开云体育

Try it with some known cores first. -- John AE5X https://ae5x.blogspot.com/

Often a voltage doubler or tripler is used to "steal" some of the incoming RF, rectify it, and derive a high bias voltage that way, which will always be high enough to avoid conduction, since it will

Again, Fair-Rite has a wonderful YouTube presentation that outlines how to determine the mix of a ferrite. There's also a lot of additional information which may be quite useful. Visit the Fair-Rite

I didn't see this topic after a brief search, so here goes. My NanoVNA H3 (ver. 3.3) randomly reboots for no apparent reason, and it won't save configs. It's even happened when in DFU mode,

The subject of measuring toroid characteristics (ferrite and powdered iron) has been discussed in this group before. When Rune added the graphing capability of S11 R/ω & X/ω to NanoVNA Saver there

Yeah, that's cheaper than some relays. Of course, a relay won't vanish in a puff of smoke if you accidentally hook up line voltage or the B+ anode supply shorts to the output.

On Wed, Nov 9, 2022 at 10:17 AM, Manfred Mornhinweg wrote: Good points! Worth rereading again!

Yes, with 1kW PIN that affordable I question my attempt to use MOSFET with all the inherit problems it comes with

MOSFETs as RF switches are ubiquitous in cellular phones. You can never use just one FET as a switch because the gate-source/drain voltage is limited and will cause breakdown which is easy to realize

Miro, I would imagine that a MOSFET, with 10V or so on the gate, will behave like a low value resistor in series with a small inductance. Given the small size of the MOSFET chip, at HF the resistance

I come back to de Graph S11 R/ω & X/ω (?Ω/Hz) Already, numerically, it's not /ω but /F (frequency). Do not forget to reset the graph I still haven't understood what it can be for torus. How can

But the FET idea is interesting, and the NanoVNA makes it possible to easily test it. Not so expensive $10 each for the UM9415 direct from Microchip.

Since this is an antenna switch, one really doesn't have to worry about timing issues. It would be a very simple straight forward design.

Thanks!! That should be very helpful. I will try it out very soon - several unknown cores to investigate. -- Doug, K8RFT

Once I get time to put this on my bench I hope that "off isolation" will not be a big deal given that the load on another switch is 50 ohm antenna As power dissipation will be fairly small I will try

I'd expect MOSFET to behave in a similar way, with benefit that I have some high voltage (>400V) and decent current (>6A) handy. Another question that came to mind - how will the the AC (RF is not DC,

On 11/8/22 5:58 PM, Eamon Egan wrote: > Miro: > As far as your "academic" question goes, it's clear that any frequency specs of a MOSFET pertain to how fast it can be turned on and off, not how high

Miro: As far as your "academic" question goes, it's clear that any frequency specs of a MOSFET pertain to how fast it can be turned on and off, not how high frequency current they can pass. In fact,

This feature is already in NanoVNA Saver. Wind a few turns on the ferrite. Select the graph shown below and look for the "crossover" frequency. Then compare that with manufacturer specs for complex

I'd suggest that as a start, this be a feature to one of the PC applications that controls a NanoVNA. Or a standalone application. It's hard to fit things into the firmware, and at some point there