35M-4.4G simple RF signal generator LCD Display USB Frequency - Page 1
Forum section: electronics / testgear

author: eurofox
author_rank: Unknown
timestamp: August 26, 2017, 01:13:42 pm
content: Nobody tested this one?http://www.benl.ebay.be/itm/35M-4-4G-simple-RF-signal-generator-LCD-Display-USB-Frequency/121989367098?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649

author: nctnico
author_rank: Super Contributor
timestamp: August 26, 2017, 01:37:33 pm
content: No. What would be interesting to know is whether the output is filtered or not so it doesn't have so much harmonics compared to other ADF4351 frequency generators.

author: texaspyro
author_rank: Super Contributor
timestamp: August 26, 2017, 03:04:37 pm
content: I have one of the little color LCD touchscreen models. It can generate a fixed frequency or sweep a range. It has two square wave outputs (I/Q ?) It is built on a two layer board and the signal seems to degrade to a sine wave at higher freqs, but it could just be my scope is rounding things off... it only goes to a GHz. I need to break out the Tek 7603 with the 20 GHz sampling head.The user interface is a bit sucky... tiny on screen keyboard must be manipulated with a stylus. It has no documentation. There are 5 push buttons on it, but they don't seem to do anything. Also a header with VCC, GND, RX, and TX (firmware upgrade port? computer serial interface?). Also has a USB port (power only? computer interface?)

author: nctnico
author_rank: Super Contributor
timestamp: August 26, 2017, 07:16:47 pm
content: Given the price and it is designed by DG7TBL the one Eurofox is pointing to this version has to be somewhat nicer.

author: eurofox
author_rank: Unknown
timestamp: August 26, 2017, 08:02:14 pm
content: Quote from: nctnico on August 26, 2017, 07:16:47 pminside TCXO, accurate frequencyMulti stage amplitude calibration with precise range (-25dBm to max)100 groups memory are convenient to useencoder to adjust, and it is easy to operateUSB interface, providing communication protocol, can do program-controlled signal source10MHz reference inputs and outputs.

author: technogeeky
author_rank: Frequent Contributor
timestamp: August 27, 2017, 06:56:47 am
content: Quote from: nctnico on August 26, 2017, 01:37:33 pmThis is clearly powered by an ADF4351, so the fact that he only shows frequency counting and doesn't show any spectral information gives you your answer: no, it's going to have all of the same distortion problems that the other units have.Still, if you had some external means to filter or buy or construct a programmable filter it could be useful at least to get a pure tone. As for the shape of the phase skirt of the primary tone... don't expect it to be very nice.

author: eurofox
author_rank: Unknown
timestamp: August 27, 2017, 08:37:26 am
content: Interesting video about the chip used

author: nctnico
author_rank: Super Contributor
timestamp: August 27, 2017, 10:26:52 am
content: Quote from: technogeeky on August 27, 2017, 06:56:47 amIt is not distortion. The ADF4351 outputs a square wave and the output stage seems to have a bandwidth of about 6GHz. With only 4 or 5 filter stages you can create an RF generator based on the ADF4351 which has a second harmonics below 30dB which is on par with commercial RF generators.

author: Kalvin
author_rank: Super Contributor
timestamp: August 27, 2017, 11:02:55 am
content: Quote from: texaspyro on August 26, 2017, 03:04:37 pmYou can use an oscilloscope costing $ $ $ $ $ for measuring the output purity or use a $ $ $ spectrum analyzer to accomplish the same thing.

author: technogeeky
author_rank: Frequent Contributor
timestamp: August 27, 2017, 01:22:05 pm
content: Quote from: nctnico on August 27, 2017, 10:26:52 amI wasn't talking about the harmonics. Of course you'd have to filter out the harmonics. If you want a sine wave, you'd have to filter nearly all of them out.But there is distortion on the output as well, which you'd have to filter out. And unlike harmonics, the spurs and leakage won't be far away from the primary tone. And it's worse the further down in frequency you go. (As do the harmonics: if you park the primary tone at 4.3 GHz, then none of the harmonics will be available).And to be comparable to the best synths out there, I think you'd need more than 30dB. I think you'd want almost 60dB to be comparable to the great synths out there (not that you'd realistically expect that for $100 or even $500, but that is still the target one aims for).

author: nctnico
author_rank: Super Contributor
timestamp: August 27, 2017, 02:05:16 pm
content: There are not many RF generators out there with less than -40dB 2nd harmonics. Just below -30dB is quite common.

author: eurofox
author_rank: Unknown
timestamp: September 27, 2017, 10:56:34 pm
content: Quote from: eurofox on August 26, 2017, 01:13:42 pmI order oneI will make a mini tear down and test when I get it.

author: eurofox
author_rank: Unknown
timestamp: September 29, 2017, 11:29:58 am
content: Got the generator today, just 8 days from order to delivery from China!I did not expect for 100€ to get a generator that output a perfect sinusoidal waveform, in fact on the lower frequency’s is more square than sinusoidal, it is improving in the Ghz.Output level and frequency is quite OK measured on the oscilloscope, I will do more accurate testing when I calibrate my frequency/power meter.

author: texaspyro
author_rank: Super Contributor
timestamp: September 29, 2017, 03:29:13 pm
content: QA PASS on the silkscreen... they know it's good before they even assemble it!

author: eurofox
author_rank: Unknown
timestamp: September 30, 2017, 12:32:04 pm
content: Screenshots @-10Dbm from 40Mhz to 1.6Ghz, the last one is over the 1.5Ghz (-3db) of the scope and level is not the real output value anymore due to bandwidth limitation of the scope.

author: ebclr
author_rank: Super Contributor
timestamp: September 30, 2017, 10:30:27 pm
content: Another option ad compatiblehttps://pt.aliexpress.com/item/ADF4351-development-board-137M-4-4G-signal-source-ADF4351-DEMO-official-software/32814603012.html?spm=a2g03.search0104.3.120.MhEb6P&ws_ab_test=searchweb0_0,searchweb201602_4_10152_10065_10151_10068_10344_5560015_10342_10343_10340_10341_10307_10060_10155_10154_10056_10055_10054_5370015_10059_10534_10533_10532_100031_10099_10338_10339_5580015_10103_10102_10052_10053_10107_10050_10142_10051_10173_10084_10083_10080_10082_10081_10110_5590015_10111_10112_10113_10114_143_10312_10314_5570015_10078_10079_10073,searchweb201603_2,ppcSwitch_2&btsid=30a2bb38-8f54-4fa9-a328-8a18bbba7b94&algo_expid=c1664422-553a-49ca-a6b1-9f2548f9bc60-16&algo_pvid=c1664422-553a-49ca-a6b1-9f2548f9bc60