Articles, videos and links (international)

articles, videos and links
(international)

here you can find a collection of interesting links to articles and videos that I found interesting

In this fast-paced world, I decided to create this section with direct links to articles and videos of my interest. This approach will let me to keep the site up-to-date, recognize the deserved merit of other good colleagues and will give me more free time to devote to my passions and projects.

Water-based and trees antennas

added on 07-aug-2022

I found this really interesting and straightforward concept to create a continuous tunable antenna (2 Mhz – 400 MHz) by using a column of salt water as radiating element.

A water pump is pumping sea water through a nozzle placed inside an annular current probe; the current probe has the function to ensure the proper impedance matching between the water column and the transceiver.

The toroid has a primary winding connected to the RF port, secondary winding is the fluid column passing through the toroid.

The magnetic core mix and the exact turns ratio is unknown but can be selected depending on operating frequency and antenna configuration (1/4 wave, 1/2 wave, ecc)

The same principle can be applied not only to water columns but also to other elements containing water, like trees!

If you want to learn more about the topic of liquid antennas, I suggest you also read the following article (link).

Liquid antennas are classified in: metallic and non-metallic (water-based and non-water-based).

Liquid Antennas: Past, Present and Future

The working principle is described in several patents that I resume here below. (Click on the patent name to view the full document on Google Patents)

US7898484B1 – Electrolytic fluid antenna

This is the patent related to the antenna in the video, where a water pump is pumping sea water through a nozzle placed inside an anular current probe

US5633648A – RF current sensing coupled antenna device

US6492956B1 – RF current injecting antenna device

These patents are both related to the coupling method between the current probe and the radiating element.

The RF current injecting antenna device is made of a toroidal magnetic core, employing the principles of an instrument transformer, it couples RF energy from a transmitter to a linear conductive surface. The useful frequency range that has been demonstrated for the device is 2 MHz to 1 GHz,

Turns ratio, for the transformer coupled to a linear conductor, seems to be in the 2:1 range.

The current probe seems a type of Current Injection Probes from Fischer Custom Communications (https://www.fischercc.com/type/bulk-current-injection-probes/)

US8094083B1 – Multi-Band tree antenna

By using the same concept described above is possible to use also live trees as transmitting antennas, the tree branches ensure also the possibility to create multi-band antennas.

Probably there are trees that perform better than others thanks to different sap properties.

LoRa and mesh networks - Meshtastic
(An open source, off-grid, hiking, climbing, skiing, GPS mesh communicator

added on 19-oct-2021

Recently I discovered a really fascinating project that combines the efficiency of LoRa radio technology and the infrastructure advantages of mesh networks.

Meshtastic is essentially (but not only) a GPS assisted “SMS style” communicator based on LoRa (Long Range) modulation combined with mesh networks. It’s composed of a radio module, loaded with the open source software, combined with an Android application as user interface.

Below you can find a very well done and interesting video done by Andreas HB9BLA which sparked my interest in this technology; I suggest to visit his Youtube channel where you can find a lot of information regarding LoRa and LoRaWAN projects.

In Meshtastic project:

LoRa modulation guarantees long distance communication using the license-free sub-gigahertz bands like 433-868 MHz in EU, thanks to its narrowband waveform combined with spread spectrum techniques and low bit rates.
The mesh network topology has the direct effect that each node creates a bridge to distribute messages and position to all other nodes.

Right today 19th Oct 2021, also Josh KI6NAZ jumped on Meshtastic and published in his HRCC Youtube channel a first video on LoRa and mesh networks, we’re waiting next ones Josh!

I learned that it’s possible and simple to install a beta release of Meshtastic on iPhone: you need to update the iOS to last version, download TestFlight app from the App Store and then participate to beta testing by opening the following link:

Visit following websites for more information:

Here a link to Mehstastic nodes in your area:

(click “Next”, no log-in is needed)

There is also a commercial project similar to Meshtastic, its name is goTenna, its products are available for consumer and professional uses:

LoRa is the physical layer of the LoRaWAN protocol that is becoming more and more popular for IOT projects where there is a need of long range, low power (battery operated device) and when high data rates are not needed.

Here a self-explaining video of LoRa modulation:

LoRa range thanks to its high link budget guarantees long distance communications, here some examples:

A wireless Mesh network is a

distributed network in which the nodes connect directly, dynamically and non-hierarchically to as many other nodes as possible and cooperate with one another to efficiently route information and keep the network itself alive.

Here a self-explaining video of LoRa Mesh networking showing the network’s behavior in realtime, with Simple Arduino-Based modules and the RadioHead library. Using a realtime visualization, the author show how the network forms and how it heals itself when network nodes become unreachable.

Focus on LoRa radio modulation and the LoRaWan protocol for IOT systems (commercial applications)

added on 18-Oct-2021

The Things Network is a website where you can find all detailed and well explained information regarding LoRa radio modulation (physical layer) and its implementation in LoRaWAN IOT protocol.

Here I collect a link to TTN website and a really interesting video that explain all details of LoRa (first part) and LoRaWAN (second part)

The LoRa Alliance® is an open, nonprofit association that has become one of the largest and fastest-growing alliances in the technology sector since its inception in 2015. Its members closely collaborate and share experiences to promote and drive the success of the LoRaWAN® standard as the leading open global standard for secure, carrier-grade IoT LPWAN connectivity.

Focus on Radio Mesh Networks

added on 18-Oct-2021

Mesh networks are not a new technology..first attempts are dated as far as back as the early 1970’s with with the development of packet radio networks by the US Defense Advanced Research Projects Agency (DARPA), that sought to replicate the ARPANET (the forerunner of the current Internet) over wireless.

Here I collect two articles from that cover a lot of useful information related to radio mesh networks:

LoRa antennas

added on 18-Oct-2021

Here an article of a simple and effective J-Pole antenna project that is enough to guarantee reliable communication between nodes.

Please note that in many regions the use of high gain antennas (e.g. collinear, Yagi) on LoRa frequencies is not allowed.

LoRa satellites - TinyGS, the Open Source Global Satellite Network

added on 18-Oct-2021

TinyGS is an open network of Ground Stations distributed around the world to receive and operate LoRa satellites (mainly on 433 MHz band), weather probes and other flying objects, using cheap and versatile modules.

WebSDR network: a new way to listen radio transmissions over internet

added on 10-Jan-2021

source: http://www.websdr.org/

A webSDR is a Software-Defined-Radio receiver connected to the internet, allowing many users to listen and tune it simultaneously. For every node connected you can find useful informations like its location and the frequency range.

One of my favorite, in Europe, is the wide-band webSDR receiver located in the University of Twente (NL) that covers 0 – 29 MHz with a miniWhip antenna. (Click on the following image for a direct link).

radio direction finding with KiwiSDR network

added on 03-Jan-2021

Source: https://www.youtube.com/user/hoshnasi

This interesting video explains how to locate any radio signal over the world by using the network of KiwiSDR stations. Thanks to the synchronous timing of the GPS included the KiwiSDR receivers it’s possible to triangulate any radio signal.

EFHW Antenna: End Fed Half Wave Multi-Band HF Antenna 80m - 10m with 49:1 UNUN transformer

added on 02-Jan-2021

Source: https://www.youtube.com/c/TechMindsOfficial

I really like the EFHW antennas, especially for mobile activations because they are easy to build, half-wave and resonant on multiple frequencies. Usually they don’t requires a tuner.

Follow this Facebook page where you can find many resources for EFHW antennas design and guides to be downloaded.

EFHW Antenna: an easy build for 11m band.

added on 01-Jan-2021

Source: https://www.youtube.com/c/RadioPrepper

In his Youtube Channel Gil presents several variants of this kind of antenna for HAM bands.

This particular project refers to a simple and effective antenna for the 11m band; with a total length of about 4.85m of speaker wire it can be easily attached to a not conductive pole like a tree or a fiberglass fishing rod. It gave me several satisfactions on many QRP DXs during Summer 2020.

Chameleon CHA F-LOOP 2.0 (10-80m magnetic loop antenna)

added on 12-Jan-2021

Source: https://www.youtube.com/user/hoshnasi

This it the video is the one that convinced me to purchase this antenna, mainly due to the high quality of construction, the easy and quick deployment, and the modularity (it can me configured as single/double coax loop, rigid aluminum big loop) and the option to install a power compensator tu upgrade the max power capability up to 60W (SSB).

In the review Josh explains clearly all the features and does some WSPR transmission tests to evaluate the performance of the antenna.

Great review, remember to follow his channel!

4nec2: NEC based antennas modelling software

added on 1-Jan-2021

source: https://www.qsl.net/4nec2/

I have not yet had time to investigate and test this software but I include it in this section for future insights as it seems very interesting.

4nec2 is a completely free Nec2, Nec4 and windows based tool for creating, viewing, optimizing and checking 2D and 3D style antenna geometry structures and generate, display and/or compare near/far-field radiation patterns for both the starting and experienced antenna modeler.

HamMap.org: upload your AIDF logbook and see all your contact on a nice map

added on 10-Jan-2021

source: https://www.hammap.org/

HamMap.org is a nice website that allow you to view all your contacts on a map in 3 easy steps: register (for free), upload your ADIF logbook (e.g. from qrz.com), enjoy your map!

Several map styles are available, you can edit them in the “Update your profile” menu, where you can also include your QRZ API KEY.

To get yours, log into QRZ and go to your Logbook, under Settings (far right of the screen), under the heading Logbook Info, you’ll see the API key.

Below one screenshot of my first week of HF activity.

my approach to CW learning

added on 01-Jan-2021

Unfortunately in Italy, as in many other countries, knowledge of the Morse code is no longer required to pass ham license exams. I find CW very fascinating as well as being a very efficient narrowband mode also in QRP.

Here you can find my favorite tools to train CW listening. The tip is to focus on the “sounds” without concentrating on the dot-dash patterns.

lcwo.net website

On LCWO you can learn CW online in your browser by listening (and also transmitting) groups of letters, numbers and symbols with adjustable difficulty levels.

Use the link above to open LCWO on a new page, you can use username “test”, password “test” to access and test it.

"Zen and the art of telegraphy" pdf free eBook

This is a free pdf ebook written by IK0YGJ ” and available in English, German, Italian and French.

Yaesu FT-891 power consumption

added on 02-Jan-2021

source: https://oh8stn.org/

Even if the Yaesu FT-891 is one of my favourite rig for mobile/portable operations I think that it’s quite hungry of current, in particular at low power and in receive mode.

In this video Julian OH8STN performs and show us some direct current drain measurements.

Below the synthesis of the measured current where I added a column that represent a sort of efficiency:

Mode	Current consumption	Efficiency
RX	0.9 – 1.03A	n/a
TX 5W	5.7A	6.7%
TX 10W	6.9A	11.1%
TX 20W	8.3A	18.5%
TX 30W	9.3A	24.8%
TX 40W	10.45A	29.4%
TX 50W	11.5A	33.4%
TX 60W	12.2A	37.8%
TX 70W	12.9A	41.7%
TX 80W	13.7A	44.9%
TX 90W	14.4A	48.1%
TX 100W	15.2A	50.6%

The efficiency is calculated as: TX Power [W] / Supply Power (13.1 [V] * drain current [A]), it has not to be considered as a precise value because some effects like power electronic heatings and fan cooling are not considered but this is a starting point for my next conclusion.

For portable use, looking at these data, I found that the sweet spot for transmitting power is 20-30W, it has no sense to use the FT-891 at low power like 5-10W except maybe when magnetic loop antennas with low power rating are used.

Have a look at the OH8STN website and follow his Youtube channel, you can find a lot of contents and ideas focused on man-portable off grid communications on HF, latest technologies for portable power and DIY projects (LiFePO4 battery packs, antennas, etc).