hybridfree/eevblog-posts huggingface dataset:
DC blocking caps selection for a Filter(Band pass). - Page 1
Forum section: electronics / rf-microwave

author: madhu.wesly01
author_rank: Regular Contributor
timestamp: March 26, 2019, 02:09:35 pm
content: Hi,I am going to use the below Filter in my RF application. One thing I could not understand is: finding out the DC blocking capacitors' values which are recommended as a part of supporting circuit. Please, let me know if I should use the DC blocking caps, if yes, what should be the capacitors values??https://www.johansontechnology.com/datasheets/0868LP15A020/0868LP15A020.pdfTIA!Best regards,Wesly.

author: chrisl
author_rank: Regular Contributor
timestamp: March 26, 2019, 05:50:04 pm
content: The IN/OUT ports of the filter are DC short to the GND.If your circuit does not have any DC component on those ports you do not need the DC block caps.Otherwise 100 pf ~ 200 pf range of caps will do.
Validation required: Connecting PA boost to UART interface! - Page 1
Forum section: electronics / rf-microwave

author: madhu.wesly01
author_rank: Regular Contributor
timestamp: March 26, 2019, 07:13:09 am
content: Hi everyone,Can anyone give me some clarity on the below statement -Connecting PA04 (UART TX) and PA05 (UART RX) pins to the PA_Boost pad directly can emit higher order harmonics.How can people connect PA boost to UART interface, is this valid statement???Connecting PA04 (UART TX) and PA05 (UART RX) pins to the PA_Boost(SX1276) pad directly can emit higher order harmonics. If these traces are connected to a PC with an un-shielded cable, the cable and these two traces can potentially become an antenna for the harmonic. Therefore, it is recommended to use a low pass filter on each pin to suppress the harmonic (see the following figure). Ideally, these filters must be placed right next to the PA04 and PA05 ports of the micro-controller, inside the metal shield. Keeping this filter away from the radio reduces the suppression on harmonics.TIA,Regards,Madhuwesly.
Low phase noise 400 - 500MHz sources? - Page 1
Forum section: electronics / rf-microwave

author: rf-fil
author_rank: Regular Contributor
timestamp: March 22, 2019, 04:55:51 am
content: Hi there - here's an interesting one. Besides purchasing an expensive (but brilliant) Wenzel source, is there a cheaper / easier way to get a source that produces below to -130dBc/Hz at 10kHz offset, when running at 500MHz? Preferrably tunable, but OK if not. In the past, I'd just build an overtone crystal oscillator and multiply it up, which is what the Wenzel units do as well, but.. I'd prefer to avoid building my own thing yet again. Am I missing any other options?I'm thinking a low noise PLL evaluation board from the likes of TI or Analog Devices..

author: hendorog
author_rank: Super Contributor
timestamp: March 22, 2019, 06:03:54 am
content: Have you seen these:http://www.crystek.com/microwave/spec-sheets/rfpro/RFPRO.pdf

author: rf-fil
author_rank: Regular Contributor
timestamp: March 24, 2019, 09:35:14 pm
content: Good one, thanks.

author: Mechatrommer
author_rank: Super Contributor
timestamp: March 25, 2019, 01:26:26 am
content: Quote from: hendorog on March 22, 2019, 06:03:54 amsearching for it, maybe their VSCO inside...500MHzhttps://www.digikey.my/product-detail/en/crystek-corporation/CVS575-500.000/744-1053-ND/1643968https://www.digikey.my/product-detail/en/crystek-corporation/RFPRO33-500.000/744-1325-ND/20746511GHzhttps://www.digikey.my/product-detail/en/crystek-corporation/CCSO-914X-1000.000/744-1254-ND/1767708https://www.digikey.my/product-detail/en/crystek-corporation/RFPRO33-1000.000/744-1326-ND/2074652
designing the simplest 433Mhz AM receiver - Page 1
Forum section: electronics / rf-microwave

author: apblog
author_rank: Regular Contributor
timestamp: March 21, 2019, 04:33:39 am
content: Topic moved here:https://www.eevblog.com/forum/rf-microwave/advice-needed-for-experimenting-with-simple-rf-circuits/
Uniden HH980 marine handheld - Page 1
Forum section: electronics / rf-microwave

author: stj
author_rank: Super Contributor
timestamp: March 13, 2019, 03:59:55 am
content: looking for schematics.rx is fine,but when i tx i get a scream from the speaker - so rx is not muting.no idea if it's actually tx'ing over the air while it does this!this is pretty old, and Uniden docs are pretty hard to find anyway.
NFC over Pin Header - Page 1
Forum section: electronics / rf-microwave

author: snx
author_rank: Contributor
timestamp: March 07, 2019, 08:55:59 am
content: Because of restricted space, it would be either possible to create a pcb containing a NFC PCB Antena + Reader frontend and connect to the master board with a pin header (2,45mm -6pin SPI). This soultion would provide very short connection from the NFC-Chip with matching network to the Antenna (only around 1mm). But because of restrcted space, the antenna would be shrinked by the NFC Chip + PartsThere would be the possibility to use the full pcb space for the antenna, and connect the antenna via a 2.54mm 2-pin Header to another PCB. The size of the Antenna would be nearly doubled then.But i've read that nfc circuits are problematic in case of inpedance matching between antenna network and antenna.Is it possible use to connect the antenna via the pins or would it be a big risk / problematic in series production.?

author: Fred27
author_rank: Unknown
timestamp: March 07, 2019, 11:58:55 am
content: I think you'd get away with it, even if it's not ideal.A better solution might be to have the antenna and matching components on the small PCB and connect it to the main board via uFL connectors and a short coax cable. I'd this feasible for your setup?

author: snx
author_rank: Contributor
timestamp: March 07, 2019, 01:05:57 pm
content: I thought of this, but the coax cable would have to be extremly short, the boards are only 10-15mm away and the boards are stacked, so there is little space for a cable and would be tricky to connect

author: Andrey_irk
author_rank: Regular Contributor
timestamp: March 11, 2019, 08:46:49 am
content: Don't see any problems here.You'll have to match an antenna if you decide to design your own variant or substantially modify the existing one, but if the length of the interconnection is relatively small, then, likely, you won't have to change anything at all. After all, it's 13.56MHz.
Homebrew open source automatic antenna tuner works! - Page 1
Forum section: electronics / rf-microwave

author: profdc9
author_rank: Frequent Contributor
timestamp: March 10, 2019, 03:43:05 pm
content: Hello,I have made an open source automatic antenna tuner. It is a modular design, so I hope that it can be used to experiment with different configurations, integrating with the antenna, etc.The project is athttp://www.github.com/profdc9/ModularTunerYou can see a video of it in action:https://youtu.be/jCvtdcwGg9AThere is a main controller unit that is connected to inductor and capacitor bank modules. Up to 8 modules can be connected at once to the controller. There are two right now that forms an "L" network.73,DanKW4TI

author: radiolistener
author_rank: Super Contributor
timestamp: March 11, 2019, 05:42:46 am
content: What is impedance range which can be matched with this tuner for 1-30 MHz?Where did you get modules?
Filter for 2.4GHz ISM Band?  - Page 1
Forum section: electronics / rf-microwave

author: conducteur
author_rank: Regular Contributor
timestamp: March 06, 2019, 07:16:48 pm
content: Hello,We have a device that generates noise from DC up to a few GHz. We want to filter the output between 2.4GHz and 2.5GHz.We don't have strict requirements for this filter.At that frequency inductors and capacitors have values that don't exist (or are equal to parasitic inductance/capacitance)What are other options to get noise in the ISM band?

author: Ice-Tea
author_rank: Super Contributor
timestamp: March 06, 2019, 07:53:01 pm
content: The output... of what? There are tons of 2.4GHz -2.5GHz bandpass filters for Wifi, BT and whatnot. Is this what you mean?https://www.digikey.com/products/en/filters/rf-filters/844?k=RF+filter&k=&pkeyword=RF+filter&sv=0&pv1989=0&sf=0&FV=ffe0034c%2C22c03fe%2C22c061d%2C22c0683%2C22c0684%2C22c074d%2C22c07e4%2C22c07f2%2C22c07f6%2C22c0269%2C22c1e6f%2C22c1e70%2C22c1e81%2C22c2014%2C22c0347%2C22c0378&quantity=&ColumnSort=0&page=1&pageSize=25

author: rhb
author_rank: Super Contributor
timestamp: March 10, 2019, 02:11:42 pm
content: Another option is a shorted coaxial stub. Open end is a notch, shorted end is a band pass. At 2.45 GHz, a 1/4 wave is ~ 30.6 cm in free space, so a short length of air dielectric hardline should be pretty good.Here's a brief discussion of it:http://dl4xav.sysve.de/coax.filter/coax-filter.html
New precision n connectors for coaxial waveguide filters? - Page 1
Forum section: electronics / rf-microwave

author: coppercone2
author_rank: Super Contributor
timestamp: March 07, 2019, 05:33:23 pm
content: I have a bunch of coaxial filters for region between 2 to 18 ghz.They mostly have n or sma connectors. They are from various manufacurers.Some of them i.e. old hp thread in. Others are soldered in.Are there any known standards for these types of connectors or are they precision machined for individual applications? These are lpf and hpf. I also have one waveguide one with sma. The rectangular ones have standard bulkhead launchers.Are they typically brazed or soldered in?Some of these threads are severely shady and i would like to make a roadmap around themJig grinder to repair 50$ of shit. Ill fucking do it if necessary

author: coppercone2
author_rank: Super Contributor
timestamp: March 07, 2019, 07:52:49 pm
content: some of them look like they can unscrew too but their extremely tight. Do they need to be unscrewed hot maybe? Might they some how solder or glue the center conductor in after threading? i.e. apply solder paste and heat the whole thing, or put a dash of conductive epoxy on it.When I fixed a isolator before, despite having a bulkhead screw connection, the center pin was actually glued to the ceramics etc inside. Kinda fixed it i dunno though it was

author: KJDS
author_rank: Super Contributor
timestamp: March 07, 2019, 08:27:50 pm
content: They may be push fit, which were a cheaper connector than one with a flange. This did mean you needed a press rather than a screwdriver to fit the connector, but if you had a press then it was quicker, so lower production cost.

author: coppercone2
author_rank: Super Contributor
timestamp: March 08, 2019, 03:15:04 am
content: well it looks like someone on Ebay solved this issue for me.Instead of going through crazy efforts I will categorize them and put sacrificial connectors on all of them so long they don't have big flaws. I noticed someone already did this with one of the HP LPF, they managed to find a nice set of adapters that fit well with the original filter. I actually thought it was a factory job at first, if not for the paint difference.It did not occur to me because you need two of them per filter.
How to design BAW filter for LTE co-existence in Dual-band WiFi ?. - Page 1
Forum section: electronics / rf-microwave

author: sangar
author_rank: Regular Contributor
timestamp: March 04, 2019, 06:21:54 am
content: Hello All,I have a dual band WiFi module which does not support LTE coexistence internally.So, I want to put a BAW filter between WiFi trx and Antenna(Dual band). But, I don't see a BAW filter that can pass both 2.4 GHz and 5GHz WiFi channels. If I put a 2.4 GHz BAW filter, I would lose 5GHz WiFi signals. Please, anyone, tell how to do this?Thanks,Sangar

author: sangar
author_rank: Regular Contributor
timestamp: March 05, 2019, 04:42:48 am
content: Could anyone give their suggestion on this ?.
Quarter Wavelength Transformer on PCB - Page 1
Forum section: electronics / rf-microwave

author: josefmtd
author_rank: Contributor
timestamp: March 04, 2019, 03:49:31 am
content: HelloI am trying to create a quarter-wavelength transformer for my VHF power amplifier application with RF switch PIN diodes and quarter-wavelength transformer. I am making a lumped elements quarter wavelength transformer with a wire-wound inductor and two MLCC capacitors (fixed C0G dielectric).But I am having a trouble realizing this circuit on a PCB and managed to end up with this attempt as shown in attachment. I have two quarter-wavelength transformers in this PCB, as suggested in my previous thread. I tried using a polygon to realize the connection between two inductors, in doing so, I created a capacitance that is (between L6 and L8). Is it feasible to connect two RF components with a polygon rather than a transmission line? Since transmission line with a two layer board is about 3 mmI have a pi filter between the RF switch and the antenna, this is also connected via a polygon, is this better done with polygon instead of a transmission line as well?Thanks for your inputs
Are cheap chinese RF toroids usable? - Page 1
Forum section: electronics / rf-microwave

author: necessaryevil
author_rank: Regular Contributor
timestamp: February 13, 2019, 05:32:29 pm
content: I've ordered some chinese toroids, T130-2 and T130-6 for a very low price. I want to test them to see if I can use them for a low pass filter (=< 400w). I'm curious and I can't wait for them to arrive, so I am asking: Has anyone ever tested cheap chinese RF toroids?I'm planning to test the AL; although I don't expect this parameter to be the problem. I'm more interested in core loss and power handling, but I'm not sure how to test this since I don't own a spectrum analyzer.

author: radiolistener
author_rank: Super Contributor
timestamp: February 16, 2019, 07:12:36 pm
content: they are slightly worse than amidon, but works ok

author: CJay
author_rank: Super Contributor
timestamp: February 18, 2019, 10:49:01 am
content: Haven't even seen these, have you a link to a source?

author: radiolistener
author_rank: Super Contributor
timestamp: February 18, 2019, 10:58:15 am
content: https://vvvv.aliexpress.com/store/group/Iron-Power-Cores/346423_507303475.html

author: JohnPen
author_rank: Regular Contributor
timestamp: February 18, 2019, 03:02:29 pm
content: I purchased 4x25 piece lots of toroids from kitsandparts in the US recently as they seemed quite low in price. Sadly by the time I paid international postage plus being charged an import tax in the UK they were no longer particularly cheap. Final average price £0.43 each for T37-2,6 50-2 and FT37-43 sizes. $21 for the 100 toroids, $16 postage and then £13.48 import tax. Was it just bad luck or is it more likely if you buy from the US? Numerous purchases from China in similar price range never had an import charge.

author: CJay
author_rank: Super Contributor
timestamp: February 18, 2019, 03:47:42 pm
content: If you buy regularly you might want to consider either AMTools/SPRATReader in Wigan who are eBay only (and a regular at GQRP/Ham rallies) or perhap joining the GQRP club might be worth your while for the club sales?

author: JohnPen
author_rank: Regular Contributor
timestamp: February 19, 2019, 08:46:38 am
content: Thanks for the information on the UK sources CJay. However having bought so many toroids as a one off purchase I believe it will be a long time before I will need any more.John

author: lordvader88
author_rank: Frequent Contributor
timestamp: February 22, 2019, 03:19:14 pm
content: Well I least they have labels rather than just the color. I bought some greens and yellows so far from ebay. I want to get a selection of quality ones, but they are pretty expensive it seems, for some bad reason.

author: necessaryevil
author_rank: Regular Contributor
timestamp: March 02, 2019, 11:42:00 am
content: The 130-6 Toroids are in. the AL seems a bit higher than usual. One of the T130-6 toroids is now with a friend, he has way more experience and equipment and he 's goint to do some more testing.T130-6
Hp crystal detectors - Page 1
Forum section: electronics / rf-microwave

author: xwarp
author_rank: Frequent Contributor
timestamp: February 25, 2019, 08:38:04 am
content: I'm drawing a blank on trying to search for answer to this possibly basic question, so I'll ask it here.When would you use a positive polarity output, or a negative polarity output detector?

author: Tony_G
author_rank: Super Contributor
timestamp: February 26, 2019, 06:41:39 am
content: Interesting question, I think that most HPAK gear was designed to use negative detectors and thus they were the standard. As far as I'm aware the only reason to use a specific polarity is it the downstream device/circuit needs that polarity (I.e. No actual detector use case drives it).Willing to be enlightened on this though as I've only used the negative ones with my gear.TonyG

author: LaserSteve
author_rank: Super Contributor
timestamp: February 27, 2019, 10:55:09 pm
content: I'll ask if any of the former HP RF staff on a certain mailing list know why...Steve

author: LaserSteve
author_rank: Super Contributor
timestamp: February 28, 2019, 06:36:09 pm
content: The replies are trickling in on the Microwave Mailing List...Results so far:0. TraditionI. Negative bias is better for vacuum tube based controls or instruments. Pulling the grid voltage downwards is the easy way to get results.2. Negative bias allows for having one less diff amp or op-amp and the associated poles/zeros/transfer function in a leveling loop.Steve

author: Bud
author_rank: Super Contributor
timestamp: February 28, 2019, 07:11:04 pm
content: Isn't it the trivial better immunity to noise, as most of the noise in the system would have positive swing in respect to ground.

author: LaserSteve
author_rank: Super Contributor
timestamp: March 01, 2019, 10:25:06 am
content: After asking those who would know... On the microwave mailing list.. Good question, it had baffled me as well for a long time.Two Quotes:"The answer to the detector question should be obvious.The backside of a diode die is the cathode which easy to bond to ground and leaves the anode as the negative output.For a positive detector the die must be bonded to an insulator like ceramic to reverse the polarity."KI4NPV"I don't claim to have the definitive answer, but I have always suspected that the preponderance of negative detector is influenced by the diode construction. The majority of Schottky diodes are fabricated on N-type silicon. However, when zero-bias operation and low flicker noise are required such as in connectorized instrument detectors, p-type doping is substituted for n-type (HP/Avago appnotes AN1088 and AN956-3). The bottom of the p-type chip is the anode, and the hot end (connected to RF) is the cathode - hence, the negative output from a shunt detector."73, 9W2LCSteve
RF transmission lines on a pcb - Page 1
Forum section: electronics / rf-microwave

author: LeLyfa
author_rank: Newbie
timestamp: February 26, 2019, 07:35:06 pm
content: Hi,I'm currently working on an antenna-switching project (f = 1 up to 30MHz), which includes, that I need a Z0of 50 ohms in my transmission lines.I'm planning to get the PCBs manufactured by JLCPCB, they are providing every characteristical data I need, to calculate the width of the Trace in KiCAD to get to Z0=50.However, the calculated trace width is .3mm (&1oz. copper), but I need to get 100W through it and I think that .3mm is too thin.Red is for RF and I've got a ground plane between RF & "data":http://prntscr.com/mqia4eHow could I solve this problem?Thank you for help.

author: radiolistener
author_rank: Super Contributor
timestamp: February 26, 2019, 08:04:13 pm
content: At a glance you can increase height of dielectric (use thicker PCB to increase distance from trace to the ground).It will allow you to increase trace width.For example:dielectric height = 0.16 mm; trace height = 0.0347 mm; trace width = 0.3 mm => 50 Ohmdielectric height = 0.506 mm; trace height = 0.0347 mm; trace width = 1 mm => 50 Ohm

author: radioactive
author_rank: Regular Contributor
timestamp: February 26, 2019, 08:05:57 pm
content: Use layer 3 for the microstrip ground reference. This will allow you to make the trace much wider and will keep manufacturing tolerances from becoming an issue (core material thickness is consistent between runs).

author: LeLyfa
author_rank: Newbie
timestamp: February 26, 2019, 08:54:07 pm
content: Thank you very much for this idea.I'm now able to make my trace 2,28mm thick. I think this width should be sufficient. =D
Compact variant of SM1000 digital voice adaptor for use inside equipment - Page 1
Forum section: electronics / rf-microwave

author: richard.cs
author_rank: Super Contributor
timestamp: February 11, 2019, 09:16:22 pm
content: I've been working on a simplified, more compact, version of the SM1000 FreeDV Adaptor. For those who don't know it's a small box that translates between analogue voice and baseband digital modulation. It uses the codec2 audio codec, current firmware supports the most common 1600 bps mode, with a possible update in the future supporting a 700 bps mode. The hardware is an open design (TAPR), detailed here:http://www.rowetel.com/?page_id=3902designed by Rick Barnich KA8BMA and David Rowe VK5DGR.Basically my intention was to strip out the isolated interfaces and the power supply, and compress it down to a dual-in-line module that can more easily be built into other equipment.The schematic of a standard SM1000 is here:https://svn.code.sf.net/p/freetel/code/smartmic/SM1000-F/MFG-SM1000-F/SCH-SM1000-F.pdfand the whole device is around 80 by 100 by mm. I've turned it into a square PCB 30 mm on a side, with two 12-pin headers. The intention is to run the same firmware and to that end no microcontroller pins have been remapped or functionality changed. I've attached my schematics and a few pretty pictures of the layout. I'm intending to release this under the same license, but if no-one else is interested I'll just make up a couple for myself.1) If anyone who is interested could take the time to review the schematic against the SM1000 and spot any sillies that would be much appreciated, thanks.Edit:one error found so far, thanks Steve. I screwed up some pinning where my symbol differs from the eagle one.2) Bare PCBs are looking to be about £2 (China prices), and the total BOM about £15. Does anyone want any boards? If so I'm happy to combine with my order.The board is 4 layer, 6/6 track and gap, 12 thou minimum drill. It's just over 30 mm square. The original design was Eagle but I've done mine in Altium because that's what I am familiar with. Passives are all 0603 plus a couple of larger capacitors. I've tried to break as many spare microcontroller pins out to testpoints as I could.

author: richard.cs
author_rank: Super Contributor
timestamp: February 25, 2019, 04:14:34 pm
content: My boards have arrived :-)Now to get around to ordering parts and assembling a couple.

author: Wirehead
author_rank: Regular Contributor
timestamp: February 26, 2019, 07:19:50 am
content: Hey that's nice! this could fit in the bottom of e.g. a Yaesu MD-100 mic and would allow switching modes for TX. Double that up for the RX path and it could be practical for retrofit..
Cavity filter feeding probe length - Page 1
Forum section: electronics / rf-microwave

author: jujun
author_rank: Regular Contributor
timestamp: March 02, 2019, 10:26:58 am
content: Hello,I don't understand what is the relation between the wavelength and the length of the feeding probe of a cavity filter.It seems very small compared to a 1/4 wavelength.In everything I read about cavity filter they don't explain how.For example at 2.4Ghz it's 7mm.Do you have any pointers ?Thank you

author: KJDS
author_rank: Super Contributor
timestamp: March 02, 2019, 12:04:04 pm
content: The feed probes provide a coupling factor that is related to the filter bandwidth.The coupling is easily measured, either using a physical model and a network analyzer or else using a 3d EM solver such as HFSS and tweaked until it gives the required performance.

author: jujun
author_rank: Regular Contributor
timestamp: March 02, 2019, 12:57:04 pm
content: Quote from: KJDS on March 02, 2019, 12:04:04 pmSo it's totally normal that it's not a resonant length on it own I guess.

author: tggzzz
author_rank: Super Contributor
timestamp: March 02, 2019, 05:44:16 pm
content: From memory, an antenna that much shorter than the resonant frequency, the coupled power is proportional to the square of the frequency.

author: radiolistener
author_rank: Super Contributor
timestamp: March 02, 2019, 06:45:14 pm
content: I think it depends on impedance. The impedance of a loop depends on a number of turns of the loop, frequency and impedance of a coupled load. The coupling loop no needs to be in resonance with input signal. It needs to match input impedance, because the goal of the coupling loop is impedance match.

author: tggzzz
author_rank: Super Contributor
timestamp: March 02, 2019, 06:52:51 pm
content: From memory, again, the frequency squared would be for a dipole. That corresponds to the probe in the OP's question.I have no comment about loops.

author: radiolistener
author_rank: Super Contributor
timestamp: March 02, 2019, 07:11:05 pm
content: As I understand, the feed probe in the cavity filter (mentioned by topic starter) is nothing else than a coupling loop.It works in the same way as a coupling loop in a magnetic loop antenna.And can be considered as a first coil of RF transformer used for impedance transformation.Transformer impedance ratio is a square of it's turns ratio.Correct me if I'm wrong.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 02, 2019, 07:31:13 pm
content: Right, the whole point is not to get 100% coupling (as a resonant monopole might, or by terminating the cavity into the line directly -- which would be called a stub), but to use a fraction of the near field to just tease the fields inside, and thus get a low coupling factor and high system Q as suits the filter response.Tim
crystal oscillator breaks on EMF - Page 1
Forum section: electronics / rf-microwave

author: bullonwheels
author_rank: Contributor
timestamp: February 18, 2019, 06:54:45 pm
content: Hello all,The external 32khz crystal is throwing garbage values when we move the AC light ballast closer to it. I guess 60hz frequency causing the issues.Also, what are the sources which would break the crystal ?What methods do i take to prevent. Not a metal can fix.

author: Gyro
author_rank: Super Contributor
timestamp: February 18, 2019, 08:53:04 pm
content: Very hard to say without seeing the PCB layout.32kHz crystal drive levels are very low (= high impedance) so noise pickup is very likely on a non optimal layout. Grounding the crystal can (Aluminium) with a wire loop might help.

author: tkamiya
author_rank: Super Contributor
timestamp: February 23, 2019, 12:59:04 am
content: 32K piezo device is more like a tuning fork. It is possible for a piece to break off or bonded wire to come off.I'm not sure if I know what "AC ballast" is.... but if that's the only time it misbehaves, can it be located elsewhere? Did it happen suddenly or never worked right before? It may be just shielding that is required. Is there a reason you keep saying "no metal can"??Can you take an image of the setup?
Best way to arrange NFC, ethernet and zigbee on a board - Page 1
Forum section: electronics / rf-microwave

author: kuon
author_rank: Regular Contributor
timestamp: February 17, 2019, 10:31:42 am
content: Hello,I am building a carrier board for a toradex module (https://developer.toradex.com/products/colibri-imx7), and I need to put ethernet, NFC and zigbee (xbee) on it.The final product will be something looking like an android tablet, except a little bit thicker (monitoring station for a medical product) with a few connectors on the side. For my application, I need a bit a greater range (15cm), and the required antenna is about the size of my display (10"). I already did a PCB with only the the NFC chip and the trace antenna and it works.The general PCB layout would be like so:I plan to put the NFC (13.56Mhz) trace antenna and the Xbee (2.4Ghz) module on the back of the PCB (facing outside), and the rest (ethernet jack, toradex module and all the supporting components and connectors) on the front of the PCB, squeezed between the PCB and the display. I might also squeeze a battery between the display and the PCB (on the module/connectors side).Would this configuration be a problem? (NFC crossing ethernet, NFC interfering with the module...)Any input would help me greatly.

author: LtPluto
author_rank: Newbie
timestamp: February 18, 2019, 12:46:04 pm
content: Hi kuonThere is a big Toradex Community Channel, where you can ask questions regarding Toradex Modules directly to the engineers.https://www.toradex.com/community/From my small expierence withhttps://b2bsol.panasonic.biz/semi-spt/apl/en/tool/nfcdesignnavigator/#I wouldn't suggest you to put any additional metal plates within the antenna. You will get disturbances and have to retune the antenna.The Toradex Modules have Ground and Power Supply planes.If you don't have any space problems, I would separate electronics and antenna.Here some nice webinars about PCB and antenna design:https://www.nxp.com/pages/nfc-antenna-design-3-metal-environment:TIP-ANTENNA-METAL-ENVIRONMENT-VIDEOThere are 6In your case, I would put the Toradex Module as close as possible to the connectors.It is also good for the Ethernet MDI signals to be as short as possible.https://docs.toradex.com/102492-layout-design-guide.pdfAs a result you have a lot of space for the antenna and no metal plane within.But that is only my suggestion for you.Good LuckLtPluto
Horizontal quad loop HF antenna and ground question - Page 1
Forum section: electronics / rf-microwave

author: Chris Wilson
author_rank: Super Contributor
timestamp: February 24, 2019, 10:17:21 am
content: Circa 480 foot circumference horizontal quad loop with lowest corner at about 25 feet and highest corner at about 35 feet. Fed at one corner with window line direct to an upstairs room and Yaesu antenna tuner set in balanced mode. I use the loop on HF and for 136kHz LF, (where I strap the window line at ground level and using a big matching coil and an impedance transformer outside to RD-213 co-ax which goes back upstairs). On LF the ladder line acts as the vertical and the loop as a capacitance top hat. I have a buried wire ground system that runs directly under the loop perimeter and in an X from its 4 corners with 5 six foot ground poles. I use this ground for LF.My question is, on HF is the ground needed with a loop, and if so how do I connect as as on HF I currently do not use the ground connected to anything in the shack at all. Bear in mind the shack is upstairs please...Thanks
Discrete vs. IC MOSFET Characteristics - Page 1
Forum section: electronics / rf-microwave

author: beeboopbeep
author_rank: Contributor
timestamp: February 17, 2019, 11:36:07 pm
content: Hi everyone,I'm trying to build a circuit with discrete MOSFET components as I would when designing circuits on an IC (e.g., using Cadence to design and build IC schematic and layout) for RF applications but I'm noticing something I can't explain.I was planning to use RF MOSFETs like this one here:http://toshiba.semicon-storage.com/info/docget.jsp?did=17964&prodName=3SK291If you look at the DC characteristics (Page 3, first figure), and if you use the saturation current equation I_D = (1/2)*k_n*((V_gs - V_th)^2) for different V_gs values, you notice that the value of 'k_n' differs significantly! I calculated for k_n with known I_D, V_gs, and V_th from the figure. My initial thought was maybe this is because V_th changes for different V_gs and I_D but the source is tied to the body in this circuit which means V_th should stay relatively constant with no body effects.I noticed in the datasheet that V_th will vary as indicated on the first page (Gate 1 & 2 cut-off voltage values) but I don't understand why this is the case since source is tied to body. There are clearly some second order effects that I am unaware of and was wondering how would one calculate the V_th for various DC conditions for a discrete component like this?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 18, 2019, 01:56:29 am
content: Yeah, literally no one uses that toy of an equation.Even Ebers-Moll is out, in the real world -- at least, for BJTs, you're likely to have encountered the Gummel-Poon model in a typical EE curriculum (if not work with it much, directly). Which is the more-or-less standard model used by SPICE.AFAIK, practical MOSFET models are all much more complicated than this, and so you really only encounter them in SPICE: numerically, not symbolically.Some detail here:http://nitkkr.ac.in/docs/MOSFET_LEVELs.pdfLEVEL 1-3 models use KP, for varying reasons, mostly with a lot of tweak parameters to account for behavior and geometry of real devices, and parasitics (resistances and capacitances). The tweaks get more numerous, and the models more advanced, as you go up in level (more or less).A lot of general models available, are in levels 3 and 6, good enough for board-level work; BSIM and EKV are the most accurate (and rich), used by real foundries.But, good luck getting example models, they're tightly controlled, proprietary! But, if you [or your employer or school] can afford Cadence IC design tools, this is probably no problem. That does leave the question: why haven't you been introduced to SPICE, and the fab's models, yet? You may want to ask!Tim
Play with ADS54J60, 1Gsps 16bit direct sampling receiver - Page 1
Forum section: electronics / rf-microwave

author: cnxunuo
author_rank: Regular Contributor
timestamp: February 16, 2019, 08:12:11 pm
content: Got it purely for fun 2 years ago when the chip just came out, no actual use for it until now.its the TSW54J60EVM board, such a bargain considering it includes clocking chip and 2 VGA with no extra cost then buying the chip itself from TI.The chip is TI's new 1Gsps 16bit 2ch ADC with JESD204B,on HAM's hand, its basically an DC-512MHz direct sampling receiver.also bought an conveniently FMC-USB3.0 dev board from TI with a fairly decent FPGA. Dump 32Gbit of single capture (1 full seconds for 2 ch running full speed!) thru usb3.0 is rather quick, but matlab filter is extremely slow thou, with DDC and resampling. took me a full night to finally decode some FM broadcast (still only 1 second long).Just stick an antenna in ch0, and capture a chunk of data, have fun with all the signals you can dig out from it, Shotwave, broadcast, VHF, UHF recordedall at once...really cool when matlab finally calculated all the FFT segment, and displayed it in a sequency, RTSA with 500MHz RTBW...This could make an nice short wave receiver if fitted with proper frontend, much better then the flex-6700's antique ADC choise with obsolete performance....
Availability of uBiTx transceiver  - Page 1
Forum section: electronics / rf-microwave

author: Dom13c
author_rank: Regular Contributor
timestamp: February 14, 2019, 09:22:03 am
content: Anybody knows whether or not the uBiTx transceivers are still available or not? Checked their official website to order one. But the every time I had been to the checkout link the server crushed! Is it just the server's problem or they have just got it discontinued?

author: vk3yedotcom
author_rank: Frequent Contributor
timestamp: February 14, 2019, 09:35:13 am
content: For everything uBitx, this is a good place to go for information, even if as a reader.https://groups.io/g/BITX20There were problems with spurious emissions at some frequencies and audio amplifier stages and some changes have been made. The one on the website is version 4.Having said that I've had good results with mine (Version 3). Here's a demo:
Do I need WPC certification for 4G and WiFi module to be used in our project? - Page 1
Forum section: electronics / rf-microwave

author: sangar
author_rank: Regular Contributor
timestamp: February 12, 2019, 09:34:08 am
content: Hello All,I have a doubt regarding certification for Wireless product which includes 4G-LTE, GPS and WiFi...All are the off-the-shelf module and antennas for them will be passive...If I am right, the off-the-shelf modules that we are buying for the above wireless communication are already certified, I don't think that there will be a problem with them...But, for the end product, we need to get certification ?... If anyone from India has gone through this, please share the details...Thanks,Sangar
RFM69 help? - Page 1
Forum section: electronics / rf-microwave

author: nfmax
author_rank: Super Contributor
timestamp: February 15, 2019, 08:47:30 am
content: I'm trying to use a Hope RF RFM69 module to receive remote control transmissions on 433.92 MHz. Eventually, I will need to handle FM signals, but after struggling without success for a while decided to start simpler and pick up some basic OOK remotes. I still can't make it work! No matter what I do, I never get any data bits out, either in the FIFO or on the data output pin. However if I poll the RSSI register I can see the signal is being received.I have tried two different modules, in case I had a damaged device, but get exactly the same results. I set the chip registers up based on my reading of the data sheet, but this is fearsomely complicated. Can anyone provide me with a set of register values that are known to work, for a simple OOK remote signal? All I have been able to find on the Internet is demo code using the built-in packet engine, which is no use to meAny other help and advice also welcome!Thanks

author: georges80
author_rank: Frequent Contributor
timestamp: February 15, 2019, 08:49:41 pm
content: I've used the RFM69 modules. There's quite a bit of register setup that is required.The easiest way to start with them is to get some known functional code, since there is more involved than just the register settings.I used the radiohead code as a starting point and then removed a lot of the general purpose stuff. For added 'challenge' I also recoded to run the source as C code versus C++. This is on my own hardware, so all the arduino 'stuff' got removed as well to target the STM32 that I'm using.This running FSK encoding. Comms over SPI. After all that the modules work well and reliably over a few hundred metres with a basic 1/4 wave on each end. I'm using the 900MHz 'version' of the modules, but that's neither here or there...cheers,george.

author: nfmax
author_rank: Super Contributor
timestamp: February 16, 2019, 08:51:59 am
content: Thanks for the tip. I hadn't come across that project before, and it looks a bit more - how shall we say - professional than the typical code dump I found while looking. I will download it and have a detailed look.P.S. I'm also using C, on a Raspberry Pi
Protecting the 1st Mixer in a Transceiver application on transmit - Page 1
Forum section: electronics / rf-microwave

author: Xnke
author_rank: Regular Contributor
timestamp: February 08, 2019, 11:23:19 pm
content: So I am working through bits of the radio I've been puttering with for a few years now, and while the low-power part of things is done and works quite well, it's time to add the final amplifier, the low-pass filters, and the antenna transmit-receive changeover relay.The relay isn't a big deal, I thought it was but turns out it's not too terrible. The final output should be about 50W of transmit power, and I need to make sure that on transmit, there is enough isolation through the disconnected relay contact that the input of the mixer doesn't get damaged. It *shouldn't* be a problem, because the first mixer is actually going to be driven as the balanced modulator during that time and should have an audio frequency signal to work with.But, testing the TRX relay (which is the same Axicom D2-sized signal relay as the rest of the receiver), the isolation between the selected and deselected contacts is about 43dB. 50W is 47ish-dBm. That comes out to about 2.5mW of power leaking into the mixer input. There's another 1-2dB of loss through the preselect filter, so it's not a LOT of power that's going to get through.I could use a second relay on the mixer's input to add another 43db of attenuation, but since it's a Mini-circuits ADE-1ASK (Or I could use Mini-Circuits RMS-2) is it even going to be a problem? The rated RF power for the ADE-1ASK is 50mW, and the RMS-2 is 200mW.It doesn't *seem* like this would be an issue power-wise, but signal-wise, would it be enough worry about it causing issues?Essentially, the TRX relay is switching the antenna port between the transmit LPF board, and the receive BPF preselect board, and the receive BPF's are feeding straight into the mixer's IF port.

author: radioactive
author_rank: Regular Contributor
timestamp: February 09, 2019, 12:04:00 am
content: You might consider adding a pin diode shunt to the rx path during transmit if you are concerned that it could be an issue.

author: German_EE
author_rank: Super Contributor
timestamp: February 10, 2019, 09:34:55 am
content: A number of things may help here:1. If your receiver has a switchable attenuator then enable this during transmit.2. Have a large relay to switch your antenna from transmit to receive, this can be as slow as you want so long as you take account of the delay in your QSK switching.3. Have a small reed relay directly across the receiver front end that activates as quickly as possible to protect the front end.

author: KJDS
author_rank: Super Contributor
timestamp: February 10, 2019, 12:44:15 pm
content: I'd use a few PIN diodes instead of the relay. The only real issue is that you'd need about 70V to ensure that the RF signal didn't turn them on when you want them off.
Need suggestion to design LTE, GPS,Dual-band WiFi antenna on the same PCB... - Page 1
Forum section: electronics / rf-microwave

author: sangar
author_rank: Regular Contributor
timestamp: February 10, 2019, 05:20:24 am
content: Hello All,I need to have three antennas, LTE (Quadband-698-960MHz,1710-2170MHz, 2300-2400MHz & 2500-2690MHz), GPS (1.5GHz) and Dual-band WiFi (2.4 GHz & 5 GHz) on the same PCB whereas the respective transceivers will be on the different PCB...RF outputs of the transceiver PCB will be connected to their antennas with UFL cable...Do I need a SAW filter for both GPs and WiFi as LTE band falls in their bands to avoid coupling?...I have no prior experience in designing the antenna for multi radios though I have designed standalone Wifi and 915MHz trx ...Please suggest...Thanks,Muthu
Radio modules for 500m communication Product Prototyping - Page 1
Forum section: electronics / rf-microwave

author: speechsupply
author_rank: Contributor
timestamp: February 08, 2019, 11:33:39 am
content: Hi EEV,I have worked with both HOPE RF 95 LORA modules and the infamous NRF24L01+.Both Chips have their own use and limits.The thing is, I have a babymonitor/radio for my toddler. It has a quite impressive range, going through both concrete walls (multiple) and a decent batterylife.My question is, do any of you know of a module, that can transmit sound (in decent quality but not HiFi), with decent range (Open air line of sight max 500m) ?ideally, I can interface to it with either SPI or I2C.Best regards,Speechsupply

author: OwO
author_rank: Super Contributor
timestamp: February 08, 2019, 11:37:48 am
content: FM transmitter QN8027 or QN8007 + amplifier.

author: speechsupply
author_rank: Contributor
timestamp: February 08, 2019, 12:10:50 pm
content: Yup, that looks pretty good!Do you know of any that uses digital encoding/decoding?So that the data transfer won't be picked up by any nearby Car radio
Question about posting announcements - Page 1
Forum section: electronics / rf-microwave

author: piranha32
author_rank: Unknown
timestamp: February 07, 2019, 10:09:52 pm
content: Hello,I would like to ask about posting announcements for streams from ham radio talks. I'm already posting them on "Contests&Events" subforum, but very few people seem to lurk there. Since these are time-sensitive announcements directly related to the topic of this subforum, would it be permitted to post this information here? Or just short notes about new announcements in C&E section?

author: vk3yedotcom
author_rank: Frequent Contributor
timestamp: February 07, 2019, 10:33:40 pm
content: I, for one, would welcome your posts on this topic here.Maybe it would work if all in one thread?

author: piranha32
author_rank: Unknown
timestamp: February 08, 2019, 05:03:36 am
content: You're right. Having one thread for all the announcements is a great idea. I'll repost the information in new thread, and 'll be using it for all new announcements in the future.
Effect of Multi radio antennas on the same PCB ?.  - Page 1
Forum section: electronics / rf-microwave

author: muthukural001
author_rank: Regular Contributor
timestamp: February 08, 2019, 09:59:28 am
content: Hi All,I need to design a board with 4G with GPS module , WiFi transceiver, Processor and others in 50 x 50 mm. As a result, I can't keep the antennas for 4G, GPS and WiFi in the same PCB. I want to create one more board which will have all the antennas and stack up with the other board.The transceivers RF output and the respective antenna will be connected with UFL cable ...With keeping all the antennas which radiate at different frequency on the same PCB, how it will affect the performance of the other antenna.What should I take care to reduce them?... It needs any simulation?Please suggest...P.S:All the antennas are off-the-shelf antenna1. 4G antenna with Quad band ( 698-960MHz,1710-2170MHz, 2300-2400MHz & 2500-2690MHz)2. GPS - 1.5 GHz3. WiFi - 2.4 & 5 GHzThanks,Muthu

author: OwO
author_rank: Super Contributor
timestamp: February 08, 2019, 11:39:31 am
content: Quote from: muthukural001 on February 08, 2019, 09:59:28 am

author: bson
author_rank: Unknown
timestamp: February 13, 2019, 06:52:01 pm
content: Since the bands don't overlap there's a good chance it will just work. You might want to measure their mutual interference and/or emission patterns so you know what to avoid. Then position them in each others' nulls.
Agilent E4401B Frimware Upgrade - Page 1
Forum section: electronics / rf-microwave

author: Nitrousoxide
author_rank: Regular Contributor
timestamp: February 05, 2019, 05:55:57 am
content: Hi all,Ive attempted to ask this in the repair section but after a while, to no avail, there seems to be no one with an answer.I recently acquired an old E4401B. It is a fairly old model as it has an earlier serial number (less than 4144), and thus does not come with the expanded memory upgrade. I would like to install this as it allows the latest firmware to run on the device and allows for features such as 1 Hz RBW (It also has the high accuracy source upgrade, however, they only added 1 and 3 Hz RBW in a later firmware upgrade).My attempts so far have been somewhat successful. There are two components to upgrade, the DRAM SIMM and the flash SIMM. The DRAM simm was trivial as any old stick that has comparable timings would work (and in fact did so), the devices detects that it now has 32 MB of RAM.The flash SIMM was not as trivial. I had managed to source some identical chips off ebay from China (they are obsolete, that was the only source I could find). Another source on the internet stated that the last two jumpers (out of the four) on the flash SIMM should be opened, whilst the top two should be shorted.Before attempting that, I wanted to check if the device could boot into the firmware updater. Alas, it could not. This is where my problem is.I followed the instructions given by the firmware update guide. I tried formatting the disks both from windows and from the spectrum analyser, and then dropping the files onto the floppy. But once I insert the disk and reboot (as said by the service guide), it just boots straight into the operating system.The spectrum analyser is running possibly the earliest firmware version of A.01.03. The bootloader listed is 310.Does anyone have any tips, suggestions or experience?EDIT:I tried formatting the floppy disk in the ESA, then proceeded to copy the bootloader onto the disk in linux. The machine attempts to boot from the floppy disk, It seeks a few times and then loads. However, the screen remains white and the machine sits in a locked up state.