2.4Ghz Oscillator

Gentlemen,

Has anyone got any ideas for a simple, low-power (milliWatt level) VCO for the WIFI band? Something with a minimal range of just a few feet? I just want to ensure my phone can't access my home network WIFI unless I expressly allow it. TIA.

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what's wrong with disabling wifi on the phone, not giving it the password or blocking it on the router?

On a sunny day (Sat, 20 Oct 2018 15:05:42 -0000 (UTC)) it happened Cursitor Doom wrote in :

Feeding some voltage into the base via a resistor changes frequency a bit. Can you read the resistor values?

In an normal world that would be fine, but this is Google's Android and I don't trust Google one iota. If they had nothing to hide they'd disclose the source code of their various 'contributions' to the O/S which are opaque blocks of machine code which could do *anything* without the user's knowledge.

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Interesting suggestions, there. I like your thinking, but I'd be a bit worried about forgetting it was in the oven in your first idea and the effects on my electricity bill in your second!

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: I I

just store in in your tinfoil hat then

And you trust the wireless carriers more?! I can't even trust AT&T to define the word "unlimited" correctly. :)

I'm not the only one!

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Now I can see why you thought my soldering was OK, Jan. ;-)

Seriously, this looks interesting. I can't read the values and I can't tell what the active device is. You have a circuit for it?

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: I I

google listening station, gchq etc

NT

On a sunny day (Sat, 20 Oct 2018 20:28:41 -0000 (UTC)) it happened Cursitor Doom wrote in :

It is part of a locked loop, that is how I know it is 2.4 GHz, or whatever, but anyways: this is the basic oscillator with frequency control:

The 2 x 75 ohm in series can be 150 Ohm of course, just grabbed in the junk box.

It is from:

experiments of the third kind by El Pante.

Thanks. You must have *excellent* eyesight to be able to read your own schematics! :-D

However, under the BFR91 it appears to say it's designed for only ~1.6GHz rather than 2.4, so there enough adjustment wrt the voltage determining level to get up where I need it?

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ics! :-D

< >

if you need something in finite time.

tegards, Gerhard

Thanks, Gerhard; certainly looks like an interesting device for sure.

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Gerhard Hoffmann wote

mm better use ebay then:

The center frequency depends on the length of the twisted wire segment. Just cut the twisted wire to 1/8 wavelength as in the other picture, this circuit was tuned for a lower frequency with a longer twisted wire section, but the oscillator components are the same

The simple initial gross way to tune it is to make a long twisted feedback wire section and then cut pieces of until you are at frequency.

As you see I use a divide by 256 chip, that changes 2400 MHz into 9.375 MHz. So then I can measure it directly with this simple frequency meter:

Just multiply reading by 256, save expensive huge heavy weight meter.

Or you could use a short wave radio, one with a SSB BFO is even better, to listen for 9.375 MHz, been doing something like that all day testing circuits.

Ah! OK, I see what you mean. I'd assumed that twisted pair was some sort of 'adjustable' method for obtaining the right amount of positive feedback for maintaining reliable oscillation and easy starting. That's much clearer now, thanks!

You're one of these ingeniously resourceful fellows, clearly. I'm literally tripping over myself with high-end test gear of the boat-anchor variety here, so at least tuning it won't be an issue. The biggest problem will be deciding which meter to use - and finding it! :)

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What type of cell phone or smartphone are you using? If your unspecified carrier supports Voice over WiFi, Advanced Calling, or other trademarked name for using WiFi for making phone calls, your question makes some sense.

If you don't want your phone to suddenly become self-aware by connecting to the outside world without your permission, the easiest fix is to turn off the WiFi feature in your smartphone. However, if you're worried that the mind control division of your government communications authority might take control of your phone and use it to spy on your evil and nefarious activities, then some manner of WiFi jammer might be appropriate.

The problems is that WiFi uses spread spectrum modulation, which is largely immune to interference from an unmodulated carrier. A simple oscillator, without any modulation, will not work. Even the same style of DSSS (direct sequence spread spectrum) modulation will not produce adequate interference unless it uses the same PN (pseudo noise) spreading code. At best, it might reduce the receiver sensitivity somewhat.

For your paranoid scheme to work, you need either the same type of modulation, as found in a proper WiFi jammer, or a similar but incompatible PN modulation scheme, such as FHSS (frequency hopping spread spectrum). WiFi jammers are commonly available: Most are based on an EPS8266 module. You can also build one using a Raspberry Pi board: Using any one of these, you should have little difficulty trashing WiFi for yourself and anyone within range and put you on the road to global WiFi domination.

Another method is to modulate with FHSS instead of DSSS. Direct sequence is fairly immune to interference from other DSSS sources, but FHSS will usually cause your WiFi to go comatose. A higher power BlueGoof transmitter will do the trick. This might help: "Jamming and Anti-jamming Techniques in Wireless Networks: A Survey"

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Jeff Liebermann     jeffl@cruzio.com 
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I suspect it'd work well enough if P_out were say 800W :)

NT