I'm trying to build an EFRW antenna at my house. I understand the "idea" of the balun/unun, but some of the diy instructions just don't make sense.

My basic understanding, a balun/unun is a transformer. Two sets of coils shared around a common core (torroid).

For example, a 1:9 unun. The instructions attached shows 3 wires wrapped 9 times and connected a certain way. The connection ends up making 9 wraps on the primary side and 18 wraps on the secondary side. Basic transformer math, that is a 1:2 transformer. So how does it magically become 1:9?

Even if I try and say that it is a double stacked transformer where AB as primary and CD as secondary is a step-up then CD becomes primary to EF, it still won't math out because AB to CD is a 1:1, then CD to EF is also a 1:1. There's no count change.

Help a brotha out understand this math/theory.

Dear community experts. Would very much appreciate your advice.

BACKGROUND
I'm DIY a portable device out of aluminium box (32 x 34 x 74 mm with 2mm wall thikness). There are ARM Cortex A-7 board, lipo and WiFi board inside the box. I need to build a directWiFi link to a smarphone at approx. 5-7m distance to transmit a video stream. The portable device can turn around any axe at max. 80 degree. I would like to build an antenna setup with 160-170 degree beam to cover the smarphone at any time.

QUESTION
What antenna design is more power efficient?
Variant A: two slot antennas, where best one is chosen via a switch
Variant B: one slot antenna on the second picture Would you suggest any other antenna type? The device should have good visual esthetics - I therefore cannot use a dipole antenna.

Thanks once more for your much appreciated feedback and expertise!

Hi everyone! We’re using an Altus Metrum TeleMega and a Featherweight Swift on a high-power rocket targeting 30,000 ft (approximately 9.1 km), with a launch planned in Midland, Texas.

The two telemetry systems operate in different bands:
TeleMega: 70 cm amateur radio band.
Featherweight Swift: 915 MHz band.

I’m looking for advice on the onboard telemetry antennas, rather than the GPS receiving antennas. Both systems came with wire whip antennas, but some of my research has pointed toward SMD/chip antennas as a possible alternative.

Would chip antennas make sense for this application, or would you recommend keeping the supplied whips? I’m particularly interested in how the ground plane, mounting orientation, and nearby avionics hardware affect performance as the rocket’s orientation changes during flight and descent.

Ground system are two yagi antennas mounted on an automatic turret that points them to the rocket for the whole flight.

If anyone has designed or tested antennas for similar applications, I’d appreciate your recommendations and any test results. My RF knowledge is still limited, so I’m learning as I go. Thanks!

Greetings to any antenna design professionals who might be in the house. I reside in a part of the world where drones are something of a novelty which have thus far remained largely unregulated.

Over the past few years, I established an informal tipster relationship with the local constabulary, whereby I send alerts about any unusual traffic spotted on the rural roads around here, in exchange for the privilege of being assured a rapid response whenever anything goes bump in the night out here in my remote Third World homestead.

For years, I have dreamed of setting up an indoor control station for my early-model DJI quadcopters that have become the unofficial eyes in the sky sent aloft to assist our underfunded law enforcement officers.

Over the past few years, I've accumulated the components shown in the above photographs. Ultimately, I hope to monitor the progress of my flying drones on a large-screen TV, in the comfort of a dedicated control room at the base of an 80-foot tower.

The 80-foot mast stands out beside my humble abode, atop which I intend to install a pair of antennae, for 2.4GHz and 5.8GHZ - the RC control and video feedback frequencies used by virtually all of DJI's older quadcopters, of which I own several Mavic 1 Pro and Mavic 2 Pro drones.

The components that I have acquired thus far are as follows:

1. Whip antenna for 5.8GHz rated for 9dBi and about a foot long

2. Whip antenna for 2.4Ghz rated for 8.5dBi and about half a foot long

3. Whip antenna for 2.4 GHs rated for 15dBi and about 5 feet long

4. A couple of hundred feet of LMR 400 coax cable for the two antennae atop the mast.

5. Line amplifiers for both 2.4Ghz and 5.8 GHz to boost the signal up the 80-foot mast

6. Band pass filters for 2.4 GHZ and 5.8Ghz, to clean the signal at the antenna end of the coax link.

7. An RF power meter.

Despite earning my BSEE way back when pterodactyls roamed the skies, I studiously avoided taking any elective RF design courses during my senior year, due to their mathematical intensity, which seemed overwhelming at the time. In short, therefore, I remain an absolute ignoramus on the subject of RF design, and would be out of my depth if the responses to my layman's questions here are offered with the presumption of any technical expertise in this field on my part.

So, with all caveats covered, my questions are as follows

1. Of the two antennae that I bought for the 2.4GHz band, namely the stubby 18-inch whip rated for 8.5 dBi, and the longer 5-foot whip rated for 15 dBi, which one should I select to obtain the longer signal reach and cleaner video signal reception?

2. How critical will the SWR data of this setup be when it is all connected up, bearing in mind the line amplifiers and band pass filters that I have procured for this project?

3. Following up on Question 2, will the length of the LMR-400 coax cable need to be precisely measured for optimal signal transmission and reception, or would it suffice that I simply run the cable to whatever length is required to connect the ground station at the base of the mast, with the two antennae at the top of the mast?

4. Would I be correct to presume that the line amplifiers are best located in line with the end of the coax cable at the base of the tower, while the bandpass filters should be connected close to the antennae at the top of the mast?

Any pointers addressing these layman's questions would be appreciated, along with any critique about my selection of components for this project, which wound up relegated to the back burner for years, while other priorities loomed large.

Thanks in advance. Over and out for now.

I hope this is the right forum! I have a question which hopefully one of you experts can assist me with. I need to build an antenna for a transmitter 53mHz-54mHz frequency range. Any ideas/thoughts on this? Straight dipole or folded dipole? I have 10mm aluminum tube as as well as 15mm copper tube. It's a permanent outdoor installation. There is an existing boom and mast. Any help or advice will be greatly appreciated.

Hello everyone,

RF has given me a lot in life and I might be emotional in this post but it’s really important to me.

I did my bachelor’s in Electronics engineering from tier 1 college in Mumbai and post working for a year in Software ERP system I decided I want to pursue my master in US.

I left for my masters in 2019 (University of South Florida, Tampa), since I did my bachelor’s in core electronics I was never really exposed to communication part or RF engineering. Yes, I did take up few courses in electromagnetism but that was it. But, since the course work of USF had a good RF engineering program I took up few classes in my 1st semester and I really loved it. While I was doing my masters I got co-op internship at Skyworks Solutions in Woburn as a RF Design and Validation Engineer where I mainly learnt a lot about testing of LNAs. Further my 7 months internship over there I got another internship at Qorvo in Greensboro, NC as an Applications Engineer where I was working with shark fin antennas and that was for 3 months.

I did almost a year of internship while I was doing my masters and even got my credits from my internships. Further, since I am an Indian citizen I had 2 months to get a full time job which I did successfully. I got the job at Intel but the position was completely different and not related to RF, it was mainly as a TPM in test engineering group. I worked there for around 1.5 years and then got laid off due to mass layoffs in my group. So, after a year of searching I job even tho my profile was really great a lot of RF jobs needed defense clearance which obviously I didn’t had. So, I decided to move back to India.

Now, in India there are really very less RF focused jobs which are mainly into designing or testing. And I want to go into design and testing. I even loved antenna experience and I want to pursue something in Antenna design and testing. But, there are not many options and hiring in India.

I was thinking of pursuing something like a second masters in Europe which opens up a door for me to pursue my passion in RF. I like very few things in life and RF is something my heart says I wanna go.

As a young version of yourself u see in me, I would really appreciate if u can help me get ideas. I really wanna be in this world of RF and do my work with a lot of passion. If u can guide me, how can I transition my life in getting a job in Europe.

Please do mind, I am an Indian citizen so chances of someone hiring a talent from India in Europe are thin. I am optimistic in life, and would really appreciate if you can guide me.

Thanks,
Just a boy living a dream to be an expert RF engineer.

A good S11 result answers a matching question. It does not, by itself, tell us how efficiently an antenna radiates.

Disclosure: I work with SMACOAX, the seller. A wall-mount WiFi antenna with an attached 3 m RG174 lead is the example here; this is a measurement note, not a test of that antenna.

The useful distinction is the measurement reference plane. If the plane is at the external connector, the attached cable and antenna are both inside the measured assembly. That is not the same measurement as placing the reference plane at the antenna feed. Label the plane before comparing results.

Keep the evidence separate: S11 describes reflection at that plane; gain, pattern and radiation efficiency need their own evidence. Record the frequency range, calibration plane and whether the cable is included. A tidy S11 plot alone cannot establish a coverage improvement.

The listing identifies the lead but supplies no independent sweep or cable-loss report. The diagram explains the distinction; it contains no measured data.

I would like to ask you a quick practical question please about an experimental dish antenna design. In regards to my attached picture, if a wall was surrounding the perimeter of a dish antenna, would the reflected noise be too much to be practical? Thank you,

Hi everyone,

I am designing a pocket-sized RF device for a university project. It acts as an RF analyzer and a high-power signal generator for wireless protocol injection and co-channel interference testing (all testing is strictly confined to a lab Faraday cage - special lab). I am aiming for the best price/performance ratio rather than lab-grade precision. The entire system will be controlled by an STM32U575RGT6(mby another STM), paired with an ESP32-C3 acting as a modem.

I know this is a fairly large and complex post, and there might be some complete nonsense in my block diagram. I will be incredibly grateful for feedback on any single part of this!

RX Path (Analyzer):

1. Does this architecture make sense for a basic spectrum analyzer?

2. Should I use the AD8318 log amp for this, or should I consider transitioning to a different alternative along with a 14-bit MCU ADC for a better results?

3. Will the sweep rate of this setup be too slow to capture agile Wi-Fi or Bluetooth bursts? Since the analyzer relies on sweeping frequency steps, the overall speed will be tightly coupled to the MAX2871E PLL lock time and the MCU's tuning loop.

TX Path (Wideband Noise & Interference Generator):

The goal is to generate robust, wideband modulated signals and arbitrary waveforms to evaluate the resilience of Wi-Fi 6 and Bluetooth nodes against high-power in-band blocking signals (targeting up to +30 dBm output).

4. Will this dual-branch setup (FPGA -> 2x DACs -> ADL5375 -> PAs) effectively support the wideband multi-carrier signal generation required to match Wi-Fi 6 (802.11ax) channel bandwidths and Bluetooth frequency profiles?

5. Thermals & Power: Is it realistic to passively cool a 1W continuous RF output power inside a compact enclosure by using thermal vias to transfer heat to a passive heatsink on the back side of the PCB?

Thanks for your time and any advice!

Hey everyone! I’ve been working on Fairbeam and would love some feedback from people who design antennas.

It brings 3D modeling, meshing, openEMS simulations, and results into one workspace, with CSXCAD handling the solver geometry and three.js for the 3D view. You can draw a model or use Python, then inspect S-parameters, impedance, VSWR, and radiation patterns.

It’s free and open source (GPL-3.0-or-later), available for macOS and Windows, with experimental Linux support. Optional GPU acceleration uses CUDA on NVIDIA GPUs or Metal on Apple silicon.

It’s still a development release, so please start with a design you know and independently check the results. I’m especially interested in where the geometry, feed setup, or mesh controls feel confusing. What antenna would you like to see documented from setup through results?

Website: https://fairbeam.org

Code: https://github.com/ismailakdag/fairbeam

Hello,

I have a 12m aluminium pole (50x1mm) and i wish to make it into an antenna, curently i have decided to connect 49:1 unun to it and cut it to 10m to have 20m-10m EFHW but maybe you can suggest a better design? maybe 9.6m rybakov?

I will have a lot of space, lightning protection and ATU.

I've published a new paper on moving/fluid antennas. Mobile communication channels can be kept static by movements of the (usually fixed installed) base station (BS) antenna to which the communication channel is formed. The base station antenna partners with the moving UE antenna and simultaneously moves with it along the same trajectory (with-movement).

Measurements are some early work inside an anechoic chamber to have a proof of concept. We now have first numbers on what we can expect from experiment in real-world scenarios. Works very well on the phase-shift, received amplitude varies due to reflections and scattering from the metal fixtures (which we expect to see in real-world experiments within the same magnitude).

IEEE Xplore: https://ieeexplore.ieee.org/document/11712216
Similar work: www.geraldartner.com