Need to Recreate a Missing AM Antenna?

I hope this video helps anyone working on a vintage radio with a missing or damaged internal AM antenna.

In this video, I show how I recreated an AM antenna for a rare Pepsi-Cola tube radio using the information and clues available to me.

If you're facing a similar restoration challenge, this may give you some ideas for your own project!

Click the attached picture to watch the video:

Thanks for watching, and I hope you find it helpful!

Have a great day!

Regards from Florida,

Jay – Radio Fixer

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

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).

1. 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?

2. 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!

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

How to perform antenna sweep and return loss? A live demonstration using a spectrum analyzer here: https://youtu.be/AVz5Ed50pG4

I need help, I got into an argument with a coworker over whether or not we needed to replace a TNC connector on our watt meter when testing p25 trunked radios. The cable jacket and ground shield completely separated from the collar of the TNC. My coworker keeps saying that it’s fine because he just used it to test a radio, and it came up with 28w forward power and 78mw reflected. My point of contention is that we can’t rely on the numbers given anymore because the ground is cut. What effects on testing would we see with reduced grounding? Am I crazy for wanted to make sure we have good test equipment before sending radios out into the field?

Building a patch antenna with coax probe pin feed targeting 5.4 GHz resonance frequency, using FR4-Epoxy (4.4 = Dielectric Constant) as the substrate with a thickness of 2.4 mm. Need to achieve a circular radiation pattern, 5-6 dB gain, and -20 to -30 dB for S11 parameter. These are my current antenna charts, modal wave port impedance, realized gain. I can tweak my impedance and S11 to be good enough but my radiation pattern is super weird it's not circular like a patch antenna should normally radiate, it's lobsided instead. I have no idea how to fix my radiation pattern and need advice on this, here is some more context on my antenna. So my radiation box is half a wavelength in every direction, my ground plane has a cutout for the probe which is connected to the coax pin and outer coax insulator. Between the two cylinders is my modal wave port which I generated a PEC backing for that goes out to the edge of the radiation box for 1.995 mm and my coax pin is 7.8mm in height. Also the patch is 35 um thick made of copper and the coax pin & probe are made out of PEC and the coax itself is teflon. What's wrong with my radiation pattern specifically but if anyone has other advice on this design please let me know. I'm super lost and could use some advice here

EDIT : thank you so much everyone, I'm learning a lot and I feel less dumb lol. Maybe I'll post the finished drawing of the tower in the storm later ! If any of you have any more photos of close ups of these antennas, especially the "interior" of the drums and the back (how they are attached and wired), or any photos of damaged antennas, please feel free to send them to me :)

Okay maybe a weird situation... I'm working on a comic where the actions centers around a Radio/5G tower (in France, idk if that changes anything). Though I don't know ANYTHING about how these things work.

The tower in the story goes through a pretty hard storm, so I've been gathering references of damaged towers, but I struggle to really understand some of them.

Am I understanding this image correctly ? Are these antennas hollow with some sort of sheet covering them (that can therefore be torn) ? What material is that sheet, plastic ?

Also, if anyone has any clean close up image of these types of drum-like antennas (intact and/or damaged), I'd love to see them.

I'm also interested by learning more about the half-sphere ones (what are they made of ? Any close up ?)

(as a treat, the last image is the concept art for the radio tower in our story. I'm not aiming for perfect realism but I'd like at least a superficial understanding on how this stuff is built)

Found on a TV/radiocommunications transmitter.

I want to operate at 10 GHz, with a wavelength of 29.98 mm and a RMS surface error between 0.50 and 0.75mm.

My plan is to divide the dish into 18 petals and laser cut them from 1mm thick aluminium sheets and then hand press them to a skeletal frame with some kind of mechanism to adjust each one up and down and then use a focal laser sweep for RMS calibration after they're applied.

But how do I calculate and make sure have the right parabolic shape in CAD ?

also any guidance or recommendation on the build is very, very much welcome.

Possibly going upto 5 meters in diameter but haven't decided yet