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please don't say pozar.

I am an avionics lead on a university rocketry team, and we are trying to design a radio system that can provide us downlink telemetry while our rocket is in flight. Our rocket has a max altitude of 30,000ft.

Our team has been designing our radio systems around the RN2483 LoRa chip, using the 433.05MHz frequency band at a 13.6dBm transmit power, spread factor of 7, 500kHz bandwidth, 4/7 coding rate and preamble length of 6. With these parameters we've never experienced range beyond 1.5km with line of sight, which is what Semtech's LoRa calculator also tells us should be true. In order to get up to 10km range with this chip we're basically cranking the spread factor to 12 and sacrificing our data rate down to ~18bps, which is far too low bandwidth for any meaningful telemetry (we want to send ~100 bytes at 10Hz transmit rate).

What is confusing our team is that the RN2483's underlying radio chip is the SX1276, which is also the same underlying chip used by commercial Featherweight GPS modules which claim up to 262,000ft of range (the module is the CMWX1ZZABZ, which includes the SX1276). Even taking this range with a grain of salt, we've definitely received Featherweight GPS transmitter signals much farther than the RN2483 can transmit during our previous flights, including at ~29,000ft. The Featherweight manual claims they use a spread factor of 7, and they are not sending an insignificant amount of data in their packets either. Nothing about their antennas seems to be very different from the rubber ducky antennas we are using on our radio systems from what we can tell, and there is nothing between the SMA connector and their CMWX1ZZABZ module, just a single RF trace. No LNA.

Is it possible to be squeezing 10km+ range out of the CMWX1ZZABZ module with just a whip antenna? LoRa technology seems to be limited to very low data rates at this range from our research, but we're not very experienced with RF design and are wondering if we're missing something obvious?

How is an EMP engineered?

I understand it's simplified to a power source and a coil.

What do the following affect:

• coil diameter
• coil number (windings)
• wire diameter
• wire length (total)
• voltage
• amperage
• core (soft iron) (optional)

My goal is impedance match an S11 file from HFSS. My frequency range is 600-7GHz. Does anyone know a good method to complete this task? My S11 is all over the smith chart for such a large range. 600 MHz-900 MHz is the most challenging part. The better I tune this region, the worse another band gets. My spec is fairly lenient but I’m not getting any further now and I’ve hit a road block. Spec is -7.5 db RL or ~3 VSWR. Antenna is electrically small and there’s no way I can increase the size, it’s a very tight space. The impedance is as low as -3dB at the poorest impedance points (namely 960 or 620MHZ)

Thus far I’ve tried lumped element methods (high pass PI networks). I’ve experimented with micro strip lines in ADS as well but couldn’t get anywhere better. Any guidance? My best model is using a co-simulation of my ADS PCB EM model and lumped elements.

I'm trying to implement the following article,

Title: Thru-Reflect-Line: An Improved Technique for Calibrating the Dual Six-Port Automatic Network Analyzer

Authors: Engen, G. F. and Hoer, C. A.
DOI: https://doi.org/10.1109/TMTT.1979.1129778
PDF: https://www.nist.gov/system/files/documents/calibrations/mtt27-12.pdf

In modern terms, the 2-port matrices of Error-box, Cal-Standards can be re-formulated in terms of T-parameters.
After the first occurrence of Equation (38) the authors has said that, if the reflection coefficient of the reflect-standard is known, the unknown 'a' can directly be evaluated. This corresponds to TSD calibration methodology.

Just before this Eqn.(38) the author has said that determining the unknown 'a' is sufficient to write the 2-port model of the Error-Box.
This is part i'm unable to comprehend.

The unknown Error-Box has 4 parameters. Considering lossless reciprocal network, it has only 3 independent parameters. So three linearly independent equations are sufficient to determine all the 4 parameters. And here comes the unknowns 'a', 'b', 'c'. The unknown 'b' can be determined from Eqn.(31) with appropriate assignment of polynomial-root as per Section.5. The unknown 'a' can be determined from the measurement of Short-Standard and solution of Eqn.(30,31).
But I don't see that the unknowns 'a', 'b', and 'c' are not linearly independent in the case of reciprocal network.

So what am I doing wrong and how do I get by this problem?

~Thank you.

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edit
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Found the mistake in my implementation. I was using my own system of variable names. And during the calculation of Reciprocal Network, i did the mistake. The matrices were in T-parameter form but written in different alphabet, and I eventually did T12 = T21 which got overlooked.
Now I've fixed it and it is alright.

Sorry for the somewhat clickbaity title.

I have to choose between a few options for my masters diploma thesis. I have a bunch of theoretical knowledge on analog IC design but little in terms of RFIC's and havent worked on a real world design yet, this will be my first one.

Basically I have to design a component of a transceiver at either 60 or 77ghz, it can be the PA, LNA, mixer, switch etc. My professor assigned me the 77ghz PA, but from a quick search I got the sense that PA's are more difficult and esoteric than other components. Should I ask him to switch to an LNA for something more manageable or is the difficulty not that different?

This weather station is at a pond near my house. It presumably must transmit weather telemetry, but I see no antenna (nor do I think I see a transmitter, although it could conceivably be housed with the solar charger & battery, or in the base of the rain gauge. (I'm pretty sure those spikes on the rain gauge are solely to prevent birds from nesting on it, and do not constitute an antenna.) I've identified the components I recognize, and labeled a couple of items that possibly look like RF connectors (could only get so close; I'm zoomed in about as far as I can). Is anyone familiar enough with these setups to provide additional information (including frequency and mode typically used)? Thanks!

https://preview.redd.it/d9doea5jri1e1.jpg?width=655&format=pjpg&auto=webp&s=887aae239cc6a2e2f927bde9ea6b5a1a3ff253d7

I'm poking around at the design of a GaN RF amp. I'm looking at the bias sequencing, and this AD part looks pretty good for this. Does anyone have some experience on how well this one works?

Hi all,

I work in the marine industry, on an inland ferry, and I am down in the engine room surrounded by an inch of steel on all sides as well as some insulation, EMF, etc. Depending on our daily route I may have no signal or unresponsive signal on my phone about half the time as we bounce between islands. I used a diagnostic tool to watch the bands/strengths of the towers we pass by, then I tried a cheap but well-rated band 12/13/17 automotive booster kit to see if it helped. My signal strength on 12 improved quite a bit, but it was already the only/most reliable and consistent band without a booster. The problem bands are like 2/3/5/13/14/66. Most of the time my phone typically registers a few bars and an LTE data connection on those but won't actually connect a call or load anything. I was thinking about trying a more expensive booster that covers those bands but then comes the next issue - I can get the antenna outside in the fresh air but there's no way I can mount it where it isn't obstructed overhead, and on at least one side. My strength on 12 still jumped 15-20 dB despite this hurdle, depending on if it had clear line of sight of the tower, so I remain hopeful that I may get functional service on the others if I can get a little boost. Any thoughts about whether this is probably going to be a waste of time and money? Or does anyone have advice on a better solution? Also, any ideas why I get unresponsive service even if I show a signal <-100db and a couple bars of LTE?

I want to make a simple circuit in which the set reference frequency can be compared to the input signal and then the difference between the two would be the output. So as an example: if I input a 1KHz signal and set the reference signal to 400Hz, then the output would be 600Hz. Likewise; if I input a 100KHz signal and set the reference signal to 99.4KHz: the output product should also be 600Hz. If I changed the reference signal to 99.8KHz: the output product would be 200Hz.

I've seen a few ideas on it but I'm struggling to understand how to approach this. A modified PLL perhaps? I basically need a mixer of some sort, a tunable low pass filter, and something like a VCO to make the new signal from the remainder right? Are there any single chip solutions for this or any circuit designs you would recommend? Thanks.

I’m in my graduate years, how novel the master thesis should be? What do you think? Digging up some thesis and some are kind of novel, some are kind of only analysis of existing things.

Don’t know if this is the right sub but want to ask that question.

I’m a little bit confused about the market at the moment and would know what are the best companies, from your (direct or not) experience to work for in the RF sector.

With best companies I mean places with not only competitive salaries but also technologically advanced in their specific field.

I just received a stackup showing Prepreg between layers L1 (outer top layer) and L2 (it's an 8 layer board).

I work mostly with alumina substrates - not so much with PCBs.

In the past it has been my understanding that the copper is attached to the core and that the prepreg is a sort of insulating glue to sandwich the cores together. I did not know you could add a single sheet of copper foil to a prepreg and therefore had always thought a core would always exist between layers L1 and L2 on any PCB.

In this particular case there are some RF circuits on L1 in the 1 to 5GHz range - just lumped elements - no printed filters or anything like that.

My immediate questions would be:

1. is prepreg a stable thickness?
2. does prepreg have a stable Er?

The cores are 370HR by isola. I've only used Rogers in the past.

I'm guessing there might be some cost savings by using prepreg on the outer layers - since that approach uses one less core.

Here is a graphic of the stackup

https://preview.redd.it/5axx6vj3m41e1.png?width=772&format=png&auto=webp&s=909f2a80a20803539edb4c90d776ec276d3a245e

Hi I recently joined a company where we work on home low power devices
The devices all connect with a hub on 900 MHZ . The office is full of RF for testing and development . We have a farm of devices to SOAK amd test . And recently I am thinking of getting pregnant but I keep worried about the harms of being exposed to these RF 5 days a week while pregnant

I undersrand 900 MHZ is not harmful, but what about the multiple devices exposure . Can you please tell me what do you think?

Not sure if this is the right sub for this, but I couldn’t find any better place for RF advice. I’m trying to estimate the noise figure for a system of amplifiers and attenuators (I’m grouping filters/cables/switches/couplers/etc as attenuators), and I’m stuck on a few things that don’t make sense.

I have an excel sheet set up to calculate signal power and noise power (and SNR) through each step of the system using the Friis equations for cascaded noise. It seems to work and matches values from many examples I can find online, except I can only seem to find resources on cascaded analysis for a receiver system. The base assumption is always an initial noise floor of -174 dBm/Hz from the room-temperature antenna receiving the signal. Then through the system, the noise can never drop below that level no matter what (which makes sense for an Rx system assuming constant component temperature).

So my first question is if there’s a way to change the noise floor limit based on component temperature. E.g. initial noise floor is -174, but then later in the chain I have some hot components at >290K. How can I make it so a hot attenuator has a higher noise floor than the initial condition of -174?

Second question is broader in scope. Is there any way to do a cascaded noise analysis for a transmitter? There are internal components in the Tx system, so by the time the signal reaches the first external component, it feels like it would be picking up in the middle of the Friis calculation process. Can this be solved by setting the initial conditions in such a way that incorporates those black-box effects in the transmitter? And sort of related to the first question, the initial condition will likely not be at the minimum noise floor, so how can I make it so later components can reduce the noise below that arbitrary “starting” point for the calculation.

Thanks for any help!

You can find these antennas on this link: https://signaltronics.eu/product/rohde-and-schwarz-he200/

If the image is not enough, you can look at its datasheet on the link, two of the loop antennas are made with solid metal, the 3rd seems like cable loop. Log periodic could be PCB but it's in metal enclosure. They also seem to require batteries.

This is my first time matching an antenna.

It is a LoRa module with a pi-matching network and a pcb antenna. Frequency range is 863-870MHz. I use a LiteVNA (www.litevna.org). The LoRa module has been removed and the VNA is connected instead, using a coax directly soldered to the PCB.

Apparently there are two ways of calibrating the VNA :

• OSLT calibration on the VNA's RF connector + compensate for coax cable length by adding an e-delay.
• OSL calibration on PCB by changing the values of the matching network (open, short, 49.9ohm resistor).

What I see (if I did things correctly) is that the two methods give completely different results. The first one creates many loops in the smith chart, while the second method gives cleaner results.

Question: Are the two methods supposed to be equivalent ? Which one do you recommend ?

I bought an edifier hi-fi r360db with Bluetooth and and a 5.8ghz wireless subwoofer. I always get a bad headache whenever listening to these speakers.

Bluetooth has never given me a headache, and the headache goes away soon after turning off the speakers. Could it be the 5.8ghz? The product fcc testing suggests a wireless power level of -0.7dbm at 3m, which would be my distance from the speakers, and it doesn't seem a lot. However my other wireless devices (router) have a much weaker signal at around -30dbm.

https://preview.redd.it/a0juzozrfx0e1.jpg?width=1486&format=pjpg&auto=webp&s=100f9aa9c10d0ecc976bd3a1402711061e27c255

Hey guys,

a friend of mine has this garage door opener. It is supposed to open with a remote, but that has really poor range. For that reason, he added a shelly (makes dumb devices smart). He also showed me this picture of the antenna and asked me if I had any idea. The overall length of the blue cable looks like it would match the frequency of 434MHz but I have never seen an antenna folded up like that. Wouldnt that change the resonant frequency? My suggestion would be to unbend the antenna and check if that improves things. Do you have different suggestions?

Also I hope that this kind of post is allowed in this sub

Thanks for your help

Hi I am building a helical aluminum antenna due to the one that make from copper rusted couple months ago, but I dont know how to connect it to the antenna feed make out brass/copper. I currently crimp both wire together and connect them. Is there better way for this ? If you could link any product that you use, I would be very appreciated !!

Hi all,

I'm making a transformer Push-Pull amplifier for the HF amateur bands. The individual amplifiers have 6dB of gain when measured in their single ended form. I have designed a board that uses Coilcraft 1:1 impedance transformers as my power splitter and combiners, and I'm getting 3dB of gain in the push-pull configuration that I have made up.

My question is this : obviously I'm not using a proper RF splitter here, i.e a transmission line transformer, but I would have thought that the 3dB loss in the splitter is made up by the fact I'm combining voltages at the output?

The Coilcraft transformers have 0.5dB loss, so I'd expect 5dB of gain, but for some reason I'm getting 3dB of loss compared to the single ended version. Am I missing something fundamental about using Transformers as power splitters?

My reasoning for using a Coilcraft transformer was that this article http://www.thegleam.com/ke5fx/norton/lankford.pdf (which the amplifiers are based off) uses a 1:1 bifilar transformer as the power splitter + combiner, so I'm not sure what I'm doing wrong here.

I've got a Trimble AV28 GNSS antenna - Linky

It comes with a 120 mm circular ground plane. It's my impression that this style of antenna is meant to be mounted on the roof of a vehicle, plane, or boat effectively using the metal body as a ground plane.

Can I get a larger (than 120 mm) piece of metal, cut it in a circle, and get a useful increase in antenna performance from have a larger ground plane?

For my project I have developed some polarized RFID tags and used a vivalid antenna, and I was suggested to replace it with a horn antenna, but they are just very expensive.

Hi,

I’m trying to use the BB60c spectrum analyzer by signal hound to locate radio frequencies reaching my home from another country.

This is the spectrum analyzer below:

https://signalhound.com/products/bb60c/

If one uses a directional antenna, such as this one below:

https://signaltronics.eu/product/rohde-and-schwarz-he200/

and potentially a GPS, is there a way this can be achieved? Basically, can I identify and trace where a radio frequency signal is coming from? From thousands of miles away?

If yes, how precise can the location be?

Thanks, timatuu

Hello,

So a couple years ago we got a new garage installed and now my father tried to get another remote, but when he called the company they wanted to charge us 70€ for another remote. My dad went and got a rolling code copyable remote for much cheaper online and now we both use it no problem.

The question is sometimes after not using for a while i have to click multiple times before it grabs and if my dad is gone for a time then he has to click multiple times. Are they are interfering with each other?

Apologies if this isn’t the right subreddit, and sorry if my question lacks technical detail—I’m still learning. I’m hoping to dive into automating RF test routines by experimenting with SCPI commands in Python. I thought a good starting point would be using a signal generator and oscilloscope, but the cost of these instruments is quite high. My budget can go upto £500. Are there any affordable instruments with SCPI capability that won’t break the bank? Or perhaps any simulation software that could help me learn the basics of PyVISA and SCPI without needing physical equipment?

I noticed my code for wide band FM did not work for NOAA 162.5MHz narrow band.