hybridfree/eevblog-posts huggingface dataset:
RF Explorer ghost carriers? - Page 1
Forum section: electronics / rf-microwave

author: elraval
author_rank: Newbie
timestamp: February 11, 2020, 10:43:54 pm
content: Hi.Trying to figure out the reason extra carriers show up when scanning my wireless mics. Signals are Shure ULXD 200kHz digital modulated signals, but same thing happens with WFM analog wireless mics.I'm attaching pictures of 2 trasmitters when alone, together and also a clean spectrum sweep.Cheers,Diogo

author: tautech
author_rank: Super Contributor
timestamp: February 11, 2020, 10:53:59 pm
content: Welcome to the forum.There's some discussion about these units here:https://www.eevblog.com/forum/rf-microwave/rf-explorer-6g-combo-ghost-signal-4-8-5-1-ghz/You might like to Move Topic to the RF board. Bottom left of your page has the option to do this.

author: elraval
author_rank: Newbie
timestamp: February 11, 2020, 11:00:47 pm
content: Glab to be here, sorry for my newbieness... Topic moved.Cheers

author: radiolistener
author_rank: Super Contributor
timestamp: February 12, 2020, 12:02:20 am
content: These "ghosts" are images which appears here due to non-linear distortions, parasitic mixing with spurious components and leaks from oscillator, synthesizer and other wave sources in the receiver (or nearby equipment). Also it may be images sampled from some high Nyquist zone (mirrored across half ADC clock frequency border).In short, these carriers are result of bad performance of your receiver - dynamic range, IMD, etc...According to your screenshot, it looks very likeIMD3distortions in your receiver. It happens because some components of your receiver has some small non-linearity, which leads to some distortions.You can detect and measure IMD3 distortion by applying two clean frequencies (with a small delta between them) mixed together on the input of your receiver and measure the difference between real carriers level and these "ghost" peaks. Such method is known as two-tone measurement, for more explanation see "Linearity analysis" in this article for example:https://www.la1k.no/2017/07/25/measuring-lna-characteristics/

author: elraval
author_rank: Newbie
timestamp: February 12, 2020, 02:56:29 pm
content: Thank you radiolistener for the answer and the links. I apprecciate it.According to RF Explorer team it is actually aliasing:"These spike signals at 1.8MHz are called Image Frequency, and are visible only for strong signals with about 30dB attenuation for the images in the WSUB1G left-side connector.However, you have a 3G Combo model and, as such, can use the WSUB3G right-side SMA connector including an advanced DSP mode to remove the spikes automatically for you. We suggest you use the right-side not the left-side connector in your 3G Combo."https://groups.google.com/forum/#!topic/rf-explorer/3VSAWWy32MAI've checked the WSUB3G module and it produced no aliasing on the measurement.My understanding of IMD is it requires a couple of transmitters to exist and I was noticing effects with any of the single carriers.Cheers,d
RF Current vs. Electrical Current - Page 1
Forum section: electronics / rf-microwave

author: vinlove
author_rank: Frequent Contributor
timestamp: February 15, 2020, 01:37:05 pm
content: Hi AllI am wondering if the RF current radiated from your TX antenna is same or similar in nature to that of Electrical current DC or AC.If different, then how different?Could it be measured with normal electrical Amp meter?

author: EEEnthusiast
author_rank: Frequent Contributor
timestamp: February 15, 2020, 02:24:33 pm
content: RF current and AC current is very much similar. Just that the RF current is at a higher frequency. (Typically 10s of MHz and above, although this is not a strict definition)No, the RF currents cannot be measured with a standard meter. Typically in RF, the current and voltages are seldom measured. It is usually the power which is measured. You may use a RF power meter to measure the RF power level.

author: ejeffrey
author_rank: Super Contributor
timestamp: February 15, 2020, 06:31:48 pm
content: There is more to it than that.RF currents in a coaxial cable are the same as regular AC currents in a low frequency circuit, just higher frequency. You can measure them with any instrument that can handle the frequency. This doesn't include most DMM type instruments (voltmeter / ammeter), but you can easily see FM radio waveforms on an inexpensive oscilloscope. Higher frequency RF such as used by wifi and cellphones requires much more expensive oscilloscopes if you really need to see the waveform, but normally you don't. Instead you use dedicated RF instruments like RF power meters and spectrum analyzers.However when you say "RF current radiated by an antenna" it sounds like you are talking about the EM radiation through free space rather than just the feedline to your antenna. That is entirely displacement current. In electomagnetism current is composed of 2 terms: one is motion of charge and the other is displacement current which is dE/dt: the time derivative of electric field. Inside conductors we pretty much have only the first term because electric field inside a conductor is zero, but in vacuum there is no free charge to move and thus there is only displacement current.Total current is the correct thing to call current as that is what obeys Kirchhoff's current law.
Locus Mystery box - Page 1
Forum section: electronics / rf-microwave

author: Haasje93
author_rank: Contributor
timestamp: February 03, 2020, 01:57:03 pm
content: Hi!last Saturday i have bought this box on a local HAMfest. Initially i purchased it for the box, to use it in another project.But i am intrigued by the content, as i am not an RF guy. I need your help, i can't find any data on it. May by someone here can help me?I think it is a amplifier of some sort.I have pictures attached off the box.It is a LOCUS, INC. RF194DRegards,Christiaan

author: EEEnthusiast
author_rank: Frequent Contributor
timestamp: February 03, 2020, 02:49:14 pm
content: To me it looks like an LNA for the VHF band or lower. Nothing more can be inferred from the pics.

author: vk4ffab
author_rank: Frequent Contributor
timestamp: February 03, 2020, 11:32:13 pm
content: I could not find a datasheet for the HP 35821E rf amp, but from another agilent paper, i think its a 1 to 2 gig rf amp.

author: Bud
author_rank: Super Contributor
timestamp: February 04, 2020, 02:41:48 am
content: Judging on the filters coils size it is UHF or higher amplifier. Interestingly it has high pass filters between stages which makes me think it may be a harmonic multiplier.

author: TheMG
author_rank: Frequent Contributor
timestamp: February 07, 2020, 03:39:24 am
content: Hook up a sig gen and spectrum analyzer and sweep it!

author: Haasje93
author_rank: Contributor
timestamp: February 12, 2020, 09:02:51 am
content: Hi Guys,Sorry for my late reply, its been busy..Thank for for the responses, i treid to measure it, but i couldn't get any signal out of it.For now it goes on the shelf.Regards,Christiaan
Antenna Matching help - Page 1
Forum section: electronics / rf-microwave

author: LakshmiN
author_rank: Contributor
timestamp: February 11, 2020, 02:34:48 pm
content: Hi,I'm using this Chip Antenna FR01-S4-224 for my application(Cellular)(https://fractusantennas.com/mobile-antenna/)And Have followed this document for clearance(60mm)https://fractusantennas.com/files/AN_FR01-S4-224_LengthClearance.pdfDid measurements and saw few variation.We're actually interested in 3 Bands.Band 3: 1.71GHz-1.785GHz(Uplink) and 1.805-1.88GHz(Downlink)Band 5: 824-849 MHz (uplink) and 869-894 MHzBand 8: 880-915 MHz and 925-960 MHz.I've attached the Matching/Tuning values and measurement.But measurements are way off at these frequency and Please suggest on matching.Thanks.

author: ThomasDK
author_rank: Regular Contributor
timestamp: February 11, 2020, 08:02:12 pm
content: How big is your groundplane?

author: LakshmiN
author_rank: Contributor
timestamp: February 12, 2020, 07:27:42 am
content: 70*50mm on the ref(GND) plane(i.e. on 4th Layer)Clearance from Ref plane(CPWG top layer) to chip antenna is 9mm.

author: EEEnthusiast
author_rank: Frequent Contributor
timestamp: February 12, 2020, 07:46:22 am
content: Matching from 0.1dB return loss is almost impossible. Either there is something wrong on the PCB or the antenna part is having a mismatch.Can you please check.

author: LakshmiN
author_rank: Contributor
timestamp: February 12, 2020, 08:12:46 am
content: Yeah but another thing here is antenna manufacturer recommended ref plane for the transmission line to be more than 1mm. So L4 is considered as ref plane(h-1.5mm,w-1mm).
RF Matching help - Page 1
Forum section: electronics / rf-microwave

author: LakshmiN
author_rank: Contributor
timestamp: February 11, 2020, 02:32:36 pm
content: Hi,I'm using this Chip Antenna FR01-S4-224 for my application(Cellular)(https://fractusantennas.com/mobile-antenna/)And Have followed this document for clearance(60mm)https://fractusantennas.com/files/AN_FR01-S4-224_LengthClearance.pdfDid measurements and saw few variation.We're actually interested in 3 Bands.Band 3: 1.71GHz-1.785GHz(Uplink) and 1.805-1.88GHz(Downlink)Band 5: 824-849 MHz (uplink) and 869-894 MHzBand 8: 880-915 MHz and 925-960 MHz.I've attached the Matching/Tuning values and measurement.But measurements are way off at these frequency and any suggestions on matching.Thanks.
Danling Ground copper areas on PCB - Page 1
Forum section: electronics / rf-microwave

author: madhu.wesly01
author_rank: Regular Contributor
timestamp: February 08, 2020, 05:40:37 am
content: Hi,Can someone share the best practices to avoid dangling ground on PCB, and mitigating tips in-case of unavoidable cases.Is using polygon cutout good practice for eradicating the dangling ground copper areas? In this method will there be any impact in performance for signals or components if there is no GND copper around(near) them?TIA.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 08, 2020, 01:53:59 pm
content: 1. For the most part, don't bother pouring outside or signal layers on a multilayer board. Can be helpful in demanding cases, but isn't worth the trouble for the most part.2. In 2-layer designs, pour the same net (GND) both sides, and stitch with vias. This connects peninsulas, crossings and islands, and provides a ground nearly as good (in terms of impedance and average distance from trace to ground) as a multilayer board.3. Any islands remaining, should simply be too small to bother pouring or connecting (set a minimum island area threshold).Tim

author: DaJMasta
author_rank: Super Contributor
timestamp: February 08, 2020, 10:31:13 pm
content: Does your CAD tool have an option to do this automatically? In the software I've been using (CircuitMaker, basically Altium Designer with a less useful UI) you just check a box when you define your polygon pour and the system won't generate any part of the plane that would be floating.For high speed signals using controlled impedance models, the distance to a ground is important but this is probably not your application. For using ground as 'shielding', if it's not there it doesn't provide the benefit, but it's otherwise no difference. Via stitching in key points can usually connect stray bits of the pour, but leaving it out in an area you can't connect isn't likely to have a big effect - things are probably dense enough that there's not going to be much stray signal penetration there anyways.

author: Miti
author_rank: Super Contributor
timestamp: February 09, 2020, 02:25:53 am
content: Quote from: T3sl4co1l on February 08, 2020, 01:53:59 pmIn Eagle there's a check box in the polygon properties named "Orphans" that can leave or eliminate the unconnected islands.I use a healthy amount of stitching vias between top and bottom with reasonably big drill size to minimize the via resistance.

author: madhu.wesly01
author_rank: Regular Contributor
timestamp: February 11, 2020, 05:42:24 am
content: Hi,@Miti, in my case there are no unconnected islands. All the (GND)copper pour(even islands if any) connected to Ground some how on my 4 layer PCB.@DaJMasta, I use KiCAD, I am not sure if it has that check box.Please have a look at the image attached.

author: EEEnthusiast
author_rank: Frequent Contributor
timestamp: February 11, 2020, 06:00:22 am
content: you can set a larger clearance area for the ground pour so that it does not creep into smaller spaces.May be a 1mm spacing
multiplexed mic input on Yaesu FTM 400 - Page 1
Forum section: electronics / rf-microwave

author: turnermason
author_rank: Newbie
timestamp: February 11, 2020, 05:39:36 am
content: Hey, fellow EEVblogersI have an ftm-400xd here in the shack and I have been working on an external mic connector. The MH-48 uses an electret mic. So out of default thought I went ahead and connected an electret mic to the correct pins in the pinout (rj11 connector). Upon further research, I think the mic signal may be multiplexed with other control signals from the mic. I am wondering is anyone can help me out here. All i need is ptt and mic input. I got the ptt working but no luck on the mic.Thanks,Mason AF4MT
Certification for a LoRa Transceiver Module  - Page 1
Forum section: electronics / rf-microwave

author: madhu.wesly01
author_rank: Regular Contributor
timestamp: February 08, 2020, 05:31:17 am
content: Hi,I am designing a LoRa transceiver module with providing provision for two RF connectors - 1. Plated through hole(PTH - for Helical antenna) and U.FL(Whip antenna/any LoRa antenna with U.FL connector). At a time only one antenna can be populated as they both share common footprint area.Will the design be certified Under one certification ID? What can be the pros and cons with this approach?Thank you.

author: madhu.wesly01
author_rank: Regular Contributor
timestamp: February 11, 2020, 05:22:27 am
content: Hi,Any inputs on this query.TIA.

author: EEEnthusiast
author_rank: Frequent Contributor
timestamp: February 11, 2020, 05:32:15 am
content: Anytime there is an RF change, the product has to be re-certified. This is to ensure that the radiation pattern and therefore the radiated power does not violate any FCC limits.In short, you need to have 2 IDs for the product.FCC publishes a list of permissible changes from time to time. you may refer to the FCC site for latest update.
HP8563E question - Page 1
Forum section: electronics / rf-microwave

author: chipso
author_rank: Newbie
timestamp: March 13, 2019, 05:42:33 pm
content: Hello everyone !I have just logged in and i am new in this forum.I bought a HP8563E in the bay - it seems very good to work- but the first time it is switched on (when cold) it takes about 30 seconds to start up.When warm, it seems to work normally (start-up 5-10 sec.)Is this normal or a sign of a beginning defect?Thank'sJohn

author: KJDS
author_rank: Super Contributor
timestamp: March 13, 2019, 06:50:35 pm
content: I've just tried my 8563A. This takes about 30 seconds from powering on to finishing its start up routine.

author: chipso
author_rank: Newbie
timestamp: March 13, 2019, 07:23:39 pm
content: Thank you for your prompt reply*** Great ***The part has only the option 5 - maybe I find a way to expand the options.is there a way to read the operating hours of the HP8563E?Thank's KJDS

author: Tony_G
author_rank: Super Contributor
timestamp: March 13, 2019, 07:53:33 pm
content: Front panel key "Recall", look for the option "Elapsed Time" - It's on the second page.Mine has over 32K hours of run time so far - Good units.TonyG

author: chipso
author_rank: Newbie
timestamp: March 13, 2019, 08:17:00 pm
content: *** super ***the "Elapsed Time" of my unit is 5239 hoursis like newthank you Tony

author: Tony_G
author_rank: Super Contributor
timestamp: March 14, 2019, 12:53:15 am
content: NP - Happy to help - You should grab the manuals from Keysight as they're actually PDF outputs from the original authoring files so they're very readable (but lack graphics).TonyG

author: chipso
author_rank: Newbie
timestamp: March 14, 2019, 08:29:57 am
content: i have downloaded some pdf like this:Service GuideAgilent Technologies8561E/EC and 8563E/ECSpectrum AnalyzersPart Number: 08563-90214does anyone have the schematics?are they available as pdf?

author: Tony_G
author_rank: Super Contributor
timestamp: March 14, 2019, 04:18:03 pm
content: You want the CLIPs for that (basically a component level service manual). They're available for purchase from ArtekManuals.com - I've bought a bunch of manuals from them, they're officially licensed by Keysight to provide high quality searchable scans of HPAK manuals.Check them out.TonyG

author: chipso
author_rank: Newbie
timestamp: March 14, 2019, 05:57:17 pm
content: good to know where i can buy the service manual (component level)thank's Tony

author: scopeman
author_rank: Frequent Contributor
timestamp: February 11, 2020, 04:10:56 am
content: Dave Henderson atwww.artekmanuals.comHigh Quality PDF scans of manuals and CLIP.For 25.00 you can get the whole shebang.SamW3OHM
Mystrey Samsung TV detector coils - Page 1
Forum section: electronics / rf-microwave

author: Dom13c
author_rank: Regular Contributor
timestamp: February 10, 2020, 08:05:13 am
content: Recently an electronics parts supplier shop nearby was having a shop cleanup. Thinking this might be a chance to get some old stuffs I hit by that shop and saw a bunch of canned/ shielded inductors/ toko coils ready to be thrown.after asking the shopkeeper he gave me a whole buch of them ( 100 nearly) . amongst them I found some weird coils named"Samsung detector coil"These coils have got two capacitors at the bottom and a diode( silicon diode. (Vforward was ≈.7v) with no markings) connected to one side of the two tuned coils. Googling "Samsung detector coil" produced nothing informative.Do you guys know what they are and what their proper application is?Sorry for poor quality images. my camera has gone out of focus, so you might find it a bit problematic to clearly see the parts of the coil

author: TheMG
author_rank: Frequent Contributor
timestamp: February 11, 2020, 01:46:14 am
content: Detector and de-modulator are two terms often used interchangeably, so very likely these would have formed part of either the video or FM audio de-modulation circuits in an analog TV.Integrating other components inside of the coil can helps cut down on interference and keeps parasitic inductance between components to a minimum especially since the L and C form a high Q resonant circuit typically.

author: radiolistener
author_rank: Super Contributor
timestamp: February 11, 2020, 03:11:48 am
content: Such inductors usually used in different RF equipment, for example radio receivers. Their main goal is to make LC circuits for filters. But their working frequency is limited with about 100-500 MHz. This is why it is not used for nowaday GHz range RF equipment. Their main target is HF band (30-50 MHz and below).
Active bias for LNA design help  - Page 1
Forum section: electronics / rf-microwave

author: jsr38
author_rank: Newbie
timestamp: February 12, 2020, 10:54:26 pm
content: While it might not be required as I think the actual variation due to temperature changes can be practically accommodated for by a diode/LED drop in the bias circuit, I'm trying to design an active bias circuit to aid my own understanding.I read around the Widlar and Brokaw bandgap reference papers and settled on the design in Horowitz and Hill 2nd edition figure 6.24 where an op-amp I used (I think) in a way that provides the constant current. In my simulation sweeping temperature I see evidence of the higher order temperature dependency. So far, so good.Now that I have a circuit that behaves this way - see attached circuit and simulation outputs. What are my options for providing my desired current of the 10's or 100's of microamps to the base of my RF transistor?* Precision resistor divider from the constant voltage? - no because this has PTAT , right?* Take the constant current from the op-amp arm and current mirror to the RF transistor? How to set the current ratios given this is built with discrete components? How to configure this?Any input welcomed :-)

author: David Hess
author_rank: Super Contributor
timestamp: February 13, 2020, 03:00:26 am
content: Reference your discrete reference from the positive instead of negative supply and then use the operational amplifier to control a current source.
LoRa SX1262 Matching Circuit - Page 1
Forum section: electronics / rf-microwave

author: JeWe37
author_rank: Newbie
timestamp: January 23, 2020, 07:50:48 pm
content: So I have been working on a board which includes an SX1262 LoRa Transciever IC for communications. I am configuring it for 22dBm TXCO 868MHz operation(Europe, the 869.4-.65MHz band allows 500mW) but only need it to transmit. Due to space constraints I decided to go with 0201 components rather 0402 components, as Semtech recommends(https://lora-developers.semtech.com/knowledge-base/forum/viewthread/191/https://semtech.my.salesforce.com/sfc/p/#E0000000JelG/a/2R000000HSSf/GT2IXjK2nH8bw6JdEXfFBd.HmFATeLOpL402mZwpSho) and decided to drop the RF switch which has no use if one is only transmitting. On the PCB I am aiming to keep the signal path straight, albeit while diverging from that occasionally for caps to ground. I have also taken care to match my RF transmission lines to 50 Ohms using the parameters provided by my PCB manufacturer. Additionally attempted to verify that the components were going to produce roughly the same characteristics by using QUCS to model the relevant parts of each(i.e. the impedance matching and filtering) giving me the picture shown below for the transmission gain in dB, which I hope is close enough.This is my first more in depth RF Project and I would be thankful if anyone could confirm that what I did was sufficient or point me towards other theoretical tests I can conduct, as I want to avoid blowing an additional $80 on a second prototype board.

author: Peter_SB
author_rank: Newbie
timestamp: February 06, 2020, 03:01:12 pm
content: From my experience you will have to measure and adjust the matching circuit once you get the PCBs. There are always slight deviations from what the reference design suggest. Ref design is good starting point but verification is always needed.

author: JeWe37
author_rank: Newbie
timestamp: February 06, 2020, 09:26:18 pm
content: Right, I expected that, but I am hoping that given the frequency isn't excessive and that the tolerances should be fairly large those deviations will not be deal breakers. I will definitely test it, but rework could be difficult given the component size. I don't need to certify it nor is power overly critical, so as long as leakage does not get into the illegal range I should be good.
Identify Connector - Page 1
Forum section: electronics / rf-microwave

author: veedub565
author_rank: Frequent Contributor
timestamp: February 04, 2020, 09:35:05 am
content: Hi, does anybody recognise this connector type ? one end is standard N-Type the other end is unidentified. It screws into an old Weinschel attenuator and apparently conforms to MIL-C-39012C.

author: jlake
author_rank: Contributor
timestamp: February 06, 2020, 05:47:46 pm
content: What's the outer diameter and thread specifications?

author: mc172
author_rank: Frequent Contributor
timestamp: February 06, 2020, 06:22:46 pm
content: I reckon that the N connector is the part that conforms to the MIL standard and that the other interface is custom.

author: Mildi
author_rank: Contributor
timestamp: February 06, 2020, 06:39:54 pm
content: I think this is not a standard, constructive interface.Custom-made production, for non-standard sections of coaxial lines and inputs into the device cases.
Measure antenna characteristics using NanoVNA - Page 1
Forum section: electronics / rf-microwave

author: todorp
author_rank: Regular Contributor
timestamp: February 04, 2020, 04:52:29 pm
content: Hi all, please bear with me as I am a perfect newbie when it comes to RF.I would like to "build" a 1/4 lambda vertical antenna trying different materials and trimming the lenght to match a certain band of frequnecies. I would like to use a "simple metallic stick". My question for you experts is what would be a practical setup (solder/connectors) to test the antenna attaching it to the NanoVNA inputs? Can I just solder "the stick" to a SMA connector? Is there anything more elaborate where I could change "sticks" without having to solder/desolder each different one?Thanks for any advice,Tod

author: PA0PBZ
author_rank: Super Contributor
timestamp: February 04, 2020, 07:45:27 pm
content: Just buy a bag of these, can't go much cheaper:https://www.ebay.com/itm/10pcs-SMA-Female-Jack-PCB-Edge-Mount-Solder-0-062-RF-Adapter-Connector/113921729871But keep in mind that a quarter wave vertical antenna on its own is not an antenna at all, you need a ground plane to make it work:https://www.electronics-notes.com/articles/antennas-propagation/vertical-antennas/quarter-wave-vertical.php

author: Mechatrommer
author_rank: Super Contributor
timestamp: February 04, 2020, 09:16:10 pm
content: if you dont want to solder, just put the stick in the female hole... (the male end goes to the female vna input)...https://www.ebay.com/itm/copper-SMA-male-plug-to-F-female-jack-RF-coax-Connector-wholesale/153572569739?hash=item23c1a3728b:m:mCqPWRmXiOZuogKeBcw-qFAif you want more permanent soldered type, you can mod this...https://www.ebay.com/itm/Gold-plating-5-pin-SMA-Male-Solder-Edge-space-PCB-Mount-Straight-RF-Connector/133216036148?hash=item1f044b6534:m:mvCtff-lXTrS-wshWwbxB6wwas trying the single stick vertical antenna, including the spiral type normally found in cheap crap antenna to sma in ebay, it was pretty much useless... i ended up with radiating and "ground" stick at the same length ~135 degree apart.

author: todorp
author_rank: Regular Contributor
timestamp: February 05, 2020, 10:25:49 am
content: Thanks for the links. I am aware that I need a good ground when using 1/4 lambda. I will try to solder the "stick" to the sma connectors and tinker/experiment a bit :-)
How do you use latched type RF relays? - Page 1
Forum section: electronics / rf-microwave

author: tkamiya
author_rank: Super Contributor
timestamp: February 04, 2020, 07:21:23 am
content: I have LOTS of nice RF relays. The problem is, they are all latched type and spec sheet prohibits continuously supplying current to the coil.Say I have two push buttons and give a short pulse to one terminal. One would assume relay switched to the corresponding port. But how do you know for sure? Relay could get stuck, coil can burn out, all kinds of things could happen.I know there are latched type relays with separate contact just for this purpose. That's not what I have. I have 1 sma port for input, 2 sma ports for output, and 3 DC pins. Ground, port A enable, and port B enable. I am thinking of creating a switching matrix. I could, perhaps pass DC via DC block and coil, and pick up at output the same way, but that's a lot of work with possible degradation of signal.My tired brain can't come up with any good solution. I am hoping someone has an answer.Anyone?By the way, my use case is to switch between different GPS antenna, so frequency range is about 1.5GHz. To begin, will have 4 ports out, 1 port in. That means signal coming in are almost identical and selection will stay for a while. I need some kind of an indicator.Taka

author: Kalvin
author_rank: Super Contributor
timestamp: February 04, 2020, 08:49:24 am
content: Use three other RF relays for testing the actual relay. When you switch the actual relay, you will get an interruption anyway, so you could use these three other relays to check what is the state of the contacts of the actual relay. Say you have port 1 for the common path and ports 2 and 3 for different antennas. Now, you place three RF-relays to these three ports, and feed the actual signal through these relays. However, you can use these three relays to switch in a DC-voltage signal which can be used to testing the actual relay contacts. Increasing circuit complexity will also reduce its reliability, but you can at least figure out whether the relays are working ok, including the actual relay you are trying to monitor. I am not sure whether this will degrade the GPS signal too much to be a useful idea, but at least you can get some good use to your RF relays

author: ejeffrey
author_rank: Super Contributor
timestamp: February 04, 2020, 04:20:34 pm
content: Those relays are super reliable when driven properly, but if you want you can detect the armature motion by looking at the voltage/current waveform as you drive it. We have used that technique when driving these type of relays with a marginal drive pulse.

author: KrudyZ
author_rank: Frequent Contributor
timestamp: February 04, 2020, 04:42:09 pm
content: Most latching RF relays have secondary contacts that are used to break the coil current once the relay has switched.Check out the data sheet for the HP 33311 series of relays.
Looking for the best solution about pre-certified RF modules - Page 1
Forum section: electronics / rf-microwave

author: josmA
author_rank: Newbie
timestamp: February 20, 2020, 10:26:35 am
content: Hi,I need to communicate 2 devices wirelessly, 1 or 1.5 meters away from each other. I just need to send a command, it means, I send HIGH value to receive HIGH value in the receiver, actually the transmitter side is a button.The constraint is to use a pre-certified module to avoid a future process certifying it plus the money to get it certified.Could you suggest the best RF module solution in terms of cost, consumption and simplicity?Thanks in advance

author: brabus
author_rank: Frequent Contributor
timestamp: February 20, 2020, 11:09:42 am
content: Quote from: josmA on February 20, 2020, 10:26:35 amThe pre-certification of the module does not imply that the final product is certified as well. You will need to run the certification process anyway.The big advantage of using a module is that you can avoid some specific Tests (e.g.: RE-D), which are expensive and time consuming on a custom module.Anyway, for such a short distance and information content, I would look at some intelligent alternatives such as ultrasound or IR. In that case you can dramatically simplify your certification process (hey, no radio!).If you absolutely must use a Radio, then go for Zigbee or BLE.

author: josmA
author_rank: Newbie
timestamp: February 20, 2020, 01:26:17 pm
content: I understand that ultrasound or IR needs to have direct sight of each other, so it wouldn't be possible.I am looking for a simple certified 433mhz transmitter and receiver but they are very expensive, maybe BLE is the best solution, but complex for just a button...Thank you for your reply!

author: brabus
author_rank: Frequent Contributor
timestamp: February 20, 2020, 02:31:35 pm
content: You are welcome!I would take a look at the home lighting solutions from Philips: they are in fact based on Zigbee, with button interface which are even 100% passive (e.g.: piezoelectric switches).Otherwise, do you know the protocol EnOcean? May be worth a look.You could even buy the button without developing it at all, so it is already certified, and you only have to work on the receiver side.BLE is a piece of cake, you need one chip at all and a bit of SW...

author: josmA
author_rank: Newbie
timestamp: February 20, 2020, 03:00:51 pm
content: Can you specify or send a link to this Philips solution? About the EnOcean, I never heard about it, I will have a look. thanks

author: brabus
author_rank: Frequent Contributor
timestamp: February 20, 2020, 03:43:00 pm
content: https://www2.meethue.com/en-gb
FSK Complex Envelope - Page 1
Forum section: electronics / rf-microwave

author: Ralphy007
author_rank: Contributor
timestamp: February 03, 2020, 03:16:01 pm
content: I have been working through a derivation to find the Complex Envelope of an FSK signal. It starts with the message signal m(t) which is a square wave :m(t) = ∑ Ak p(t – kT) and Ak = + / - 1 p(t) = 1 for 0 ≤ t ≤ T otherwise p(t) = 0 k=0, 1, 2, 3........I have built a simple model on SIMULINK, which agrees with this, the only thing is my model uses a unipolar square wave i.e. 0 to 1, whereas the above equation seems to use bipolar i.e. Ak = + / - 1.The equation above gives the attached complex envelope and this is what I get on SIMULINK.However in my unipolar case Ak = 0, 1, gives a sine and cosine wave for each alternate time period, T ?
Concept for Precision Vpeak Display - Page 1
Forum section: electronics / rf-microwave

author: Mosaic
author_rank: Regular Contributor
timestamp: February 01, 2020, 01:17:11 am
content: Hi All:I am looking at designing a new Peak voltage display to use as a precision reference when calibrating Oscilloscopes or similar.Typically I use a Tektronix SG504 leveled sine wave generator with an optimized leveling head I designed for it.https://www.ebay.com/itm/132801983494I am hoping to create an equally precise Peak Voltage meter so any decent RF grade Signal Generator (up to perhaps 2 GHz range) can effectively be used to calibrate/validate O'scopes up to 2GHz.In effect it will be a hybrid of the leveling head used for the SG504 with an onboard digital display for the Vpeak.Thus it would be a suitable reference calibrate instruments such as the Tektronix SG503, SG5030 & 504 as well.The RF calibrated gear (Sig gen, Spectrum analyzer, NF analyzer, O scope, RF microwattmeter etc) I have available to me typically tops out at the 3GHz range so doing 2GHz validation for this project with minimal losses should be fine.Would anybody be interested in such a device? It will be both BNC & SMA compatible and should be around 2.5" x 1" x 1" in dimensions.
NEW Australian Ham Radio Handbook (ad) - Page 1
Forum section: electronics / rf-microwave

author: vk3yedotcom
author_rank: Frequent Contributor
timestamp: August 24, 2019, 08:34:46 am
content: A quick plug for a new book that could be handy for Australians into (or wanting to get into) amateur radio.The Australian Ham Radio Handbook.Foreworded by Dick Smith, it will help you become a radio amateur, set up a station and make contacts on air.It covers practical topics that existing licence study and theory books miss.For beginning and experienced hams alike, it's an ideal read for anyone interested in taking up, continuing in or returning to amateur radio.It's available as an ebook with a paperback version coming soon.More about it is athttp://home.alphalink.com.au/~parkerp/handbook.htmor in the video below

author: haydenph
author_rank: Contributor
timestamp: August 24, 2019, 09:19:51 am
content: Nice work Peter

author: vk3yedotcom
author_rank: Frequent Contributor
timestamp: February 02, 2020, 02:11:40 am
content: Good news for those in Australia who prefer a paperback edition.You can now get it from Jaycar stores or via their website.$24.95 Cat No BM2492https://www.jaycar.com.au/australian-ham-radio-handbook/p/BM2492
Brain Exercise - replicating an old garage opener running at 26.895MHz, OOK - Page 1
Forum section: electronics / rf-microwave

author: Warhawk
author_rank: Frequent Contributor
timestamp: January 31, 2020, 09:22:59 am
content: Hello guys,I gave my remote to the GF when she bought her first car. What one wouldn't do for the significant other, right?I do not need it desperately and we may move soon anyways but hey, I am an engineer and need to tinker with things. I fired up my SDR and sniffed the remote control. It runs at 26.895MHz and sends just a constant code using an OOK modulation. It is one of these super old garage openers. I would like to replicate it.Would anyone be able to recommend a simple RF circuit that generates the carrier? I saw that ICs are not an option now - all run higher frequencies. Google shows many discrete circuits, which one to take?The RF stuff is completely unknown to me. I am good with analog circuits, power, micros, but not with RF...It should be just a brain exercise. I know that I can buy a new opener for 30 bucks.Thanks for any tips!

author: Warhawk
author_rank: Frequent Contributor
timestamp: January 31, 2020, 11:40:43 am
content: Unfortunately, I am not able to crack it open. I can get access only to the battery compartment and dip switch. I would probably damage the housing trying otherwise.

author: Warhawk
author_rank: Frequent Contributor
timestamp: January 31, 2020, 11:43:29 am
content: Quote from: CJay on January 31, 2020, 10:14:39 amhah, interesting. It has 9x DIP switch. There's big chance it is MC145026.
Lora Module  - Page 1
Forum section: electronics / rf-microwave

author: shangaoren
author_rank: Regular Contributor
timestamp: January 21, 2020, 08:53:17 am
content: Hello everyone,i'm looking for a little LoRa module, i found RakWireless solution and Rak4200 seems good, any feedback about this vendor ?Any other suggestion for Lora module ?Thanks !

author: Dave_PT
author_rank: Frequent Contributor
timestamp: January 21, 2020, 10:31:55 am
content: Do you want a LoRa or LoRaWAN module?You write "LoRa module", but the links are from LoRaWAN modules...Diferences:LoRa modules: only radio with RF stuffLoRaWAN modules: "LoRa module" plus a MCU with LoRaWAN stack

author: shangaoren
author_rank: Regular Contributor
timestamp: January 28, 2020, 12:22:20 pm
content: Sorry te reply this late,I'm looking for LoraWan Module
AD9106 Evaluation Board clock source/1440 MHz - Page 1
Forum section: electronics / rf-microwave

author: ezalys
author_rank: Frequent Contributor
timestamp: January 26, 2020, 03:04:49 pm
content: Hey folks, I'm building a phase synchronous RF source for a physics experiment and am looking for a pile of boards I can stick in a rack mount box to get the necessary signals. The AD9106 dev board meets my specs for the source, but I need a high quality 1440 MHz clock source for it. I would prefer not to buy an RF source box to clock it. Anyone have a suggestion for an existing development board (ideal) or part (less ideal) which would provide a high quality clock signal for it? Ideally this board would remember its programming settings across power cycles. Ideally the dev board is under around 600 dollars, targeting 200 or so or less.

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: January 26, 2020, 03:24:45 pm
content: Some of the single-chip PLL+VCO combinations have reasonably priced eval boards and good phase noise. Some even include a halfway decent on-board reference. Examples: LMX2594, HMC834/835.

author: awallin
author_rank: Frequent Contributor
timestamp: January 26, 2020, 03:35:07 pm
content: for 1GHz clock to an AD9912 we've used the ADF4531 eval-boardhttps://www.analog.com/en/design-center/evaluation-hardware-and-software/evaluation-boards-kits/eval-adf4351.html(~145eur on digikey)it does have an on-board TCXO, but you might want to provide an external stable 10MHz source, or an OCXO...can't remember if it requires programming at each bootup - probably not (?), once the right settings are found and saved.

author: toastedcrumpets
author_rank: Regular Contributor
timestamp: January 28, 2020, 09:50:44 am
content: ADF4351 certainly needs programming every boot, does the eval board also contain a microcontroller?

author: awallin
author_rank: Frequent Contributor
timestamp: January 28, 2020, 11:33:10 am
content: Quote from: toastedcrumpets on January 28, 2020, 09:50:44 amYes, a Cypress uC IIRC - dev-board connects over USB and there's a GUI-software (windows) included for playing with the registers.
op-amp transimpedance model vs. reality + design-tips? - Page 1
Forum section: electronics / rf-microwave

author: awallin
author_rank: Frequent Contributor
timestamp: January 27, 2020, 06:05:07 pm
content: Hi all, I'm hoping some of you have experience with explaining/modeling the noise and signal spectra of transimpedance amplifiers.(after all, if we believe Hobb's book , then we must "explain every 0.5 dB")With a basic TIA-circuit (image) I get good agreement (image2) between measurements and the model -BUTI need to "de-rate" the GBWP of the OPA657 op-amp from the datasheet value of 1.6 GHz to about half, around 800 MHz, so that the noise-bump and signal/gain-bump fit my data!??Is that realistic - what could cause the op-amp GBWP to be halved?If I plot the model with the datasheet GBWP of 1.6 GHz the noise-bump should be significantly higher in frequency. (image3)OTOH if we accept the 1.6 GHz GBWP as correct we need to radically increase the source/diode-capacitance to move the noise-bump down. If I increase CD10-fold (!)to 16 pF I get the signal spectra to match again, but now the dark-noise model is 10dB too high? (image4).OK, so to now explain the noise peak height we'd need to have an op-amp voltage noise that is sqrt(10)-fold lower than the datasheet spec of 4.8nV/sqrt(Hz). If I further tweak the op-amp model like this, I get reasonable agreement again!What seems more likely,the op-amp I happened to get (from digikey) has only a 50% GBWP ? (worse than spec)I get 10-fold source-capacitance wrt. what I want, and the op-amp I got has a voltage noise of 1/sqrt(10) wrt. the datasheet value? (better than spec)Finally, any comments on the layout? Obviously there's things too close together and wrong close to the inverting input, if the source capacitance is 10-fold...?The grounded guard-trace between RF and CF was an idea from the LTC6268 datasheet[2, page 15] - and it should reduce parasitic capacitance - but maybe I am doing it wrong??thanks,Ahttps://www.hobbs-eo.com/Building_ElectroOptical_Systemshttps://www.analog.com/media/en/technical-documentation/data-sheets/62689f.pdf(FWIW images of the completed board in my blog:http://www.anderswallin.net/2020/01/one-inch-photodetector-v1/)
Identifying components in a handheld radio & hash-calculations - Page 1
Forum section: electronics / rf-microwave

author: oh2ftu
author_rank: Regular Contributor
timestamp: January 25, 2020, 10:07:16 am
content: Hello,I'm trying to figure out how a device checks whether an entered license code is valid or not.The device has an identifier, let's call it IET. IET is 15 digits (0-9). Starts always with 000, ends with 0.The license code is a 36char HEX-code AABBBBBBBBBBBBBBBBBBBBBBBBBBBBBBCCCC calculated from enabled options and IET.C defines options (0,0,0,0 - F,F,F,F) that are binary; Option 1 is 1000, Option two is 2000. With both enabled, CCCC is 3000 etc.if CCCC changes, B changes drastically.If CCCC changes, but IET does not, AA remains the same.A few examples;IETLicense00010917902751034A5DC53FA1CF7B9D8CFD3C9EAD442C6C000000109179028660988D33765CEE08CD5E3FD90ABC0FDBD9400000010917902866098365298CD1081B2AD6AEF5A08554B674100Thus far, I've had no luck other than the last four. Changing any char will lead to a fail. Validation is done INSIDE the device.I'm inclined to chop up one device to find out what's inside.Rear side, cans from top to bottomCan1:EM09AC, LMX2354,- PLL synthhttp://pdf.datasheetcatalog.com/datasheet/nationalsemiconductor/LMX2354.pdf?fbclid=IwAR3Y9w62vl8dHAkSzWxhBbMEsaqlZRLsk_FJv3sfEfC9Q2Y4FLLew0wmKBcC25R, 8pin- Buffer SN74LVC2G125Can2:EM09AC, LMX2354 as aboveCan3:Atmel MEGA544 20MU1121~32kHz oscAEU I BM, 6pin- MAX6900 RTCFront side:ST 84008- RF Power amp?https://www.st.com/resource/en/datasheet/pd84008l-e.pdfCan1:CML CMX998Q1,- IQ transmitterhttps://www.cmlmicro.com/wp-content/uploads/2017/05/CMX998_ds.pdf?fbclid=IwAR3xgsgAGtpcKaGxoBsGo3VTVFbraepA6ksiqb3cOD38siFC0sJDq4BMjwsCan2:Just passives and padsCan3:Maxim 2309E,- I/Q demodulator2690 EUB 10pin- MAX2690, 2.5GHz mixerCan4:WM1697S- Audio PA?SPR-02215, manufacturer stamped chipAnalog Devices AD6528DABCZ- GSM Baseband chipM36L0T806 0B3ZAQ,-https://datasheetspdf.com/pdf/682878/STMicroelectronics/M36L0T8060T1/1N223, osc?Can5:13TI BGB, 10pin. 2pcs, TPS62051DGS?http://www.ti.com/lit/ds/slvs432d/slvs432d.pdfOutside Cans:AAEI 12T, Probably TPA6203A1 audio amp01P32D ??Any help identifying these, and/or tips on how to calculate the hash would be greatly appreciated.These are for radio amateur use, no business plan involved.
UK use of 13.56MHz  - Page 1
Forum section: electronics / rf-microwave

author: CJay
author_rank: Super Contributor
timestamp: January 22, 2020, 02:39:10 pm
content: Experimenting with low power beacons and wondering if it's permissible to use 13.56MHz in the UK without a licence for that purpose?All I will be sending is a few Morse characters at acouple of milliwatts but of course, I don't want to fall foul of any law/regulation.

author: Dek
author_rank: Regular Contributor
timestamp: January 23, 2020, 07:57:23 pm
content: You can search Ofcom for what use is allowable and what restrictionshttp://static.ofcom.org.uk/static/spectrum/fat.htmlThere is alsohttps://www.ofcom.org.uk/__data/assets/pdf_file/0028/84970/ir-2030.pdfA very quick squizz, 13.56MHz looks like a unlicensed ISM band to me and about 10mw max erp.Dek.

author: nardev
author_rank: Unknown
timestamp: January 23, 2020, 08:00:47 pm
content: Quote from: CJay on January 22, 2020, 02:39:10 pmWell, few miliwatts, nobody cares, unless you are distributing devices. Some RFID readers/cards are at that freq.

author: Theboel
author_rank: Frequent Contributor
timestamp: January 24, 2020, 03:31:10 am
content: Quote from: CJay on January 22, 2020, 02:39:10 pmJust curious what kind of experiment You want to do ?are WSPR not good enough ? in 20m band73.
Stand alone SDR Transceiver with RedPitaya and STM32F7Discovery - Page 1
Forum section: electronics / rf-microwave

author: DH1AKF_Wolfgang
author_rank: Contributor
timestamp: January 23, 2020, 07:55:13 pm
content: Hi all,please let me show you a project, realized with assistance from Pavel Demin, started in 2016.The first photos of the "DiscoRedTRX" you can find at this link:http://www.wkiefer.de/x28/red_pitaya_stand_alone.htmA newer article (in German) is here:http://www.wkiefer.de/x28/Red%20Pitaya.htmMy part was the programming of the user interface, touchscreen and to connect the necessary components.My next goal is: to implement the FT8 and WSPR capabilities , without using an external PC or Laptop.

author: Theboel
author_rank: Frequent Contributor
timestamp: January 24, 2020, 03:35:35 am
content: excelent looks very decent unfortunately my programming skill is nothing to add anything
40m dc receiver - Page 1
Forum section: electronics / rf-microwave

author: vk4ffab
author_rank: Frequent Contributor
timestamp: January 23, 2020, 11:18:27 am
content: I am building a hand held for 40m. I got the receiver working tonight. The tx is on another board and does 5w.https://youtu.be/jNbyFvQ9uxc
Wandel & Goltermann SPM-3 - Page 1
Forum section: electronics / rf-microwave

author: geggi1
author_rank: Frequent Contributor
timestamp: January 22, 2020, 11:37:55 pm
content: I'm looking for the schematics for the Wandel & Goltermann SPM-3 selective level meter. My plan is to use the sckematics as a basis of design for a VLF reciever but with modenrn components. Not all features will be implemented but all the reciever function will be used.

author: PA0PBZ
author_rank: Super Contributor
timestamp: January 23, 2020, 11:06:34 am
content: https://www.opweb.de/nederlands/bedrijf/Wandel_and_Goltermann/downloaden/Wandel_and_Goltermann--SPM-3--service_and_user--ID8456.pdf
CTCSS board problem - Page 1
Forum section: electronics / rf-microwave

author: @rt
author_rank: Super Contributor
timestamp: January 30, 2020, 05:14:57 am
content: Hi,I made a board to generate CTCSS tones, to add to an old 2 meter radio that does not generate it’s own tones.It’s a pic generating 915Hz (for this example), then a decade counter to divide that to 91.5 Hz,then a series of low pass filters that can be tapped at various stages.I connected the tone output to the deviation centre wiper in the transceiver.Now when I set up a receiver channel on another radio to match the frequency, and require the 91.5 Hz tone to open squelch,I hear the 91.5 Hz tone on the receiver, and my transmit mic audio is very soft. Any ideas how to solve this?Cheers.

author: @rt
author_rank: Super Contributor
timestamp: January 30, 2020, 05:52:56 am
content: It appears it was jus the amplitude still too high.Plus I capacitively coupled it since that pic.All seems well now