hybridfree/eevblog-posts huggingface dataset:
Rewire a 700W+1300W heater for series instead of parallel, using 2 SPDT relays? - Page 1
Forum section: electronics / beginners

author: Freesurfer
author_rank: Regular Contributor
timestamp: June 03, 2025, 05:46:36 pm
content: I have a heater with 2x 230V heating elements, where one is 700W, the other is 1300W, and together they are 2000W.However I am trying to rewire the elements in such a way that instead of a 2000W mode where both run in parallel, I would rather have them running in series to reduce the overall power, so that I have the 4 options: Off, ~455W, 700W, 1300W. A mode for 2000W would have been preferable, but that gives a total of 5 different power states, which I know is not possible with 2 relays (Possible switch combinations are 00 01 10 11 = 4 possibilities)But I have been scratching my head for ages trying to figure out how to do this, and if it is even possible.I have drawn the scenario below, where the 2 elements are tied together in a center tap, but it is very possible that this needs to be modified. If a center tap is needed, all I know is that it must have a state where the center tap is open rather than connected to either L or N. But I still cannot figure out what to do with the other relay in that case.I am not worried if the final solution involes one element being connected to live (L), even when the heater is turned "off"And to answer some questions people may have:Can't you just add another relay?Yes, probably, but if I did, it would defeat the purpose of the question in the first place. I am hoping to avoid it.Can't you get a different heater?No, this was the lowest power I could find, suitable for the purpose.Can't you control the duty cycle with a timer?No, I need to control the instantaneous power, not average power.Can't you use a thyristor or something similar?I would prefer to avoid it.Does anyone have a clever idea?

author: Freesurfer
author_rank: Regular Contributor
timestamp: June 03, 2025, 07:02:03 pm
content: Nevermind, I figured it out.

author: SteveThackery
author_rank: Super Contributor
timestamp: June 03, 2025, 08:08:55 pm
content: Nice one. Thanks for posting the solution - someone in the future might find it useful.

author: BeBuLamar
author_rank: Super Contributor
timestamp: June 05, 2025, 02:34:07 am
content: Quote from: Freesurfer on June 03, 2025, 07:02:03 pmBut you know that when you run the 2 heaters in series the 700W heater is hoter than the 1300W heater right.
Rework station safety screw(what's the problem?) - Page 1
Forum section: electronics / beginners

author: TNb
author_rank: Regular Contributor
timestamp: January 26, 2015, 11:33:29 pm
content: This is just curiosity question.I just bought hot air smd rework station and it has sticker saying that I need to remove screw that holds the pump during transportation and quote "otherwise it can cause a serious problem". How does the screw that just holds the pump will cause any kind of problem? What are they talking about? And I googled a bit and it seems most hot air rework station has this kind of rule of removing the screw, but nobody tells why exactly. I'm confused, wouldn't it be even better to leave the screw there since it will hold the vibrating pump?

author: amyk
author_rank: Super Contributor
timestamp: January 26, 2015, 11:43:54 pm
content: Usually the pump is mounted on some compliant feet to absorb vibration, but the mass of the pump might break those during shipping. The screw might be to lock the internals of the pump in place too, in which case you *will* cause damage if you leave it in.

author: tautech
author_rank: Super Contributor
timestamp: January 26, 2015, 11:49:17 pm
content: Amy has given a reasonable answer, but if you also think of a vinyl record turntable... it has screws for transport mode to protect the internal dampening.
RF amp to go from 0 to about 10 or so dBm @ 136kHz? - Page 1
Forum section: electronics / beginners

author: Chris Wilson
author_rank: Super Contributor
timestamp: December 14, 2014, 05:17:15 pm
content: I need to build or buy a simple amp to increase the output of my Kenwood TS-590 transceiver. It only transmits via the "DRV OUT" socket at 136kHz, at 1mW (0dBm). I need to feed it into the circuit in the link below, a frequency doubler, that needs about 10 to 17 dBm drive power. Any links to anything to build or buy please?The device I need to feed the signal through is shown here:http://www.w1vd.com/X2LinearClassDinterface.html

author: SeanB
author_rank: Super Contributor
timestamp: December 14, 2014, 05:26:27 pm
content: You can use a CFB opamp, or any opamp with a GBW product over 1GHz, or just use a few simple common emitter transistor stages ( your choice of tuning them to make a band pass filter, but that would be good on the final stage or so) cascaded together to get the required gain, and with the final stage being an emitter follower ( which will drop some gain, but gives a useful current boost to drive the transformer) to drive the frequency doubler reliably. Probably 3 stages in total.Try this one.....http://www.w1vd.com/VLFLFMFpreamplifier.pdf

author: dannyf
author_rank: Super Contributor
timestamp: December 14, 2014, 06:29:23 pm
content: Quote136Khz is nothing - even the slowest of the slow small signal transistors will do.If you want fancy (optionality later), use mmic -> 17db is fairly standard for those things.But really, a transistor is all you need.

author: dannyf
author_rank: Super Contributor
timestamp: December 14, 2014, 06:32:43 pm
content: BTW, what is this all about? I thought you were trying to divide some frequencies and now you are trying to multiply some frequencies?Rather than showing people pieces of what you are trying to do and going down the wrong path, you may want to show people also the big picture and maybe there are better / different ways to get you where you want to go.
RF Amplifier Questions - Page 1
Forum section: electronics / beginners

author: joblessalex
author_rank: Contributor
timestamp: February 18, 2013, 09:24:28 am
content: Hello everyone out there on the forum! Someone is going to yell at me for this one I'm sure, but I've looked all over Google on and off now for a few months and can't find any tutorial on theory behind a simple RF amplifier! I have tried designs and had success with many of them working, but I still don't understand how or why they work, and the calculations behind the choosing of components. Perhaps there is a cover all circuit calculator or a diagram that you just change values to match frequency/transistor? Where is the best place to start learning how to do this? Before you ask, yes I have an amateur radio license so I can legally use what I build.

author: michaelym
author_rank: Regular Contributor
timestamp: February 18, 2013, 10:07:42 am
content: It's black magic...

author: joblessalex
author_rank: Contributor
timestamp: February 18, 2013, 10:40:46 am
content: Quote from: michaelym on February 18, 2013, 10:07:42 amYup. Guess I'll never learn until I go through years and years of college!

author: fcb
author_rank: Super Contributor
timestamp: February 18, 2013, 11:43:20 am
content: google Class C amplifiers

author: jerry507
author_rank: Regular Contributor
timestamp: February 18, 2013, 05:01:07 pm
content: Buy the handbook. RF amps are a reasonably complex subject and there are a lot of differences between something in the HF region to VHF and UHF and up.Years and years of school won't cut it either, need lots and lots and lots of practice

author: PA4TIM
author_rank: Super Contributor
timestamp: February 18, 2013, 07:27:27 pm
content: Experimental methods in RF design by Hayward is probably the most easy.There are many books on RF design, but most assume a good knowledge about electronics. But RF at 80 meters or 23 cm ?Bowick has a nice book, the old books from Terman, and the art of electronics is a good base.Together with maybe The ARRL radio handbook for the basics.

author: kg4arn
author_rank: Unknown
timestamp: February 18, 2013, 09:55:09 pm
content: Ditto on Experimental methods in RF design by Hayward.Introduction to RF design by Hayward is a great introduction tothe theory. Sadly it just went out of print so it may be hard to find.

author: joblessalex
author_rank: Contributor
timestamp: February 21, 2013, 11:55:32 am
content: Thank you to everyone who posted! I found the book and from just the first few pages I am already on my way to understanding what I needed to learn!
RF Amplifiers - Page 1
Forum section: electronics / beginners

author: Goature
author_rank: Contributor
timestamp: July 14, 2014, 11:24:42 am
content: Hello!I've been working on this RF project lately, and some questions have poped up along the way. I'm working on a transmitter based on the CC1050 chip from TI (http://www.ti.com/general/docs/lit/getliterature.tsp?literatureNumber=swrs044), but i want more juice (Yes, I've got a HAM license, callsign LB3TG)! So I figured i needed to add an RF amplifier on the RF output.My problem is basically that I don't know anything about RF amplifiers. I've configured the CC1050 to transmitt at about 433MHz on 10dBm (10mW). I want to boost the RF output to atleast 100mW.I've tried to browse the RF amplifiers on Digikey, but I dont know that I'm looking forCan you give me some examples on RF amplifiers that will work for this application, please?I'm quite blank!

author: w2aew
author_rank: Super Contributor
timestamp: July 14, 2014, 01:38:44 pm
content: You may want to browse the amplifier selections athttp://www.minicircuits.com. They've got many amplifiers that will meet your frequency requirements and +20dBm output level.

author: XFDDesign
author_rank: Frequent Contributor
timestamp: July 14, 2014, 01:46:21 pm
content: Since you seem to be after a canned solution, instead of a home-rolled one, you're looking for MMICs (Monolithic Microwave Integrated Circuits). From the datasheet, you'll still need to use their matching network (page 9) before you drive anything else. An amplifier like the Analog Devices' ADL5536mightdo the job, but its P1dB compression level is right at your output want. You would also need an attenuator to knock your output powerdownbefore gaining it up. Overall, this might be the most easy option if you don't mind the distortion introduced from the compression.Personally if linearity is important, I might use an off-the-shelf power splitter, use two of the amplifiers, then another splitter as a combiner. (Something like the minicircuits SBTCJ-1W+http://www.minicircuits.com/pdfs/SBTCJ-1W+.pdf). This route offers a few benefits for the cost: A 6dB attenuator feeding a 3dB splitter means 3dB of my power is actually doing something useful. When I gain up the two signals, they each stay below their compression point so they're more linear. Combine them again to get the 3dB summation boost. 20dBm with good linearity, at the expense of cost and power (the ADL5535s burn a lot of it).

author: theatrus
author_rank: Frequent Contributor
timestamp: July 14, 2014, 06:04:21 pm
content: The CC1050 has a programmable output power and should be able to meet the input spec of an amplifier. Also, you will likely require an RF switch to bypass the PA in RX mode or to add an LNA in that path.
RF attenuator formula. I am confused ... - Page 1
Forum section: electronics / beginners

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: July 09, 2015, 08:16:46 am
content: Dear All,I do not understand the RF attenuator formula that I find in many places on the Web.As for example inhttp://www.qsl.net/4f5aww/module5p.htmIf I compute the resulting voltage divider ratio, I findR1/(R1+R2) = 2k/(k^2+1) ~ 2/kand not 1/k as one would expect for a k factor attenuation.I am sure I am missing something, but what ?Thanks

author: w2aew
author_rank: Super Contributor
timestamp: July 09, 2015, 12:12:46 pm
content: What you're missing is the fact that both ends of this attenuator are terminated in 50 ohms when used in RF applications.

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: July 09, 2015, 08:48:46 pm
content: Thanks, w2aew, for the comment. This was missing in the web sites I looked to.It is also missing on your video, which is nevertheless very interesting.So I have added a Z impedance in parallel to the R1 resistors.Now the ratio of the voltages is (using the formula given above)Vo/Vi = R1*Z/(R1*R2 +(R1+R2)*Z) = 1/kSo exactly what is needed.This means that the impedance of the attenuator needs to be adjusted to the impedance of thesource and of the receiver.Thanks again.

author: w2aew
author_rank: Super Contributor
timestamp: July 10, 2015, 12:29:02 am
content: Quote from: JacquesBBB on July 09, 2015, 08:48:46 pmYes, this is one of those *given* or *assumed* things in RF applications.

author: LukeW
author_rank: Frequent Contributor
timestamp: July 10, 2015, 04:50:15 am
content: Yep, it is assumed that the attenuator you're designing is going into a system with some impedance given, say 50 ohms. And if you build that attenuator and then move it to a 75 ohm system it will not work as intended.
RF Cans - Page 1
Forum section: electronics / beginners

author: DroneBuster
author_rank: Contributor
timestamp: January 07, 2014, 09:15:21 pm
content: Hi,I'm designing controller board for UAV (not flight controller but for controlling other misc stuff that is on plane). Also in that board will be whole power supply, it will have about 4 different switching regulators. I thought I should put them in RF can, but I'm quite newbie in electronics and need some start points: what can to choose, how to design it into my board? I would prefer SMDThank you for help

author: KJDS
author_rank: Super Contributor
timestamp: January 07, 2014, 09:35:07 pm
content: These people are my go to supplierhttp://www.perancea.com/prod-fr.htmI think that Farnell stock some of their more common sizes.

author: JackOfVA
author_rank: Unknown
timestamp: January 07, 2014, 09:43:44 pm
content: In the USA, check Tekohttp://www.tekoenclosures.com/en/products/product-group/RF-- Teko is an Italian company so their products are also widely available in Europe.
RF choke blowing in microwave power supply - Page 1
Forum section: electronics / beginners

author: beergut
author_rank: Newbie
timestamp: June 14, 2020, 05:54:28 am
content: G'day all,My microwave has a blown 2200uH axial rf choke.Couldnt get the right one locally so replaced it with a 1000uH one while I wait for delivery.Powered on and the choke blew instantly.Is the choke blowing because the choke is too small, what else can I check?Powered on with the dead choke still in place I am getting about 1.2v to earth on both sides of the choke.Microwave is not worth saving, just using it for target practice.Any help appreciated.

author: JustMeHere
author_rank: Frequent Contributor
timestamp: June 14, 2020, 08:33:54 am
content: You didn't clear the fault.
RF-DC converter - Page 1
Forum section: electronics / beginners

author: Mukhtarkarim
author_rank: Newbie
timestamp: October 13, 2015, 05:55:15 pm
content: AOA.i want to design a radio frequancy to Direct current convertor.any one has any idea about this project?

author: Jeroen3
author_rank: Super Contributor
timestamp: October 13, 2015, 05:57:21 pm
content: As in wireless charging?

author: Mukhtarkarim
author_rank: Newbie
timestamp: October 13, 2015, 06:03:15 pm
content: the idea here is ,i will use high frequancies and convert them into direct current or voltage

author: Mukhtarkarim
author_rank: Newbie
timestamp: October 13, 2015, 06:06:10 pm
content: like this...........

author: Mukhtarkarim
author_rank: Newbie
timestamp: October 13, 2015, 06:07:30 pm
content: Quote from: Mukhtarkarim on October 13, 2015, 06:03:15 pm

author: Marco
author_rank: Super Contributor
timestamp: October 13, 2015, 06:14:12 pm
content: Only one idea, typerf energy harvestinginto google(Also try google scholar.)

author: Mukhtarkarim
author_rank: Newbie
timestamp: October 13, 2015, 06:30:09 pm
content: oi am suffering problems in hardware.

author: Marco
author_rank: Super Contributor
timestamp: October 13, 2015, 06:53:26 pm
content: Oi, you're making vague questions so you'll get very generic answers. You can find papers which will walk you through the basics of energy harvesting (ie. impedance matching, rectification and it's losses, etc). A lot of them have test circuits they build with discrete components as well you could just copy or you could even buy some of the existing COTS chipsets or their development kits.All the general information on how to do this is widely available, if you have a specific problem you'll have to ask a specific question.

author: DimitriP
author_rank: Super Contributor
timestamp: October 13, 2015, 07:19:07 pm
content: Quote from: Marco on October 13, 2015, 06:53:26 pmYou can say that again.

author: w2aew
author_rank: Super Contributor
timestamp: October 13, 2015, 09:40:14 pm
content: Quote from: Mukhtarkarim on October 13, 2015, 05:55:15 pmHere's a video I did showing a simple RF detector probe

author: rx8pilot
author_rank: Super Contributor
timestamp: October 13, 2015, 09:53:33 pm
content: OP....Are you planning to power something with this harvested RF energy? You may find it troublesome to get an LED lit up.

author: rjeberhardt
author_rank: Regular Contributor
timestamp: October 14, 2015, 09:26:35 am
content: Some years ago someone living near a powerful short wave transmitter in the U.K. was prosecuted for theft of electricity when he erected an antenna and used it to power lights in his house!Russell

author: Mukhtarkarim
author_rank: Newbie
timestamp: October 14, 2015, 04:01:09 pm
content: thanks for replying me
RF Design book for Educator/Students. - Page 1
Forum section: electronics / beginners

author: firewalker
author_rank: Super Contributor
timestamp: November 14, 2013, 09:44:11 pm
content: Can someone suggest a book for RF design? More like a practical guide.I have to teach to students (not a university. Vocational training after high school) about radio communications and a part of the course is about rf oscillators, buffers and amplifiers.This is the first I teaching about rf stuff. I know how to explain why and how a simple common emitter, base Colpitts/Hartley/Clapp/Xtal oscillator works. But when I see a real life transmitter I don't know what everything I see does.I would like a book that would take a real life circuit and would explain it.Alexander.

author: lewis
author_rank: Frequent Contributor
timestamp: November 14, 2013, 10:13:33 pm
content: RF Circuit Design by Chris Bowick is recommended -http://www.amazon.co.uk/RF-Circuit-Design-Christopher-Bowick/dp/0750685182/ref=sr_1_1?s=books&ie=UTF8&qid=1384467114&sr=1-1&keywords=rf+circuit+designAs is the ARRL Handbook:http://www.amazon.co.uk/s/ref=nb_sb_noss_1?url=search-alias%3Dstripbooks&field-keywords=ARRL

author: Six_Shooter
author_rank: Regular Contributor
timestamp: November 15, 2013, 12:58:11 am
content: I have the Bowick book. I haven't even opened it yet, and we are JUST starting to get into needing to use that book in my course. That being said, it's apparently a better book than the more expensive book by the same name (different author), according to my prof.I'm, in Electronics Engineering Technology (telecom), College, 2nd year.

author: firewalker
author_rank: Super Contributor
timestamp: November 15, 2013, 10:34:20 am
content: Thanks you.Alexander.

author: JackOfVA
author_rank: Unknown
timestamp: November 15, 2013, 09:47:52 pm
content: Experimental Methods in RF Design - highly recommended. Make sure you download the author's corrections as the published book has a lot of errors.http://www.arrl.org/shop/Experimental-Methods-in-RF-Design/and also available from the usual on-line sources.

author: Prizmatic
author_rank: Regular Contributor
timestamp: November 19, 2013, 01:21:46 pm
content: Another very good publication for the educator: RF Components and Circuits (Joseph J. Carr). ISBN 0 7506 48449
RF inductor using gyrator - Page 1
Forum section: electronics / beginners

author: promach
author_rank: Frequent Contributor
timestamp: December 31, 2018, 11:58:14 am
content: I am trying to reproduce an active inductor as inhttps://github.com/promach/frequency_trap/tree/developmentHowever , according tothis spreadsheet calculation, I could not get a working inductor and S11 simulation result does not match gyrator expression computation result.I have also tried ROUT maximization, but it does not help.Could you point out what possibly went wrong ?

author: vk6zgo
author_rank: Super Contributor
timestamp: January 02, 2019, 12:50:09 am
content: This is what I learnt years ago, & as such devices are still not commonly used at RF, would still seem to be correct.Gyrators, by and large, are not useful in RF circuitry, as at higher frequencies, stray capacitance & inductance become large enough to affect the circuit performance.Real LC circuitry can be designed which minimises such effects, or even incorporates them.Possibly, if Gyrators are built as an integral part of specialised ICs, it may be possible to overcome these pproblems.
rf interference with SIMPLE RF T4 RECEIVER - 315MHZ TOGGLE TYPE - Page 1
Forum section: electronics / beginners

author: aes92000
author_rank: Newbie
timestamp: December 14, 2014, 08:07:43 am
content: products being used:https://www.adafruit.com/products/1097https://www.adafruit.com/products/1095http://www.midwestmodelrr.com/product/mie2701/i am trying to control 4 receivers on channel 'A' at same time with a 3v EL inverter with 9 ft. of EL wire on each. the 4 receivers will be in contained 6'x10' spacingthe inverters are @ 1.428kHz and are creating major interference with key fob when powered on.i have 2-CR123 3.7V 2000mAH batteries paralleled for receiver @ 7.3V, mid-tapped for inverter @ 3.7v .i have tried ferrite coils on inverter outputs - both wrapped together in one ring and each separately wrapped with no luck either way.i wrapped inverter in 4 layers of foil. (may need to put on head also LOL)i tried to contain inverter and output wires with foil, inside an Altoids tin wrapped with foil. no gofor my design, the inverter needs to be within a few inches of receiver, unfortunately, from limited space.i need some help trying to limit the interference or options to filter for better reception from key fob.will changing the antenna to larger and/or longer make a difference?do i need to design a low pass filter?is there some type of amplifier circuit for receiver?any help and/or suggestions are very appreciated (especially since i bought all this crap for a project already.)

author: mikerj
author_rank: Super Contributor
timestamp: December 14, 2014, 09:51:55 am
content: Try using separate supplies for the receivers and EL inverters (i.e. power inverters from their own 3v cell) with the grounds commoned at a single point. If this improves things then the interference is likely being conducted through the supply lines.How are you switching the EL inverters from the receiver outputs, e.g. MOSFETs?

author: aes92000
author_rank: Newbie
timestamp: December 14, 2014, 11:03:49 am
content: using 3904 with 1K from receiver controlling dpst relaysee if i understand -separate battery supplies but make common ground between them???can i omit relay and just use 3904???including design
rf jfets - Page 1
Forum section: electronics / beginners

author: LaserTazerPhaser
author_rank: Regular Contributor
timestamp: May 13, 2019, 03:11:11 am
content: Are there any commonly discarded industrial or non industrial items which are rather easy to get a hold of perhaps form ebay - which contain high power RF JFETs?

author: LaserTazerPhaser
author_rank: Regular Contributor
timestamp: May 13, 2019, 10:58:10 am
content: Mostly anything relating to a power RF JFET is almost certainly going operate far greater frequencies than any typical power RF MOSFET. The majority of HEMT transistors appear to be JFETs and very few other types.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 13, 2019, 01:39:26 pm
content: Are you answering your own question, or answering his..?Tim

author: Nitrousoxide
author_rank: Regular Contributor
timestamp: May 19, 2019, 04:20:23 pm
content: Whare frequency ranges are you expecting to work in? I take it frequency range is the main criteria here? How about power?I'm sure you can get some LDMOS devices that would be suitable for the power/frequency.
RF module for an AVR project - Page 1
Forum section: electronics / beginners

author: ElCerrajero
author_rank: Newbie
timestamp: August 31, 2023, 04:11:14 pm
content: I want to build a controller with a joystick to control a dc motor (direction and speed) remotely. I am looking for the best module to use in communication and the most popular is the NRF24 but they also say that they cause many errors and that they are not able to make it work. My question is if anyone knows of a somewhat more reliable alternative, I'm just starting out and I would like an option that isn't too problematic when it comes to making it work.

author: liaifat85
author_rank: Regular Contributor
timestamp: September 03, 2023, 11:14:59 am
content: Here are some suggestions that you can take a look at:https://wonderfulengineering.com/10-best-rf-modules-for-arduino/

author: Infraviolet
author_rank: Super Contributor
timestamp: September 03, 2023, 06:35:58 pm
content: Depending on what it is, you could also consider TV remote style infrared LEDs and receivers (with automatic filtering for 38KHz, or similar, modulated signals) if your application is, in practice, always within line-of-sight.As for the errors you talk of, how about putting some checksums on the messages to be sent, so any corrupted ones will be ignored, and then transmitting the messages multiple times. This way you get a good chance of one of them getting through uncorrupted,and any which are corrupted aren't acted upon. Also look up about hamming distances, there are ways to send self-correcting messages in far less bytes than you'd expect, so even if all your messages were corrupted by 1 bit, the receievr might be ableto recover the meaning. This checksumming and/or error correction can apply to messages sent over RF, IR, sound, visible light or even along wires.You will need a microcontroller (arduino device or equivalent) on both the sending (reads joystick, transmits RF data) and receiving (reads in arriving RF data, operates motor accordingly) ends, each running a different program you'll write.
Rf module stops working in between transmission! - Page 1
Forum section: electronics / beginners

author: electroguy98
author_rank: Newbie
timestamp: June 17, 2019, 10:32:04 am
content: Hello. I'm trying to make a gesture controlled car using adxl335 and atneag328p. 433mhz rf module is being used for wireless transmission along with ht12e and ht12d. The code and schematic is fine and works well with LEDs. However, when i connect motors using l293d they start spinning when i tilt my hand forward but don't stop when i return my hand to rest position. It's like the reception has stopped entirely and is restored by manually stopping the motor. I've tried different supply for RX and l293d but doesn't work. I've also tried soldering ceramic caps across motor terminals, decoupling caps across vcc and gnd of ic, electrolytic caps but nothing worked( please guys help me out with this as I'm almost done with this project.Thanks

author: mikerj
author_rank: Super Contributor
timestamp: June 17, 2019, 10:38:58 am
content: If you replace the motor with a resistive load and measure voltage across it, does the circuit behave correctly? If yes then the problem is interference from the motor; to fix that you are going to have to pay careful attention to supply decoupling and to grounding.

author: Zero999
author_rank: Super Contributor
timestamp: June 17, 2019, 11:09:51 am
content: Yes, it sounds like the motor is emitting radio waves which are interfering with the transmitter. Try connecting a ceramic capacitor from each of the motor terminals to its metal case. If that doesn't work, add a ferrite bead with a few turns wrapped round it in series with both motor terminals.

author: Etesla
author_rank: Regular Contributor
timestamp: June 17, 2019, 03:17:33 pm
content: Also try adding a flyback diode across the motor terminals, and maybe an RC snubber circuit.
RF MOSFET in LTSpice - Page 1
Forum section: electronics / beginners

author: init
author_rank: Contributor
timestamp: May 24, 2016, 10:02:12 am
content: Hey guys, I'm trying to do some RF simulation in LTSpice and can't seem to find any MOSFETs that have RF capabilities. Most of them seem to have a transition frequency below 100MHz and I need one with higher for a LNA. Any suggestions from the standard massive list that comes with LTSpice?

author: danadak
author_rank: Super Contributor
timestamp: May 24, 2016, 01:22:45 pm
content: Ordinary Spice sims not suitable for RF work as it does not handle boardlayout which is a significant contributor in RF design to performance.Take a look at this (google RF simulator)http://www.skyworksinc.com/downloads/press_room/published_articles/ICSICT_102014.pdfAgilent seems to be widely used.Regards, Dana.

author: Marco
author_rank: Super Contributor
timestamp: May 24, 2016, 03:15:15 pm
content: NXP has models for their BF9XX models of dual gate MOSFETs, Simetrix has them in their standard library and even their free version can simulate relatively complex circuits with them.

author: richard.cs
author_rank: Super Contributor
timestamp: May 25, 2016, 09:26:35 am
content: You very definitely can model RF in SPICE but you need to explicitly add all the of the parasitics of your components and layout so you get quite an ugly hard-to read schematic.
RF PCB layout questions - Page 1
Forum section: electronics / beginners

author: that_guy
author_rank: Contributor
timestamp: October 21, 2015, 02:41:25 pm
content: Hi, for a hobby project I've decided to step outside my digital comfort zone and implement an FM (88-108MHz) broadcast receiver around one of Silabs' devices, probably theSi4770. I've never 'done RF' before so I've been researching best practices and have so far decided to use a 4 layer board arranged as [component,GND,split power,routing].The questions I'd like to ask are around grounding. I will have an uninterrupted ground plane at layer 2 so do I need to split it into RF and digital regions? Where online opinion can be found that comes down onto one side of the fence the consensus seems to be for uninterrupted instead of split. But the SiLabsEV boardseems to have a split in the copper (see attached and fig. 37-40 inPDF) that runs through all 4 layers with no obvious footprints that connect the two planes. Are they relying on the metal can to join the two halves do you think?I assume that the top layer should have a ground fill with a grid of vias. Correct? I know about the clearance rules between the fill and the antenna microstrip lines but should the top fill extend out to below the antenna connectors? Silabs do it; but I've seen other designs where the top fill does not extend out to below the connectors.Guard traces and via fences. Most designs seem to feature the RF IC and its dependencies fenced in with an exposed guard trace and then boxed under an aluminium can. Should the LDO that supplies the analog (and/or digital) circuits be within this protected region?Any words of experience would be helpful.
RF Probe help  - Page 1
Forum section: electronics / beginners

author: Flump
author_rank: Frequent Contributor
timestamp: April 22, 2015, 02:55:11 pm
content: I have a Fluke RF probe, it's my 2nd as I blew the first one upThe highest RF voltage it can read is 30Vrms, I would like to read much higher Voltages with itlike 100+Vrms but I would like to keep the accuracy of it.is there something I can plug inline with it that will do this ?thankshttp://en-us.fluke.com/products/all-accessories/fluke-85rf.html#techspecs

author: ivaylo
author_rank: Frequent Contributor
timestamp: April 23, 2015, 06:28:03 am
content: What are you measuring? If I were you, I would be careful with those 100Vrms, that probe blew up for a reason. You may be able to cook up a voltage divider, but better give us more details.

author: tautech
author_rank: Super Contributor
timestamp: April 23, 2015, 07:04:42 am
content: Have you not got a scope?
RF: Silly U.FL to SMA pigtail question - Page 1
Forum section: electronics / beginners

author: rthorntn
author_rank: Frequent Contributor
timestamp: October 27, 2024, 11:11:37 pm
content: Hi,I'm messing about with LoRa, so I have a radio connected to a Pi, does the threaded SMA connector on the pigtail actually have to be secured to metal to form any part of the connection, I don't think it does but the question is niggling at me?Thanks.

author: tooki
author_rank: Super Contributor
timestamp: October 29, 2024, 07:19:50 pm
content: If you are using a metal enclosure for shielding, then you’ll want for it to make contact so the case will act as a shield. The antenna will work regardless of how the SMA is mounted.

author: bson
author_rank: Unknown
timestamp: October 31, 2024, 06:45:57 pm
content: It doesn't, although if you have an enclosure it's a good idea to use a nut just to hold it in place. If it's a metal enclosure it's probably already grounded so will act as a shield (and if not grounded, make sure to do so), and adding another path between ground and the antenna isn't going to make much difference. The SMA plug will only use about half of the available thread. Note that SMA has a torque spec, which for casual applications like this can be stated as "until you feel resistance with a 3 inch spanner wrench", ballpark speaking. Err on tightening lightly.
RF Simple Design Issue  - Page 1
Forum section: electronics / beginners

author: Anthonycolossus
author_rank: Newbie
timestamp: May 02, 2023, 12:01:21 pm
content: Hello everyone, so i have recently found this design on mod wiggler and i wanted to implement it to another design im doing, anyway everthing on the PCB is working fine exceot for this design, the thing is abolutely dead, im using 1N5819HW diodes and the LT07, the op amp is working fine and the diodes too, the guy who made it said is working fine, but i coulndt get to work not even on my breadboard.anyone have any clue? or is practical with RF receivers?attached the original and the eagle schematic im working on (i know R17/18 shouldnt be there)

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 02, 2023, 02:18:48 pm
content: What frequency are you trying to sense? What kind of antenna?1N5819s have about 100pF each so you'll need a rather low impedance antenna to get any RF detected by them.Tim
RF switch  - Page 1
Forum section: electronics / beginners

author: abhijitrkjr
author_rank: Newbie
timestamp: September 06, 2024, 10:22:24 pm
content: Hi. I want to make an rf switch. I have two rf signal inputs and one output. I want to channel one of the inputs to the output using a TTL. The frequency range of my rf signal is 2kHz-1MHz and amplitude is 10V peak to peak. Any ideas how can I achieve it?

author: themadhippy
author_rank: Super Contributor
timestamp: September 06, 2024, 10:34:28 pm
content: simplest way would be a relay

author: G0HZU
author_rank: Super Contributor
timestamp: September 06, 2024, 11:21:01 pm
content: CD4066 or CD4053 ? You would have to add a level shifter from TTL to the required control voltage for the CD4066 or 4053 when running it from about 15V. I think it can cope with 10V pkpk at 1MHz but I can’t be certain.

author: abhijitrkjr
author_rank: Newbie
timestamp: September 08, 2024, 12:29:36 am
content: I want the switching speed to be in microsecond. Relay switches are slower

author: ArdWar
author_rank: Frequent Contributor
timestamp: September 08, 2024, 03:12:17 am
content: Switching 1MHz at microseconds is a bit redundant, no?1MHz isn't that high of a frequency. Almost any CMOS analog switches can do that (and more). Maybe DG419 if you only want SPDT and no need for T switches or unused input termination.

author: Solder_Junkie
author_rank: Frequent Contributor
timestamp: September 08, 2024, 08:12:32 am
content: I have used a 4066 to route RF in a home made transceiver where the frequencies involved were up to 20 MHz. The switching capability is +/-7.5V and switch times of a few nS.Data sheet:https://www.ti.com/lit/ds/symlink/cd4066b.pdfSJ

author: Infraviolet
author_rank: Super Contributor
timestamp: September 08, 2024, 03:14:26 pm
content: Doesn't the 4066 give quite a spike/dip (of a few tens to hundreds of nanoseconds length) on the passed-through signal whenever you switch it? So if you're only switching infrequently you're fine, but if you're switching very often you'll find these spikes replacing non-insigificant perods worth of the signal you're switching.

author: geggi1
author_rank: Frequent Contributor
timestamp: September 09, 2024, 05:10:47 am
content: look in to FET rf switches.

author: Zero999
author_rank: Super Contributor
timestamp: September 09, 2024, 07:17:10 am
content: Quote from: abhijitrkjr on September 08, 2024, 12:29:36 amWhat's the load?
RF Transmitter (433MHz) without using an HT12E and receive it using an HT12D on - Page 1
Forum section: electronics / beginners

author: Mahmoud_Adel
author_rank: Newbie
timestamp: January 29, 2025, 02:00:56 pm
content: I am trying to send data from an Arduino using an RF Transmitter (433MHz) without using an HT12E and receive it using an HT12D on the receiver side. I connected the RF Receiver to the HT12D, but the signal is either not received or not correctly decoded. I attempted to manually adjust the timing and analyze the signal, but I could not establish a stable connection.What I Have Done:Used Arduino instead of HT12E to send data directly through the RF Transmitter.Ensured that HT12D is correctly wired on the receiver side.Tried adjusting the Pulse Width manually to match the expected timing of HT12D.Used a 51kΩ resistor between OSC1 & OSC2 on the HT12D to set the decoding speed.The Valid Transmission (VT) Pin on HT12D does not turn ON, indicating that the signal is not being correctly decoded.What I Need Help With:The correct timing settings so that HT12D can properly decode the signal coming from Arduino.Any successful attempts or examples of sending data from Arduino to HT12D without using HT12E.Whether there is a library that can simulate HT12E on Arduino to simplify transmission.

author: wasedadoc
author_rank: Super Contributor
timestamp: January 29, 2025, 02:12:29 pm
content: Start by omitting the RF Tx and Rx, ie connect Arduino to HT12D. Does that work?Do you have an oscilloscope?

author: ahsrabrifat
author_rank: Regular Contributor
timestamp: January 29, 2025, 05:40:43 pm
content: This is quite detailed. You can follow this tutorial.https://randomnerdtutorials.com/rf-433mhz-transmitter-receiver-module-with-arduino/

author: gardner
author_rank: Regular Contributor
timestamp: January 30, 2025, 08:37:24 pm
content: One thing I have noticed is that the turn-on time for the cheap 433Mhz radios can be substantial -- 10us to 150us is what I've seen, between the point the data line goes high and the RF output reaches 1/2 of its nominal power. You may have to include timing adjustments in your signalling to compensate. Here is one example with a ~110us delay. Channel 1 is the TXD signal, Channel 2 is the RF output. You can see the delay in the cursors and it's quite substantial relative to the signal pulse. I think the delay can be battery level and temperature dependent too.

author: Terry Bites
author_rank: Super Contributor
timestamp: February 04, 2025, 11:33:15 am
content: Yeah, I've seen that too. Delay the data for a a mS.
RF transmitter to transmit signal over a long distance? - Page 1
Forum section: electronics / beginners

author: Refrigerator
author_rank: Super Contributor
timestamp: January 16, 2016, 04:42:24 pm
content: This thread is a follow up from my first one where i managed to make a simple PPM decoder using discrete transistors.Now i want to make a transmitter to transmit PPM signal over a long range at the 27 MHz band, i'm aiming for more that 50m range, 100m would be about ideal.I previously tried to modify an existing R/C RX and TX that gave me range of about 30m before, which is quite good for a simple toy.Unfortunately i managed to brick both the receiver and the transmitter in the process.The way i test my RF circuits is with a simple RF probe that i made, i pretty much poke a RF point and see if the LED lights up, it's simple but effective.Now i want to make a new transmitter and receiver, the receiver part i already worked out and will use a simple regenerative receiver circuit although i have many questions regarding the output stage of the transmitter.I've reverse engineered a few TX output stages and looked up a few circuits online but i can't get my head around one thing in particular.What i'm thinking so far is to make a simple pierce crystal oscillator like W2AEW made on his YT channeland feed the signal to an output stage, but also have a transistor in between to disable the RF to generate the AM signal.The thing is I often notice PI networks right at the antenna output and when i want to calculate the values to give me the maximum output power i just don't know what to look for, i know that the PI network gives a controlled impedance but i don't know what impedance would work best.Sounds simple in theory but it's quite a fiddle to get it to work in practice, especially when appropriate test gear is not available, although surprisingly enough during experimenting i found out that my UT136B can measure the 27MHz frequency no problem.I would like to find out what circuit configurations and parameters give the best output at the antenna.I would also like to know if the signal shape ( square, sine, half-sine ) and the output transistor bias could cause significant effect to the output of the transmitter.Any suggestions, articles, pointers or circuits are appreciated.Thanks.
Rf/ham radio- variable caps in the uk?? - Page 1
Forum section: electronics / beginners

author: daemonix
author_rank: Contributor
timestamp: August 03, 2014, 09:28:58 pm
content: Hello,Where do you get variable caps (i have only found some trimmer not caps for the front panel) in the Uk or Europe?ThanksTasos

author: rob77
author_rank: Super Contributor
timestamp: August 03, 2014, 09:54:41 pm
content: to be honest.. i haven't seen such a thing for a looong time.. trimmer capacitors are common, but tuning variable capacitors not really (even if someone still manufacture them, those must be freaking expensive).

author: IanB
author_rank: Super Contributor
timestamp: August 03, 2014, 09:57:38 pm
content: Maybe you can reclaim them from old radios?

author: Andy Watson
author_rank: Super Contributor
timestamp: August 03, 2014, 10:04:45 pm
content: Try searching for "Jackson variable capacitor". The last time I looked (hmm, may be a decade ago!) the original company were still in business. I've no idea who or where they would be stocked now-a-days. You might get lucky and find some NOS.

author: daemonix
author_rank: Contributor
timestamp: August 03, 2014, 11:03:58 pm
content: Thanks andy! Your pointer was great! I found a site that seems to have air caps.

author: rob77
author_rank: Super Contributor
timestamp: August 03, 2014, 11:34:11 pm
content: those prices !if i would knew it 20 years ago, i would never ever trash a single one

author: DonRon
author_rank: Regular Contributor
timestamp: August 04, 2014, 05:33:27 pm
content: There are some companies in Germany which offers variable caps.http://www.schubert-gehaeuse.de/prod04.htm(offers kits - u have to assemble the caps by urself)and another company which also offrers variable inductorshttp://www.winklerantennenbau.de/konden.htmandhttp://www.die-wuestens.de/eindex.htmCheers,Ron

author: German_EE
author_rank: Super Contributor
timestamp: August 04, 2014, 09:17:15 pm
content: http://mainline-group.com/?option=com_content&task=section&id=12&Itemid=38They took over the production equipment of Jackson Brothers who used to make variable capacitors and reduction drives.
RFID - Page 1
Forum section: electronics / beginners

author: zerorisers
author_rank: Regular Contributor
timestamp: March 22, 2015, 03:43:22 pm
content: Hello zerorisers here.I have been given a project from the CEO of a small company called drift America RC. Originally it was just going to be an ultrasonic sensor to see how close cars drifted to the goal with lights to indicate how many points they have received. He has added on a few more requests such as a scoreboard and RFID to indicate multiple rc cars that pass along the track. We are building the prototype using arduino and RFID is not one of my specialties. How would I go about this in arduino? With no libraries as everything will be transfered to smaller and cheaper microcontrollers.

author: sacherjj
author_rank: Frequent Contributor
timestamp: March 22, 2015, 03:59:33 pm
content: I would use 900 MHz Gen 2 style tags for the distance reading. Then you need a reader. I've used the ALR-9650 from Alien and it seems to be the best value for the money. It has the ability to mount a second antenna to read from multiple locations on the track. This allows serial and network reading. You might be able to get this going with Arduino, but it is going to be much faster initially to run on a PC. Setting up this with PoE to a network makes install simple with no local power.This reader can be setup to push new tags it reads to an IP address, while constantly scanning. It will queue up the tags and feed a stack of recently seen tags. Individual label tags can be under a dollar. You would need to make sure that they are placed away from metal (which shouldn't be a problem on RC cars, with mostly plastic bodies.)I'm talking to this reader with a simple Python script over ethernet. We will also be using it to detect when things get close and send indications to an IP address.http://www.alientechnology.com/readers/smart-antenna/