Nano VNA and LF Frequencies

Lounge
1

Call for help for anyone that has a Nano-VNA.

I have the newest iteration of my prototype LF Repeater. I just am having the hardest time finding a reliable way to scan it with a nano vna. I have a homemade loop probe i made with Magnet wire but i also have a variety of H-Probes at my disposal. I have adjusted the range, scale, and calibrated every adjustment i cannot seem to find any way to reliably get a read of LF devices.

any help would be appreciated because the group.io forum for Nanovna seems to have no info for me either.

Current settings are:

Range: 110Khz - 150khz
scale/div: .5

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2

What’s the impedance of your coils at 125khz? Are they acting as a choke at that frequency?

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3

It’s hard to estimate the impedence with the extra bias I have but my issue is I can’t even get a decent reads on a 125k fob enough to be able to start testing the coils

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4

Dumb question, but have you tried extracting the coil from an existing fob? Ideally and identical coil from an identical fob you want to read?

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5

Yeah I have a bunch of coils that are raw.

It’s just I can’t find the right settings of the vna to measure the resonance.

It’s definitely user error here

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6

I will be reunited with my VNA tonight, I’ll see what I can do, but bear in mind, I am a bumbling idiot, so don’t set your expectations high

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7

Me either buddy

I tried cards, fobs, iButtons, even a 134kHz chip
Range: 110kHz - 140kHz

How much will you rely on build guides for D4? : r/diablo4

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8

This. At least it eliminates questions??

9

I guess I should rephrase.

I’m not trying to read the chip. I’m trying to measure the coil with the vna probe.

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10

I have an idea I can try this weekend.
Will see what I can brake this time :sweat_smile:

11

Odd question… have you checked the output of the VNA with an oscilloscope to confirm it’s actually capable and is actually outputting the correct frequency?

12

You stop it with your smart point and logical reasoning!

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13

So the VNA basically is used to measure where on the frequency spectrum power is being drawn from.

I’m not outputting a signal with the probe in trying to see whay frequency the power is being drawn at.

14

Aren’t you? Isn’t that exactly how it detects power draw? It sweeps the frequency with an output signal… right? Attach a probe to your coil and see what you get on the oscope

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I sadly don’t have an oscilloscope in my testing tools yet

16

Frequency counter?

17

Another vna? Hah

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Honestly though I just don’t think I have the settings of my vna correct or I need a different probe.