Tagged: antennas

CENOS Antenna Design and Simulation Software Looking for Testers

Back in March 2020 we posted about CENOS, a company creating a new antenna modelling and simulation design package. Back then they were offering applications to beta test the software for free. CENOS has now reached V1.0 status, and they are now wanting to enroll another 300 testers. The benefit to the testers is that they will receive a 90% lifetime discount on the software, and testers who provide lots of active feedback will be granted free licenses.

CENOS Antenna Design version 1.0 will be available for closed testing starting from March 17, 2021.

During the free 14-day testing trial, users are expected to share their feedback about the software and usability, thus making an impact on further software development. 

In reward, they will get a generous discount or lifetime-free-licenses (for best contribution), once the software is available for public use (we expect to launch it shortly after rigorous testing completes).

More details will be announced on March 17!
 
Sign up here:
Software benefits
 
​CENOS is fast-to-learn and easy-to-use specialized antenna design simulation software for budget-sensitive customers.

CENOS integrates FreeCAD geometry editor to handle geometry of any complexity, provides built-in utilities for handy design of microstrip antennas and arrays, feed networks, wire antennas (including import of NEC files), and arbitrary 3D structures. FreeCAD also allows to import CAD files from external editors like Autodesk Inventor or similar.

CENOS ensures automatic meshing, as well as allows building manual mesh of any detalization level in the specially designed FreeCAD workspace.

For antenna calculation, the current software version utilizes FEM solver to provide accurate simulation for geometries of any complexity, including multi-port, high Q and other cases. Already now, CENOS R&D is pointing to combining the FEM solver with MoM and FDTD methods to provide a unique, optimized (fast and accurate) solution for any particular case.

CENOS provides very powerful visualization capabilities that includes full visualization of fields and graphs powered by Paraview, spreadsheet for data like S11, VSWR, reflection coefficient, etc, and pdf report.

That all makes CENOS a good alternative to well-known general purpose software like HFSS, CST, FEKO and Comsol for budget-sensitive customers looking for specialized antenna design simulation software.
Software functionality
• One-stop software: from CAD geometry to full visualization of results and analysis
• Desktop (on-premises) installation for Windows 7-10
• CENOS leverages open-source tools to ensure full stack of CAD/CAE software: FreeCAD, GetDP, ParaView
• User experience optimized for RF antenna design
• Supports the use of CAD geometry files prepared by any design program (.step or .iges formats)
• Pre-defined templates for basic antenna geometries
• Full-stack geometry editor powered by FreeCAD
• Material database, possibility to add and save custom materials

Simulation capabilities
• Wide range of antennas, antenna arrays, geometries of any complexity, inhomogeneous structure
• Finite element method (FEM) solver optimized for high frequencies
• Lumped port type, multiple ports (feeds) with phase shifts
• Frequency diapason (wide, multiband) 
• Ports: S11, VSWR, power, reflection coefficient, impedance, reactance, and resistance
• Fairfield pattern: directivity (gain), radiation intensity
• Antenna: Electric field, magnetic field, vector plots 
• Frequency-dependent dielectric constant and loss tangent
 
… all you need for antenna design in an easy-to-use way, because this is the software specialized on RF antenna design with full spectrum of necessary functionality. And we are constantly working to add more value.
 
Hardware requirements
You don’t need a supercomputer to run antenna design simulations with CENOS. Intel i5 or i7 (or similar) are good enough. The faster processor you have, the faster calculation will go.

We recommend to have at least 16Gb RAM to calculate 3D cases, 32Gb is better. Actually, the more RAM you have, the bigger (more complex) 3D geometries you can simulate. Some of our customers use 128 Gb machines and that’s like for rocket-science-cases. MS Windows OS.
CENOS Antenna Simulation
 

Comparing Shortwave Antennas with an RTL-SDR and FT8 Monitoring

Eric had an inverted L and T3FD antenna set up in his backyard and he wanted to test both at the same time to see which received HF better overall. Rather than relying on subjective 'by ear' measurements he decided to use the digital FT8 mode as his comparison signal. FT8 is quite useful for this purpose as the decoded data includes a calculated signal-to-noise (SNR) reading which is a non subjective measure that can be used for comparisons. It also contains information about the location of the signal which can be used for determining the DX capability of the antenna. 

To perform the comparison he used two or our RTL-SDR Blog V3 dongles running in direct sampling mode, and also added an additional low pass filter to prevent excessively strong TV and FM signals from overloading the input. Each antenna is connected to it's own RTL-SDR, and a modified version of GQRX with remote UDP control is used to switch between multiple FT8 frequencies so that multiple bands can be covered in the experiment. WSJT-X is used for decoding the FT8 packets.

After logging SNR values for several days he was able to plot and compare the number of packets received by each antenna, the maximum distance received by each antenna. His results showed that his inverted L antenna was best in both regards. He then performed a relative comparison with the SNR readings and found that the inverted L performed best apart from at 14 MHz, where the T3FD performed better.

In further tests he also compared the antennas on which signal headings they were receiving best from. The results showed that Erics inverted L was receiving best from one direction only, whereas the T3FD received signals from more headings.

Eric's post includes full instructions on the software setup and also Python code which can be used to replicate his experiments. We think that this is a great way to objectively compare two types of antennas.

Antenna directionality measurements via FT8 received headings

Building an Underground Earth Probe Antenna for 0 – 14 MHz TX/RX

Thank you to Jean-Marie Polard (F5VLB) for letting us know about his work in creating underground "earth probe" antennas that work for both RX and TX between 0 - 14 MHz, and are especially good at VLF and below. He writes:

Can't install an antenna at home? Madame refuses the masts, taut son? One solution, The Earth probes antenna.

Our group (https://www.facebook.com/groups/earthprobes/) started in January 2019. At first everyone made fun of me, the professionals called me crazy and today with more than seven hundred members, we installed underground antenna systems and the results are there.

Between 0 and 14MHz, in transmission and reception, it works!

This system dates from 1914/1918 but has been brought up to date.

It doesn't take much to get started, just the urge to try.

Mad of vlf - elf - ulf ? come here https://www.facebook.com/groups/VLF.ULF.ELF/ nearly 1000 members are waiting for you.

So when? Welcome everyone.

To access the Earth Probes and VLF.ULF.ELF groups you'll need a Facebook account. The groups contain a number of research papers documenting the concept, and the photos section. From the photos, an earth probe antenna appears to consist of two long grounding rods spread over a distance, or a grounding rod and long buried wire, combined with a balun.

An example of an underground antenna setup from a 1935 shortwave magazine.
An example of an underground antenna setup from a 1935 shortwave magazine.

Sign up to be an Early Beta Tester of CENOS Antenna Design and Simulation Software

CENOS are a company specializing in 3D modelling and simulation software for induction heating applications. However, they are now branching out and are creating software for antenna design and simulation. Final pricing of the software is not yet advertised, but they write that it has been made affordable thanks to "open source algorithms". Hopefully it will be affordable to hobbyists, but judging by the heat simulation software pricing it may not be (although they offer to software free to students, researchers and teachers).

However, it appears that they will soon be running a beta testing program that should hopefully be free to use during the testing phase. You can sign up to their email list and wait for their announcement on their website.

CENOS Antenna Design Program Screenshots
CENOS Antenna Design Program Screenshots

A Discone Antenna Made from 3D Printed Parts and Aluminum Tape

A Discone is a type of antenna that is designed to be resonant over a wide range of frequencies. Most antenna designs only really receive well on a few resonant frequencies, but a Discone is resonant over a much wider frequency range. This makes it a good partner for RTL-SDR and other SDR units as many SDRs tend to have wide tunable frequency ranges. With a wideband antenna like a Discone connected to an RTL-SDR one can scan over the almost entire tunable frequency range without needing to change antennas for each band. The drawbacks to a Discone however is that the antenna gain is not very high, and that it makes the SDR more susceptible to out of band interference. They also tend to be fairly expensive and difficult to build.

However now over on Thingiverse, mkarliner (aka Mike) has a remedy for the difficulty in building a Discone with his 3D printable Discone design. To construct it you simply need the 3D printed parts, some .3mm and 2mm plastic sheets, a 25mm plastic conduit and some aluminium tape. Mike's design works from 400 MHz and up, but the design could be easily enlarged for better performance on the lower frequencies. He writes:

The Discone antenna is remarkable in that it is capable of receiving and transmitting over a wide range of frequencies with good matching. Because of this, it is a good match for SDR receivers such as the popular RTL-SDR sticks.

The only really tricking thing about making a discone is that the disc has to be balanced at the very top of the cone, which is mechanically awkward.

The two parts here allow the cone to be solidly clamped and provide an adequate base for the disk. There also two holes for bring the coax centre and braid out to the disc and cone.
The base part has a socket at the bottom for 25mm (1 inch) plastic conduit for mounting

This antenna illustrated is designed for 400MHz and up, and as such transmits well on the 70cms amateur band, US and UK PMR channels and 23cms. It also receives aircraft ADS-B signals very well. I used .3mm plastic sheet for the cone and 2mm plastic for the disc, and then covered them with aluminium weatherproof tape. Be sure to check for continuity across the tape stripes.

The screenshot is of a calculator by VE3SQB which can be downloaded from http://www.ve3sqb.com/ if you want to make attenna's for other ranges.

A 3D Printed Discone
A 3D Printed Discone

If you're interested in building wideband antenna there is also the planar disk antenna (pdf) which can be built out of pizza pans.

The K9AY Loop Antenna: A Directional E-H Antenna for HF

Thank you to Frank Sessink (PA0FSB) for submitting to us his document describing the K9AY loop antenna (pdf), which is the antenna that he successfully uses with his RTL-SDR for HF reception. The antenna combines magnetic (H) and electric (E) field reception in order to create a directive radiation pattern. Frank extends the idea by showing a method that can adjust the directivity electrically with some simple resistor switching.

The antenna that I use is for medium wave DX, specially to receive MW from USA here in Europe/The Netherlands. The antenna is a combination of a magnetic loop and a sense antenna for the E-field. The magnetic loop is directive, but has no front-rear ratio. The E-field antenna has omnidirectional sensitivity. The combination, in correct phase and amplitude, results in a front-rear ratio of more than 25 dB over the frequency range from 500 kHz to around 3 MHz. Higher frequency makes no sense, since skywave signals distort the ground wave directivity pattern.

A simple modification is used as directional antenna with remote control: two orthogonal loops that combine E and H-field in a simple way. I can make 8 selectable directions.

The full document is available here in PDF format.

The K9AY E-H HF Antenna
The K9AY E-H HF Antenna

Building a Ground Plane / Spider ADS-B Antenna for 2€

Thanks to Manuel aka Tysonpower for submitting to us his extremely cheap ADS-B antenna build. Manuels ADS-B antenna consists of a simple SMA connector with flange and some wires cut to the correct resonant length for 1090 MHz ADS-B. This ground plane design has been around for years on the internet with atouk’s guide being the most commonly used, although atouk’s design uses a larger SO-239 connector instead. Manuel takes the design one step cheaper by using cheap single core copper wire for the elements, and a low cost SMA connector. The wires are soldered onto the SMA connector flange so you will need to know how to solder to complete the antenna.

Manuel has uploaded a video which shows the build steps for his cheap antenna in a step by step guide. We note that the video is narrated in German, but there are English subtitles.

[EN subs] ADSB Antenne für 2€ – DIY

Radio For Everyone New Posts: Building an ADS-B Station, Easy Homemade Beginner ADS-B Antennas

Akos the author of the radioforeveryone.com blog has recently added two new articles to his blog. The first post is a comprehensive guide to setting up your own ADS-B station. The guide focuses on creating a system that is easy to use, has good performance and is value for money. In the post he shows what type of computing hardware is required, what software can be used and what RTL-SDR dongles work best. He also shows what choices are available when it comes to amplification and filtering to improve signal reception and goes on to talk a bit about adapters and the antennas that work best for him.

BuildingADS-Bstation
Building a ADS-B station

 In the second post Akos shows more on how to build your own beginners antennas for ADS-B reception. The post focuses on showing how to modify the stock magnetic mount antenna that comes with most RTL-SDR dongles, and how to build a half-wave ‘spider’ antenna entirely out of coax cable. The post is full of easy to follow images which make it great for beginners.

EDIT: It’s been pointed out in the comments by antenna experts/enthusiasts that the 1/2 wave ground plane antenna described by Akos in his tutorial may not be technically correct. A 1/2 wave antenna has a huge impedance which requires some sort of matching. Without matching there is going to be about 10 dB of loss due to the mismatch, and so the antenna will perform poorly. We recommend sticking with a 1/4 wave design, which is essentially the same as Akos’ 1/2 wave ground plane antenna, just with the element lengths halved.