Oldish signal generators that can do 10-100Mhz square, sine, pulse signals - Page 1
Forum section: electronics / general

author: maiakaat
author_rank: Regular Contributor
timestamp: August 16, 2012, 02:46:26 pm
content: HiMy second topic, I have been put off many signal generators that generate AM/FM signals, that go for lowish prices, so I was wondering if anybody knew of relatively simple reasonable quality signal generators that can do these frequencies for simple testing for under $100 (older second hand instruments) PWM would probably be useful. I thought a list of good low cost test instruments might be useful, as many of the new/second hand signal generators are effectively useless at less than 10Mhz to most people doing highish speed digital electronics I would have thought.A pulse generator with a very fast rise-time would also be useful for a similar or slightly lower priceAfter registering and looking around the forum I cooked my dinner three times over :O(

author: maiakaat
author_rank: Regular Contributor
timestamp: August 16, 2012, 04:42:50 pm
content: "But then i hope I misread your message. you ask for 100MHz, digtal signals, DC and 40-50 pound in one sentence, to speak with Airosmith: dream on And why you want to measure the current of a digital signal ? To measure the powersupply you are only talking DC. So why the 100MHz question.Contact Keithley or Agilent, if you pay enough the maybe develope one for you. A TRMS meter with very high crest factor and a 100 MHz bandwidth will cost a fortune. "I should clarify this...I am looking for any older second hand signal generators that can cover from 10Mhz up to 100Mhz approximately, or the upper end of this range.They only need to do a sine wave and a square wave, although a pulse would be niceEven the Arduino can do 16Mhz or so (I think) so what use is a 2Mhz Signal generator these days, such as many of the low end and Chinese ones around, or the 20 year old equivalents that go for under £50.I have seen RF generators go for less than £100 (close to £50) although I don't know whether they can send an unmodulated signal, as I am just looking for a simple signal, not an AM or FM radio signal, some of them go over 1Ghz, I don't know how they differ from a 2Mhz signal generator for them to sell at such a low price.TRMS is really irrelevant, its for testing quality of ADC circuits, and digital signal quality, propagation etc, I don't intend on working with power beyond the essentials.If there is no such thing (the Ebay ones are not capable of a simple signal) then I will think about the £100 to £300 range, but Ebay is filled with crap Chinese products or very expensive second user equipment, and in-between is a lot of older and not-so old RF equipment, so advice on the usability of these for simple signal generation is probably useful for me and other newbies.)I don't believe that the only options are custom builds from Agilent, or £1000 units, but then my posts were not so clear.As a side note, I've seen a colour 20Ghz scope with 18Ghz trigger go for £770 combined, and a 1-3Ghz colour CRT scope go for £350.If you are patient and diligent Ebay can offer some unbelievable bargains.I know a lot of people probe forums (and other companies and forums) for business, but in software/server hardware they are often 3-400% more than a typical Ebay price in some cases, hence why the sites often do not list the actual price.)

author: free_electron
author_rank: Super Contributor
timestamp: August 16, 2012, 05:55:15 pm
content: If you are going to be testing adc's you will need a spectrally pure generator with very low thd .... Ain't gonna find that below 2k$ even old and used...As for the pulse you need a machine with fast rise time. Pulse delay is not important.I would look toward a 8110 style machine or 8112.DO NOT BUY A BROKEN 8112 ! 99% of the broken ones on ebay have the shaper hybrid shot and that is unobtainium....

author: nctnico
author_rank: Super Contributor
timestamp: August 16, 2012, 06:14:00 pm
content: I have a working R&S SMDA with manual and schematics (in German) which could use a new home...http://www.radiomuseum.org/r/rohde_am_fm_messsender_smda.html

author: maiakaat
author_rank: Regular Contributor
timestamp: August 16, 2012, 06:48:49 pm
content: @free_electronThanks, that's really good advice.We really wanted to save that sort of money for an upgrade to the Rigol DS1102E. I have seen some options for around £600-700.I was thinking of getting the equipment to test basic functionality in the near future, and then getting better quality instruments in a year or so.Does this mean the RF signal generators can often be used without any modulation for a pure input signal?I was thinking of using a home made pulse generator and signal generator in the mean-time just for very basic learning and testing (over the next month or so)

author: maiakaat
author_rank: Regular Contributor
timestamp: August 16, 2012, 07:00:35 pm
content: I noticed this add FS: HAMEG Modular System Series 8000 Bench Multimeter & Function Gen PRICE DROP!, I am in the UK though, so postage is high, and if there is a problem its practically impossible to sort out, not to mention the risks involved in buying from a forum

author: maiakaat
author_rank: Regular Contributor
timestamp: August 16, 2012, 07:10:57 pm
content: @nctnicoWe are in the UK, so postage is likely to be very expensive

author: nctnico
author_rank: Super Contributor
timestamp: August 16, 2012, 08:28:21 pm
content: Postage from NL to UK is about € 41 maybe cheaper if the manual and the box are lighter than expected. I've used the SMDA primarily as a sine wave generator. The output is supposed to have low noise and distortion because it is intended to be a transmitter for a wide range of frequencies.

author: saturation
author_rank: Super Contributor
timestamp: August 16, 2012, 10:36:39 pm
content: For simple testing, look at the thread on the Hantek DDS 3x25.

author: T4P
author_rank: Super Contributor
timestamp: August 17, 2012, 12:09:02 am
content: Placing mechatrommer's GolTek unlocks 100MHz sine wave ...

author: Mechatrommer
author_rank: Super Contributor
timestamp: August 17, 2012, 03:46:17 am
content: you are dealing with devils if talking about cheap and > 20MHz stuffs. getting good signal and measurement is a pure luck or delusional. my 2cnts. YMMV.

author: vk6zgo
author_rank: Super Contributor
timestamp: August 17, 2012, 05:00:35 am
content: There are many Signal Generators which can do better than 100MHz with sinewaves,in fact,500MHz & above is common.These do not do this frequency span all in one range,so each range can be optimised.Square waves at 100MHz imply a frequency response in all the internal generation equipment & amplifiers,flat from 100MHz to around 500MHzto produce a reasonable square wave at that frequency.Wide range Signal Generators as used in RF work,do not usually have square waves as an option,as is common in many "Function Generators",as they are used for different purposes.There are Generators which are designed to produce square waves with fundamental frequencies in the 100MHz region,but they are either special orders & very expensive,or small volume lines,& again,very expensive.

author: nctnico
author_rank: Super Contributor
timestamp: August 17, 2012, 10:54:56 am
content: Not really. Just get an ADF4351 based frequency generator board. It will output square waves with harmonics into the GHz regions.

author: free_electron
author_rank: Super Contributor
timestamp: August 17, 2012, 10:58:00 am
content: I would look for a used HP 865x type generator like a 8656b or 8657.These have true sine oscillators and are controlled by a fractional divider pll system.These generators easily do 900MHz and are very clean at the output. Can be had cheap.Better would be 8647 but those are pricey....Using awg's is not a good idea... The dac in those things is 14 bit at most.... Good luck doing distortion measurements on a 16 bit adc with a 14 bit dac ...

author: vk6zgo
author_rank: Super Contributor
timestamp: August 17, 2012, 11:43:34 am
content: Quote from: nctnico on August 17, 2012, 10:54:56 amaIt's a board!A real Signal Generator is a lot more than that!

author: maiakaat
author_rank: Regular Contributor
timestamp: August 17, 2012, 03:09:16 pm
content: I've got a couple of AD chips, a pre-assembled AD9850 for £4.00, and a low spec AD9832 TSSOP from Farnell, but eventually - this year, along with a slightly better scope we are going to need a good signal generator, at least I know where a significant chunk of any money should go.The project is first a bottom of the range singal gen/oscilloscope/logic analyzer for the Raspberry Pi (but useful not cheap crap, properly researched design) followed by a better design about 12 months later. The design is open hardware and open software. So it gives you an idea of how the instruments will be used.Mostly I am in the theory at the moment, so there is no absolute need for an instrument, and I am good at the Ebay waiting game, my background is in software engineering so forgive the vague terminology, I am learning though. I have access to some research libs, but lack of access to IEEE is a downer, along with Wiley/Elsevier, who have better material than ACM (of which I am a member) and the open research on the web. My strength is in the software, but I'd also like to look at ways to innovate, rather than just patch up the weaknesses of such a hardware design.The sign-gen could be a lower range variant, say 1-25MHz or something for now, for the low hundreds of pounds if available. We wanted to save for a Agilent 3000 series MSO, but it looks like the signal generator in the high hundreds is more important when we do get a new instrument. So going up to around £600 is not impossible, although it will not be for a few months.Would an older analog gen of a similar specification be better than a newer signal gen in the £200-£500 range for this sort of task?On the pulser, I'm not confident enough yet to make a good pulser, although I am aware of a few circuits out there, I also have bought a couple of comparators, the LT1721, and a Maxim device that I manage to get eventually through Farnell. Above 50MHz things get much tougher, so I want to learn more before delving into the design of higher frequency stuff, I appreciate it's really challenging some of the engineering at high frequencies. The pulser is purely to measure the rise time of a circuit (or components for suitability) I am aware our current scope limits the performance of a good pulser significantly.The suggestion of the RF generator needing a new home has really interested me, although I don't know if it could be used for all tasks, mainly for sending in an analog sine to help with learning and basic design testing. I have no idea how accurate these older instruments are, and how well they hold their quality over time.I'll post some stuff I am keeping an eye on for others who might be looking, despite if I go for any they will push the price up. Some feedback would be interesting too, this is not a endorsement of the seller of condition of the instrument. I've noted in the US there is a lot of instruments sold without warranty, or even a confirmation it works, I think in the UK laws are a bit tougher to get around, sellers are less keen to auction too, with fixed prices.Advantest TR6846 bench multimeter - Auction - £20 so farhttp://www.eBay.co.uk/itm/330775739799?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649#ht_500wt_1366(unrelated HP bench PSU)http://www.ebay.co.uk/itm/290759974129?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649#ht_500wt_1413HP 8112 pulse generator - Auction £60 approx (a comment earlier warned of faulty units being sold)http://www.ebay.co.uk/itm/320962738226?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649#ht_859wt_1401R&S signal generator - £100 so far at auctionhttp://www.ebay.co.uk/itm/221104242484?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649#ht_890wt_1401Racal Dana - £265 at auction - synthesizerhttp://www.ebay.co.uk/itm/110934785901?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649#ht_557wt_1401HP E9340A (faulty) for reverse engineeringhttp://www.ebay.co.uk/itm/290761501523?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649#ht_500wt_1413HP/Agilent Autoranging MM £200 - Buy it nowhttp://www.ebay.co.uk/itm/380458242687?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649#ht_1299wt_545HP/Agilent 3466A MM £130 - Buy it nowhttp://www.ebay.co.uk/itm/380459165338?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649#ht_920wt_1401Fluke 8050 MM £30 in the UShttp://www.ebay.co.uk/itm/130745882653?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649#ht_2524wt_1401These are probably better posted (or duplicated) on the buy/sell thread, but since it's part of the discussion I'll add them here for comment and if anybody wants to add them to the other forum feel free.Those more experienced feel free to post your recommendations for instruments (that might not be obvious) as I am sure it would help a good number of people out, it also gives an idea of the sort of stuff I am looking at. (I have left out a few I am interested in)

author: Mechatrommer
author_rank: Super Contributor
timestamp: August 17, 2012, 04:03:58 pm
content: Quote from: maiakaat on August 17, 2012, 03:09:16 pmget a good and high bandwidth oscilloscope or spectrum analyzer first before anything else if you plan to design anything speed. otherwise you are playing witchcraft like i am with my DS1052E.

author: JuiceKing
author_rank: Regular Contributor
timestamp: August 17, 2012, 04:51:18 pm
content: For your pulse generator, are you interested mostly in rise/fall time or pulse rate? If you can make do with slower pulse rates (max 1Mhz) then an old HP 215A could be a good choice--it has rise time of around 1nsec, and a pulse rate that can be controlled with the built-in oscillator or with an external trigger. They are inexpensive dinosaurs, but not as common on eBay as the 8112A. The 8112A goes up to 50Mhz and has a lot of control options, but its fastest rise time is around 5nsec.

author: T4P
author_rank: Super Contributor
timestamp: August 17, 2012, 04:58:35 pm
content: It's like trying to go faster with a Golf GTI engine, some people place a too big turbo on a too small car,just like trying to view 433MHz RF with a 100MHz(hacked) DS1052e (i read your website shafri...)

author: nctnico
author_rank: Super Contributor
timestamp: August 17, 2012, 05:08:25 pm
content: Quote from: vk6zgo on August 17, 2012, 11:43:34 amA signal generator often does a lot of different things which make it expensive. In many cases you don't need all the extra bells and whisles. A small board for 1 specific purpose is much cheaper.

author: maiakaat
author_rank: Regular Contributor
timestamp: August 17, 2012, 05:25:06 pm
content: @mechatrommerWe do want to upgrade to an Agilent MSO (although it will probably be at the lower end of the 3000's and it may take some time to come to terms with the price even then, thanks for the advice, the upgradeability offers a better investment over the 2000X series, and they seem to use much more advanced sampling techniques compared with our Rigol - if I have interpreted some of the articles I have read correctly)If we can afford it it will likely be 6 to 12 months away, and push the money for a sig-gen right down.

author: maiakaat
author_rank: Regular Contributor
timestamp: August 17, 2012, 05:30:01 pm
content: @juiceking, that's awesome info, thank you, it is purely rise time measurements that is needed (although the oscilloscope limits this to a simple pass or fail given its bandwidth limitations)@nctnico, building stuff is something I'd like to do, I just want to develop confidence with easier stuff for now (I want to understand the circuits I/we build) but it could definitely work out cheaper.

author: KTP
author_rank: Frequent Contributor
timestamp: August 17, 2012, 06:19:09 pm
content: You just need a fast rising edge pulse?Put your favorite microcontroller or even a 555 on a breadboard, then solder up a tinylogic 3 buffer chip like the NC7NZ34 (about $0.20 each) deadbug style on a little bit of copper. Presto! 700ps risetime 4V to 5V pulses into 50ohms.Here is what it looked like on a X3024A:

author: Mechatrommer
author_rank: Super Contributor
timestamp: August 17, 2012, 08:31:45 pm
content: my point is, gather all your money to get a good dso (like KTP's MSO-X-3024A above, my 2cnts recommendation is 4-10X the frequency you want to design, ie 100MHz circuit requires 400MHz scope or higher) forgetting anything else, so you can shorten the afford time from 12 months to say 6 months? ok fair you already got a rigol dso? and desperate need for FG? right, just get the Hantek DDS3x25 and start playing blairwitch right away, at least you'll learn many magic spells during the 12 months, but beware of your hair, they either grow white, or not grow at all later on. i cant recommend a standalone FG that can go 50-100MHz at your price point, someone may have had/will gave you a suggestion.(ps: i wish i have the money)

author: maiakaat
author_rank: Regular Contributor
timestamp: August 18, 2012, 02:09:14 pm
content: We decided a few months ago to upgrade the DSO once we can justify the need for the scope (ie once at least once of us - me - has learnt enough)The cost of a fully features Agilent 3000X series means well have to use the upgrade feature and pick which features we can afford (unless they are a bit cheaper in 6 months or so)

author: KTP
author_rank: Frequent Contributor
timestamp: August 18, 2012, 03:10:20 pm
content: Quote from: maiakaat on August 18, 2012, 02:09:14 pmIf you do go for the 3000x, keep in mind the December deadline to get the free AWG option (although maybe by then they will have another different kind of sale). Also I think eventually they will give everyone the 4Meg memory free like they do now on the 6000 and 7000 series so I am holding off buying that option unless really need it.Keep an eye on Agilentused on ebay. Same 3 year warranty but the scopes are about 30% or more off list price. Right now they only have 500mhz 3000x scopes though.

author: PA4TIM
author_rank: Super Contributor
timestamp: August 18, 2012, 04:15:13 pm
content: I restored an old Philips 100 MHz 1nS pulser and aligned it 3 times. first time using a Rigol 1102.I was pleased with the result, but for 100 MHz you need a 1GHz scope. But it looked good at 10MHz and the signal was a sinewave at 100MHz but not distorted.Then i go a Tek 7704 with 280MHz pulse response option. The square wave was not as nice as I thought. So i did it all over.Then I got a 1GHz scope. The 100 MHz squarewave looked like shit. The pulses were not symetrical, snd at 100MHz the low periode was a fraction of the high period, it did not even got to zero volts. The lower bandwidth scopes did not show that. Also lots of overshoot and ripple. So Aligned it again. Now I had a nice square wave on all the scopes.You havePulse generators ; pulsewidth, periode, rise and falltime adjustable, delay, sync in/outputs, adjustable amplitude and offset, output varies from fast units dat do 0,5V in 50 Ohm but I have two units that go over 80V.Function genertors: square, sine, triangle and sometimes more like step, pulse ect. Most units do max 1 to 10MHz, the better ones upto 20 MHz, dome extreems go over 20 ( my R&S AGFU does 50Mzhz in one mode) but there is a wide range in outputpower. Many modern units do no more as 10Vtt in a high Z load ( 5Vtt in 50 ohm) , some older units do 30Vtt in 50 ohm ( or more)There are lso programmable versions.Audiogenerators: they make a clean sinewave and older unite often in 600 ohm. Some can make large signals, my HP does 30Vrms/600 ohmRF generators, most start between 500 KHz and 10 MHz and go up to as fancy as you can affort. Most times not in one range. Outputlevel in 50 ohm, but there are 75 ohm versions. The good ones have a adjustable attenuator as output regulation and a range from -140 dBm to + 20 dBmImportant is they have good harmonic attenuation.Pulsers can be made easy with fast Tr and fixed output/ frequency but fast Tr and high frequency combined with adjustable output is more difficult.They are not hard to find, philips, HP, tetronixs made fine ones. I have around 10 pulsers ordo, non was more as 30 euro. The fastest is 250 MHz ( that was for free)Function generators is another story, everyone is looking for one. There are good ones. Bad ones but cheap ones are hard to find and with the specs you want you need a huge wallet. Tek TM5000 plugin FGs are not to hard to find and not to expensiveRF generators are a bit easyer to find as function gens. As 100 MHz is enough they will be cheap. Most people want the high frequency units ( hp8640 is a famous one)