Geo-Tracking using Maidenhead Grid Designation

[James]

Hello MicroTransat Team!

For the past three years I have been on a crawl-walk-run progression toward taking on the MicroTransat Challenge.  I believe that this year (2025) I will make my entrance for doing so.  Below is a link to a YouTube video that I put together that summarizes my autonomous vehicle development effort as of 31 December 2024 (EOY 2024).  It describes the conceptualization, design, development, construction, testing and troubleshooting undertaken during the whole process.  This video showcases my successful model-sized autonomous car, motorboat and "special purpose" sailboat field tests that provides insight into future autonomous sailboat efforts.

https://youtu.be/YAEgiewf7-0

Review of your historical listing of transAtlantic crossing attempts reveals that many of the failures cite loss of radio contact and thus inability to adhere to the MicroTransat rules regarding position reporting.  My intention is to use a SPOT Trace satellite-based tracker as my primary means of position reporting which uses UHF frequencies.  I am, however, exploring a back-up position reporting mechanism using a high frequency (HF)-based amateur radio beacon transmitter and posting location identification via the Weak Signal Propagation Reporter (WSPR) website.  For more information about WSPR please explore this website:

https://www.wsprnet.org/drupal/wsprnet/map

WSPR beacon transmissions are extremely limited data-wise and position reporting is thus limited to 4-digit or 6-digit Maidenhead Grid designations.  For example, a WSPR position report that includes a 4-digit grid designation requires a 2-minute broadcast while a 6-digit designation requires a 4-minute broadcast.  The benefit, however, is that WSPR requires minimal transmission power (on the order of 0.1 to 0.2 Watts) and yet is able to reach global receiver sites and, upon reception, immediately make the message data (to include the GPS-based Maidenhead Grid location) publicly available.

The disadvantage of even the more precise 6-digit Maidenhead grid designation is that it is not as high-fidelity as GPS latitude/longitude coordinates.  As an example, for my latitude here in Norfolk, Virginia, USA the 6-digit Maidenhead Grid accuracy is on the order of +/- 4 kilometers.  This accuracy, i.e., +/-4 kilometers, is still well within the accuracy required of the MicroTransat requirements for goal achievement.

https://www.m0ahn.co.uk/interactivelocatormap.html

The MicroTransat rules do not address location data accuracy or position reporting format so I interpret this omission as permission to officially report my boat’s location via the 6-digit Maidenhead Grid designation and have it accepted by the MicroTransat Challenge judges.   I believe that doing such will still testify to the judges that my boat has, indeed, entered within the 25-kilometer radius of a pre-designated location even if without the accuracy afforded by more well-known GPS-based geocoordinates.

In light of this, I hereby request via e-mail reply official MicroTransat Challenge authorization for me to report my sailboat’s position using a 6-digit Maidenhead Grid designation and thus expect that that data will be found acceptable to the judges upon completion of the event.

I welcome any questions or comments you may have.

James Hull

Norfolk, Virginia, USA

[Robin Lovelock on robin@gpss.co.uk]

Good Moaning* James ! ( * for my German friends - from old 'Allo 'Allo TV comedy :-)

Thanks for those exchanges, off this Microtransat Group, late yesterday Sunday night 2 Feb 2025.

I prefer emails on this forum, wherever it is practicable, including the risk of upsetting some guys.

One reason for them being private was concern about this group being "rudderless" after Colin Sauze

stepped down - but that little group of volunteers have done a great job on things like the website.

My only reservation is that it was not kept up to date ( minor one line changes easily drafted )

after Snoopy disappeared on some previous attempts - his "rescues" were legendary ! ;-)

Also, it would be good if members of this group could at least see the list of members,

even if what is disclosed, such as name, is up to the member. I understand Colin's policy

of keeping things as they were, since some members are in places such as Russia.

I experienced this on my own google group - guys did not want to be seen with others.

We have plenty of Russians & Ukranians not far from us in Sunninghill.

In last night's emails, James  said I would probably not remember our exchanges almost exactly

2 years ago in 2023. Easily found from my email search - LOTS of stuff, but here is a short extract >>>

Hmmm… a little bit about myself.  I am just shy of 63 years old, recently retired from the Department of Defense, and a Mechanical Engineer by education (bachelors and masters).  I spent most of my adult life learning how to break things so I am having a lot of fun building something now that I have the time to do so. 

<<<

I recall coincidences of name, and you saying you were NOT ex US Marine Corp - USMC - Seal.

Of course, the UK Royal Marines have (allegedly) played an important role in Snoopy's "missions".

Also, our oldest Team Joker member, Stuart, had a nice 88th Birthday lunch - and a suitable "Under Siege" birthday cake ;-)

Now into important things in your email. Yest SPOT Trace is a good solution - with good mapping & history.

Snoop's problems are clearly documented on http://www.gpss.co.uk/autop.htm 

Don't think I can say better than already on "Design" page http://www.gpss.co.uk/rbdesign.htm

e.g. KISS = Keep It Simple Stupid ;-)

Your talk about alternative wispr comms, made me think you were a radio ham ...

http://www.gpss.co.uk/radio.htm  - see what I wrote back in 2011 - just discovering SPOT then,

and SPOT improved a lot over those recent years.

Of course, those "nasty Chinese" have some good, VERY low cost, GSM solutions,

that might be worth adding as an extra, since failures may happen near the coast.

That old bottle tracking project showed a good few miles off the coast.

Reckon that will do for now - LOTS of stuff to do here - and nothing to do with Snoopy ;-)

I'll CC to my ROBINLOVELOCKSFRIENDS Google Group, rather than CC family, as normal.

Take Care

Robin

http://www.gpss.co.uk and http://www.nhscare.info and http://www.gpshobby.info 

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[Francis Roussel]

Bonjour à tous,

L'idée d'utiliser une balise pour signaler la position est excellente, d'après mes lectures c'est un projet pas trop compliqué à première vue

https://vk3hn.wordpress.com/2021/10/01/20-meters-200mw-12000-miles-wspr-magic/?wref=tp

Après il faut l'adapter à notre sujet.

Après j'en sais pas plus car complètement ignorant dans le domaine des radio-amateurs mais cela peut permettre d'utiliser un moyen pas cher de suivre ses essais car mon opinion est faite quand je lancerai  mon bateau pour un grand test j'ai peu d'espoir de le revoir un jour !
En revanche s'il est récupéré avec un beau trajet c'est un bon moyen d'aller ensuite à la pêche aux sponsors pour un achat de ce qu'il faut pour une liaison satellite.

Hello everyone,

The idea of ​​using a beacon to signal the position is excellent, from what I have read it is not a very complicated project at first glance

https://vk3hn.wordpress.com/2021/10/01/20-meters-200mw-12000-miles-wspr-magic/?wref=tp

Then you have to adapt it to our subject.

After that I don't know more because I am completely ignorant in the field of radio amateurs but it can allow you to use a cheap way to follow your tests because my mind is made up when I launch my boat for a big test I have little hope of seeing it again one day!
On the other hand, if it is recovered with a good journey it is a good way to then go fishing for sponsors to buy what is needed for a satellite connection.

Regards

fr

Sans virus.www.avg.com

[Dermot Tynan]

In lieu of a long email from Robin saying very little, and having been somewhat involved in rule discussions… As I understand it, the key piece of data is the final log which would be GPS-based. The interim position reports are more about maintaining comms during the voyage. I suspect no-one would complain if your regular positions were less precise as long as when you recover the boat after the finish you can present (and defend) accurate position information in the form of a mission log. Ideally for research purposes, other data such as power consumption and solar charge would be informative for others but not essential. I don’t speak in an official capacity for the Microtransat and I would request that other people disagree if they think my interpretation is incorrect. Good luck with the voyage!

        - Der

PS:

Officially the rules are discussed annually in a separate forum. Feel free to propose an alteration. Generally the rule changes don’t take immediate effect but that is to prevent disadvantaging teams who are already a long way towards launch.

—

Dermot Tynan

Kalopa Robotics

https://kalopa.com

On 3 Mar 2025, at 15:29, Francis Roussel <minij...@gmail.com> wrote:

 Bonjour à tous,

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[James]

Francis:

MANY thanks to you for your two e-mails.  It has been 50 years since I had French class and am very happy that Google Translate enables us to converse despite the language difference.

I warmly encourage you to design, build and launch an autonomous boat.  It is one of the most challenging projects I have ever done.  If Elon Musk can build autonomous cars, satellites and spaceships we can certainly try to successfully make boats.

Yes, you listed several of the challenging skills required to make an autonomous boat (reading / writing to an SD card; reading GPS, IMU and other sensor data; controlling servos / DC motors).  I hope that my videos highlighted my solutions to some of those problems for your consideration (numerical accuracy of microcontrollers, electromagnetic interference, etc.).

Yes, the electronic compass must be tilt-compensated.  The IMU you use, the MPU9250, looks to be well documented and capable.  I now use the BNO085, the successor to the BNO055, and use the Adafruit libraries for computer code to perform that correction.  It is inexpensive, accurate and able to calibrate itself.  For more details, see this:

https://www.adafruit.com/product/4754

I use an Adafruit Metro M4 microcontroller and it is programmable using Circuit Python.  Adafruit has many libraries for Circuit Python, Circuit Python is a well-supported programming language and that makes getting data from an IMU easy.  Here is a link to that microcontroller:

https://www.adafruit.com/product/3382

I have been an amateur radio operator for many years, hold an Amateur Extra license and have a few WSPR beacon transmitters that I have been testing.  I have been consistently successful in sending messages from the USA to Europe, Australia and Antartica all on 0.1 Watts of power.  Yes, in the USA you do need a license to transmit on WSPR beacon frequencies and I assume the same would be true in Europe.  Getting an amateur radio license is not all that difficult so I encourage you to explore that as well.  The best WSPR beacon transmitter that I have come across is this one:

https://www.zachtek.com/product-page/wspr-desktop-transmitter

The primary limitation for using WSPR on a small boat is the antenna.  WSPR operates on the high frequency band and that requires a rather long antenna to be efficient.  I am working with a team from a local university who are working on that problem and I will relay their proposal after testing.  I strongly recommend that you find a local amateur radio club in your area, attend some of their club meetings and chat with the more experienced radio operators about what you are trying to accomplish.

Again, THANK YOU for the e-mail.  I hope that my response above helps you.

James Hull

Norfolk, Virginia, USA

Francis :

MERCI BEAUCOUP pour vos deux e-mails. Cela fait 50 ans que je n'ai pas suivi de cours de français et je suis très heureux que Google Translate nous permette de converser malgré la différence de langue.

Je vous encourage chaleureusement à concevoir, construire et lancer un bateau autonome. C'est l'un des projets les plus ambitieux que j'ai jamais réalisé. Si Elon Musk peut construire des voitures, des satellites et des vaisseaux spatiaux autonomes, nous pouvons certainement essayer de réussir à fabriquer des bateaux.

Oui, vous avez énuméré plusieurs des compétences difficiles requises pour fabriquer un bateau autonome (lecture/écriture sur une carte SD ; lecture des données GPS, IMU et autres capteurs ; contrôle des servos/moteurs à courant continu). J'espère que mes vidéos ont mis en évidence mes solutions à certains de ces problèmes pour votre considération (précision numérique des microcontrôleurs, interférences électromagnétiques, etc.).

Oui, la boussole électronique doit être compensée en inclinaison. L'IMU que vous utilisez, le MPU9250, semble être bien documenté et performant. J'utilise maintenant le BNO085, le successeur du BNO055, et j'utilise les bibliothèques Adafruit pour le code informatique afin d'effectuer cette correction. Il est peu coûteux, précis et capable de s'auto-étalonner. Pour plus de détails, voir ceci :

https://www.adafruit.com/product/4754

J'utilise un microcontrôleur Adafruit Metro M4 et il est programmable à l'aide de Circuit Python. Adafruit dispose de nombreuses bibliothèques pour Circuit Python, Circuit Python est un langage de programmation bien pris en charge et cela facilite l'obtention de données à partir d'une IMU. Voici un lien vers ce microcontrôleur :

https://www.adafruit.com/product/3382

Je suis opérateur radio amateur depuis de nombreuses années, je suis titulaire d'une licence Amateur Extra et j'ai quelques émetteurs de balises WSPR que j'ai testés. J'ai toujours réussi à envoyer des messages des États-Unis vers l'Europe, l'Australie et l'Antarctique, le tout avec une puissance de 0,1 W. Oui, aux États-Unis, vous avez besoin d'une licence pour transmettre sur les fréquences de balise WSPR et je suppose que ce serait également le cas en Europe. Obtenir une licence de radio amateur n'est pas si difficile, je vous encourage donc à explorer cette possibilité également. Le meilleur émetteur de balise WSPR que j'ai rencontré est celui-ci :

https://www.zachtek.com/product-page/wspr-desktop-transmitter

La principale limitation à l'utilisation de WSPR sur un petit bateau est l'antenne. WSPR fonctionne sur la bande haute fréquence et cela nécessite une antenne assez longue pour être efficace. Je travaille avec une équipe d'une université locale qui travaille sur ce problème et je transmettrai leur proposition après les tests. Je vous recommande vivement de trouver un club de radio amateur local dans votre région, d'assister à certaines de leurs réunions de club et de discuter avec les opérateurs radio les plus expérimentés de ce que vous essayez d'accomplir.

Encore une fois, MERCI pour l'e-mail. J'espère que ma réponse ci-dessus vous aidera.

James Hull

Norfolk, Virginie, États-Unis

[Francis ROUSSEL]

Hi James,

Un grand merci pour vos réponses très rapides et bien documentées.

Ce sujet de balises WSPR est très intéressant.
J'ai repéré des sites
https://f8kly.fr/balise-wpsr/
http://www.rotilom.com/F6IDT/balise_wspr.htm
https://vk3hn.wordpress.com/2021/10/01/20-meters-200mw-12000-miles-wspr-magic/?wref=tp

J'ai bien compris que c'est la recherche de performances pour savoir jusqu'où un émetteur a été capté qui est à l'origine du système.
Que c'est un site collaboratif qui gère les données https://www.wsprnet.org/drupal/wsprnet/map

En revanche comment la même balise peut-elle transmettre le carré Maidenhead ? Et surtout qui va recevoir et transmettre sur le web le contenu ?

J'ai été membre de https://electrolab.fr de Nanterre qui rassemble pas mal de radio-amateurs et j'ai posé la question sur le forum, je ne doute pas qu'un membre va répondre mais cela n'empêche pas de nous informer toi-même.

Nous sommes tous intéressés par le voilier autonome (accessoirement par la microtransat) mais avec des compétences très diverses.  Je suis davantage pour une mise en commun des compétences techniques : pratique de la voile, pratique d'arduino, ou ses semblables, pratique des transmissions, etc... Il y a bien des choses qui ensuite peuvent permettre d'être le meilleur de tous, le meilleur parmi toute une flotte de voiliers autonomes.

Là où j'ai des compétences (la voile radiocommandée) je vois beaucoup de gens qui viennent à la voile, par le maquettisme, par la régate, mais de plus en plus par l'achat d'un bateau tout fait (raidy to sail ;-)), dans un sens c'est bien car il y a de plus en plus de pratiquants mais aussi c'est la mort des constructeurs donc de ceux qui peuvent apporter quelque chose. On est donc cantonné à être de tous petits groupes si on veut sortir de cette chose.

Il faut partager ses connaissances, au moins les bases pas un paquet tout fait (ready to microtransat) afin de faire progresser le groupe que chacun apporte l'aide là où les manques existent chez d'autres.

Par exemple les sujets sont multiples : utiliser freeship pour créer sa propre coque de bateau, utiliser des système innovants : les voiles épaisses, j'adore les travaux de Peter Worsley https://www.youtube.com/watch?v=jGo4bRHI22o, etc...


fr

Le 03/03/2025 à 16:46, James a écrit :

Francis:

MANY thanks to you for your two e-mails.  It has been 50 years since I had French class and am very happy that Google Translate enables us to converse despite the language difference.

I warmly encourage you to design, build and launch an autonomous boat.  It is one of the most challenging projects I have ever done.  If Elon Musk can build autonomous cars, satellites and spaceships we can certainly try to successfully make boats.

Yes, you listed several of the challenging skills required to make an autonomous boat (reading / writing to an SD card; reading GPS, IMU and other sensor data; controlling servos / DC motors).  I hope that my videos highlighted my solutions to some of those problems for your consideration (numerical accuracy of microcontrollers, electromagnetic interference, etc.).

Yes, the electronic compass must be tilt-compensated.  The IMU you use, the MPU9250, looks to be well documented and capable.  I now use the BNO085, the successor to the BNO055, and use the Adafruit libraries for computer code to perform that correction.  It is inexpensive, accurate and able to calibrate itself.  For more details, see this:

https://www.adafruit.com/product/4754

I use an Adafruit Metro M4 microcontroller and it is programmable using Circuit Python.  Adafruit has many libraries for Circuit Python, Circuit Python is a well-supported programming language and that makes getting data from an IMU easy.  Here is a link to that microcontroller:

https://www.adafruit.com/product/3382

I have been an amateur radio operator for many years, hold an Amateur Extra license and have a few WSPR beacon transmitters that I have been testing.  I have been consistently successful in sending messages from the USA to Europe, Australia and Antartica all on 0.1 Watts of power.  Yes, in the USA you do need a license to transmit on WSPR beacon frequencies and I assume the same would be true in Europe.  Getting an amateur radio license is not all that difficult so I encourage you to explore that as well.  The best WSPR beacon transmitter that I have come across is this one:

https://www.zachtek.com/product-page/wspr-desktop-transmitter

The primary limitation for using WSPR on a small boat is the antenna.  WSPR operates on the high frequency band and that requires a rather long antenna to be efficient.  I am working with a team from a local university who are working on that problem and I will relay their proposal after testing.  I strongly recommend that you find a local amateur radio club in your area, attend some of their club meetings and chat with the more experienced radio operators about what you are trying to accomplish.

Again, THANK YOU for the e-mail.  I hope that my response above helps you.

James Hull

Norfolk, Virginia, USA

Francis :

Sans virus.www.avg.com

[James]

Francis:

Yes, and as you correctly pointed out, the design intent for WSPR was to enable radio propagation testing.  The atmosphere’s physical properties change with weather and the Sun’s impact upon the Earth all of which impacts an amateur radio operator’s ability to make long distance communications.

For example, some radio frequencies propagate well during the day but are unusable at night and other frequencies are usable at night but not during the day.  Amateur radio operators use a radio signal’s ability to “bounce” off of different layers in the atmosphere in order to go around the curvature of the Earth.  Without the ability to “bounce” signals a radio would propagate only in a straight line into outer space.  WSPR enables a radio operator to determine where he/she might have success making communication under these changing conditions.

The different WSPR radios go about location identification differently.  Some require the radio operator to configure their radio with a single and user-specified Maidenhead Grid designation that will not change.  Others, like the radios offered by https://www.zachtek.com/, require the attachment of an external GPS antenna to the radio and the radio's internal software then determines the Maidenhead Grid designation.  As such, the ZachTek WSPR radios can then be used as a GPS-based tracker.  That is what my intention is: to use a WSPR beacon transmitter as a backup position reporting system.  The MicroTransat Challenge rules prioritize continual position reporting so highly that I do not want to rely upon a single, commercially-based and satellite-reliant communications medium.

Radio operators around the world listen for WSPR beacon transmissions and post what they receive on the WSPR data server.  That server, in turn, makes that data publicly available almost instantaneously.  Thus, a MicroTransat boat with a WSPR beacon transmitter can use amateur radio services to publicize the boat’s location for all to see and to monitor in real time.  One website I read stated that there are approximately 3,000 WSPR beacons operating every day and I would venture a guess that there are a couple of hundred WSPR receive sites around the world.

On the other subject that you brought up in your e-mail, that of boat building, I agree with you.  When I was younger I built many control line and R/C airplanes from kits and from paper plans.  A trip to a hobby store today reveals that they do not stock balsa model kits anymore and everything is “ready to fly.”  Those of us in this Forum are more prone to building something that is unique than rely upon a manufactured kit and that is a skill future generations will miss.

James Hull

Norfolk, Virginia, USA

Francis :

Oui, et comme vous l’avez souligné à juste titre, l’objectif de la conception du WSPR était de permettre des tests de propagation radio. Les propriétés physiques de l’atmosphère changent avec la météo et l’impact du Soleil sur la Terre, ce qui a un impact sur la capacité d’un opérateur radio amateur à établir des communications longue distance.

Par exemple, certaines fréquences radio se propagent bien pendant la journée mais sont inutilisables la nuit et d’autres fréquences sont utilisables la nuit mais pas pendant la journée. Les opérateurs radio amateurs utilisent la capacité d’un signal radio à « rebondir » sur différentes couches de l’atmosphère afin de contourner la courbure de la Terre. Sans la capacité de « rebondir » des signaux, une radio ne se propagerait qu’en ligne droite dans l’espace. Le WSPR permet à un opérateur radio de déterminer où il/elle pourrait réussir à établir une communication dans ces conditions changeantes.

Les différentes radios WSPR procèdent différemment à l’identification de l’emplacement. Certaines nécessitent que l’opérateur radio configure sa radio avec une désignation de grille Maidenhead unique et spécifiée par l’utilisateur qui ne changera pas. D’autres, comme les radios proposées par https://www.zachtek.com/, nécessitent la fixation d’une antenne GPS externe à la radio et le logiciel interne de la radio détermine ensuite la désignation de la grille Maidenhead. Ainsi, les radios WSPR de ZachTek peuvent alors être utilisées comme un tracker basé sur GPS. C’est ce que j’ai l’intention de faire : utiliser un émetteur de balise WSPR comme système de rapport de position de secours. Les règles du MicroTransat Challenge accordent une telle priorité au rapport de position continu que je ne veux pas m’appuyer sur un seul moyen de communication commercial et dépendant des satellites.

Les opérateurs radio du monde entier écoutent les transmissions des balises WSPR et publient ce qu’ils reçoivent sur le serveur de données WSPR. Ce serveur, à son tour, rend ces données accessibles au public presque instantanément. Ainsi, un bateau MicroTransat équipé d’un émetteur de balise WSPR peut utiliser les services de radio amateur pour faire connaître la position du bateau afin que tout le monde puisse la voir et la surveiller en temps réel. Un site Internet que j'ai lu indiquait qu'il y avait environ 3 000 balises WSPR en fonctionnement chaque jour et je dirais qu'il y a quelques centaines de sites de réception WSPR dans le monde.

Sur l'autre sujet que vous avez évoqué dans votre e-mail, celui de la construction de bateaux, je suis d'accord avec vous. Quand j'étais plus jeune, j'ai construit de nombreux avions à commande de ligne et R/C à partir de kits et de plans papier. Une visite dans un magasin de loisirs aujourd'hui révèle qu'ils ne stockent plus de kits de modèles en balsa et que tout est « prêt à voler ». Ceux d'entre nous qui sont dans ce forum sont plus enclins à construire quelque chose d'unique qu'à compter sur un kit fabriqué et c'est une compétence qui manquera aux générations futures.

James Hull

Norfolk, Virginie, États-Unis

[Francis ROUSSEL]

Si je lis bien, mais peut-être trop vite, le modèle qui nous faudrait
est https://www.zachtek.com/product-page/wspr-tx-mini-transmitter ,
lequel n'est pas disponible mais les sources sont-elles disponibles ?
Je pense qu'on doit trouver des fabrication DIY quand on connaît le
monde des radioamateurs

Pour l'antenne, mes faibles connaissances me disent que pour les
antennes, une antenne de la taille de la longueur d'onde est la
meilleure mais que des antennes demie, ou quart d'onde sont utilisables
mème si elles provoquent une perte de puissance.
Quelle longueur pensez-vous utilisable en ménageant tout ? Peut-on
penser que les types d'antennes utilisées pour les multicopteurs sont
envisageables...
Placée en tête de mât elles ne sont pas handicapantes face au vent : du
genre https://drones.altigator.com/images/fpv/Terry-Build-5.8GHz-SMA.jpg
mais adaptées à la fréquence de 20m ?
fr


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[James]

Francis:

My recommendation was the ZachTek’s WSPR Desktop Transmitter, linked below, because it is a complete package,  available for purchase and performs very well.  The WSPR Mini you highlighted is specifically designed for lightweight requirements… which you really do not need to address on a boat.  Additionally, the WSPR Mini’s output power is 0.020 Watts and is 1/10th that of the Desktop’s capabilities.

https://www.zachtek.com/1012

No, an antenna with full wavelength elements is not the most efficient.  For simple dipole antennas you can use the calculator, linked below, to determine those lengths.  Vertical antenna are similarly best served by quarter wave elements.  As mentioned in my previous e-mail, you may be best served by finding and attending a local amateur radio club and getting familiar with this very interesting subject.  Honestly, amateur radio communication success is more due to the type of antenna used than it is the radio.

https://www.omnicalculator.com/physics/dipole

James Hull

Norfolk, Virginia, USA

Francis :

Je vous ai recommandé l’émetteur de bureau WSPR de ZachTek, dont le lien figure ci-dessous, car il s’agit d’un ensemble complet, disponible à l’achat et très performant. Le WSPR Mini que vous avez mis en avant est spécialement conçu pour les exigences de légèreté… dont vous n’avez vraiment pas besoin sur un bateau. De plus, la puissance de sortie du WSPR Mini est de 0,020 W et représente 1/10 de celle du Desktop.

https://www.zachtek.com/1012

Non, une antenne avec des éléments à pleine longueur d’onde n’est pas la plus efficace. Pour les antennes dipôles simples, vous pouvez utiliser la calculatrice, dont le lien figure ci-dessous, pour déterminer ces longueurs. Les antennes verticales sont également mieux servies par des éléments quart d’onde. Comme mentionné dans mon e-mail précédent, il peut être préférable de trouver et de fréquenter un club de radio amateur local et de vous familiariser avec ce sujet très intéressant. Honnêtement, le succès de la communication radio amateur est davantage dû au type d’antenne utilisé qu’à la radio.

https://www.omnicalculator.com/physics/dipole

James Hull

Norfolk, Virginie, États-Unis

[Colin Sauze]

Hi James,

I think transmitting the position as a 6 digit Maidenhead coordinate
is good enough for a backup tracking system. As you said the
Microtransat rules don't say anything about the level of precision for
transmitted coordinates, but the jury will be using this as evidence
that you reached your target point on the finish line within 25km. The
6 digit grid equates to an accuracy of around 9.3km which should be
enough to allow the jury to determine if you hit the target, but you
would have to get within 18.6km for this to be unambiguous. I wouldn't
suggest it as a primary system though. Although I do wonder if you are
forced to fall back on your secondary system then you are probably
more concerned about recovery than crossing the finish line and then
you will need an accurate position to find the boat.

I'm not so sure about your initial premise that the reason many boats
are lost is because their tracking system fails. I think they are
being lost because some kind of catastrophic failure happens to the
electrical system or the entire boat. Although this is difficult to
know for sure when we don't get to see many of those lost boats again.
But I would definitely aim to have any backup tracking system on it's
own independent power system so that an electrical failure on the rest
of the boat won't stop your tracking.

Using amateur radio to track with WSPR (and APRS) has been discussed a
few times before. I think (some) other country's have more liberal
rules, but under the UK's license terms you need to be able to
shutdown a beacon within two hours if instructed to do so by OFCOM (UK
equivalent to the FCC in the USA). This would also apply to a boat
entering UK waters and operating under a CEPT reciprocal license
agreement. I'm sure this is regularly ignored by many people such as
high altitude balloon operators, but it is technically what the rules
say. OFCOM's predecessor was known for draconian enforcement of these
rules but these days things are much more relaxed, but you might want
to check the rules of any other country who's waters you might sail
through. You could use the satellite link to remotely control the WSPR
beacon, this might reduce its utility as a backup transmitter but
would allow you to comply with the rules while the satellite link
works (and perhaps let you argue you did your best to comply with
them) and could still provide some useful information on how well WSPR
would work in this situation.

On the choice of transmitter, another one to look at is the QRP Labs
U4B (https://shop.qrp-labs.com/otherkits/u4b) which is a popular
choice among the high altitude balloon community. It looks a bit
smaller, but uses the same frequency generator chip so I expect radio
performance is similar.

Colin


Colin

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[James]

Colin:

Many thanks for the very informative e-mail below.  Your comments regarding the UK OFCOM’s legal requirements are, however, concerning.  This still leaves me with a few options that I now need to investigate further.

Again, many thanks.

James Hull

Norfolk, Virginia, USA

To view this discussion, visit https://groups.google.com/d/msgid/microtransat/CAE5zsDESbmL7%2BAP1wiYiaAxvaOJKRuYm%3D_FFDHuJwQANMGKCXQ%40mail.gmail.com.

[Marie Pauly]

You can transmit extra grid letters in a second "telemetry" transmission to get it down to +/- 1/4 mile. We use 17M or 12M for WSPR transmissions at 10MW power and get all of NA and Europe reception, but you MUST be a ham.