hybridfree/eevblog-posts huggingface dataset:
First geostationary satellite with an amateur radio payload - Page 1
Forum section: electronics / rf-microwave

author: iMo
author_rank: Super Contributor
timestamp: November 23, 2018, 07:42:03 pm
content: Es'hail-2 is the first geostationary satellite with an amateur radio payload and a joint project by Qatar's Qatar Amateur Radio..https://amsat-uk.org/tag/geostationary/Es’hail-2 (launched successfully Nov 15th) carry two “Phase 4” amateur radio transponders operating in the 2400 MHz and 10450 MHz bands. A 250 kHz bandwidth linear transponder intended for conventional analogue operations and an 8 MHz bandwidth transponder for experimental digital modulation schemes and DVB amateur television.Narrowband Linear transponder2400.050 - 2400.300 MHz Uplink10489.550 - 10489.800 MHz DownlinkWideband digital transponder2401.500 - 2409.500 MHz Uplink10491.000 - 10499.000 MHz Downlink

author: cdev
author_rank: Super Contributor
timestamp: December 03, 2018, 09:17:52 pm
content: Good for them! This should be really quite cool.Wish it was a bit farther west but I'm sure we'll get one eventually.

author: Kalvin
author_rank: Super Contributor
timestamp: December 04, 2018, 01:25:15 am
content: Now we need stable and low noise transverters. That satellite may turn out to be very useful also for amateur radio emergency communication as it should cover quite large area at once with lots of bandwidth.

author: coppercone2
author_rank: Super Contributor
timestamp: December 04, 2018, 02:19:43 am
content: Hmm i would hate to see amature national security get in the way of radioscience. How much did that cost ?
Small signal diode to make broadband RF detector/FS meter? - Page 1
Forum section: electronics / rf-microwave

author: cdev
author_rank: Super Contributor
timestamp: November 11, 2018, 01:28:32 am
content: I am wondering what my best choice would be in diodes to make an simple RF detector that can detect RF of all kinds around the house, from wifi access points to the sources of RFI that may be fairly low frequency.. kHz range (with different antennas) ?1N34 or something else?

author: KJDS
author_rank: Super Contributor
timestamp: November 11, 2018, 12:42:42 pm
content: I always like the BAT63 dual diode with two TLC2652, one using teh second diode to provide temperature stability and the second to give lots of gain.Make sure you put the diodes with the anodes facing the op-amp input pins.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: November 11, 2018, 01:05:35 pm
content: What upper frequency range and what sensitivity do you want to cover?As you maybe know, there are various log-detectors; like the AD8307 which starts at ~ -75dBm but only covers upto 500MHz.Maybe you take a lot at this option

author: Wolfgang
author_rank: Super Contributor
timestamp: November 11, 2018, 10:32:08 pm
content: Quote from: cdev on November 11, 2018, 01:28:32 amyeah, either good old Germanium or some more recent Schottky diode, like an 1N5711 or something in SMD. Careful SMD construction on an RF PCB and good Schottky diodes could give to a useful detector to 3GHz without too much effort.http://www.dl5neg.de/diodesensor/diodesensor.htmlhas some info about this

author: David Hess
author_rank: Super Contributor
timestamp: November 12, 2018, 01:38:27 am
content: Low barrier (zero bias) schottky diodes are ideal but any small signal schottky diode will do. I have used 1N270s to good effect up to 1.2 GHz and they might be considered improved 1N34s. If you are going to directly drive a 50 or 100 microamp meter, then the diode type becomes less important as long as it is fast enough.The detector configuration matters also. More complex designs forward bias the diode reducing the effect of forward voltage drop and may chop the input or use a second diode for temperature compensation.If I were experimenting with a new biased detector design, I might use transistor base-emitter junctions as RF diodes.

author: cdev
author_rank: Super Contributor
timestamp: December 03, 2018, 09:15:17 pm
content: David,thank you for this info!I have some old meter movements that would be perfect for this. It will be interesting to see if they can rectify 2.4 GHz!Quote from: David Hess on November 12, 2018, 01:38:27 am
Any good ways to find out what SW signals you are listening to? - Page 1
Forum section: electronics / rf-microwave

author: Beamin
author_rank: Super Contributor
timestamp: November 24, 2018, 01:03:03 pm
content: One thing I have found with listening to short wave is there are no good sites that list what your listening to, that I know of anyways. Some times on some sites might have what they get in their local conditions, but many sites don't even say where or when they heard the signal when trying to identify them. One mysterious signal I have been trying to figure out are those repeating upsweep signals. They are obviously something important as the electric bill and equipment isn't cheap.Looking up the FCC frequency table of allocated spectrum is usually really generic. Especially with VHF and UHF for many signals it's just listed as "ISM" which could be anything, but rarely medical or industrial devices. That table also doesn't work with SW and foreign countries. Also of interest would be a map that has a day/night of how far so many watts could travel during average conditions. For instance being in the central Atlantic area of the US we get Cuba SW better then say closer states in the south because the first "hop" seems to land on us. I only know this from listening. On the plus side it does make HF kind of mysterious and appealing to listen to!

author: AF6LJ
author_rank: Unknown
timestamp: November 25, 2018, 12:49:47 pm
content: Here is a good place to start.http://worldofradio.com/

author: cdev
author_rank: Super Contributor
timestamp: November 25, 2018, 04:57:32 pm
content: You can search by frequency here to figure out what you might be listening to. You can also locate when and where any given shortwave broadcaster transmits and/or/in whatever language you want to hear broadcasts in.http://www.short-wave.info/index.php

author: jujun
author_rank: Regular Contributor
timestamp: November 25, 2018, 05:36:42 pm
content: There is also :https://www.sigidwiki.com/wiki/Signal_Identification_Guide

author: Beamin
author_rank: Super Contributor
timestamp: December 02, 2018, 12:52:31 am
content: Quote from: AF6LJ on November 25, 2018, 12:49:47 pmThat site is cryptic and looks like he made the entire page using notepad and then changing .txt to .htm and posting it to the site. Remember when making web sites were simple and fun, and when they didn't work you could figure out why?Any where in particular to look on that site?Or do you just scroll through thousands yes thousands of pages of text like this: This was maybe 0.005% of the text on that site, not exaggerating at allMOD: Ton of useless off-topic material removed.
Application differences of flexible vs. hand-formable (semi-rigid?) cables @6Ghz - Page 1
Forum section: electronics / rf-microwave

author: pratiken
author_rank: Contributor
timestamp: November 28, 2018, 07:26:22 pm
content: Hi everyone,I'm trying to understand where and when to use which type of cable.I have an application (up to 6Ghz only) that will not require any disconnecting/reconnecting of cables. Once it's setup, it won't be changed. Shielding is important as well.With that in mind, it seems like the hand-formable cables are superior to flexible cables, even high quality LMR? But I don't know if I'm understanding that correctly.Just looking at the Spec sheets between say, 12" of LMR400 vs. a 12" stretch of hand-formable, it seems like the hand-formable is superior in every way (and is cheaper too!)If the configuration remains the same with no changes, is hand-formable/semi-rigid cable always better?Thank you so much for your help!

author: pratiken
author_rank: Contributor
timestamp: December 01, 2018, 07:05:46 pm
content: Anyone have any advice on this?Thanks!!

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: December 01, 2018, 07:56:23 pm
content: Very simple: semi-rigid is always better (for the same diameter, number of screens, dielectric class).The drawback is that it is not possible to bend it more than once. Also, you can't restraighten it.

author: Mechatrommer
author_rank: Super Contributor
timestamp: December 01, 2018, 08:09:31 pm
content: Quote from: Neomys Sapiens on December 01, 2018, 07:56:23 pmi think you are talking about rigid coax. semi rigid can be re bend or straigthen, just not as easy as normal (flexible) cable. when you use semi rigid or rigid? i think on higher freq something like 10+ GHz, slight change in coax dimension will change its characteristic impedance making compensation or characterization of the cable or system difficult or inconsistent, so you want fixed dimension cable. you have to have an instrument to see this changes otherwise it doesnt matter, you can shoot with both eyes closed anything you like, who cares?

author: cdev
author_rank: Super Contributor
timestamp: December 01, 2018, 09:10:28 pm
content: What is the very stiff but not rigid or semi rigid stuff? I have some patch cable made of it in blue. I had not seen it before fairly recently. I am not in a position to test it.
Confused: Insertion Loss with power combiner same as divider? - Page 1
Forum section: electronics / rf-microwave

author: pratiken
author_rank: Contributor
timestamp: December 01, 2018, 07:13:34 pm
content: Hi,I'm measuring a 1:8 power splitter and getting about 10dB of insertion loss at 2.4Ghz with my Anristu VNA. I'm measuring S21 with Port 1 on one of the input ports and Port 2 on the single output with all other ports terminated.When I flip them, so port 1 is on the output and port 2 is on one of the 8 inputs, I get the same insertion loss.I'm confused because I thought when used as a power combiner, there should only be the insertion loss of <2dB or so, but when you use it as a power divider, you have the full 9dB+/-<2dB.Can someone explain what I'm doing or understanding incorrectly?Thank you so much!!

author: rfeecs
author_rank: Frequent Contributor
timestamp: December 01, 2018, 08:06:30 pm
content: A power splitter (with no ferrites) is a passive reciprocal device. So S21=S12.To get minimum insertion loss as a combiner, all 8 inputs signals have to be the same amplitude and phase in order to combine in-phase.

author: awallin
author_rank: Frequent Contributor
timestamp: December 01, 2018, 08:09:14 pm
content: Quote from: rfeecs on December 01, 2018, 08:06:30 pmthis seems to be what the last paragraph over here is saying also:https://www.microwaves101.com/encyclopedias/basic-network-theory

author: chrisl
author_rank: Regular Contributor
timestamp: December 01, 2018, 10:49:53 pm
content: Quote from: Neomys Sapiens on December 01, 2018, 08:34:34 pmEh? Is this a continuation of this thread spilling over to the RF section?? LOL.https://www.eevblog.com/forum/projects/need-help-with-emc-problem-and-audio/?all

author: chrisl
author_rank: Regular Contributor
timestamp: December 01, 2018, 11:04:04 pm
content: The 10 dB insertion loss on a 8 port splitter/combiner sounds about right.If you put two 8 port splitters/combiners back to back in such way that the 8 ports are directly connected to each other via the same length of cables (i.e. barrels) you will see the insertion loss between the 2 common ports will be <4 dB ( <2 dB for each combiler) since all the phase/amplitude on each ports are the same.

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: December 02, 2018, 10:42:09 pm
content: Quote from: chrisl on December 01, 2018, 10:49:53 pmSorry! too many open tabs!
3G modules for PCB - Page 1
Forum section: electronics / rf-microwave

author: Glomumu
author_rank: Newbie
timestamp: November 27, 2018, 11:57:09 am
content: Hi!I'm new in this web and I want to ask if someone here knows about 3G modules?I'm searching for a 3G module that I can use in a pcb and I only find this kind of modules for Arduino. I find a lot of information about Wifi Modules but I didn't found about 3G.Thank you!

author: brabus
author_rank: Frequent Contributor
timestamp: November 27, 2018, 12:11:17 pm
content: https://www.u-blox.com/enTop quality (but also top price!)Otherwise Digikey should have plenty of them, from other manufacturers.

author: Lord of nothing
author_rank: Super Contributor
timestamp: November 27, 2018, 02:03:36 pm
content: https://forum.sierrawireless.com/Huawei?

author: mjs
author_rank: Regular Contributor
timestamp: November 29, 2018, 06:53:40 am
content: If possible, go for 4G/LTE. Most operators have already planned when they will shut down the 3G network to make space for 4G/5G.

author: tszaboo
author_rank: Super Contributor
timestamp: November 29, 2018, 09:09:32 am
content: Quote from: mjs on November 29, 2018, 06:53:40 amBut of course 4G modules are twice the price of 3G modules. And 3G modules are twice the price or 2G modules. I wonder what will be for 5G (if you need more than LPWAN)? 80 EUR modules?

author: Lord of nothing
author_rank: Super Contributor
timestamp: November 29, 2018, 09:48:04 am
content: LTE have a better coverage.

author: DaJMasta
author_rank: Super Contributor
timestamp: November 30, 2018, 07:36:11 am
content: They certainly exist, but they don't do a lot of sales outside of commercial products, I think, so the low demand means they aren't found that much at distributors. Needing a sim card or a plan attached means doubly so, because to test anything out you need the service side as well, so the maker-oriented integrated solutions are often sold with some cut down data plan. Something like Particle's offerings could be an option if you're looking for an ARM core integrated with your radio.That said, 3G is being phased out, so it's going to be even harder to find. As mentioned, LTE generally offers 3G as a fallback, but also incorporates the longer range/higher speed radio that networks will likely support for longer, so if you can find a decent price on a 4G/LTE module, I'd design around that instead.
(Lack of) discrete GHz active RF components - Page 1
Forum section: electronics / rf-microwave

author: kvide
author_rank: Newbie
timestamp: November 21, 2018, 10:40:31 pm
content: What are folks using in their C-band LNB design?Since Broadcom EoL'ed their (well, ex. Avago's, ex HP's) pHEMT product line last year, I don't seem to find anything that performance wise comes even close to the ATF-3xxx and ATF-5xxx series GaAs FETs, with regards to NF and OP1 in the 4 - 8G Hz range.For a two stage receiver LNA, the first stage should preferably have a NF < 0.5 (at ~5 GHz) but such FETs or transistors does not seem to be available anymore.Skyworks 65050 has a NFmin round 0.8 and CEL CE3512K2, while having a low NF, is designed for Ku-band and below 8 GHz the S-parameters are almost off the chart.

author: dcarr
author_rank: Regular Contributor
timestamp: November 22, 2018, 05:13:23 am
content: This is a really good question.There are some interesting SiGe parts in the 0.5-0.8dB NF space but their performance still isn't as good as a pHEMT (eg: BFU730).David

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: November 27, 2018, 03:57:12 am
content: What motivates someone to pursue such a strategy? They must be well aware that lacking those 'simpler' components, the systems designs using their more profitable integrated product lines won't come to fruition?

author: dcarr
author_rank: Regular Contributor
timestamp: November 27, 2018, 04:28:01 am
content: Maybe we'll find some Chinese pHEMTs emerging to fill the gaps? I imagine it's a very strategic technology to develop.David
Help sought on TRW/Aertech RF detector data - Page 1
Forum section: electronics / rf-microwave

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: November 27, 2018, 01:39:57 am
content: can anyone help me out with data on the following RF detectors:Aertech DS1052 (Schottky)Aertech DMM408B (Tunnel)TRW Microwave DX1483-S (Tunnel)All are SMA in, SMC outThanks in advance! They are in immaculate condition and would close a capability gap, if I knew more of them!
RFID Reader - Page 1
Forum section: electronics / rf-microwave

author: trungosu
author_rank: Contributor
timestamp: October 26, 2018, 08:01:20 pm
content: I would like to build a box which I will store some items inside.I already have an LCD with ATmega328P on top of the box.I want to add an RFID Reader into the box so I will know how many items inside the boxand when I open the box and take out the items, I know which one been taking out.I have used the RFID-RC522 but the problem is I have to place the items really close to the reader in order to read the RFID tag.The box size is 14"x14"x14".Right now, I'm using lipo battery to power for the system but I even could put a small 12V battery inside the box if necessary.The idea is only wake up and read when the lid is open and will go to sleep.I could not find any RFID reader could cover this range and with low power supply and also if it could be used with Arduino (optional)Please let me know if you have any idea. Thank you very much

author: GeoffreyF
author_rank: Regular Contributor
timestamp: October 26, 2018, 08:30:07 pm
content: This may be more than you were intending but it is what you want. With the right antenna, a UHF RFID tax can be read at 10 meters away. It sounds like you have been working with inductive or VHF tags which indeed have very short ranges.https://www.sparkfun.com/products/14066Thing Magic makes other products, for example one that connects by USB.I worked for them awhile back on a project that reads tags on tools in the back of a truck or van. I was amazed how well it worked, even a midst a box of tools or other supplies one might find in a contractors truck. It was all integrated with a dashboard computer that did all the usual GPS stuff but also connected to Microsoft office. The idea is that if leaving the shop in the truck, an instant inventory of all needed for the days work would be taken. Then when returning the truck would know what had been left behind at the job sight, with the GPS coordinates.

author: trungosu
author_rank: Contributor
timestamp: November 26, 2018, 08:50:45 pm
content: Thank you very much. The price and the range are more than what I want but definitely, I will give it a try.Your project is absolutely amazing. We also try to help reduce the time on inventory.Quote from: GeoffreyF on October 26, 2018, 08:30:07 pm
Self built wide band SWR meter - Page 1
Forum section: electronics / rf-microwave

author: rodolfok
author_rank: Contributor
timestamp: November 23, 2018, 01:17:34 pm
content: Hello,I've built a SWR-meter following the article "https://ludens.cl/Electron/swr/swr.html".I initially used a small meter which successively was damaged, so I changed the housing and put everything in an old analog multimeter, which also has a big meter (galvanometer); you can see it in the attached picture.The new meter is a 40kΩ/V, i.e. has a 17,5uA end of scale current and 5000Ω coil resistance.To extend the range to 100uA I've put a 1kΩ shunt resistor in parallel to the coil.I now get a strange behaviour because the movement of the needle is very slow, it needs about 15-20s to get to a stop, either in direct or reflected mode.This should be somehow linked to the type of galvanometer, but how?thanks and regardsrodolfo
Proper way to cable these 8 port RF devices with SMA cables? - Page 1
Forum section: electronics / rf-microwave

author: pratiken
author_rank: Contributor
timestamp: November 19, 2018, 11:31:24 pm
content: Hi everyoneI have to cable these 8 port devices positioned 90 degrees from eachother. The grey box is a splitter.I'm trying to keep insertion loss in mind and consistent across all 4 ports. What would be the proper way to do this?edit: working up to 6GhzThanks!!

author: ejeffrey
author_rank: Super Contributor
timestamp: November 20, 2018, 05:13:16 am
content: Definitely the second option. Firstly because it is simpler: only one cable to stock instead of 8 cables and 8 attenuators. Secondly, because getting the attenuators correct will be incredibly annoying, and even in the best case only work at one frequency since cable loss is frequency dependent while good attenuators have flat response. Finally because you might at some point care about phase. Identical cables keep each signal at the same phase.If you don't like the crossing because it is annoying to trace, put color coded labels or heat shrink on the cable ends.All that said, I think you may be making something out of nothing. Loss in high quality short cables at 6 GHz is pretty small especially if you use hand formable semi-rigid cable. So the skew in loss for option 1 should be very minor.

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: November 20, 2018, 06:39:45 am
content: If this was a metrology-grade setup, using phase-matched sets of cables. would be the way to go.Even without being metrology, going for same-length seems the logical choice, since it requires less part types and less drift.

author: DaJMasta
author_rank: Super Contributor
timestamp: November 21, 2018, 05:01:51 pm
content: +1 to what's been said. Using different length cables will mean different phases into the receiving device, which is likely to cause trouble in a lot of applications, plus unless your cables are very long, you're talking a few tenths of a dB worth of attenuation - it wouldn't be worth the time or effort to source or make those parts, and they would likely be several times the price of the matched cable set in the required values.Just making a sag or a loop to compensate lengths and connecting like the drawing on the left while using same length cables would also be an option. Maybe not if you're trying to optimize weight or are building it into an art installation, but it will do the job just fine.

author: pratiken
author_rank: Contributor
timestamp: November 22, 2018, 10:54:46 pm
content: Thanks for your help!Another thought, this setup will not change at all once completed. Would semi-ridged cables make more sense? It seems like the properties of quality semi-ridge cables are much better than even good quality LMR. What do you think?
identifying unknown toroids - Page 1
Forum section: electronics / rf-microwave

author: cdev
author_rank: Super Contributor
timestamp: November 16, 2018, 07:01:43 pm
content: Is there a good procedure for looking up the manufacturer (or determining the relevant parameters of) unknown magnetic elements one's come into possession of?The two pictured components are good examples of unknown magnetics I'd like to know more about.The first one is a balun I bought - for better or for worse forgetting to ask what the ferrite ring that it uses is. I've never seen one in this color. (the toroids' actual color under the tape is white and it looks like its decent quality). The unun works well but I've never used it in a transmit application. (Edit: This one may be a T130-7 core, which is similar to a T130-2 but a little more favoring of higher frequencies than the type 2 material. So I am tentatively identifying it as that.)Its largest dimension is around 33 mm. Its wound as a 9:1 unun.Also, I have a bunch of the flat noise suppression ferrites in the second picture.They work well, but I bought them as-is and don't know anything about them. The seller didn't know the manufacturer. I'd like to be able to identify the mix they use, and whether its more effective at HF or VHF.I have a 25 MHz signal generator and a 50 Mhz analog scope.Nine turns of insulated multistrand hookup wire tightly wound through it reads 0.06 mh on my AVR Transistor Tester.I also have quantities of some other smaller magnetics, particularly a bunch of nicely made small toroid beads that I also know nothing about. Ive successfully used them in things, but wish I knew more about what they were.

author: rhb
author_rank: Super Contributor
timestamp: November 22, 2018, 03:20:24 pm
content: I'm trying to get set up to do the same thing. In your case, to measure the hysteresis loop, you need an analog integrator. With an upper limit of 25 MHz, that should not be too much of a problem to build using an op amp.Much to my annoyance, except for some of the LeCroys, DSOs with math functions will not let you choose a math trace as one of the XY inputs. I now own a DDA-125 for that reason.I assume that by making hysteresis plots at a number of frequencies one can derive many of the parameters, but have not yet gotten into the details. I pretty much took it as a sine qua non.You should be aware that physical construction of the test fixture is important. I've read a number of things about it, but can't recall if it was here (most likely) or the hp-agilent-keysight group on groups.io or the VNWA list. I highly recommend joining both.

author: cdev
author_rank: Super Contributor
timestamp: November 22, 2018, 07:54:24 pm
content: An analog computer, kind of?Thank you, thats a great idea.Sounds like a useful, fun and likely quite affordable project!

author: rhb
author_rank: Super Contributor
timestamp: November 22, 2018, 10:44:25 pm
content: It's not really an analog computer. It's a measurement technique.Read this:https://meettechniek.info/passive/magnetic-hysteresis.html
UWB and detection of NLOS path - Page 1
Forum section: electronics / rf-microwave

author: kamtar
author_rank: Regular Contributor
timestamp: November 13, 2018, 11:48:43 pm
content: I'm FW developer so RF is a little bit outside mine understanding. I would like to ask about details on how detection of a signal which came via NLOS is possible.I'm talking about UWB radio (concretely decawave). From user manual, it should work by comparing first path power vs estimated RX power.It works with that when it's a NLOS signal first path power is less than overall RX power.I get now that when it gets reflected or diffracted then some interference happens, some frequencies are attenuated in a different way etc.. but I'm trying to understand what exactly happens, why first path signal gets attenuated more in this case?I don't need full explanations just some hints into where to look, I went through a few of studies and other materials but wasn't able to find an answer on why just that it happens.

author: rhb
author_rank: Super Contributor
timestamp: November 22, 2018, 10:19:19 pm
content: When a wave is reflected or refracted, the propagation direction changes. For a multipath UWB signal this means that different frequencies experience phase cancelation at any given reception location.Think back to optics in 2nd or 3rd semester physics. You should have encountered it in that context.I suspect that the real problem is you're expecting it to be more complicated than it is. Of course, if you're trying to predict it, it *is* more complicated than you think. The reflected and direct oath single plane wave impulse is easy. The real world gets seriously messy.Be happy. If this were seismic, you'd have to deal with spatially varying velocity.
Nokia Siemens Flexi BTS base station teardown: Power amplifier (part 1 AND 2) - Page 1
Forum section: electronics / rf-microwave

author: madsbarnkob
author_rank: Frequent Contributor
timestamp: October 28, 2018, 07:35:44 pm
content: Teardown of a Nokia Siemens Networks Flexi BTS base station. This have been in service as a 6 antenna GSM system for mobile telecommunications.GSM/EDGE, WCDMA/HSPA and LTE capable. 2x40 Watt output power.also a picture of me pointing at where a remote radio unit or base station amplifier is usually mounted. Technically seen this is a TMA (tower mounted amplifier)

author: madsbarnkob
author_rank: Frequent Contributor
timestamp: November 22, 2018, 09:10:40 pm
content: I finally got the circuit analysis finished and there is a whole lot fo ground trying to be covered in just roughly 20 minutes, so many details are left out only trying to cover some of the basics and let people catch the interest and seek out more information.The high resolution pictures can not really be attached here, so please see them at my website where it has some more description aswell:http://kaizerpowerelectronics.dk/teardown/nokia-siemens-flexi-bts-base-station-teardown-circuit-analysis-part-2-of-2/
vswr and reflected power readings - Page 1
Forum section: electronics / rf-microwave

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: November 21, 2018, 12:15:17 am
content: OK, I'll preface this to say that I've always thought that if you had 1KW forward and 200W reflected then you are only getting 800W out the antenna. I am working a problem and read up a bit on VWSR to refresh my knowledge and came across several places that say that my preface is incorrect. They sound knowledgeable and have lots of measurements to back them up. Now here is my setup. I have a 1KW forward power going out through a high power circulator then a fwd/rev directional coupler and out to the antenna. Say I read 1KW fwd pwr and 200W reflected. In this specialized setup the 200W will end up in the load of the circulator and my "out the antenna" pwr will be 800W. It makes sense to me!Am I missing something???

author: KJDS
author_rank: Super Contributor
timestamp: November 21, 2018, 07:33:34 pm
content: The bits you are missing are the uncertainties.If your directional coupler has perfect directivity and your circulator has perfect return loss then anything not reflected back is either going out the antenna or lost as heat in the cable loss.

author: hagster
author_rank: Frequent Contributor
timestamp: November 21, 2018, 07:41:52 pm
content: Totally possible to have an antenna with good VSWR and low efficiency. The difference is being converted to heat somewhere. This could be ohmic losses in the metal or dielectric losses in antenna materials.A 50ohm resistor has very good VSWR.It may be possible in your case to rule out many sources of loss and get a reasonable level of confidence that VSWR is giving you a good approximation of radiated power.

author: tkamiya
author_rank: Super Contributor
timestamp: November 21, 2018, 09:47:37 pm
content: You are forgetting loss in coax.Reflected power will have double the coax loss + loss due to mismatch. If your test instrument is by transmitter, returned power will read a lot lower than doing the same by antenna.In extreme case, such as frequency being 440MHz and coax RG-174 for 1000 feet. Even if you don't have any antenna connected, swr by your transmitter will read almost 1:1. Not only did little power reach the antenna, reflect power was also consumed by the coax loss. The end result is nothing coming back.

author: izsurk
author_rank: Newbie
timestamp: November 22, 2018, 12:39:38 pm
content: Quote from: hagster on November 21, 2018, 07:41:52 pmJust for the antenna theory: Are the factors degrading antenna efficiency itself only ohmic and dielectric or is it possible to think that the antenna radiates in an ineffective way. Like the antenna geometry being "bad" and thus producing radiating fields which do not necessarily lead to "productive" or "usable" propagation in the far field. Or would these "ineffective" fields (probably near field) have an effect back into the antenna itself thus degrading the matching / resonant frequency of the antenna?
What is this MMIC ? - Page 1
Forum section: electronics / rf-microwave

author: TSL
author_rank: Regular Contributor
timestamp: November 22, 2018, 06:50:56 am
content: Hi all,I've spent hours googling but I just cant seem to find out what this MMIC is. See pic.It has 414 printed on the top of it.Does anyone know ?This is the MMIC behind an NE42484A FET in the front end of an old AIDC 3733 down converter.thanksTim

author: EVS
author_rank: Contributor
timestamp: November 22, 2018, 07:55:15 am
content: HiLooks similar AT-41486 FET

author: TSL
author_rank: Regular Contributor
timestamp: November 23, 2018, 05:15:58 am
content: Quote from: EVS on November 22, 2018, 07:55:15 amActually you are right, it is an AT-41486I wrongly assumed it was an MMIC, I should have looked closer at the circuit the first time!thanksTim
Very odd nfc design, help wanted - Page 1
Forum section: electronics / rf-microwave

author: snx
author_rank: Contributor
timestamp: November 20, 2018, 07:06:04 am
content: Hello,My task is to build a nfc (mifare) reader/writer that writes tags. But in my application the mechanical parameters are very odd. I try to explain the details here and are looking for advice.1.) Imagine a plastic tube (abs) with inside diameter of 20mm2.) This tube is inside another tube with around 25mm inside diamter, which means only a flexible pcb antenna can be used, since it has to be bended and placed between the two tubes.3.) Trough the tube of 20mm travels a NFC Tag with rather slow speed. The size of the tag is a rectangle 15x33x5mm in size. Because of the 33mm in lenght, the position is given,4.) The tag therefor falls always in the same direction, but the angle of the tag surface can be any value.5.) Currently i'm using a flexible Antenna that is sticked on the 20mm tube outiside and goes half around (-90° to 90°). This allows me to read the tags when they fall in an angle of 80-100° +- from the antenna middle. But all other positions can't be read properly.My question is, how can i design an antenna that can read the tag regardless of angle.If you need a drawing or something please notify me, so i can provide a drawing of this abstract task!Any help appreciated

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 20, 2018, 08:41:54 am
content: Start with a "butterfly" coil (a loop coil, projected onto a cylindrical surface so that, for the rectangular loop case, two sides are parallel with the cylinder axis and the other two sides are semicircles linking the sides together), then twist it as a helix.That should be the form that your coil takes, once wrapped up. Sounds like you're fine on that.Using flex makes this even easier I think, because you can just twist that into a helix in the first place, maybe making it slightly wider to account for the effective change in circumference.It won't have 360 degree "sight" in any point, but if the tag is not rotating as it falls, then it should still interact at some point.As for having enough time to interact, no idea. Mechanics are usually very slow compared to electronics, but NFCs can take their sweet time starting up. If you have ~unlimited length over which to read it, then it won't much matter that some given angle is unreadable for only a short portion of the fall.Tim
AQI and APRS - Page 1
Forum section: electronics / rf-microwave

author: metrologist
author_rank: Super Contributor
timestamp: November 16, 2018, 06:12:05 pm
content: It's the fad around here now to watch the air quality indicators. The air quality management district only has so many indicators, so I thought someone on the APRS network would have one linked up, but I could not find any.Anyone know about the hardware to get that done?Also, there is a WX station just about every block, hundreds in the area. Are these usually canned systems and just plugged into a network?

author: metrologist
author_rank: Super Contributor
timestamp: November 19, 2018, 10:47:45 pm
content: Well, I found something similarhttps://www.purpleair.com/map#1/25/-30

author: coppercone2
author_rank: Super Contributor
timestamp: November 19, 2018, 11:10:07 pm
content: is this at all useful without wind and temperature modeling incorporated? Don't they behave like plumes? Can you get any information from a point?

author: metrologist
author_rank: Super Contributor
timestamp: November 20, 2018, 12:40:25 am
content: Quote from: coppercone2 on November 19, 2018, 11:10:07 pmI'm unsure of your meanings there, but information yes, even if you can't overlay the data with other sources...This is a measure of specific particulates at a certain time.
LFB182G45SG9A272 filter - Page 1
Forum section: electronics / rf-microwave

author: Ammar
author_rank: Regular Contributor
timestamp: November 14, 2018, 06:21:55 am
content: I am using this filter in the image shown below. The bluetooth link is bidirectional, but it will be receiving much more data than it is transmitting. Is the direction in the application note set correctly? What would happen if the "in" of the filter were facing the chip and the "out" was facing the antenna?The datasheet for the filter doesn't say much about what is going on internally.

author: RadioNerd
author_rank: Regular Contributor
timestamp: November 16, 2018, 10:53:53 am
content: The large majority of HF filters is usually almost petfectly reciprocal, i.e. S21 = S12. There might be some minor differences in return loss or power handling (the port defined as IN is usually slightly better) but this can be neglected in 99% of the cases
Another Ham Radio Youtube Blogger - Page 1
Forum section: electronics / rf-microwave

author: German_EE
author_rank: Super Contributor
timestamp: October 25, 2018, 07:01:03 pm
content: I've just made an interesting discovery:https://www.youtube.com/channel/UCSNPW3_gzuMJcX_ErBZTv2g/videos?disable_polymer=1He's into lots of homebrew radios and there's an interesting method of modular construction that I intend to try over the weekend.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: October 25, 2018, 07:11:23 pm
content: Looks good; he still seems go for non-smd parts mainlynot a YT channel but worth to mention in that context is Peters DK7IH homebrew transceiver blog:https://radiotransmitter.wordpress.com/tag/dk7ih/he is already shrinking down sizes in all-smd constructions

author: james_s
author_rank: Super Contributor
timestamp: November 18, 2018, 06:32:43 am
content: I think there's room for both approaches. I generally use SMT parts in my projects and have for quite a while, but sometimes it's fun to build something out of chunky old style through hole parts. Heck for a while now I've been itching to go further retro and build something out of vacuum tubes wired point to point on a metal chassis.

author: MarkF
author_rank: Super Contributor
timestamp: November 18, 2018, 03:18:07 pm
content: You may also enjoy Alan Wolke's channel:https://www.youtube.com/user/w2aew/videosHe does many projects and gives very informative explanations.
2GHz 2-nd LO, missing step recovery diode? - Page 1
Forum section: electronics / rf-microwave

author: orbanp
author_rank: Regular Contributor
timestamp: November 23, 2018, 05:56:47 pm
content: Hello Everyone,I am repairing a pair of Polarad 632B SAs, I am writing about it here:https://www.eevblog.com/forum/repair/polarad-sa-repair/msg1917425/#msg1917425In the SA #2 the second LO does not seem to be working properly.The manual, which is for the 632A version (mine are the B) mentions that for the second mixer the LO drive must be about 2dBm at 1.995GHz.The LO source is a ~100MHz crystal oscillator, doubler and amplifier stages and then a step recovery diode generating overtones. The output from this comb generator goes through a three-chamber helical pass band filter, having about 2dB insertion loss.So the comb signal before the filter should be about 4dBm or so.With the repaired SA I can only see about -75dBm signal produced at 2GHz, and about -15dBm at 200MHz which is the doubled and amplified base oscillator frequency.(That repaired SA shows correctly the 100MHz cal signal, and the output from my HP-8640 sig gen which has the 1GHz option.)The interesting point is that in my version of the the SA in the LO unit there is no step recovery diode!I can only see, and measure, a 330 Ohm carbon composite resistor at the output!How is that supposed to work? Well, it obviously does not work for me!It looks that the unit came like that from the factory and is not the result of some repair or modification.I would like to hear some explanation for this!I am enclosing the schematics of the A version 2-nd LO, the output stage of my LO, and a few pictures.The step recovery diode in the A version is the HP-0112, a glass diode.HP has good description of the step recovery diode and its application in the '64 December HP-Journal and in HP AN-918.Thanks, Peter
Calculating frequency offset for FSK - Page 1
Forum section: electronics / rf-microwave

author: joeyjoejoe
author_rank: Frequent Contributor
timestamp: November 10, 2018, 01:46:28 am
content: I've got a nice test circuit with a MICRF112 (http://ww1.microchip.com/downloads/en/DeviceDoc/MICRF112.pdf), that I am using in frequency-shift mode. It is working nicelyThe specs have a bit of info on how it operates.I'm wondering how I can calculate XTAL_MOD, so that the FSK offset is closer to 35kHZ. Right now it is closer to 6khZ.This is my current schematic, with XTAL_MOD using a 3.3pF capacitor.I'm hoping the math isn't too far above my head.

author: joeyjoejoe
author_rank: Frequent Contributor
timestamp: November 10, 2018, 01:59:11 am
content: Might be on to something...http://ww1.microchip.com/downloads/en/appnotes/00826a.pdfCrystal PullingSeries or parallel resonance crystals can be pulledfrom their specified operating frequency by adjustingthe load capacitance (CL) the crystal sees in the circuit.An approximate equation for crystal pulling limits is:Where ∆f is the pulled crystal frequency (also known asthe load frequency) minus fs

author: joeyjoejoe
author_rank: Frequent Contributor
timestamp: November 11, 2018, 02:42:35 pm
content: So I'm not quite sure what fs and C0 are.This is the data sheet for the crystal, which tells me Cl and C1.https://www.mouser.ca/datasheet/2/741/LFXTAL036679Bulk-998814.pdf
Quick and dirty 8 GHz notch - Page 1
Forum section: electronics / rf-microwave

author: ezalys
author_rank: Frequent Contributor
timestamp: November 10, 2018, 12:13:14 am
content: If you needed a super quick and dirty notch filter at 8.something GHz with a 50 MHz bandwidth with a little tunability what would you do? I could just shoot something out with a circuit board mill but I have to imagine there’s a clever way to do it with an sma pin connector and some pipe fittings or something. 30 dB of suppression or more in the notch would be ideal. I have some eccosorb too if that would be useful.

author: tggzzz
author_rank: Super Contributor
timestamp: November 10, 2018, 01:06:44 am
content: You could always try the techniques mentioned herehttps://www.eevblog.com/forum/rf-microwave/rf-construction-technique-in-microwave-region/msg1944931/#msg1944931on whatever substrate you are using.

author: hagster
author_rank: Frequent Contributor
timestamp: November 10, 2018, 07:47:50 am
content: A simple 1/4 wave stub would be the first thing I would try. You can build it out of coax rather than printed microstrip.You could get an idea of bandwidth by creating a quick model in QUCS.
Where can I get some beamlead diodes? - Page 1
Forum section: electronics / rf-microwave

author: Mrt12
author_rank: Regular Contributor
timestamp: November 09, 2018, 09:12:14 am
content: I would like to make some experiments in the higher RF regions, e.g. frequency doubler, mixer and detector for up to 50 GHz.I would like to use some beamlead diodes; I know these are difficult to handle but I got a microscope and I also have a box of silver epoxy - in many application notes from beamlead diode manufacturers I read that glueing them with silver epoxy is fine (even though bonding appears to be *the* method).So I wonder where I can get a bunch of diodes. Mouser has them, for an acceptable price of 2..5 EUR per piece, but they sell them only in lots of 100 - which becomes quickly quite expensive ;-)RF-microwave.com has also some beamleads, but there it is already 20 EUR per piece, so if I took 10 pcs, I am already at the same price as Mouser.... so does someone know where to get a few such beamlead diodes, e.g. MA4E2037 or something similar?
FCCID related information - Page 1
Forum section: electronics / rf-microwave

author: lorth
author_rank: Contributor
timestamp: November 08, 2018, 08:37:09 am
content: Hi all,First of all, sorry if this is not the right place to post this.I got a new "toy" an Anki Vector, the small robot that it's an evolution of the Cozmo.I was looking into its FCC ID, i wanted to check pictures, documents etc, and it's not available 2AAIC00010. Neither at fcc.gov nor at fccid.io, however, the cube that comes with it it does have an entry on FCC:https://fccid.io/2AAIC00011All the Anki entries can be found here:https://fccid.io/2AAICSo my question, why is it not published? When can yo not publish this data?Thanks!

author: Neilm
author_rank: Super Contributor
timestamp: November 08, 2018, 08:09:16 pm
content: It might be using an approved module - these would be registered by the module name, not the final product. However, IIRC the FCC ident should be on the product somewhere. If not, it should be in the user guide.
HT 25-19 HF Transistor data - Page 1
Forum section: electronics / rf-microwave

author: Amper
author_rank: Frequent Contributor
timestamp: November 12, 2018, 07:45:43 pm
content: Hi!First of all im sorry to open a thread for this kind of topic, but i have found other people in other places not getting answers to this question, so i decided to try here anyway.I have several 13,65MHz power amp boards and i would like to know what they are capable of. They are built around two power trasistors each markedCode:CHT 25-199021I could not find any documents on the web related to them.Does anyone have some info?It should be around 50V operating voltage and 200W Pout.Im mostly interested in the maximum voltage, is there some way of determining that by careful measurement non destructively?
Tube Amps - Browning Mark 100 Mobile and ABC Electronics 150 - Info? - Page 1
Forum section: electronics / rf-microwave

author: FB72
author_rank: Contributor
timestamp: November 06, 2018, 10:39:29 pm
content: Hi all,I have two tube RF amplifiers, a Browning Mark 100 Mobile and an ABC Electronics 150.I wasn't able to find much info on the ABC, but the Browning appears to be a mobile version of the model 170? The 180 looks to have one relay and one tube for switching between receive/transmit, but mine has two relays instead. The Browning also appears to be unused. it is S/N 2204Both amps came from a CB/radio repair shop in my hometown that closed sometime in the mid 70's, when the owner passed my grandfather received quite a bit of stuff from his estate. These two amps were in the mix and have been sitting in storage for about 15 years or better.Pictures for drooling if need be:Browning has two 6JG6A tubes.Still have the mounting bracket even.Inside topinside bottom:rear:The ABC 150 has three tubes:6B05, 6K6V, Eimac 8875I couldn't find much on this model, anyone have any info?Some photos of the ABC:Inside top:It has seen a lot of use. The cooling fan must have died at some point, a baffle has been removed from the case and the rivets drilled. The mounting of the current fan was done with some strip steel scraps.rear: