hybridfree/eevblog-posts huggingface dataset:
FM stereo to mono (Si4712)  - Page 1
Forum section: electronics / rf-microwave

author: Amper
author_rank: Frequent Contributor
timestamp: May 06, 2019, 02:15:15 pm
content: Hi!For my 10GHz transmitter Project i need a 81.5MHz reference signal and since this frequency is in the range of the Si4712 fm transmitter chip i decided to give it a go. It generates a nice signal wich then is upconverted to 10G (x128).Sadly since it is a stereo transmitter the L&R channels then seperate out to 2*19kHz*128= 5MHz wich is far to much for the pll to run after and also far to much for the sdr to demodulate after coming from the lnb.Is there any way of getting rid of those signals? At 19kHz i cant just use a band pass and i doubt i can turn the chip to mono somehow.Is there some other simple way of generating the frequency i need without building an entirely new pll FM transmitter?cheers

author: radiolistener
author_rank: Super Contributor
timestamp: May 06, 2019, 03:16:33 pm
content: I think you cannot do it with stereo fm modulator.If you're need oscillator for 81.5 MHz, you can use Si5351. It allows to program any frequency from 4 kHz to 200 MHz.https://www.aliexpress.com/item/1Pcs-DC-3V-5V-5351-Si5351A-Si5351-I2C-Clock-Generator-Breakout-Board-Module-Signal-Generator-Clock/32972854971.html

author: OwO
author_rank: Super Contributor
timestamp: May 06, 2019, 03:37:23 pm
content: You can disable stereo by setting the TX_COMPONENT_ENABLE register.http://web.engr.oregonstate.edu/~traylor/ece473/data_sheets/AN332.pdf

author: Amper
author_rank: Frequent Contributor
timestamp: May 06, 2019, 04:37:15 pm
content: Thank you very much! I have missed this one in the datasheet...I will update when i have tried (probably in the next few hours or so)

author: Amper
author_rank: Frequent Contributor
timestamp: May 06, 2019, 06:22:56 pm
content: Yep, it worked, though its necessary to also disable carrier:Sadly the 10ghz is still roughly 3MHz wide and i dont know why. Ill now try building a low pass behind my output amp, we will see...
cheap chinese VNA up to 6Ghz - Page 1
Forum section: electronics / rf-microwave

author: jujun
author_rank: Regular Contributor
timestamp: May 06, 2019, 09:51:42 pm
content: Hello,I randomly found this on aliexpress :https://www.aliexpress.com/item/6G-dual-port-vector-network-analyzer-VNA6000-Bluetooth-WIFI-2-4G-5-8G-antenna-test/32857907599.htmlAny informations of what is inside ? What do you think about it ?Maybe one of you already did a teardown if it.Thank you,J

author: OwO
author_rank: Super Contributor
timestamp: May 07, 2019, 01:52:53 am
content: That's not cheap at all. Two port VNA up to 6GHz should have a BOM cost of around $200 and retail for $200*2.5 = $500.

author: richnormand
author_rank: Unknown
timestamp: May 07, 2019, 02:30:56 am
content: As stated above by blueskull:Would look at the xaxaxa unit on kickstarter.I got one and it is as described and has good performance and good support from him via Github.

author: OwO
author_rank: Super Contributor
timestamp: May 07, 2019, 02:37:53 am
content: Quote from: blueskull on May 07, 2019, 02:21:37 amI think all of those DIY network analyzers have real receivers and do DSP to detect phase and magnitude. Look at the block diagram here:http://hforsten.com/improved-homemade-vna.htmlSame thing here:https://raw.githubusercontent.com/xaxaxa-dev/vna/master/pictures/overall_diagram.pngThe directional coupler is constructed using a resistive bridge and coaxial balun:http://hforsten.com/img/vna2/coupler_finished.jpgI have tested a similar coupler like the one above and it was possible to get raw directivity of 25-30dB up to 3GHz. The calibrated directivity will be far better.

author: loxodes
author_rank: Contributor
timestamp: May 07, 2019, 03:30:40 am
content: Quote from: blueskull on May 07, 2019, 02:48:51 amCheap directional couplers constructed from a resistive bridge and coaxial balun can work down to hundreds of kHz.(See nikolay2015.pdf attached tohttps://www.eevblog.com/forum/rf-microwave/directional-coupler-150mhz-buy-or-diy/msg1388414/#msg1388414)

author: OwO
author_rank: Super Contributor
timestamp: May 07, 2019, 03:38:52 am
content: And if you rearrange the bridge so that the balun is on the coupled port, then add a differential amplifier, it can work down to DC.For example look at the resistive bridge here:http://www.yl3akb.lv/content/vna_v2/block_diagram_vna_v3.JPG
10MHz-19GHz RF Signal Generator Frequency Source Sweep & OLED & Software LMX2595 - Page 1
Forum section: electronics / rf-microwave

author: drazziweht
author_rank: Newbie
timestamp: May 04, 2019, 01:06:22 pm
content: These seem to be all over Ebay at the moment.Anyone bought one ?.Are they any good ?
BigClive attempts to reverse-engineer a microwave motion sensor... - Page 1
Forum section: electronics / rf-microwave

author: amyk
author_rank: Super Contributor
timestamp: May 11, 2019, 01:39:24 am
content: I thought y'all might be interested in how close/far he was from understanding how it works:

author: rfeecs
author_rank: Frequent Contributor
timestamp: May 11, 2019, 03:08:29 am
content: We measured and analyzed the RF part of this thing about a year ago:https://www.eevblog.com/forum/projects/microwave-black-magic-guru-needed/msg1466453/#msg1466453

author: joseph nicholas
author_rank: Frequent Contributor
timestamp: May 11, 2019, 12:48:41 pm
content: I bought one of these many months ago. It worked good for a while then: I put it away and tried to use it again, but it lost its sensitivity. I don't think they are very robust. Also when working properly, it seemed erratic. Very interesting to play with in experiments and they claim it works through walls, but I couldn't verify this.
How to wind coils for wireless power transfer ? - Page 1
Forum section: electronics / rf-microwave

author: ptricks
author_rank: Frequent Contributor
timestamp: May 04, 2019, 02:16:40 pm
content: I have been working on a few hobby projects (not cell phone related charging , though same concept), involving power transfer with varied success.I see coils wound in square shapes , round shapes, ovals, some have stacked coils. The circuit I am using right now is fairly simple.I am just using some magnet wire wrapped in a coil for L3 and L4 and I control the frequency with a function generator.How does the way the coil is wound effect the variables like power output, efficiency, and distance between the coils ?I am used to winding torroid type coils for power supplies where if a winding overlaps on the coil it doesn't change the performance much , but if you wind a coil for something like thisdoes overlapping the winding have a negative impact ? I see litz wire used in a lot of the commercial offerings and I don't really want to have to buy litz wire but I have tons of magnet wire so is it possibleto get the same performance ? What a about pc board based coils for power transfer (good or bad )?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 04, 2019, 03:59:44 pm
content: Shape, not much. The area enclosed by the winding is what's important. Square or oval or other shapes, are just a matter of convenience, maximizing useful area in a given form factor.Coupling distance is on the order of the diameter, give or take how low of a k (coupling factor) you can tolerate.Litz is used because the Q factor needs to be relatively high for reasonable efficiency (e.g., ballpark Q = 100 for k = 0.1 and efficiency <80%). At power conversion frequencies (i.e., 100s kHz), solid magnet wire will get Q in the 10-100 range; Litz can do about 10x better.If you have lots of fine magnet wire, you can make your own Litz by bundling up a bunch. Just a bunch of (7 or more) strands will help, or you can make rope by twisting multiple bunches together (which is what proper Litz does).Planar magnetics (PCBs) can be okay but it depends on how much effort you put into them. A structure resembling Litz can even be made on a multilayer board, but it of course takes up a lot of space, and is a bit of a pain to draw. The aspect ratio tends to be unfavorable (flat traces are "all corners", versus round wires that allow magnetic field to flow around them more easily), so you can't get the same performance as a wire coil of comparable dimensions (i.e., same copper cross-sectional area, different profile; same winding pitch, size, shape and turns).Tim
"Icom" systle connector to "other Standard"?! - Page 1
Forum section: electronics / rf-microwave

author: Lord of nothing
author_rank: Super Contributor
timestamp: April 30, 2019, 08:56:34 pm
content: HiI have a Radio who is not from Icom but the use there Plug like this one on the left:https://www.senaaustralia.com.au/assets/full/SC-A0113.jpgThe problem my Speaker Mic have just a strait cable thats sucks so I cant put it into my Radiopouch....So does anyone knowa) an Adapter who have an angle like this and the receiving Plug on the other endb) an Adapter to other Plug Style accessory?Maybe some from Europe?Thanks!
RFID DETECTOR PROJECT - Page 1
Forum section: electronics / rf-microwave

author: aqstephenson
author_rank: Contributor
timestamp: April 24, 2019, 06:23:54 pm
content: I'm wanting to design something that can merely detect the presence of, not actually read, an RFID tag. Most projects online are for reading or beyond. I don't need to get that complex. I'd assume the first thing I need to do is determine the frequency of RFID target (it's only one specific type of RFID tag I'll be using this on). If anyone has any links or ideas to help me get started, i'd appreciate it! Thank you.

author: David Hess
author_rank: Super Contributor
timestamp: April 25, 2019, 09:24:30 pm
content: So you need to detect the passive presence? I doubt a grid or tunnel dip meter will do it reliably but you might look the concept up.Assuming the frequencies are known, I would use a transmitter and receiver of the appropriate frequencies and use synchronous demodulation to detect the presence of the RFID while rejecting other signals. That means modulating the transmitter on and off while watching for the same modulation in the receive frequency.

author: Lord of nothing
author_rank: Super Contributor
timestamp: April 30, 2019, 05:45:53 pm
content: Why do you want this?
What's this RF white paint on microwave circuit - Page 1
Forum section: electronics / rf-microwave

author: mcinque
author_rank: Unknown
timestamp: April 28, 2019, 02:51:08 pm
content: I'm illiterate in RF, so I ask you: what's that white paint on that trace?This is of course something applied manually.Is this some RF shielding paint to comply with some EMI regulation or what?The circuit is the inside of amicrowave doppler modulefrom RF Beam with the shielding and RF adsorber removed..

author: hagster
author_rank: Frequent Contributor
timestamp: April 28, 2019, 05:00:28 pm
content: Its probably just to add some extra dielectric to that trace to lower the track impedence or make it electrically longer. No idea what type of paint it is.

author: ogden
author_rank: Super Contributor
timestamp: April 28, 2019, 11:45:31 pm
content: Quote from: hagster on April 28, 2019, 05:00:28 pmRight. Painted microstrip looks like feedback loop of oscillator and paint is means of frequency tuning. Most likely frequency was off and manufacturer decided to manually fix product using paint instead of scrapping it. Next PCB revision most likely will not need any paint.

author: radiolistener
author_rank: Super Contributor
timestamp: April 29, 2019, 07:39:35 am
content: probably it is added for precise impedance tuning

author: Gyro
author_rank: Super Contributor
timestamp: April 29, 2019, 01:05:19 pm
content: Any chance that the paint has ferrite content?

author: ogden
author_rank: Super Contributor
timestamp: April 29, 2019, 04:44:39 pm
content: Quote from: Gyro on April 29, 2019, 01:05:19 pmHighly unlikely. At 24GHz frequency paint is enough to cause significant enough changes in the microwave PCB circuit.Exampleof 2GHz filter which is bare copper versus one with solder mask, notice differences of Marker4 frequency:

author: mcinque
author_rank: Unknown
timestamp: April 29, 2019, 06:26:11 pm
content: Thank you all!
Driving Resonant Tank Circuit at 125KHZ - Page 1
Forum section: electronics / rf-microwave

author: filthyfrank
author_rank: Newbie
timestamp: April 28, 2019, 01:00:09 pm
content: Alright guys,I need a bit of help with a project I've been working on for a while. I need to make a circuit which can amplify a 125 kHz sine wave signal and place it on a magnetic loop antenna (big coil of wire). This is basically an RFID amplifier but no data needs to be transmitted; I only want to boost the 125 kHz signal and have it make a large magnetic field so it can excite a receiving circuit several feet away. I'm trying to emulate the 125 kHz field produced by a car door keyless entry system for a security research project.I think that simple TLE2301 Power-Amplifier seems to be suitable for providing enough power to the tank ciruit?I have few questions to ask:1) What should I do with TRS1 and TRS2 pins? For now I just left them unconnected.2) Do you see any problems with my simple circuit? What do you think can be improved?I'm a newbie, so any suggestions are greatly appreciated!Please see attached image for a better view of what I'm trying to accomplish.Here's the link for TLE2301 datasheet:http://www.ti.com/lit/ds/symlink/tle2301.pdf
HPAK PC based VNA UI help - Page 1
Forum section: electronics / rf-microwave

author: blueskull
author_rank: Unknown
timestamp: April 28, 2019, 11:08:20 pm
content: Got my new (used) VNA, and been struggling with its UI.The VNA is a PXI-based one, but I have reasons to believe it shares the same UI with other PC-based VNAs (standalone w/Windows 7/10, Streamline series, etc.).Two questions:1. In Smith chart mode, how can I add impedance measurement readouts? I need R+Xj or G+Bj, or better, (C+Rs)//Rp and (L+Rs)//Rp?2. In Smith chart mode, how can I thicken the trace? Sometimes the dot is too thin to be displayed. Don't know if it's a Windows RDP compression artifact or a problem with the VNA GUI, but if the trace can be thickened, it solves the problem caused by either.Thanks in advance.
What is this red glue under SMA pin? Helps RF response - Page 1
Forum section: electronics / rf-microwave

author: pratiken
author_rank: Contributor
timestamp: April 16, 2019, 05:57:02 am
content: HiI'm trying to figure out what the red material beneath the SMA pin is that helps improve the response. It seems to be similar to a wax material, almost like a very thick Loctite-type of liquid.The pin sits on top and is colored to the launch. The dried red material is easy to chip off and it's just relieved PCB below.The material improves response specifically around 6Ghz. Without it, the insertion loss is higher by about 3dB.Any ideas what this red stuff is?Thanks!

author: edpalmer42
author_rank: Super Contributor
timestamp: April 16, 2019, 03:49:48 pm
content: Quote from: Mechatrommer on April 16, 2019, 07:34:55 amThat's what I was thinking. If it is glue, it will probably be visible on at least some of the other components on the board.Ed

author: coppercone2
author_rank: Super Contributor
timestamp: April 27, 2019, 05:41:47 am
content: are you sure thats not a moisture seal? (which they tune out)tuning with goo itself seems... kinda bad. I hate goo on circuits of any kind. Its like twinkies in the kitchen vs a steak. corn meal vs hash browns.I did read about tuning-goo before, but its not applied like that. I think you typically serpentine lay it over the traces so its kind of a distributed element? and I believe its white.
Mechanical 3D filter realization from coupling matrix - Page 1
Forum section: electronics / rf-microwave

author: jujun
author_rank: Regular Contributor
timestamp: April 23, 2019, 02:56:44 pm
content: Hello,I feel the need to know more about microwave filter that are made of coaxialcavity cell that are coupled, and sometime with a topolgies like "cascaded tuplet" or "cul de sac".It seems that this kid of filter that is everywhere (like in mobile phone base station) is first made with a software that generate a coupling matrix. (ex :http://www.gwtsoft.com/) And then this coupling matrix is used to make the mechanical filter.But everything I read about it is kind of magical, because there is nothing about how it is done.For exemple here :https://www.cst.com/solutions/article/filter-design-technology-2017There is nothing about the mechanical part, it's "magical".So I guess that you have to model one 3D cell and then build your filter by cascading them ? But how to use the coupling matrix to automate it ? It must be a quick way to do it.Any pointers on how to do it ?Any pdf about it ? or book ?Is there any software that will do the work ?Thank you

author: rfeecs
author_rank: Frequent Contributor
timestamp: April 23, 2019, 11:42:31 pm
content: Here's one pdf from the website you referenced. The whole process is gone through, including determining mechanical dimensions:http://www.gwtsoft.com/Misc/Hagensen3.pdf
untuned ferrite antenna for SDR - Page 1
Forum section: electronics / rf-microwave

author: amb
author_rank: Newbie
timestamp: April 30, 2019, 09:18:30 am
content: I want to build a Software Defined Radio receiver for low frequencies (80kHz - 3.2MHz) with tuning done in the digital domain. I have previously experimented with ferrite antennas tuned with variable capacitors and varicap diodes.I'm thinking of using an untuned ferrite antenna and a high gain amplifier stage. I would put the antenna in the place of the input side inductor of a T section band pass filter (input - antenna - C - parallel LC to GND - series LC - output) with an 80kHz-3.2MHz pass band.The antenna inductance would be chosen to set its self resonant frequency well above the LF band I am targeting - maybe 50uH. Then, for a reasonable set of component values, the BPF input and output impedance is 1000 ohms.I could follow the antenna/BPF with a common emitter NPN stage with a matching input impedance, and a gain of 20-40dB. And then have a variable gain/attenuation stage, before going into an ADC.Would be grateful for any thoughts on this approach, particularly noise and gain in the first stage amplifier.

author: awallin
author_rank: Frequent Contributor
timestamp: April 30, 2019, 04:10:54 pm
content: maybe look at the various mini-whip designs out there also?the ferrite-antenna will give some directionality (and suppression in other directions), if that what you are looking for.some use obsolete transistors for the first amplifier stage, BF998 might be one of the current good ones (?)a filter for FM-radio around 80-110MHz (in most countries I guess) is a good idea.

author: Kleinstein
author_rank: Super Contributor
timestamp: April 30, 2019, 04:50:00 pm
content: Quote from: amb on April 30, 2019, 09:18:30 amThe problem with a an inductor as a wide band antenna is that the impedance changes with frequency. So there is no such thing a a matched amplifier and thus usually a poor noise performance.Another problem with a wide band antenna is that there could be quite some amplitude from some strong sources that can prevent a reception of any much weaker source. This is especially true with a pure SDR reception with usually limited dynamic range.So I would not consider this a good idea.

author: radiolistener
author_rank: Super Contributor
timestamp: April 30, 2019, 07:33:48 pm
content: Quote from: Kleinstein on April 30, 2019, 04:50:00 pmNo, wideband antenna has low impedance change with frequency. But it has low efficiency. Medium Wave ferrite antenna works good due to narrow bandwidth. It has high Q-factor which improve performance, but due to high Q-factor it has narrow bandwidth and needs to be tuned.On the other hand low Q antenna will have wider bandwidth and doesn't needs to be tuned, but it has low signal level on it's output. You can use amplifier in order to increase signal level (this is what mini-whip antenna doing exactly), but you're limited with noise floor for antenna environment and amplifier noise figure.
A good Antenna for 5Ghz Wifi? - Page 1
Forum section: electronics / rf-microwave

author: Lord of nothing
author_rank: Super Contributor
timestamp: April 22, 2019, 02:26:00 pm
content: HiI will install 2x 5Ghz Antenna for use 1W Wifi.I look for my personal favourite Chinesse - German Company what the offer me.I found this Antenna:https://www.delock.de/produkte/1468_Antennen/89537/merkmale.htmlThis Image:look like the use an PCB as Base? Vertical mean here the Antenna work like a multi directional Antenna?So with 2 Antenna I have turn one 90" to an side for a good Coverage?!Thanks

author: 0culus
author_rank: Super Contributor
timestamp: April 22, 2019, 09:25:31 pm
content: It looks like, based on those radiation patterns, that like most home wifi routers it will be radiating most of it's energy in a sort of plane parallel to the ground around the router? This is great for single level buildings, but if you need coverage on an upper floor from the same antenna(s), it may not work well even with two of them in different orientations, since perfect isotropic antennas don't exist (if they did, you wouldn't have this problem!)

author: Lord of nothing
author_rank: Super Contributor
timestamp: April 22, 2019, 09:32:02 pm
content: Its for the Rooftop to have Wifi on the Bus, Bim Station.And maybe free for guests.
Multiband WSPR on the cheap - Page 1
Forum section: electronics / rf-microwave

author: rhb
author_rank: Super Contributor
timestamp: April 19, 2019, 02:38:26 am
content: This is sort of crazy, but WB9LVI implemented a multiband WSPR transmitter using a FeelTech FY6600. Here's a link to the QEX article.http://www.arrl.org/files/file/QEX_Next_Issue/May-June2019/Steber.pdfWhile I despise F***Tech because of their lack of customer support, it's actually a good device and the FY6800 incorporates many improvements developed by forum members in this thread:https://www.eevblog.com/forum/testgear/feeltech-fy6600-60mhz-2-ch-vco-function-arbitrary-waveform-signal-generator/So far as I know there is no documentation of the RS-232 interface, but it is there and with a GPSDO to time the transmissions it would neatly cycle through all the band allocations using a PC or any cheap MCU. So it has the potential to be a very valuable tool for investigating propagation up to 6 meters. At low power levels (1-2 Vpp output) the spurs are comparable to my Keysight 33622A without the benefit of the output amp modification.

author: Johncanfield
author_rank: Regular Contributor
timestamp: April 19, 2019, 09:15:43 pm
content: Check out QRP Labs, I have built three of his U3S kits. I have one on the air now reporting to WSPR - 30 meters.

author: Lord of nothing
author_rank: Super Contributor
timestamp: April 22, 2019, 02:01:52 pm
content: QuoteNot very far.

author: rhb
author_rank: Super Contributor
timestamp: April 22, 2019, 04:29:44 pm
content: Quote from: Lord of nothing on April 22, 2019, 02:01:52 pmRather obviously not a radio guy
GPS antenna matching - Page 1
Forum section: electronics / rf-microwave

author: rilliam
author_rank: Newbie
timestamp: April 22, 2019, 09:46:19 am
content: If I modify this circuit by replacing the chip antenna with a sma connector, do I need to change C1,C2,L1 ?

author: Rerouter
author_rank: Super Contributor
timestamp: April 22, 2019, 09:48:43 am
content: The chip antenna is 50 ohm, and those components would be the matching network for 50 ohms, looks like you should be fine.
mfj-259b as a signal source - Page 1
Forum section: electronics / rf-microwave

author: m3vuv
author_rank: Super Contributor
timestamp: April 26, 2019, 10:38:11 am
content: hi all ive an old kenwood ts700 g,i need to calibrate the s meter after some mods to the radio,my sig gen doesent have a calibrated output,do you think a mfj ant analyser could be used?

author: Roger Need
author_rank: Regular Contributor
timestamp: April 28, 2019, 02:49:46 am
content: Yes the MFJ-259B will work as a signal source to calibrate for S9 on your meter. You need -73 dBm for S9 and the output of the MFJ is pretty close to 8 dBm at 14 MHz. So you will need to build/buy an 80 dB attenuator (8dBm -80 db = -72 dBm). You can build the attenuator from 3 resistors. Google for the resistor values.
ICOM IC-7100 residual AM when in FM TX mode - Page 1
Forum section: electronics / rf-microwave

author: RFDUK
author_rank: Regular Contributor
timestamp: April 21, 2019, 02:17:27 pm
content: Are there any IC-7100 users on the forum?Just got one of these and really love it but found a surprising 'feature'.When in FM (FIL1) mode, 15 kHz BW for 25 kHz channels, there is loads of AM on the output, particularly at lower power settings, say 20 to 30% of max.This can be seen on an external power meter. At lower power settings the carrier power reduces by up to 50% on a whistle!Seems worse on 4 and 6m, but still present on 2m and 70cm.Do they all do this or do I have a faulty unit I wonder.Many thanks.
PC-Software for HP437B - Page 1
Forum section: electronics / rf-microwave

author: Radiosonde
author_rank: Contributor
timestamp: April 20, 2019, 05:47:59 pm
content: HelloHas anyone written a PC-Software for a 437B or 436A power meter?I have to measure LORA-devices which just send short pulses, so I would need a SW which plots out the power over time.Is there something out?Thank you
ATmega256RFR and chip antenna - Page 1
Forum section: electronics / rf-microwave

author: sensor1976
author_rank: Newbie
timestamp: May 02, 2019, 09:56:15 am
content: Can i connect chip antenna to RFN pin and other chip antenna connect to RFP pin, and don't connect balun? What you think? Can i use two chip antenna and don't use balun?Thanks in advance.

author: ataradov
author_rank: Super Contributor
timestamp: May 02, 2019, 10:14:34 pm
content: Yes, you can. Old Meshnetics/Atmel module ZigBit A2 used this configuration. I'm not sure if there were any other matching/tuning components though.

author: sensor1976
author_rank: Newbie
timestamp: May 03, 2019, 08:06:33 am
content: Thank you very much. I will try to do so.It seems to me that you was at Avrfreaks forum and did a great help for me in doing wireless emergency buttons for hospitals. I did buttons but turns out buttons no need for medical staff.Thanks again.
New BG7BTL GPSDO Setup -- No Position Update To Lady Heather - Page 1
Forum section: electronics / rf-microwave

author: apollomaker
author_rank: Newbie
timestamp: April 07, 2019, 04:19:41 pm
content: Hello All -- Newbie to EEVBlog here -- I have retired a dead Trimble GPSDO and replaced it with a new BG7BTL unit (ver. 2018-06-05) which appears to be working fine. Noticed the position lat/long/alt data is not updating in Lady Heather (ver. 5.00) -- same issue as with my old Trimble unit. The position data in LH is not changing and is not accurate.I am probably not posting a GPSDO question in the right place??What am I missing here?? Commands?? Many Thanks for any help ----- Cheers, Bob K6WL

author: Towger
author_rank: Super Contributor
timestamp: April 18, 2019, 04:46:52 pm
content: Many GPSDOs have to do a 'Survey' to update their location. They are designed not to move, basically during the Survey they calculate their position for several hours and fix the location on the result. The location is then a constant when calculating time.I have no experience with you units, so can't say for certain if this is your issue.BTW, there is an update to the latest Windows version of Lady Heather on the form.
Mixed Signal Simulation Problem - Page 1
Forum section: electronics / rf-microwave

author: Nomi114
author_rank: Newbie
timestamp: April 17, 2019, 05:51:17 am
content: Dear All,Hope you all are doing well with good health. Here i would like t ask for one favor that i am going to design RF Transmitter at frequency of 8.2 MHz, which will be used for RFID application (i.e Electronic Article Surveillance system). For designing purpose i used Altium Designer 16.0 , schematic is ready but we are also interested to simulate this circuit in Altium Designer. For mixed signal simulation we used this software. But during simulation i am facing some problems, that's why i asked for favor from all of you. The main problem is some SPICE model files are missing or not available in libraries. i try to find but unfortunately didn't succeed. so what can i do in this situation ... i am much worried about this, and i have required to finish this task as early as possible. I have found .ibis Models but those are use less, for mixed signal simulation purpose SPICE is mandatory, kindly suggest me how can i do mixed signal simulation ......Anxiously waiting for your kind and quick response...With Humble Regards
Help with Yagi-Uda antenna design. - Page 1
Forum section: electronics / rf-microwave

author: DG41WV
author_rank: Regular Contributor
timestamp: April 16, 2019, 12:26:13 am
content: Hi,I've been given an assignment to build a 5 element yagi antenna that will work on a frequency range of 275MHz-500MHz. I've been trying to get this to work since some time and still couldn't get it properly working in CST studio suit (student edition). in most of the sources I've gone through says that yagi designs are mostly effective for a bandwidth around 2%-3% of the center frequency. I just want to know is it possible to build a yagi antenna for the above frequency range.

author: AG6QR
author_rank: Frequent Contributor
timestamp: April 16, 2019, 01:32:55 am
content: From everything I've heard, your sources are correct: A Yagi is a fairly narrow-bandwidth antenna.A log-periodic design is often used when one needs to combine wide bandwidth with directivity. They look similar, but the theory of operation is somewhat different.

author: tkamiya
author_rank: Super Contributor
timestamp: April 16, 2019, 10:22:46 pm
content: Yagi design works by having a drive element that is tuned to a frequency, a piece longer than a drive element behind it, and piece shorter than drive element in front of it. Behind element reflects and front element directs. There are only about 5% difference in length difference: not much.It would be impossible to do this for such a wide frequency range. What you want is log periodic antenna. You can get 1:4 or sometimes more bandwidth. In this design, every element is driven by RF energy. Only about 3 to 4 element are actively doing something on a given frequency. So it is not unusual to have 12 element log periodic having 8dBd gain. (standard figure for 3 element Yagi)Is this a school assignment or work? If it is work related, someone who asked you to do this have no clue how Yagi works. The correct answer is "not possible". If it is work related, only antenna that presents constant impedance over that wide of range is either a discone or logperiodic. Or, you could make a really really fat element, but if you do so, Q will be low and loss will be much greater.
sig get output - Page 1
Forum section: electronics / rf-microwave

author: quadzillatech
author_rank: Contributor
timestamp: April 15, 2019, 01:25:02 pm
content: hi all,i have an old kenwood ts-700g,i brought it non working,it was a trtansfo o/c in the nb board,it works fine but ive re aligned most of it but the s meter is way off,my sig gen doesent have a calibrated output,is there any way i can calibrate it using a scope etc,not the frequency but the level to use it to set my s meter? any ideas,cheers m3vuv.

author: CJay
author_rank: Super Contributor
timestamp: April 15, 2019, 05:58:47 pm
content: Depends what your 'scope is and what signal levels but calibrating for S9 you're looking at levels of 5 or 50 microvolts, not easy with a 'scopeCompare against a known good radio?Beg or borrow a calibrated sig gen?Build yourself a power sensor based around the AD8307 (or similar) or buy a board from eBay so you can measure the output of your sig gen and use a calculated attenuator??Or, if you're close to South Manchester, PM and we can arrange something

author: quadzillatech
author_rank: Contributor
timestamp: April 16, 2019, 08:14:42 pm
content: my scopes are a heath dso and a tek 453,only good to 50mhz tho,i think squirting my sig gen adjusted for s9 into another rig then into mine ant tweak it that way,didnt think of that,must be getting old lol 73 m3-vuv.
Sweep tuned SA + slow sweep + 802.11n channel 36 - Page 1
Forum section: electronics / rf-microwave

author: 0culus
author_rank: Super Contributor
timestamp: April 21, 2019, 09:47:01 pm
content: So I was doing some experimenting for giggles with an old wifi router I don't use anymore, and I pointed a ~900-12000 MHz directional antenna at the 5 GHz antennas in the router, antenna directly connected to the 8566A spectrum analyzer. Now at fast sweeps when looking at a spread sprectrum protocol such as wifi, the spectrum analyzer only "sees" small bursts of RF power and you have to enable max hold to eventually see the shape of the channel envelope. However, at very slow sweep times , it draws out the envelope very nicely albeit very slowly.How does this work? I was under the (apparently very wrong) impression that you needed a realtime SA to do this.

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: April 22, 2019, 07:03:07 am
content: A wifi AP will send out a constant stream (constant being a few times a second, I think) burst of data as an 'I'm here' including information like it's SSID (I think it is called 'AP Anounce' or 'Beacon Frame' but I am not sure, been years since I had a computer networks course). Considering these packets of data are sent at very low speeds (so even the far-away potential clients can hear it, it makes sense that if you sweep slowly enought, there will always be power to fill up your bins.Also, WiFi is not spread-spectrum. Quite the contrary, it is a very narow spectrum with generally high modulation depth in order to sustain those speeds.

author: 0culus
author_rank: Super Contributor
timestamp: April 22, 2019, 07:13:18 am
content: Hmmm, I think you're right for more recent 802.11 standards such as 802.11n, but 802.11b definitely used DSSS. "Beacon frame" is right, I believe. For 2.4 GHz access points, you can see the beacon from some distance. Thanks, I do believe that might explain it.
[ RFID, Amplifier ] Driving FSK signal to low impedance resonance circuit - Page 1
Forum section: electronics / rf-microwave

author: Esmund
author_rank: Newbie
timestamp: April 16, 2019, 10:36:22 am
content: Hi,I have an issue with RFID system. I have a TX antenna loop for FSK signal (Low FSK = 3.5MHz; High FSK = 4.5MHz; Center = 4MHz) that is series resonance circuit tuned to the center frequency. Both FSK frequencies have low impedance (around: 0.3+/-j2 ). I wasn't able to design impedance matching circuit for both frequencies without attenuating frequencies between (signal amplitude jitter is restricted to around +/- 1.5dB).I'm looking for a way or IC to drive FSK signal into that low impedance TX FSK antenna.Thank you in advance for help.
D6 JTGP-1033 - New low-cost "spectrum analyzer with tracking generator" - Page 1
Forum section: electronics / rf-microwave

author: Bicurico
author_rank: Super Contributor
timestamp: April 15, 2019, 02:07:52 pm
content: Hi,I discuss the D6 JTGP-1033 on my blog:https://vma-satellite.blogspot.com/2019/04/new-simple-spectrum-analyzer-device.htmlPerhaps this is interesting for some of you. This device is a clone of the NWT4000, but it is "open source", which means that upon purchase your receive a kit with the firmware and the schematics.Some people already implemented some mods to increase performance.The main advantages of the D6 is that the refresh rate is about 3 times faster than the NWT-4000, while the price is 3-4 times less!The disadvantage is the fact that it comes without a case and has higher noise floor and lower sensitivity. But these are tackled by the mods.Regards,Vitor

author: CJay
author_rank: Super Contributor
timestamp: April 15, 2019, 02:22:47 pm
content: Well that looks like a bargain and timely indeed, I'm playing with QO-100 and have a need to build an antenna for 2.4GHz
Which cellphones use AMPS system? - Page 1
Forum section: electronics / rf-microwave

author: Ben321
author_rank: Frequent Contributor
timestamp: April 03, 2019, 06:31:25 am
content: I know that the AMPS system is very much outdated, and no company in the US supports it anymore, but I'm just curious. The original "brick" cellphone from Motorola used it. I'm wondering if any other cell phones used the AMPS system too? Or did all other phones use the D-AMPS system that came after the AMPS system?

author: TheSteve
author_rank: Unknown
timestamp: April 03, 2019, 06:40:00 am
content: For years all analog phones in North America were AMPS. I am sure there are 100+ models. Phones were around for a long time before any networks went to D-amps(TDMA).

author: oPossum
author_rank: Super Contributor
timestamp: April 03, 2019, 01:55:46 pm
content: Almost everything in the USA in the 1980s was AMPS. No matter what brand or model. In the 1990s TDMA (DAMPS, GSM, IDEN) and CDMA became available.

author: AG6QR
author_rank: Frequent Contributor
timestamp: April 04, 2019, 06:04:47 am
content: Even long after the digital phones and service became available, AMPS was still supported by many phones. I was a late adopter; I purchased my first cell phone in 2003, a Nokia 3588i. It was a CDMA phone on the (all digital) Sprint network, but it would fall back to AMPS in areas where CDMA service was not available. That was not unusual for the era. I'm not sure when the last phone was made that supported AMPS, there were many, many models that supported that long-lived standard.
Analyzing tracking generator results - Page 1
Forum section: electronics / rf-microwave

author: 0culus
author_rank: Super Contributor
timestamp: April 03, 2019, 09:45:35 pm
content: As anyone whofollows the TEA megathreadknows, I have been tinkering with a tracking generator board I got for free when I bought by 8566A system. It's an early revision of the DS Instruments tracking generator, which sells for quite a bit, so I'm happy despite the early rev's shortcomings (lack of onboard signal generator). With the right setup, this enables tracking generator use on the 8566A or B's low band and band 1 to 5.8 GHz.Because I'm still building out my lab, I don't yet have a lot of interesting things to test with scalar network analysis yet, so I made up a concoction with some cheap Amazon SMA patch coax and some equally cheap SMA adapters (first pic). Don't worry, this stuff isn't going to be used much longer. I'm rapidly replacing with better quality stuff.The results (sans termination) were interesting (second and third pics). With termination, it flattened out but still some loss evident across the band (fourth pic).As someone who is just diving into RF on an autodidact basis (I'm working through Bowick's RF circuit design), and who hasn't had a tracking generator before, I have a couple questions for those of you with more experience:1) Are the losses without the terminator going to be largely radiated, reflected, or some combination thereof? I'm thinking the latter...but not sure how to reliably confirm.2) I'm doing the (as far as I can tell) normal setup for the 8566, setting up the tracking source, correcting with the display line arithmetic. Are there any other calibration "gotchas" I should keep an eye out for?Thanks!

author: 0culus
author_rank: Super Contributor
timestamp: April 03, 2019, 09:52:08 pm
content: I forgot to add to the OP that I do have semirigid 18 GHz coax from Mini Circuits to wire everything up.

author: TheSteve
author_rank: Unknown
timestamp: April 03, 2019, 10:17:50 pm
content: I guess I'd need a picture of the whole setup - why are you using a tee?

author: 0culus
author_rank: Super Contributor
timestamp: April 03, 2019, 10:20:04 pm
content: Quote from: TheSteve on April 03, 2019, 10:17:50 pmJust to make the tracking gen trace do something more interesting than a pad.I don't have a filter to test unfortunately. That coax is just connected between TG out and the the SA input.

author: TheSteve
author_rank: Unknown
timestamp: April 03, 2019, 10:34:37 pm
content: Ahhh, ok, lol.Normalize the system and look at attenuators if nothing elseThen consider a directional coupler if you want to see return loss.End of the day you'll end up wanting a VNA, so let's start looking for one of those for you.If you only need up to 3 GHz and can live with S11/S21 only then the HP 8712/8713/8714 series(3 GHz option) can be very tempting. Especially an 8714C which even has a network port for grabbing screen shots etc.

author: 0culus
author_rank: Super Contributor
timestamp: April 03, 2019, 10:38:49 pm
content: Yeah, ultimately I do want a VNA. Hopefully by the time I can afford one, I'll also have a better idea of the bandwidth I'll need.
si470x FM Radio Module - Page 1
Forum section: electronics / rf-microwave

author: @rt
author_rank: Super Contributor
timestamp: March 29, 2019, 05:36:37 am
content: Hi GuysI have this Sparkfun FM radio module (or an eBay knock off of it), and have it working on breadboard controlled by pic 16F628A.This radio has a watch crystal (32.768 kHz) as it’s master oscillator.If I clock the pic at 8MHz, it can hardware PWM a clock of 32.78689 kHz, and I assume that would be close enough to ditch the watch crystal,and clock the radio chip with the pic. Maybe there would be some band/freq offset, as this f must be PLLed up, but I don’t care.The real question is if it would be possible to shift it right into the 6m band or up to amateur VHF band. I think FM is a valid mode for both of those.it would either be %50 f or %150 f to achieve either of those, and normally some hardware bandpass filters would prevent a radio working so far out of band,but would anything prevent this module doing so?

author: @rt
author_rank: Super Contributor
timestamp: March 29, 2019, 07:15:44 pm
content: Yes, generate a PWM 46.296 kHz, attenuate the output with a resistor divider, and you’re in the VHF amateur band.

author: @rt
author_rank: Super Contributor
timestamp: April 02, 2019, 01:00:00 pm
content: That was funVK4JJY on 6 meters:VK4RAI on 146.9 MHz
30A ~5ns MOSFET driver - Page 1
Forum section: electronics / rf-microwave

author: KaneTW
author_rank: Frequent Contributor
timestamp: March 28, 2019, 03:20:02 pm
content: I'm designing a 13.56MHz Class E amp based on the IXYS RF switching MOSFETs (102N20A etc. depending on what power level I decide on). I need driver rise times to be below 5ns for this.I was going to use the IXYS RF MOSFET driver (IXRFD631), but it's going to be phased out and apparently has issues with reflow soldering so I'm looking for something else. All other drivers I see either don't have the rise time or current capability needed.From what I can see I can either reduce the maximum power and go with a smaller MOSFET (the 600V version has up to 15A peaks, which is fine using the still-active IXRFD615) or cascade a fast driver with a fast FET (GaNFET maybe?)Alternately I could just go directly GaNFET, but I'm not too familiar with the technology.(Rough simulations give me around 900W output power with 150V DC in, 90% efficency with 4ns rise times and a 600Vds max MOSFET; voltage goes up to ~550V on the drain)

author: Marco
author_rank: Super Contributor
timestamp: March 31, 2019, 06:19:47 pm
content: Reminds me ofa threadby Blueskull a couple years ago, he seems to have been quite enamoured with GanFET's since so I suppose he made it work. You could try asking him.PS. does that 90% efficiency include the losses from hard driving the gate? That gate energy becomes quite significant at 13.56MHz.

author: KaneTW
author_rank: Frequent Contributor
timestamp: March 31, 2019, 06:56:10 pm
content: It includes the main MOSFETs switching losses and reasonable parasitics for all passives, but no gate driver losses. I can add a gate driver into the sim later.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 01, 2019, 07:36:48 am
content: More transistors would seem the better deal.30A and, say, 10V of drive, is a 0.33 ohm impedance. You better have some damn short, and wide, traces to pull that off.It's not something you'll get from, say, a BJT complementary emitter follower, not without using half a dozen parts in parallel, just because of the wire bond and pin inductance.Similarly for the drain load impedance, though doing that in the 10s of ohms should be a lot easier.GaN would definitely do the job as drivers, but you need a bootstrap driver and pair of GaN just to drive one gate.Or use GaN for output properly, but they're still kinda weak in higher voltages. (If you can reduce the supply to 48-80V though, EPC eGaN would do.)Tim
Mike's Radio Repair - Page 1
Forum section: electronics / rf-microwave

author: German_EE
author_rank: Super Contributor
timestamp: March 31, 2019, 06:47:19 pm
content: Those of you who have been missing Mike for the last month or so, I have good news. He's just posted three and a half hours of videos to watch, including some ham radio repairs.https://www.youtube.com/user/trclubricants/videosLife is good
Driving RF Circuit at 125kHz - Page 1
Forum section: electronics / rf-microwave

author: filthyfrank
author_rank: Newbie
timestamp: April 21, 2019, 10:36:32 am
content: Alright guys,I need a bit of help with a project I've been working on for a while. I need to make a circuit which can amplify a 125 kHz sine wave signal and place it on a magnetic loop antenna (big coil of wire). This is basically an RFID amplifier but no data needs to be transmitted; I only want to boost the 125 kHz signal and have it make a large magnetic field so it can excite a receiving circuit several feet away.I'd like to use a pre-made amplifier IC to avoid designing a custom FET amplifier from scratch. A simple TLE2301 Power-Amplifier seems to have a bandwidth of 8MHz so I think it could work? How should I attach the output of the TLE2301 to my parallel resonant tank circuit?I do have an application for this system. I'm trying to emulate the 125 kHz field produced by a car door keyless entry system for a security research project.Please see attached image for a better view of what I'm trying to accomplish. Any thoughts are greatly appreciated.

author: radiolistener
author_rank: Super Contributor
timestamp: April 21, 2019, 01:07:43 pm
content: Quote from: filthyfrank on April 21, 2019, 10:36:32 amthis is illegal. Square wave has strong harmonics and you will make strong interference for short wave receivers

author: MasterT
author_rank: Frequent Contributor
timestamp: April 21, 2019, 03:23:00 pm
content: Your circuits is only make sense if there is dual power line, +5V / -5V.Google for wireless power charger circuits, or you may buy one.http://www.theorycircuit.com/wireless-gadgets-charger-circuit/

author: awallin
author_rank: Frequent Contributor
timestamp: April 21, 2019, 05:20:15 pm
content: with some minor modifications to the pre-amp (frontend) the BK electronics modules work up to 125-136kHz (but gain drops off quite quickly after that..)http://www.bkelec.com/MODULES/amplifiers.htmIIRC I got something like 3-400W into a 50R load at 136kHz with the 1kW BK electronics module.The DC rails on the BK are at +/-90V or so. It likes low impedance loads (loudspeaker 2-8 Ohm) so an impedance-transformer is good if you want to drive a 50 Ohm load.
Where can I get U-Blox "T" timing GNSS dev boards from? - Page 1
Forum section: electronics / rf-microwave

author: bd139
author_rank: Super Contributor
timestamp: February 05, 2019, 01:49:30 pm
content: Can't seem to find these anywhere. I need one I can set the timing pulse output to 10KHz. The N8M modules only go to 1KHz.Edit: or any other module?

author: wolfp
author_rank: Contributor
timestamp: February 05, 2019, 05:21:28 pm
content: I bought one from CSGshop. It uses ublox M8T chipset.Wolfgang

author: bd139
author_rank: Super Contributor
timestamp: February 05, 2019, 05:29:20 pm
content: Nice one. Thanks for the suggestion

author: Lord of nothing
author_rank: Super Contributor
timestamp: March 27, 2019, 02:03:11 pm
content: Why could not an ordinary Ublox work?