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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.

Here's one that will do 10V (it's far from the only one). These parts are designed for turning on MOSFET gates to I suspect they stack as many LEDs in series as they need to get the required voltage.

Besides being cheaper than an isolated DC/DC converter, they probably have lower capacitance across the isolation barrier.

Eamon

On 11/12/22 9:39 AM, Manfred Mornhinweg wrote:

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.

Apparently, those 1000V PIV (the 1n4008) *are* PIN diodes - something about the voltage rating - the 800V versions are not.

However, there's some commentary about different manufacturers being different, and needing to check the data sheet for the reverse recovery time trr - it needs to be "long enough" (which I guess implies a big I region that has to be swept clear when reverse biased)

This is the issue - As a mfr can use the JEDEC number if your part meets the required datasheet values. If, you as a circuit designer are depending on "not on datasheet" numbers, some might work, some might not. (noise properties are notorious for this..)

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.

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.

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

Dave - LogMag for S11 just sits there at 10db/0.05db no matter what connector i put on the unit, OPEN, SHORT or LOAD. It doesn't fluctuate at all. Smith Chart stays at -133mOhms 521nH. No fluctuation using any of the three, OPEN, SHORT or LOAD.
No other traces for S11.

The screen also shows two S21 values. LogMag for S21 shows a constant 10db but the number next to it is fluctuating all over the place, typically between -70 and -99. Also below LogMAG it shows Phase Angle. It shows 90 degrees and to the right of that is another angle that is fluctuating all over -110 to +10 and many values in between over and over randomly.

I didn't tell the thing to show S21 values at all. It just did it.

John

Tom - I've ordered a couple to have on hand. Will take the one out.
Thanks for the suggestion.

John

Doug, i checked all the cables and popped the lid and checked inside for a cracked solder connection possibly. Took off the shield and checked that also. No problems that I could see.
Thanks for the suggestion.

John

Hello,
The PDF file works fine for me also.
Maybe you need to download it again?
Clyde KC7BJE

Mutiple parties interested. So for now spoken for... THANKS!
Great not to send to the landfill.

Paul,

thanks i tried this; was able to see the device in the DeFuse and it completed the update but the machine still acts like its in DFU mode.

tried this today and it did not fix it.

If you own or still use the ol HP 65/67/41C series RPN machines, I have a copy of Medleys microwave routines text.
Routines include analysis and synthesis of networks driven by S data.

If interested, reply offline direct. TNX...

73' Alan W4AMV

For me too
Opens fine
Dg9bfc sigi

Am 11.11.2022 12:57 schrieb "Max via groups.io" <kg4pid@...>:

Power MOSFETS are specified in terms of max Rdson. At high frequencies one must also include the drain/source capacitance as well as gate-drain and gate-source capacitances. Spice models typically include those capacitance parameters so an AC simulation at the frequency of interest should shed light on the performance as a “switch”.

-CT

On Thu, Nov 10, 2022 at 07:53 AM, Manfred Mornhinweg wrote:

Elecraft went another path, and used an RF oscillator to generate the high
voltage needed to bias 1N4007 and 1N5408 diodes pressed into PIN diode
service.

Is this saying that they use 1N4007/5408 as PIN? If so, any details?

It opens fine for me.
Max

On Thu, Nov 10, 2022 at 11:36 PM, Michael wrote:
Michael -

Found this a long time ago and not sure if this will be useful to anybody. See
attached.

Your "cross_ref_list.pdf" sort of opens - appears blank and closes immediately.
--
Doug, K8RFT

What is needed is some kind of NTE/ECG/SK catalog for most of the makers/seller of core material. Found this a long time ago and not sure if this will be useful to anybody. See attached.

Also, is there an SDK-ish docs on interfacing with the Nano? I was a fair programmer and I am learning to use my Nano better or at least trying to.

Michael

On 11/10/22 5:53 AM, Manfred Mornhinweg wrote:

Jim, yes, ready-made DC-DC converters are inexpensive these days, and are a good option in many applications. But for RF switching, I don't see the one you linked as very usable. 15V is definitely not enough reverse bias in any solid-state RF switch that has to handle the typical power used by hams, exccept with some types of true PIN diodes. Also the DC isolation provided by these converters is rarely required in RF switches. RF isolation is indeed required, but these ready-made converters don't provide it, having 20pF of capacitance between input and output. So the RF isolation has to be provided by means of RF chokes and/or high value resistors, in any case.

You can stack them for higher voltages. The DC isolation lets you do that.
Yeah, filtering for a specific application would be application specific.

As for RFI from voltage converters, I love to run mine at a very low frequency, such as 1kHz, taking advantage of the fact that only very low power is needed for reverse biasing RF switches. So even at that low frequency the transformer can be tiny. Where the interesting radio spectrum begins, we are already at several hundred times the switching frequency, and the harmonics up there are weak and very easily suppressed.

Yes, that works.

Elecraft went another path, and used an RF oscillator to generate the high voltage needed to bias 1N4007 and 1N5408 diodes pressed into PIN diode service. They placed the oscillator between two ham bands, locking it to a crystal to make sure it won't wander away. They also made sure that its harmonics don't fall on ham bands. A brave design, I would say! But later design changes seem to suggest that they still got RFI from these converters, maybe in the form of IMD with strong broadcast signals.

Locking the converters to an internal oscillator is a common strategy. It's used in most spacecraft for instance (it's even in JPL's "Design Principles") - I have a system that is locked to the divide by 64 from a 50 MHz reference oscillator, and we just accept that there's a noise spur every 781 kHz. Other systems with lower sample rates have locked the switching rate to the sample rate. The noise appears at DC, then.

Jim, yes, ready-made DC-DC converters are inexpensive these days, and are a good option in many applications. But for RF switching, I don't see the one you linked as very usable. 15V is definitely not enough reverse bias in any solid-state RF switch that has to handle the typical power used by hams, exccept with some types of true PIN diodes. Also the DC isolation provided by these converters is rarely required in RF switches. RF isolation is indeed required, but these ready-made converters don't provide it, having 20pF of capacitance between input and output. So the RF isolation has to be provided by means of RF chokes and/or high value resistors, in any case.

As for RFI from voltage converters, I love to run mine at a very low frequency, such as 1kHz, taking advantage of the fact that only very low power is needed for reverse biasing RF switches. So even at that low frequency the transformer can be tiny. Where the interesting radio spectrum begins, we are already at several hundred times the switching frequency, and the harmonics up there are weak and very easily suppressed.

Elecraft went another path, and used an RF oscillator to generate the high voltage needed to bias 1N4007 and 1N5408 diodes pressed into PIN diode service. They placed the oscillator between two ham bands, locking it to a crystal to make sure it won't wander away. They also made sure that its harmonics don't fall on ham bands. A brave design, I would say! But later design changes seem to suggest that they still got RFI from these converters, maybe in the form of IMD with strong broadcast signals.

Manfred