Please Recommend an RF Signal Generator - Page 1
Forum section: electronics / testgear

author: xrunner
author_rank: Super Contributor
timestamp: July 21, 2013, 11:13:09 pm
content: I got an old DX-160 communications receiver and I want to align it because the dial is off. I got the service manual and managed to align the AM band because I was able to receive two known stations at the high and low ends of the band, so those markers were available just by receiving the stations.However, the other bands are not that easy because there are not any easy station markers on the shortwave bands at the high and low ends of the dial as presented on the DX-160. Yes I know there are WWV and stations in the shortwave broadcast bands I can identify but this piece of analog kit needs coils and trimmers adjusted at the high and low ends of the dial to calibrate across the dial. I really need an RF signal generator (not a function generator).Anyone know of a basic one between say $100 - $250?Thank you.

author: cosmos
author_rank: Regular Contributor
timestamp: July 21, 2013, 11:51:55 pm
content: How about a few digital oscillator? (1MHz and 5MHz or so)Give it 5V and an antenna on the output and it will give you nice silent markers at the harmonics...If you want AM modulation on it pass it trough a digital buffer where the Vdd voltage is the buffered modulation signal.

author: edavid
author_rank: Super Contributor
timestamp: July 22, 2013, 04:08:11 am
content: The military SG-1144/U is good for this... it goes down to 50kHz so you can also use it for IF. Unfortunately they are not as common as they used to be.A couple of other lower cost RF generators are the HP 8640B (analog) and HP 8656A (digital).

author: rf-loop
author_rank: Super Contributor
timestamp: July 22, 2013, 07:56:13 am
content: Quote from: xrunner on July 21, 2013, 11:13:09 pmThis is just a side note but not a direct recommendation because the price is not right.But, just comment specially only for this: "not a function generator"Where is border between function generator and RF generator? Specially if we talk about HF or low VHF.Today many modern Arb/DDS function generators can also use for RF work if we look example this need (adjust/service radio like DX-160 or other this kind of short wave or even low VHF radios.)Of course I know that they are not "real" RF generators, but they can do this work what OP talk well and they are much more than enough for this.Signal quality and example frequency accuracy is more than enough for this kind of receiver all adjustments and measurements. Only extra what need is one or two fixed attenuators if need do things with very low signal levels. What more, these can use also for receiver measurements where need two individual separate signals.There is also of course modulations, even for SSB (but usually DSB so there is together USB and LSB signal with enough attenuated carrier.)It is not so that there is function generators and then RF generators. This notion is some amount obsolete if think repair and adjust this kind of not high-end recevers for HF. But also I think OP know this. (also example I really know what are real RF high-end RF generators and why we also need them and example today modern "function generator" is just toy if need some real pure RF signals. I have example many different HP RF generators including also some state of art old high end model. Some yars ago I satill keep function generators just as they are and all "RF" work need RF gen.I have (partially) changed my opinion because the reality has also changed. And I can say this need lot of becouse I have been very conservative in these things due to 50 year hobby/work with electronics, electric and also with communication equipments in professional ans hobby class. It have been hard to change opinions.(and still for professional and higher class RF work, of course RF generator, example some R&S model or example HP old 8640B (what have nice signal) and of course high class HP8642B or ...44B as long as stay below 1-2GHz, phase noise is low, level accuracy is good etc and some of these can use even in radio "black room" for receiver tests)Today with some better "function generators" can do some RF work (I mean serious work and not only kids playing). So, it is not wise anymore underestimate these for this kind of use.Of course there is also toy class crap equipments but everyone may know these toy "function generators".It need say agen... related to this kind of work what OP talk.Example, with Siglent SDG1000 this work can do. If also have external some attenuators.(it is enough for ordinary analog HF receiver adjustments and repair work but it also depends receiver principle (becouse limit is around 50MHz and some (other) HF receivers may have first mix over this). Specially if have external frequency reference depending needs of freq accuracy..This is some kind of minimum level for some kind of RF work.If want much better tool and go up to low VHF. Siglent SDG5000 series (RF)/Arb/Function generator is well enough for this work and just with this initial freq accuracy and stability with its own internal TCXO reference (there can find data in other thread), it is well enough for this kind of needs. Also for RF work it may need some external fixed attenuator(s).Signal quality and accuracy is more than enough for this kind of work.And it have two generator for measurements where need two individual RF signals.For IF adjustments it also sweeps etc.This do not mean that it can classify as real professional true RF generator. But this kind of work and more it can do well what is here.As told, this is not recommendation for OP due to price class and as he say.. "no function generator"

author: tnt
author_rank: Regular Contributor
timestamp: July 22, 2013, 08:52:42 am
content: Well RF generator I've seen have a much wider dynamic range. I mean I can generate signals from 15 dBm downto to -135 dBm with the one I have. I think most (all?) arb siggen can't do that because the amplitude may only have a few fixed range and then it's done with changing the DAC values which reduces the signal quality.

author: vk3yedotcom
author_rank: Frequent Contributor
timestamp: July 22, 2013, 09:43:04 am
content: One possibility that's within your budget is to build a DDS VFO kit.Don't have practical experience of this one but it gets favourable reviews here:http://www.eham.net/reviews/detail/8759http://www.pongrance.com/It will need to be built in a shielded metal box with an attenuator for testing receivers. But it could then be used later for other things - eg VFO.

author: rf-loop
author_rank: Super Contributor
timestamp: July 22, 2013, 09:43:19 am
content: Quote from: tnt on July 22, 2013, 08:52:42 amBtw, if look example Siglent DAC output, how much it change due to level adjustment..But other way yes if look signal output and this is reason why I say that need external attenuator(s)Typical good RF gen go least +13dBm (nice if more)And down to least -130 - < -140dBm)Soemthing about other things in signal quality can see also in my some exmples about testing with spectrum analyzer these "function generators".Typically RF gen run always nearly full power and it have output attenuator for level adjustments. Only inside step attenuator step they adjust level. (in example many HP RF gen what I have several different)

author: xrunner
author_rank: Super Contributor
timestamp: July 23, 2013, 12:29:15 am
content: I had another idea. Since I'm going to get a ham HF rig later this year, I'm just going to store the DX-160 away for the time being. Later I can just transmit spotter markers into a dummy load from the HF rig and align the DX-160 from those signals. There's enough ham bands spread across the dial to get it aligned from those markers.

author: AG6QR
author_rank: Frequent Contributor
timestamp: July 23, 2013, 12:53:14 am
content: If you're a ham radio fan, you'll eventually want an antenna analyzer. An antenna analyzer has a variable frequency low power RF oscillator as an essential piece of it. I use my MFJ-259B as a an RF signal generator for some purposes. It has continuous coverage from 1.8 to 170 MHz. It has a not-too-precise analog frequency adjustment and a built-in frequency counter, but you can use an oscilloscope or other frequency counter for a bit more precision if needed. It should be more than adequate to align an analog radio dial.Note for non-hams, an antenna analyzer is an instrument that sends out a weak RF signal to an antenna, and measures the antenna's impedance and SWR (a measure of reflected power). Hams use them to tune antennas for best performance at a particular frequency.Quote from: xrunner on July 23, 2013, 12:29:15 am

author: dr.diesel
author_rank: Super Contributor
timestamp: July 23, 2013, 12:56:41 am
content: If you're in Indiana, come on over. I've got several HF rigs and a GPSDO, and lots of beer.

author: xrunner
author_rank: Super Contributor
timestamp: July 23, 2013, 01:00:29 am
content: Quote from: AG6QR on July 23, 2013, 12:53:14 amAh that's a really great idea. I've looked into these analyzers a little. So yea if you can set a freq. and have it "transmit" it without changing it would indeed do the job. Thanks for the suggestion!

author: ted572
author_rank: Frequent Contributor
timestamp: December 24, 2013, 12:26:43 pm
content: Low Cost 35MHz - 4.4 GHz Signal Generator:You can see the EDN Review at:http://www.edn.com/electronics-blogs/the-emc-blog/4423710/Review--inexpensive-RF-generatorThe manufacturer's Web site is:http://www.rf-consultant.com/calibrated-signal-generator/BTW I have the Calibrated RF Signal Generator ($330).I also have ordered one of the Standard Synthesizers ($200) for use as LO for: 1. RF down-converter to extend the upper frequency range of a Icom R-8500 receiver, 2. Up/Down frequency extender for DSA815-TG Spectrum Analyzer for 1.5 - 3.0GHz, and 3.0 - 4.5GHz. 3. General universal freq. conversion with external Balanced Mixer.

author: nctnico
author_rank: Super Contributor
timestamp: December 24, 2013, 02:46:50 pm
content: Note that these cheap generators have lots of even and odd harmonics! They basically output a squeare wave.

author: w2aew
author_rank: Super Contributor
timestamp: December 24, 2013, 06:43:35 pm
content: Quote from: xrunner on July 21, 2013, 11:13:09 pmI've got a DX-160 also. I bought it new in the mid 70's after saving up a summer's worth of lawn-mowing money. I realigned it a few years ago, and still surprised at how sensitive it is. Not very selective, but still fun to listen to.While there are a lot of ways to do this (cheap gens from likes of Elenco, Tenma, etc, or even a grid dip meter), I like the idea of using an antenna analyzer like the MFJ-259, since it is more than accurate enough with its built in counter, and will have many more uses in you ham radio activities.

author: ted572
author_rank: Frequent Contributor
timestamp: January 03, 2014, 11:44:47 pm
content: Quote from: nctnico on December 24, 2013, 02:46:50 pmIt is true that these 35MHz to 4.4GHz Signal Generators are rich in Harmonics (worst case -10dB). Although the RF Carrier Frequency and RF Carrier Freq. Output Amplitude is quite accurate, and with low RF phase noise.* Frequency Accuracy: +/- 1.5 PPM at normal room ambient temperature, and +/- 2.5 PPM worst case over the full temperature range.You can also use an external 10 MHz Freq. Std. for better accuracy if required.* RF Carrier Freq. Output Level Accuracy: Typically +/- 0.6dB, worst case +/- 1dB.* And it is also true that they are considered inexpensive: $310 to $330.Calibrated Signal Generator:http://www.rf-consultant.com/calibrated-signal-generator/I don't have any financial interest in this product, but I'm very excited that I can afford to buy a RF Sig. Gen. that goes up to 4.4GHz.

author: G0HZU
author_rank: Super Contributor
timestamp: January 04, 2014, 12:26:18 am
content: QuoteThe other option is to get an ADF4351 eval PCB from Analog Devices. They sent me the ADF4350 and ADF4351 eval boards when they were each introduced. I generally get all their DDS and PLL boards for evaluation.I've probably still got them somewhere. You just plug in a USB connector to the ADF4351 board and you can use the bundled software (very clunky) to drive it and you get a PC programmable signal source up to about 4GHz.I do remember that the spectral purity is quite poor especially on the upper ranges and if you deliberately select frequencies where the frac N gives high spurious levels. It can look quite scary on some frequencies! Lots of spurious and noise can appear on certain settings!You can also choose to spread the spurious terms to look more like noise but if you expect to see a clean RF signal from one of these then you might be disappointed.But if you just want a basic synthesised signal source with small tuning step sizes and you can live with minimal amplitude control range (and high spurious/harmonics) then it is a pretty neat device to have in the workshopEdit:I allowed myself the munching time of one biscuit to try and find it and I succeeded. See the image belowI assume these ADF4351 eval boards are still available but I have no idea of the cost. You can either power it via the 4mm connections or via USB. I did it all via USB so you just plug and play

author: G0HZU
author_rank: Super Contributor
timestamp: January 04, 2014, 12:49:43 am
content: I just looked up the price of the official Analog devices eval board and it is $175.http://www.analog.com/en/evaluation/eval-adf4351/eb.htmlMine arrived a few years ago (?) as a free initial evaluation sample with bundled SW on CDROM plus the fully built and tested PCB and a cable. I assume you get the same with the $175 deal today.If you put it in a nice box you could sell it for less than the $330 commercial version

author: Co6aka
author_rank: Unknown
timestamp: January 04, 2014, 03:34:15 am
content: Something like the HackRF might turn out to be a handy item because it's both TX and RX, and you generate pretty much any kind of modulation -- it's I/Q modulated. (I do the I/Q thing with my Agilent E4438C and an ASUS Xonar Essense ST sound card.)Also, check out the DG8SAQ Vector Network Analyzer:http://sdr-kits.net/VNWA3_Description.htmlMost of what I need a VNA for is under 500 MHz and so far it's performed flawlessly.And, check out this little thingy:http://www.redpitaya.com/

author: SArepairman
author_rank: Frequent Contributor
timestamp: January 04, 2014, 03:22:03 pm
content: are there any tracking bandpass filter options that would work into the 4ghz range?or maybe tracking low pass filters since we are mostly worried about the harmonics. tracking = tunableMaybe one could combine a few filter IC's to turn one of these contaminated function generators into a clean one? I know Maxim/linear can get you covered up to maybe a MHz and I think that there are some companies that provide options for the low MHz to high GHz range, but I guess these filters might introduce alot of noise.

author: edavid
author_rank: Super Contributor
timestamp: January 04, 2014, 06:14:00 pm
content: Cheap signal generators (or worse, eval boards) are not very useful for receiver testing, because they leak too much signal out of the enclosure. If you look at a lab generator (e.g. HP), the mechanical construction is very elaborate, to avoid this problem.

author: DonRon
author_rank: Regular Contributor
timestamp: January 04, 2014, 06:35:04 pm
content: Hi xrunner,I use either the antenna analyzer from miniradiosolutions - can be used as DDS synthesizer up to 160 MHz but level is limited up to 0 dBm or in the case I need higher levels I use my modified ham rig together with a homebrew dummyload and an homebrew switchable attenuator.Ron

author: G0HZU
author_rank: Super Contributor
timestamp: January 04, 2014, 07:28:14 pm
content: Quote from: edavid on January 04, 2014, 06:14:00 pmYou could still use the cheap 4GHz sig gen for...Receiver dial/channel/accuracy testingReceiver image rejection tests.Receiver IF rejection tests.Receiver blocking testsBuy two and do some basic IP2 and IP3 tests to test the receiver linearity.Set it to sweep mode and align the receiver preselector(s)You could use it with a coupler/detector to measure receiver input VSWR.It's pretty difficult to prove receiver sensitivity accurately up at 4GHz even with a lab grade generator. I'd probably use a decent noise source for this.

author: PA0PBZ
author_rank: Super Contributor
timestamp: January 04, 2014, 07:54:24 pm
content: A long time ago, in the days that I had no equipment at all I often used the local oscillator from another radio as a cheap signal generator, so if you have another multi-band shortwave radio it could be the solution. Just find out the mf frequency and if the lo is above or below the receiving frequency.

author: N2IXK
author_rank: Frequent Contributor
timestamp: January 05, 2014, 02:55:33 am
content: If you don't mind vintage, and have the room (and strong back) for it, it is hard to beat an HP 606B.Pure analog heaven, with the feel of a top-notch communications receiver. Hard to find better quality for the price.

author: DL8RI
author_rank: Regular Contributor
timestamp: January 05, 2014, 03:23:52 am
content: Hi,a rather cheap to get signal generator is the Rohde&Schwarz SMS or SMS2.Normally nobody wants them, because they're crap.But they are rather compact, fairly modern and quite useful. But don't expect an SMDU...

author: nctnico
author_rank: Super Contributor
timestamp: January 06, 2014, 03:21:34 pm
content: I just bought a Agilent E4421B (250kHz to 3GHz) from Ebay in 'for parts' condition. I just hope it doesn't need too many repairs

author: ted572
author_rank: Frequent Contributor
timestamp: January 29, 2014, 11:28:43 pm
content: Quote from: nctnico on January 06, 2014, 03:21:34 pmWere you able to get your new generator working? If so, then you have a very nice catch. So I hope a congratulations is in order here, and NOT condolences.

author: nctnico
author_rank: Super Contributor
timestamp: January 30, 2014, 06:12:42 am
content: So far the 'my' generator is enjoying a boat trip from China. It needs a new knob for sure. I've read about people having problems with the output stage but it could have any number of problems.

author: ted572
author_rank: Frequent Contributor
timestamp: January 30, 2014, 02:12:17 pm
content: Quote from: nctnico on January 30, 2014, 06:12:42 amFrom China! I hope 'for parts condition' doesn't mean needs all of it's inside parts, rather than 'for the pars in it' (the normal meaning).'V' May the odds be with you! I wish you luck.When you get your generator put up a picture of it hear, because if I have a HP knob for it, I will send it to you (free).

author: nctnico
author_rank: Super Contributor
timestamp: January 30, 2014, 03:53:30 pm
content: Thanks for the offerI'm planning on doing a small 'story' about verifying whether it works and on any repairs. Mike (Mikeselectricstuff) already did a teardown of one of these RF generators.

author: ted572
author_rank: Frequent Contributor
timestamp: February 03, 2014, 06:38:44 pm
content: Quote from: nctnico on January 30, 2014, 03:53:30 pmWere you able to find the Service Manual and all of the supporting Schematics for the Agilent E4421B Signal Generator? I'm asking because on some of the newer HP/Agilent equipment I have had a hard time finding the schematics. I'm looking forward to hearing how you make out on it.

author: nctnico
author_rank: Super Contributor
timestamp: February 03, 2014, 10:12:14 pm
content: So far I have found a service guide which has a detailed block diagram. No component level schematics though. Then again you usually don't need a detailed diagram to fix something. Some clue as where to expect a certain signal is enough to start tracing the signal flow. When trying to fix something there are two rules:- never say 'this can't be the cause of the problem'- work systematically; after checking the power supply start at the beginning of a signal pathYou still can be bitten by odd things like a power supply going into overvoltage protection because a fan isn't connected. It is not easy to find a fault in a perfectly working power supply

author: ted572
author_rank: Frequent Contributor
timestamp: February 12, 2014, 12:14:23 am
content: Quote from: nctnico on January 30, 2014, 06:12:42 amHave you received your Sig. Gen. from China?

author: DSinstruments
author_rank: Newbie
timestamp: October 20, 2015, 03:17:26 am
content: This thread is old, but for people using it as a reference later I wanted to mention that I manufacture a few entry-level wideband signal generators that are relevant here. I use PLL with integrated VCO IC's from Maxim and analog devices to cover DC-12GHz in a usb powered hand-held device. It is true that the raw output from such integrated circuits can have harmonics as high as -12dBc in some bands. I am working on a harmonic filtered version, and let me state for the record, it is NOT a trivial task in a wideband device. My company is DS Instruments and I welcome people to see what I have to offer before going to the cheaper imported electronics!https://www.dsinstruments.com/store/products/micro-rf-signal-generator-sg6000m/

author: tautech
author_rank: Super Contributor
timestamp: October 20, 2015, 03:40:13 am
content: Quote from: DSinstruments on October 20, 2015, 03:17:26 amWelcome to the forum.Please keep us updated on your range and model developments.Maybe start a DS Instruments thread, introducing yourself, describe your core business and some history of your company.We look forward to your contribution.

author: Karel
author_rank: Super Contributor
timestamp: October 20, 2015, 10:40:15 am
content: ... and don't forget there's a separate thread "Buy/Sell/Wanted" for people who want to sell/promote their products.