Cheap Sig Gens.

From edn,

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Has anyone looked at the last one? Uses ADF4351, 35MHz to 4 GHz. They are all over ebay, ali-express. I think I'll order one.

George H.

Reply to
George Herold
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On a sunny day (Tue, 7 Nov 2017 05:37:32 -0800 (PST)) it happened George Herold wrote in :

No, but I am using an ADF4350 evaluation board, only difference seems to be that the 4351 has an output phase adjustjment, but I could be wrong... Search with Bing for: ADF4350_ADF4351_Cheat_Sheet_v1.pdf

If you buy a complete signal generator of course things MAY be simpler, until you want to control it from some micro?

Reply to
Jan Panteltje

I use an ADF4351 connected to an Arduino and a touch screen.

Reply to
sdy

OK. Are you using this eval board?

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Running it over the usb?

I must admit I'd moslty just like a cheap source of RF in the

100 MHz to 1 GHz range.

George H.

Reply to
George Herold

Cool, did it take much time to get it all up and running? Do you use the eval board, or make your own pcb?

George H.

Reply to
George Herold

Did you program it yourself at register level? Or is there an app?

--
John Larkin         Highland Technology, Inc 

lunatic fringe electronics
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Reply to
John Larkin

On a sunny day (Tue, 7 Nov 2017 08:33:42 -0800 (PST)) it happened George Herold wrote in :

No, this:

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I just swapped some jumpers and tested it from the PC parport:

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and now is it connected to a Raspberry GPIO.

Was too lazy to figure out the USB interface, as that needs windows soft.

Raspberry Pi can itself do output from about 150 kHz to 500 MHz (square wave).

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Reply to
Jan Panteltje

I bought a module to do the same thing, but before I fire it up, I'm working on getting the AD9959 4-channel 500MHz DDS working, in a nice case. For under $100 you can have 4 channels up to

200MHz with .11Hz resolution, and do coordinated sweeps over frequency, phase or amplitude. Just be sure to buy one with the output transformers if you want the best channel isolation. They cost a little more.

The ADF4351 has multiple internal oscillators and dividers, and when it sweeps, it takes a little while for the VCO to lock, every time it crosses over. Please consider.

We're putting dual directional couplers with a mixer (or two, to avert the relay) and audio LPF(s) on a module, for a cheap VNA driven by the DDS. RF in, RF through, LO in, reflected IF audio out, transmitted IF audio out. Two modules = 2-port VNA. Still figuring out which way to get clean signals above 200MHz.

Clifford Heath.

Reply to
Clifford Heath

I used the eval board. Somewhere online I found an Arduino example for the ADF4351. Then I got a touchscreen and modified the example. Pretty cool little sig gen.

Reply to
sdy

Thanks, for most of the things I have in mind I only need to sweep slowly. And then sit somewhere. I'll try the pre-built thing first.

I'm not at all sure I understand your VNA thing. (I'd need diagrams/schematics.. but I've not done much above 100 MHz, until wave guide Ku band ~13 GHz.. there it was all circulators and directional couplers. Impedance matching a cavity into a bridge...

There must be some rule that says bandwidth 'range' goes down in proportion to the center frequency. (I can hardly sweep my diode laser at all. ~30 GHz out of ~3x10^14 Hz.) until something needs to be retuned.

George H.

Reply to
George Herold

Nice, maybe I can make it work too then. What are you doing with it? (I want to put side bands on a diode laser. ~385 MHz will match the FSR (free spectral range) of a 20 cm. confocal Fabry-Perot cavity. We use the cavity to put 'markers' on the laser sweep.. After that there's other things above 1GHz.

George H.

Reply to
George Herold

It's basically a low-IF receiver on the coupled ports. The multi-channel DDS means you can transmit one signal and detect using a local oscillator 10KHz away, and they sweep together in an exact phase relationship, so the phase of the recovered 10KHz IF tells you the phase of the received reflection from the port; no need to make a full I/Q demodulator. Add an audio FFT and you can see your detected signal locked at 10KHz and isolate it from ambient interfering signals that sweep past.

Most of the synthesised PLL chips like the ADF4351 use a number of VCOs. The smaller the tuning range of each VCO, the lower the achievable phase noise - but you do get jumps at the changeover points.

Clifford Heath.

Reply to
Clifford Heath

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