What tool do hobbyiest in RF need? - Page 1
Forum section: electronics / beginners

author: asgard20032
author_rank: Regular Contributor
timestamp: September 22, 2015, 01:39:01 am
content: I have a 4 channel rigol scope, 100 mhz, and the super bk precision multi-meter from the shout out from dave. But what else would i need for RF?Do i need a RLC meter? Any cheap RLC meter if i need one?Do i need a spectrum analyzer? Any cheap spectrum analyzer if i need one?Any special software on the PC?Is SDR a good thing to get in my tool box? If yes, which software/device should i look at?Any suggestion.

author: retrolefty
author_rank: Super Contributor
timestamp: September 22, 2015, 01:42:49 am
content: The ability to measure SWR is very useful in RF at times. After that even an older used spectrum analyzer makes some measurements/testing that is hard to do without.

author: pickle9000
author_rank: Super Contributor
timestamp: September 22, 2015, 01:43:46 am
content: SDR to play with

author: Neganur
author_rank: Unknown
timestamp: September 22, 2015, 06:01:51 am
content: Not sure how useful the cheap sdr things are as measurement instrument. But then again, I have not used them much except to look at a frequency hopping pattern in waterfall mode. With proper software I imagine they can be quite useful. I believe you can learn quite a bit about spectrum and modulation types with them.What frequencies are you talking about? Scope & voltmeter are enough for a lot of things already. There are also many DIY spectrum analyzer and power meter projects in the Internet. Or ham projects. Maybe grab an ARRL handbook and see if something in the index sparks your interest.

author: tggzzz
author_rank: Super Contributor
timestamp: September 22, 2015, 07:56:28 am
content: Quote from: asgard20032 on September 22, 2015, 01:39:01 amThat entirely depends on the type of RF work you expect to do.Contact your local amateur radio organisation.

author: tggzzz
author_rank: Super Contributor
timestamp: September 22, 2015, 07:59:26 am
content: Quote from: Neganur on September 22, 2015, 06:01:51 amWith imagination they are useful for more than you might expect. I'm halfway through experimenting with them, and the initial results are athttps://entertaininghacks.wordpress.com/tag/sdr/I must get around to writing up the next set of results and making my post-processing tools available.

author: VK5RC
author_rank: Unknown
timestamp: September 22, 2015, 08:22:39 am
content: +1 re contacting a local amateur radio club, lots of knowledge, some good advice and gear, and different as areas to experiment.If building equipment: an rf source, set of attenuators, and rf power meter and or spectrum analyser are pretty useful but aren't cheap esp if good /reliable.Dongle type SDRs can have problems with overload, image problems and S/N not always the best but pretty good value!

author: Gyro
author_rank: Super Contributor
timestamp: September 22, 2015, 08:53:34 am
content: 100MHz bandwidth sounds a bit low for what I would think of as RF. You might want to look for a second hand high frequency analog scope. The local amateur radio club might be able to help you out there too.Edit: you probably want to equip yourself with terminators etc as with RF you're more likely to be living in a 50 ohm world where probe parasitics (capacitance) become more of a problem.

author: Neganur
author_rank: Unknown
timestamp: September 22, 2015, 09:29:03 am
content: I would absolutely recommend against a high bw scope for RF. They simply don't have the dynamic range nor bandwidth and aren't meant for this purpose.100 MHz scope is plenty to look at clocks and baseband signals, logic signals that control vco, dds etc.Get an SA for RF work instead.

author: Gyro
author_rank: Super Contributor
timestamp: September 22, 2015, 10:15:49 am
content: I would certainly agree on the Spectrum analyser, my thought was that higher analog bandwidth might allow better chance of spotting distortions (=harmonics), parasitic osculations etc.The difficulty with the SA is high cost, the OP is specifically asking about RF tools for a hobbyist. He mentions getting a cheap RCL meter where clearly a network analyzer would be much more helpful.

author: tggzzz
author_rank: Super Contributor
timestamp: September 22, 2015, 10:26:01 am
content: Quote from: Gyro on September 22, 2015, 10:15:49 amA spectrum analyser would bemuchbetter than a scope a spotting those problems. Even an SDR used as an SA would be useful, but you would have to watch out for the SDR's limitations.

author: VK5RC
author_rank: Unknown
timestamp: September 22, 2015, 10:57:31 am
content: I would support above comments re the lesser value of a scope. I would use a spectrum analyser 10 times for every time I fire up my scope.There are some "good" SDR type analysers e.g. Signal Hound and Array Solutions VNA AIM 4170 are pretty good but a good classic type SA e.g. HP 856x 859x are hard to go past.

author: Gyro
author_rank: Super Contributor
timestamp: September 22, 2015, 11:33:56 am
content: Ok guys, I surrenderI'm from the era where our labs had plenty of decent performance scopes but only ONE communal SA and NA. Spotting a bit of 'fuzz' was the first indication of needing to start plotting for temporary possession!Needless to say, I too am interested in low cost SA / SDR options.

author: Cliff Matthews
author_rank: Unknown
timestamp: September 22, 2015, 04:42:55 pm
content: Quote from: Gyro on September 22, 2015, 11:33:56 amHere's a good example then: (it's a little funny, but he does a nice demo on SDRPlay - at $165 USD sounds very cost effective)http://www.sdrplay.com

author: C
author_rank: Super Contributor
timestamp: September 22, 2015, 05:23:31 pm
content: Look at how it was done back in the 60's & 70'sFirst a scope did not have the bandwidth & connecting a scope to circuit loaded or changed the circuit.A scope was your visual analog display device.You often used X-Y mode.When not using X-Y mode, you were often using the horizontal sweep output to create an X-Y equal.With no scope you had to use an RF volt meter.For a RadioYou could set a signal generator to a known freq. & amplitude and then use the RF volt meter to take a reading. A lot of reading later and you could plot a band pass curve.If you could use the horizontal sweep output of scope to change the freq of the signal generator then you could sweep the input and display output on scope.If the output signals were very small then you could use a tracking receiver that changed with horizontal sweep output of scope to boost the signals up to scope levels.Look at the basics hereWhit no horizontal sweep output of scope then this signal had to come from one of the other pieces of equipment and scope had to use Z-Y mode.The tracking receiver is part of the spectrum analyser.The network analyzer is part spectrum analyser & RF signal sweep generator. Notice that the two parts need to work different frequency ranges with a radio.For a transmitterYou have two inputs the transmitter freq and modulation.You need test signals for one or both and or where they are combined.Some of the old racal radios used an IF strip that was an inductor with a parallel cap and no other physical connections. A bunch of these were put in a medal tube to make the IF filter. You used Indirect readings to make adjustments here. Just the tunning wand changed the circuit.Today there are a lot of ways to get to the same basics.C

author: Gyro
author_rank: Super Contributor
timestamp: September 22, 2015, 06:35:30 pm
content: QuoteThat looks interesting at the priceI spotted a really cheap ($70) basic USB spectrum analyser + tracking generator on ebay from China. Looks interesting but it bottoms out at 138MHz which is a bit of a shame. Hard to say how it would perform in practice and no real way to tell how good the s/w is.http://www.ebay.co.uk/itm/New-USB-138M-4-4G-Signal-Source-Signal-Generator-Simple-Spectrum-Analyzer-/251600378012?hash=item3a948d189cEDIT: Actually, looking at another listing, probably not tracking.

author: tggzzz
author_rank: Super Contributor
timestamp: September 22, 2015, 07:02:13 pm
content: Quote from: Gyro on September 22, 2015, 06:35:30 pmMost cheap signal generators output a square wave, or at least something with "a lot" of harmonics.

author: Neganur
author_rank: Unknown
timestamp: September 22, 2015, 07:14:51 pm
content: uh, this reminds me of a 5 GHz frequency counter with optional power meter. Pretty affordable.They also have an LCR meter.http://www.ascel-electronic.de/kits/14/ae20401-5.8-ghz-frequency-counter-/-rf-power-meter

author: TSL
author_rank: Regular Contributor
timestamp: September 23, 2015, 07:50:12 am
content: So what RF are you going to work with ?Answers to that question will seriously determine what test equipment you might want.Go get the ARRL Handbook, this is an excellent text book for beginners in RF al the way through to accomplished hams.http://www.arrl.org/arrl-handbook-2015There are many test equipment projects you can build in this book too.A RF probe for your multi-meter is a good thing to look at levels. SDR is certainly your friend.

author: asgard20032
author_rank: Regular Contributor
timestamp: September 23, 2015, 09:13:54 pm
content: Probably sub ghz, for higher distance. 433mhz and 916 mhz + all the ham band sub ghz. I want to use RF to remote control thing.

author: tggzzz
author_rank: Super Contributor
timestamp: September 23, 2015, 09:19:05 pm
content: Quote from: asgard20032 on September 23, 2015, 09:13:54 pmI would strongly suggest buyimg ready-made RF modules, and building your application around them. Unless you are into production quantities, development will be faster and cheaper and will avoid certification issues.If you are building large quantities, then you will need specialist skills, and will have to get your device certified.

author: asgard20032
author_rank: Regular Contributor
timestamp: September 23, 2015, 10:54:29 pm
content: I am not looking for reselling or to take the easy path, but to make fun learning something new. I will be at university maybe this winter or next autumn, and meanwhile, exploring RF + many other area will help me to choose my specialization at university. I want to do computer engineering, but more in the embedded system, so computer + electronics... But exploring RF and other field will help me choosing my embedded specialty. And yes, i intend to also sometime take premade IC, like those CCxxx from TI, but i still need to learn about antenna and impedance matching.