Author Topic: Cheap RF Signal Generator  (Read 1973 times)

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Offline lasseSte

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Cheap RF Signal Generator
« on: January 10, 2019, 04:27:14 am »
Hello,
I am looking for a cheap Signal Generator able to Generate Sinus Waves from 1Ghz to at least 4 Ghz better 6Ghz.  A sweepmode would be nice too.
The purpose of use will be to reproduce the Problems during EMI-test in the test-chamber in my labratory.


In other threads here about this topic in this forums it is suggested to buy big old profi tools, but I can hardly find any used signal generators in the above 2Ghz range. Why is this so hard? Am I not searching for the right thing? The only one I found is this one, which is still 12.000€.
https://www.ebay.de/itm/Rohde-Schwarz-SMR20-Signal-generator-10-Mhz-20-Ghz-Frequenzband/183468785450?epid=22024475353&hash=item2ab7977f2a:g:emwAAOSwa9dbth3x:rk:18:pf:0&LH_ItemCondition=3000

Does anyone Know, where I maybe can find a cheap one (max. 1000€ /$). Any ideas?

On the other hand, on ebay and alibaba are a lot of cheap signal generators like these ones:

https://www.ebay.com/itm/ADF4355-250MHz-6-8GHz-Sweep-RF-Signal-Generator-VCO-Microwave-Frequency-PLL-Good/392181314026?hash=item5b4fd3f1ea:g:E5cAAOSwqLRb~TQL:rk:2:pf:0

https://www.ebay.com/itm/OLED-display-ADF4350-137-5MHZ-4-4GHZ-Signal-generator-frequency-RF-signal-source/302758416068?hash=item467dcecec4:g:IyQAAOSwGNxbFArU:rk:1:pf:0

Are they ok to use?
Has anyone expirience with one of these or a similar one?

As I am planning to use it to simulate interferences I am not so much worried about accuracy, neither in frequency nor in power.





 

Offline wolfp

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Re: Cheap RF Signal Generator
« Reply #1 on: January 10, 2019, 05:32:13 am »
Imho the ADF435x devices dont produce sinus but square wave on the lower frequencies because they use dividers.
 

Offline nctnico

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Re: Cheap RF Signal Generator
« Reply #2 on: January 10, 2019, 05:39:11 am »
Imho the ADF435x devices dont produce sinus but square wave on the lower frequencies because they use dividers.
The ADF435x produce a square wave by definition. AFAIK the bandwidth of the output is around 6GHz.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline MrW0lf

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Offline Ice-Tea

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Re: Cheap RF Signal Generator
« Reply #4 on: January 10, 2019, 06:39:26 am »
I have a slew of SMIQ06's inbound. ATE/L versions (so no display, remote controll only) but otherwise should fit your bill. 1k is going to be tough, but won't be all that far off...
eBay shop with all the gear you need!
FS: Agilent 54815A, 54825A, R&S CMU200, CRTU, SFU, SMIQ06L, SFU, HP8714B, 8595E, Marconi 6201B, Lecroy WP 960,950, 9354TM, THS720P, Anritsu MG3671A 2.75G I/Q RF gen, MS8604A 8.5GHz SA, Keithley 238 SMU
 

Offline threephase

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Re: Cheap RF Signal Generator
« Reply #5 on: January 10, 2019, 07:05:32 am »
I guess the question is how good a sign wave are you after. There is the RF Explorer, but the output may be on the noisy side for you.

https://www.seeedstudio.com/RF-Explorer-Signal-Generator-RFE6GE-p-2074.html

Kind regards
 

Offline MrW0lf

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Re: Cheap RF Signal Generator
« Reply #6 on: January 10, 2019, 07:13:45 am »
RFE6GEN is nice toy and very useful at times (forms SNA with RFEx) but exibits remarkably square output.
Edit: Quick checks. 2.5GHz output, second harmonic -17dB. 1GHz output, -20.5dB.
« Last Edit: January 10, 2019, 07:49:30 am by MrW0lf »
 

Offline nctnico

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Re: Cheap RF Signal Generator
« Reply #7 on: January 10, 2019, 07:22:15 am »
If you look at the specs of most RF generators you'll notice the 2nd and higher order harmonics are at -40dB if you have a very good one.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Online beanflying

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Re: Cheap RF Signal Generator
« Reply #8 on: January 10, 2019, 10:22:49 am »
I had an ADF4350 based unit (same as the 3rd link in the OP) land on my desk today and plan to tear it down and test over the next few days. Will be either a new thread or tacked onto an appropriate existing one in the Test Gear section.
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Offline Mechatrommer

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Re: Cheap RF Signal Generator
« Reply #9 on: January 10, 2019, 10:27:37 am »
On the other hand, on ebay and alibaba are a lot of cheap signal generators like these ones:

https://www.ebay.com/itm/ADF4355-250MHz-6-8GHz-Sweep-RF-Signal-Generator-VCO-Microwave-Frequency-PLL-Good/392181314026?hash=item5b4fd3f1ea:g:E5cAAOSwqLRb~TQL:rk:2:pf:0

https://www.ebay.com/itm/OLED-display-ADF4350-137-5MHZ-4-4GHZ-Signal-generator-frequency-RF-signal-source/302758416068?hash=item467dcecec4:g:IyQAAOSwGNxbFArU:rk:1:pf:0

Are they ok to use?
Has anyone expirience with one of these or a similar one?
i have the AD4355. the 2GHz signal looks like the attached picture. but on a 6GHz dso and probe, its really pushing the limit to look at square wave of those fundamentals, one need at least 10-20GHz DSO for that. but cheaper option might be 20+GHz spectrum analyzer (i dont have one). signal greater than 1GHz are okish sine looking (or maybe its just my dso bw limited playing the role), but going down than 1GHz something going on its like the signal going down the hill (havent took a screen capture), i guess due to ac/inductive coupling/filter on the output and impedance control traces on the output looks weird, something thats not usually practiced or adviced by any legible EE personel that i know of. but i dont know i'm not an expert.

but if your budget is GBP1000, you have more room to buy more proper SG such as this...
https://www.ebay.com/itm/Rohde-Schwarz-SMIQ06L-RF-Signal-Generator-300-kHz-6-4-GHz-Tested/254049621885?epid=1200560731&hash=item3b2689977d:g:JcsAAOSwNepcLDvy:rk:8:pf:0
https://www.ebay.com/itm/Rohde-Schwarz-SMIQ06B-6-4-Ghz-Signal-Generator/253951350045?epid=1003582624&hash=item3b20ae151d:g:zOQAAOSwQwFb00hJ:rk:14:pf:0
https://www.ebay.com/itm/Anritsu-Used-68117C-Synthesized-Signal-Generator-10MHz-to-8-4GHz-with-Opt/263972986227?hash=item3d76041d73:g:2oMAAOSwVx5btfts:rk:22:pf:0

i think the word "Synthesized" Signal Generator like the Anritsu-Used-68117C indicates that it will also producing "square" wave, not sine, but not sure never own one. ymmv.
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Online DaJMasta

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Re: Cheap RF Signal Generator
« Reply #10 on: January 10, 2019, 10:52:56 am »
If your ceiling is around $1000, consider the Gigatronics 2400 series generators.  Their support has basically just been severed completely from Gigatronics, which is a shame, but while some of the more standard features are options on some models, they can usually be had very cheaply for their output bandwidth.

I believe frequency/level sweep is an option, but getting 8GHz bandwidth for CW and modulated (internal or external source) signals at under $1000 is tough to beat - especially if you're willing to consider one without a screen.  The operating manual includes a listing of GPIB commands, but I haven't been able to locate a copy of their WaveMaker software (though, I haven't contacted the company).


Otherwise, SMIQ is a solid choice (though 6GHz models are going to be tough to find under $1000), as are many of the IFR/Marconi/Aeroflex 2000 or 3000 series generators are pretty good value (though again, hard to get high bandwidth variants below a couple thousand), and if you don't need high bandwidth, you can sometimes get an ESG-D series generator in that range, though don't expect a 4+GHz model there.


It's more complicated, but maybe a lower bandwidth generator, a doubler, and a filter are a viable option for pure tones at higher frequencies.  Not as flexible as a fully integrated unit, but if you can measure and trim the output of the doubler and are using CW tones, you could probably get usable signals out of a much cheaper generator.
« Last Edit: January 10, 2019, 10:57:00 am by DaJMasta »
 

Offline Ice-Tea

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Re: Cheap RF Signal Generator
« Reply #11 on: January 10, 2019, 06:58:49 pm »
As mentioned.. I have some R&S SMIQ's inbound. Ex VAT, shipping, Paypal and eBay I should be able to do 1k€. If they ever come in  :palm:
eBay shop with all the gear you need!
FS: Agilent 54815A, 54825A, R&S CMU200, CRTU, SFU, SMIQ06L, SFU, HP8714B, 8595E, Marconi 6201B, Lecroy WP 960,950, 9354TM, THS720P, Anritsu MG3671A 2.75G I/Q RF gen, MS8604A 8.5GHz SA, Keithley 238 SMU
 

Offline dlabanowski

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Re: Cheap RF Signal Generator
« Reply #12 on: January 11, 2019, 04:28:37 am »
It's right near the top of your budget, but I've found the ERAsynth (http://erainstruments.com/) to be pretty hard to beat for the price!
 
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Offline nctnico

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Re: Cheap RF Signal Generator
« Reply #13 on: January 11, 2019, 11:47:36 am »
It's right near the top of your budget, but I've found the ERAsynth (http://erainstruments.com/) to be pretty hard to beat for the price!
That looks neat but I'm quite sure it will output a square wave as well.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline Kosmic

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Re: Cheap RF Signal Generator
« Reply #14 on: January 11, 2019, 12:17:59 pm »
It's right near the top of your budget, but I've found the ERAsynth (http://erainstruments.com/) to be pretty hard to beat for the price!
That looks neat but I'm quite sure it will output a square wave as well.

Look like it  :)

http://e2e.ti.com/support/clock-and-timing/f/48/t/696877?LMX2594-Output-signal-waveform-sine-square-

ERASynth is based on the LMX2594
 

Offline jungle vegetable

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Re: Cheap RF Signal Generator
« Reply #15 on: January 12, 2019, 02:58:22 am »
One possible option would be taking any of the cheaper square-wave generating units and filtering the output down using a tunable YIG filter. There are many available at eBay for <$100. Most of these will actually work from 2 (fundamental limit for most YIG devices) to >20GHz even if specified for a smaller frequency range. Caveat: YIG filters come with different number of stages inside; you probably want at least two-stage filter to have >40dB harmonic rejection (also, if you find a dual-channel filter, you can cascade both to have >60dB rejection)
 

Offline Carrington

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Re: Cheap RF Signal Generator
« Reply #16 on: January 15, 2019, 01:52:01 am »
Has anyone here tried this other (SYM4400-USB)?

Website: http://www.ormelabs.com/en/?page_id=101
Datasheet: http://www.ormelabs.com/pdf/SYM4400_eng.pdf
The SYM4400-USB is the best and cheapest I could find (325€).
My English can be pretty bad, so suggestions are welcome. ;)
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Offline tkamiya

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Re: Cheap RF Signal Generator
« Reply #17 on: January 16, 2019, 01:07:20 am »
Most professional level RF generator going to 4GHz (6GHz) will be expensive.  I ran into same issues....

What I have here are three HP Sweep Generator of two generations.  Both uses modules for various frequency ranges.  If you look at eBay, they often go for $1000 or more, but every now and then, bargain can be had.  That's what mine are.  With a cartridge, I paid about $150 each.

You CAN stop the sweep but frequency is not that stable in that mode.  In sweep mode, it doesn't matter. 
 

Offline metrologist

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Re: Cheap RF Signal Generator
« Reply #18 on: March 14, 2019, 04:22:02 pm »
i think the word "Synthesized" Signal Generator like the Anritsu-Used-68117C indicates that it will also producing "square" wave, not sine, but not sure never own one. ymmv.

All of these class synthesizers produce sine wave output. Synthesizer vs generator can mean different things. Usually the synthesizer label is placed with analog sweep (vs step sweep) and a modulation suite.
 

Offline arocholl

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Re: Cheap RF Signal Generator
« Reply #19 on: May 18, 2019, 01:03:10 am »
Just in case you didn't know, RF Explorer released an improved version - RF Explorer Signal Generator Combo: http://j3.rf-explorer.com/menu-the-news/212-introducing-new-rf-explorer-signal-generator-combo

 

Offline tinhead

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Re: Cheap RF Signal Generator
« Reply #20 on: May 18, 2019, 03:07:35 am »
Just in case you didn't know, RF Explorer released an improved version - RF Explorer Signal Generator Combo

good to know, i was about to sell the "old" RF Gen, as i was completely unhappy with the signal output.
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Offline Nauris

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Re: Cheap RF Signal Generator
« Reply #21 on: May 18, 2019, 03:44:27 am »
Hello,
I am looking for a cheap Signal Generator able to Generate Sinus Waves from 1Ghz to at least 4 Ghz better 6Ghz.  A sweepmode would be nice too.
The purpose of use will be to reproduce the Problems during EMI-test in the test-chamber in my labratory.


As I am planning to use it to simulate interferences I am not so much worried about accuracy, neither in frequency nor in power.

Back in the school we had a Gunn diode osc with a knob  to tune it and horn antenna attached. Plenty cheap and gives your lab nice 60's style especially if you paint it with green hammer paint.
 


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