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AliExpress $30 35MHz-4.4GHz ADF4351 Touchscreen Signal Generator

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mawyatt:

--- Quote from: bob91343 on December 01, 2020, 06:26:39 am ---What about amplitude calibration?  Modulation?

--- End quote ---

Amplitude at 300MHz is -9.07, -6.15, -3.20 and -0.04dBm @ 4 amplitude settings which should be 3dB apart. A sweep to 3.2GHz produces reasonable flatness, can't go past 3.2GHz as I have no means to evaluate performance. There is no modulation capability, but has a SMA input for an external reference. The internal 25MHz XO reference signal is supplied to this SMA, and checking the PCB it seems you can reroute the external SMA by changing a couple SMD components.

This is basically a PCB with a ADF4351 chip without any additional chips in the RF chain, so expect typical ADF4351 data sheet performance. Not a bad little device for ~$30 IMO.

Best,

 

bob91343:
Without some means of modulation this thing has limited application.  One could build an analog amplifier with AM capability but FM is another story.

So what we have is pretty much just an oscillator that could be used as the starting point for a signal generator.

ledtester:

--- Quote from: maximvs on November 24, 2020, 11:18:12 pm ---I wonder if it is possible to take out the 25Mhz crystal and always provide an external RF source.
I have a 10Mhz. clock (GPS Sync), which has a very pure output, and I'd like to use that.
My question is:
    I read the specs on the ADF4351 and it is not clear if the reference signal
    should be square wave or could be a sine wave. Any thoughts ?

I might buy another unit and do a test but I'd like to hear what you guys think.

--- End quote ---

https://youtu.be/UFp4GFxFYco

and the previous video:

https://youtu.be/SNuPzkJFMwY

radiolistener:

--- Quote from: radiolistener on November 25, 2020, 03:53:29 pm ---There is more interesting ADF4351 development board on aliexpress:

https://www.aliexpress.com/item/33032121416.html

Two ADF4351 + IAM81008 + AD8307 + STM32F103C8T6 on the board.
Price is 24 USD. I just ordered one, it looks very interesting as a signal source and bode plot for 35M-4400M.

--- End quote ---

I got it. Here is my first impression and some measurements for this unit:
https://www.eevblog.com/forum/rf-microwave/sdr-rtl-nwt4000-hackrf-what/msg3376978/#msg3376978

At a glance 45-50 dB dynamic range up to 1.5 GHz and about 30-40 dB up to 4.4 GHz. But response is not flat above 1.5 GHz.

I got it for 20.49 USD by using discount and coupons. I expected a little better performance, but still not so bad for the price.

The output impedance according to my measurements is about 40 Ohm. It works from 33 MHz to 4400 MHz and has pretty flat amplitude level. tested it from 35 to 1.6 GHz with RTLSDR. At 1.6 GHz frequency it has some little drift for about 500 Hz/minute, but I'm not sure if the source of drift is LTDZ board or RTLSDRv3 itself.


Input impedance is about 29 Ohm and SWR is about 1.5 - 1.7. but very flat from 40 to 1500 MHz. Don't have equipment to check higher frequency. It looks that there is needs to remove 50 Ohm resistor on the input before mixer.  But it looks that output level will be too high for the input and it will require 10 dB attenuator for bode plot.

radiolistener:

--- Quote from: bb1 on September 11, 2020, 04:01:49 pm ---The lowest ADF5451 frequency permitted by AliExpress touchscreen is 35 MHz.

--- End quote ---

I tested LTDZ and it looks that the lowest frequency that ADF4351 can produce is 33 MHz.

Here is 33, 34 and 35 MHz from ADF4351 on the oscilloscope:

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