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I'm not an engineer, and don't really work in the industry. But I need various MMCX cables for a research project, and they seem both expensive and hard to find.

Do people usually make them themselves if they only need low volume? It seems that the parts are quite a lot cheaper than buying finished cables, so is that the way to do it normally?

Pretty much as the title says... i know companies do white papers, are there any other ways without being a student or professor? Project work, open source work etc ...

This is the antenna from a dual-band 2x2 MIMO Wi-Fi access point.

https://preview.redd.it/zxeobh4t7yxd1.jpg?width=4000&format=pjpg&auto=webp&s=8d33ab3d108a5f1267419cce417b42702bf59096

Would someone be so kind as to explain what I'm looking at? Are the large/small antennas 2.4 GHz/5 GHz, or transmit/receive? What is this type of antenna design called?

Edit: typo

I am trying to find a 20db and 40dB attenuator with f_LOW=DC to f_HIGH=6000MHz.

The instruments I am connecting to have a 1MOhm impedance and to match that, I am trying to find attenuators with a 1MOhm impedance.

All I could find were 50 and 75 ohm impedance attenuators

any pointers appreciated!

I'm trying to measure some high-Q resonators (Q~1e6).

Aside from the usual low IFBW, averaging, etc., are there any settings that would help to measure these resonators? Point-by-point averaging instead of sweep-by-sweep?

Related: what VNA figures-of-merit are the most important for measuring resonators? Source stability? Phase noise?

Not sure if this is the right place to ask. I've been working with some very low power BLE devices and I need to test how well they perform in a crowded area with lots of AP's, BLE headphones, lots of stuff happening on the 2.4Ghz band in general. Are there any devices out there capable of simulating such behaviour, with varying degrees of severity? I know that I'm essentially asking for a jamming device, so if this kind of post is not allowed, please let me know.

Hey all, a bit of a long shot. I have a long RF chain with automatic gain control loop keeping the output gain of the entire chain steady over life of the system and smoothes away any component tolerances. Ie every chain that is built has exactly 0dBm output after it is tuned and keeps it that way "forever". It is basically a control loop that samples output power using a directional coupler at the end of the chain, turns it into DC level that in turn controls the variable attenuator that acts in correcting fashion and keeps the gain steady. On top of that there is a resistor/thermistor network in the loop that takes care of gain variation due to temperature change. This all works great and nice.

What I am fishing for here are some ideas about how to expand this to not just have steady 0dBm output, but a range of arbitrary values. Eg an external voltage signal whith which you can adjust the output gain and keep the nice auto-correcting properties of the AGC loop.

If anyone has some articles or techical notes that seem familiar, they are welcome.

Hello everyone,

I was wondering if I could get some advice/recommendations on what to learn/read to become an RF design engineer. I was currently given an opportunity to work in a test group working with RF devices. As this is my first time working in RF. I believe testing these devices will help me learn more about RF but was hoping I could get some guidance on things I should consider or think about while working in this group to help me move onto designing. Thanks in advance!

I'm designing an RF transceiver IC for an application where the received power could vary largely, which could potentially damage the LNA and/or mixer. Instead of complicating the circuit with a VGA (because of size requirements and concerns about noise), I am considering replacing it with a limiter since I'm only worried about frequency shifts and so on, not the wave itself. Clippers being non-linear, I understand that there could be harmonics and the presence of two more non-linear components after this makes it a little complicated, but is it possible to somehow make this work?

Thank you!

Anyone happen to have a schematic of this 60 year old amp? I have to repaired a bunch of them. Trying to draw the circuit from the horrible 1960s layout makes me want to give up engineering and get into prostitution..

What's your experience with AliExpress RF enclosures?

I plan to buy one for a LNA (LNA4ALL) and for a FM notch filter. Maximum observing frequency is 1 GHz.

I need to quickly test handheld RF sensitive equipment in a perfectly protected shielding room (few hours, one time thing), so I want to rent a small room for as cheap as possible. Does anyone know where I can try to do this? Any companies that offer a service like this? It's important so I'm willing to fly out.

Hi, I'm building yagi antena like this:

https://www.qsl.net/dk7zb/2m-short/5-ele_28-180.htm

which has resistance aprox 28ohm. Author of that antena used match consist with 2x75ohm lambda/4 :

https://www.qsl.net/dk7zb/dk7zb-match.htm

I was thinking to use simple L match which I build like here (L1 was used because I have only 33pF capacitor for 1kV - I'm using 50W)

https://preview.redd.it/942zwo2ftoxd1.png?width=1710&format=png&auto=webp&s=03a3c1760574280632a6d144aaf952c8c75b9807

Now I have questions:
- can someone explain me why lambda/4 is better than L match (or any other)? It was quite anoying to cut coax by mm and measure it. WIth L match, it was just a metter of make right inductors and then finetuning on mast...
- I'm using coax for feeding, do I need to use balun?

Hey everyone, I am going to soon graduate with a Master's degree in EE. My focus has been in RF and antennas. I was wondering what are some companies I could apply to that may take me. I currently live in Florida and would like to stay here, but it seems like most companies here are looking for senior engineers. I have been using indeed and LinkedIn, but figured you guys probably know more.

About me: I am graduating with master's with a focus on RF and antennas. I have interned for L3Harris in their RF MMIC design team, and have worked at a lab in my university for two years designing patch antennas and arrays, and some RF circuits.

Any help and guidance would be appreciated. If possible.

Hi, I would like to apply for a PhD in US, but I am coming from Italy. Since I know that a lot of research groups in RF field are funded by government agencies: could be this a problem for me since I am not a citizen?

I have a youmile cc2531 which uses zigbee. Im using the software: smartrf to sniff for bluetooth signals. How do i identify what device is which signal. E.g. My phone connects to my headphones, how do i tell what signal is my headphones/phone vs everything else

Finding it difficult to find a job as a fresh graduate and wanted to make sure its not because of my resume. Any critique or advice is really appreciated I'm down bad

I just spun up a custom board with an LMX2572 synth and I'm using it to generate 435 MHz. It has two outputs so I put a BPF and an amplifier on one output and nothing on the other. The output looks pretty good, but there's barely any harmonic rejection. The BPF is supposed to have about 25-30 dB rejection but I'm only seeing about 15 at the most. The harmonics don't really decrease in amplitude the further away they are from the fundamental the way I would expect.

The BPF is a Minicircuits BFTC-415+ and the amplifier is a TI TRF37D73. The board is 4 layers. Second layer is GND flood. The board was fabbed by OSHPark. I used a calculator to get close to the trace width for 50 Ohm controlled impedance. I threw a couple of grounding vias on either side of the trace, but the distance was so short it didn't really need many.

Synth Circuit

https://preview.redd.it/x53do8739kxd1.png?width=1749&format=png&auto=webp&s=b3ae5008cb760800a5b98e1b41a20ba1f0b53d6b

Basically, the synthesizer output looks ok - chip is working, got a fundamental tone at the expected frequency, etc. But the BPF doesn't seem to be doing a great job rejecting the harmonics.

I also noticed that I was getting a surprisingly large output signal while the Tx amp was turned off. I think there's some coupling happening in my transmit amp and the harmonics are getting around my BPF.

Could I get some feedback on how to improve my board layout to help prevent this from happening? And anything that jumps as being "not great?"

I've made a similar board with a different synth that worked at 148 MHz and the filters/amps worked just fine. I'm planning on using this synth up to 915 MHz, so it'd be nice to start learning so good practices for higher frequency layouts.

Thanks!

Good afternoon you guys, I am a senior EE student who is very interested in RF and considering pursuing a graduate see degree in the background. Do you guys happen to have any good resources to help me get a better handle on this such as books,articles,videos, projects? Any help is greatly appreciated thank you!

I've been heavily researching the dark magic of RF antennas and resonance matching for NFC communication. The IC I've chosen is the popular PN532 and the antenna is a Taoglas FXR.2020.52.0075X.A.dg.

I've attempted to use a T-Match circuit for this application. Can anyone else who is slightly more wizard-like than me confirm my calculations or spot any glaring issues?

My previous design utilised a 25pf cap on each TX line to ground and 560nh inductors with a 2.7K R2 on the RX line. This worked albeit with a <1mm range. I've now tried lowering the inductance and using only one 120pF shunt cap.

TIA!

https://preview.redd.it/u74664fyiixd1.jpg?width=814&format=pjpg&auto=webp&s=248319470b16843c851e7486c4e3ead8e1a47f60

How can I measure/test an active device, such as an LNA, using a NanoVNA or LibreVNA?

What key considerations should be kept in mind when testing an active device like an LNA, and are there any changes needed in the calibration process for accurate measurements?

I'd appreciate any suggestions or advice specifically from the perspective of using NanoVNA and LibreVNA for these measurements.

I have a ceiling fan that I want to make smart.

https://preview.redd.it/jj3gdrknugxd1.jpg?width=960&format=pjpg&auto=webp&s=2836857b197dafd90e7402de03d10706312316e9

The label says that the receiver model is CT-577, which according to this page, has FCCID 2A788CT-577. Although I cannot confirm that it's the same model that I have. Maybe coincidently they have the same model name. But assuming it is, its operational frequency is stated to be 433mhz on the FCC site.

I tried to capture what the remote control transmits using a DIY 433mhz receiver but I am not getting anything. The receiver works because I am able to use it to capture the traffic of other 433mhz transmitters.

https://preview.redd.it/9etp3hexvgxd1.jpg?width=960&format=pjpg&auto=webp&s=280a7103809c1c112cc22e54defb482d28728204

So I opened up the remote control and the found a printed label "QZ.HF577-2.4G" that might suggest that it's actually using 2.5Ghz (?).

https://preview.redd.it/kx7mbr6iwgxd1.jpg?width=960&format=pjpg&auto=webp&s=28444f2a32f6e91638dcb07cbe7a5869fb3f7641

https://preview.redd.it/x7cwwr6iwgxd1.jpg?width=960&format=pjpg&auto=webp&s=7bfdab7cf3223bf8044a2fdead1a34e1924577da

It's definitely not WiFi and I don't believe it's Bluetooth. If it's in fact 2.4Ghz, could it be a custom protocol? if so, is it possible to capture with a WiFi dongle? I have a Netgear A6210 that I can put in promiscuous mode to capture WiFi traffic but not sure if it can be used to capture any 2.4Ghz.

Or maybe it's just 433mhz and doing something wrong?

My knowledge about RF is very basic. Any help would be appreciated.

Finishing my PhD and looking to start my career. I live in the US and not a US citizen. I worked on a bunch of different things non linearity compensation, antenna design, antenna array engineering, Beamforming, wireless positioning. Im keen to learn and I’m hoping for some pointers! I’m applying online but figured I’d ask if anyone here is looking for someone.

Just wondering if anyone knows what these are

I'm trying to design a drone racing timer (PCB) and I am looking for alternative methods for measuring the signal strength of the eight "race channels" simultaneously (~1KHz per channel).

The requirements of the device are:

• Measure each channel at 1KHz minimum.
• Only need signal strength, don't care about content.
• Use one directional linear antenna if possible.
• The resolution only needs to be a crude estimation of signal strength (is the drone within 1m or not...).

The center frequencies of the channels are the following: 5658, 5695, 5732, 5769, 5806, 5843, 5880, 5917 MHz.

The current version of my device is using 4–8× dedicated video RX modules called "RX5808" but only sampling the RSSI analog output pin to determine signal strength. The rest of the receiver signals such as video, audio, etc., are just unused.

The problem with that approach is that the receivers take up a lot of board space and are quite hard to come by (random AliExpress links). Also, it seems a bit wasteful to me to use 8 video receivers only to measure the RSSI output.

I asked this question here a few months ago and got a few good answers, but I'm still trying to wrap my head around this problem. If I understood the answers correctly, the general approach would be:
1× 5.8 linear patch antenna -> Split the RF input signal into 8 paths -> use 8 mixers to convert each center frequency to a predefined IF (e.g., 140MHz) -> use 8× SAW or bandpass filters at the center IF frequency -> use 8× power meters to measure the signal strength.

I must be misunderstanding something since this would cost a lot just to get crude estimations of the signal strengths of these 8 channels.

1. Is it possible to design a PCB that does this with a component cost in the $100 range (per board)?
2. Is my understanding of the general approach correct?
3. Are there any "magic" ICs I should look into for solving this problem? (filters, mixers, splitters, power meters)
4. Is this impossible for a "hobbyist" such as myself to design?