size of the screen
width = 320
height = 240

Hi,
as written just around the corner/g/tinysa/topic/tinysa_remote_py_python/94944540 there's a new tool in my toolbox:



Remote control for the NanoVNA or tinySA - mirror the screen to your PC and operate the device with the mouse. The keys + and - zoom in and out, s takes a screenshot with timestamp, ESC quits the program.

usage: nanovna_remote.py [-h] [-d DEVICE] [-t | -n] [-z {2,3,4}]

optional arguments:
-h, --help show this help message and exit
-d DEVICE, --device DEVICE
connect to serial usb device
-n, --nanovna use with NanoVNA (default)
-t, --tinysa use with tinySA
-z {2,3,4}, --zoom {2,3,4}
zoom the screen image

Martin

I don't know of any PV output optos that have 10V kind of outputs, which
is what you're going to need for Vgs on a big FET.

An isolated supply is fairly easy - as in an off the shelf DC/DC
isolated converter. You could use it as the gate drive directly, since
you're not looking for high speed.

For improving off isolation, you could put multiple identical switches in

series. I would start by simply taking the device and measuring its off state,
to see how many I might need to chain up.

Or a configuration that has a series switch followed by a shunt to ground.

Miro, yes, Elecraft uses such high voltage rectifiers as PIN diodes in several of their products. They use true PIN diodes in some others, and sometimes they even mix them. What kind of diodes they use in each case, is surely a trade-off between total cost and performance.

Many schematics are available on theyr website. Just download them and look! For example download the manual of the KPA100, which has such diodes, and also the crystal-locked DC-DC converter I mentioned. And download the K3 schematics file, where you can see the KPA3 using a combination of SMD high voltage rectifier and true PIN diodes. Also the low power final amp of the KPA3 uses a rectifier as a PIN diode. The TR switch on the K3 RF board uses a combination of rectifier and PIN diodes. Same thing with the K3S.