You need to know what is going on within 902 and 928 MHz!

Will keep this brief as a photo is a 1,000 words and a 3 part video combining for 59 Minutes and 13 Seconds is worth I do not know what, but.....

You need to know what is going on within 902 and 928 MHz! 

On September 30th 2024, I was invited to present on what is known as the 33cm spectrum to the Warren County Amateur Radio Club. This plan was hatched by the club president, Adam Koeble KD2YFY and I over the summer while attending the Sussex County Hamfest. I just needed a topic, but knew it would involve MeshTastic and something else interesting.

Thanks to the NextNav news brought to the attention of the amateur radio world by the ARRL, I think I had my plan. With not only the amateur radio community irritated, the commercial world is not happy with what they are attempting to do. Even the Electronic Frontier Foundation has something to see about this possible land grab.

In my video, I explain who are the major users and what they are doing between 902 to 928 MHz.  Amateur radio is not as important here as some may think, as a secondary user for 39 years. But, those who are using unlicensed devices plus those using licensed frequencies with higher power here are pretty irritated should this NextNav plan get approved by the FCC.

My personal opinion is that there is enough spectrum to keep everyone happy, but amateur radio should lose secondary status and be given a few portions as primary users only.  I would offer the following scenario.

• 927.000 to 927.500 MHz (Repeater Output Block)
• 902.000 to 904.000 MHz (Weak Signal Users & Repeater Input Block)
• 910.000 to 912.000 MHz (Amateur Data Experimenters Block)

This reduces from secondary status from 26 MHz of total spectrum down to only to less than 5 MHz of spectrum.  The blocks above were chosen to protect repeater users as well as weak signal activities. It then dedicates a block to be used specific for any other use, such as modified use only for ISM repurposed devices for amateur radio only. These are my summarized comments submitted to the FCC before the deadline period.

A plan like this is more than fair, offers clarity for commercial users and easy to coexist with existing licensed users in almost every area plus provides a great incentive for unlicensed users to consider a path towards amateur radio or just stay as ISM users.

Let the rest of the ecosystem fight over the remaining 21 MHz left. Has the ARRL proposed anything?  I would love to find out! 

Have watch. I broke the video down into three parts and you can play them via a playlist or one by one:

Part 1 - Mostly just focuses on some history of the spectrum and how many devices are sharing the same spectrum across all users, licensed or unlicensed.

Part 2 - Gets into more details of the commercial users and breaks down spectrum used by different types of users, regardless of what they are doing as licensed or unlicensed users plus if they are commercial minded or not.

Part 3 - Focuses 100% on the very basics of MeshTastic, which uses unlicensed devices anywhere across the entire spectrum and by those that are not licensed and thus restricted to what they can do legally compared to the benefits of an amateur radio license holder, but will face other issues too! 

Controversial SDR: Plus 3-D Printing Stuff

It has been a while since an article has posted here, so this should be a good one involving a controversial SDR plus some 3D printing tips related to designing a simple enclosure for it.

Quick Summary:  Saving you a 20 minute video

Why is everything about price? For usually under $30, this SDR can be purchased on a few websites like Aliexpress and I am NOT encouraging you to buy this. Why?  It has infringed on the intellectual property of SDRplay in some regards. The driver used to get this and other similar MSI2500 chip based devices to work not made by SDRplay is needed. 

Only until recent versions of the driver, cloned versions of the RSP1 could use the driver to work with software easily like SDRangel, but that stopped after SDRplay API version 3.7.  I am glad that SDRplay built in some functions to only allow genuine SDRplay products to work with some of its software.  

However, since reference designs have been made public on the SDRplay earlier devices, anyone can freely assemble different semiconductors to replicate a decent SDR.  The device shown in the video uses separate band pass filters which is actually nice so the user can have spectrum specific antennae in use without the extra noise or complexity of electronic switching or the need for software to control that. This is why the SDR is so inexpensive.

Now that enough time has passed since I purchased these "clone" SDR devices and there are some improvements to protect SDRplay in place, now is a great time to get back to this.

https://www.aliexpress.us/item/3256805375754709.html

Any SDR based around the MSI2500 and MSI001 are unique compared to the R820T, 828D  and RTL2832U in that these support 10 MHz of bandwidth for around the same cost for those offering 3.2 MHz.  Another example is this one in a smaller form factor around the same size as the RTL-SDR devices, but with the extra filtering loses the wider frequency coverage above 1 GHz.

https://www.aliexpress.us/item/3256804660151348.html

There is an older video from 2021 where I showed how to get the SDRplay driver working with SDRangel below, but the new video instead focuses on an enclosure I designed for these 5 port SDR devices since I forgot to order them. The benefit however is a small case and simple design.

Here is the 2021 video talking about getting the SDRplay API to allow an SDRplay. Please note that this will not work any longer due to changes made by SDRplay, but there is an alternative version available called libmirisdr you can search for on your own or until I make a video about that.

Would you like the STL or OBJ or 3MF or STEP files for my case design? Please leave some nice and friendly comments in the video called Controversial SDR: Plus 3-D Printing Stuff  and will see what happens next. :)

30 Days: Weather Balloons from NY Capital Region

 

After thirty full days of monitoring the National Weather Service balloons launched from the capital region of New York State, here are some observations. 

Hopefully this inspires you to become interested in this unique weather monitoring opportunity anywhere in the United States or other parts of the world using inexpensive and easy to set up equipment.

Twice daily and from more than 90 launch sites in the United States, the National Weather Service releases weather balloons to help monitor upper air observations for the first 15 miles of atmosphere. The closest launch site to me comes from the Albany area of New York and currently the exact location is on the grounds of University of  Albany instead of at an official NWS facility.

Even with all the advancements in space or ground based radar or other sensors, a radio sonde balloon still is one of the best ways to monitor a variety of useful measurements.

Setting up a receiver which listens for these weather balloons is relatively easy and inexpensive. Not much additional knowledge is needed and generally the project of setting up a ground receiver will teach a number of other useful things related to some basic RF and computer related skills to anyone interested in STEM related interests.

30 Days:  What Did I Learn?

Different times of the year of course will have different general weather characteristics. Here in New York, December and January are known to be a bit tricky thanks to cold and wet weather which usually includes some gusty conditions too!

From my home in Poughkeepsie shown as the radio tower on the map, I am easily able to receive the Albany area launched balloons once they generally reach around 17,000 feet AGL. 

Signals first are heard by my antenna at an average of 58 miles south of the launch point and the average furthest signals away are closer to 100 miles usually towards the north east.

Looking at the above map, green target symbols are for where the balloon signal was first received and the red target symbol is where the last signal heard by my receiver system.  A explosion icon is where the balloon reached maximum altitude before it burst and started to descend.

Given the distances involved from my home location, a quick retrieval is not very likely by me but the goal is eventually to capture one and send it back to the National Weather Service.

In general, the wind mostly blows west to east. On more than a few occasions, it got so windy, some balloons traveled so quickly and accurate telemetry was not received for too long. 

On average, locations are sent once every 10-15 seconds and more than 3000 positions are captured per flight. Here is an example of January 22nd to 29th 2024 recordings and general statistics.

The blue lines on the map are the flight paths and there is much greater granularity to be observed when plotting the path on Google Earth. Its worth noting that sometimes the GPS on the balloon sometimes sends a false report for a short time to help explain the straight horizontal or vertical lines on the map.

Within the AutoRX application which is what runs on a Raspberry Pi based receiver along with an SDR dongle, its easy to also output in real time to Google Earth to visualize in 3D, such as to see where packets were not received by looking at the lighter colored part of the map when zoomed in. Sometimes wind gusts make the balloon much faster than the reporting transmissions occur.

Here is a converted MKV to GIF video file zooming around from azimuth and elevation angles to show more details in the North East from receiving site, path and location details during the February 1st evening launch from Albany area.

It is interesting to see how the wind blows is sort of the summary of this article.  Data like this is just one of the many inputs used in more complex weather forecasting.  When the time is right and weather nice, it will be fun to retrieve a balloon once its on the ground. 

Details about that can be found on www.sondehub.org and there are also portable receivers easily created from the ESP32 LoRa boards like the Heltec V3 which also runs other projects like Morserino, HASviolet, LoRa APRS and MeshTastic.

Hey guess what? I "sonde" you up in a tree!

 

Each year in the United States, there are over 70,000 balloon based "sondes" launched by the National Weather Service.  From locations from around the country, multiple times a day these are launched and they each transmit back weather data back down to ground stations.

It is easy to receive the 400-405 MHz signals from these balloons and this is what we will cover here

It is easy to use an inexpensive RTL-SDR device and a modest antenna to receive the balloon signals line of sight. Before you even get started with building your own ground station, you can check out networks of these stations such as the ARDC backed www.sondehub.org 

Looking at your area you will see launch and receiver sites, plus those interested in tracking them once they land.  Some hunters put some nice stories up once they find them.   

If the weather interests you and you are looking for some other signals to find if you also are interesting in radio direction finding, you may have just found yourself a new side hobby. Here are some of the Grafana based analytics from Sondehub.

Getting Started:   You have the pieces. Now what?

To build a ground station for radiosonde tracking, you will need:

• A Raspberry Pi (3B or later is best)
• An RTL-SDR (Suggest the RTL-SDR V3 or V4)
• A UHF antenna (1/4 wavelength is small. Look it up)
• Auto-RX software
• A place to put your system which will need to be on 24/7

There is a great Wiki for setting everything up from a software perspective, so no need to summarize. It is a big project with great documentation. https://github.com/projecthorus/radiosonde_auto_rx/wiki 

Figuring you are starting with a fresh SD card, once you install Raspberry OS, the rest of the steps should have you up and running in less than an hour or faster.

Give some thought to your antenna though first. If you are an amateur radio person, you do not want to transmit where it may interfere with your new ground station. Some inexpensive filters help here, plus improves the overall results anyway. A nice double benefit.

Here are reception results from the author location for last 24 hours of launches from the Albany NY launch location.  Once balloon has landed and the other is still floating around. 

Not sure what else to share, but beyond using Auto-RX,  you can also use SDRangel to receive radio sonde data too, which is nice if you plan to go portable or mobile.  There was reason to include radiosonde capability in the SIGpi project too, so feel free to look into that also.

Until next time....

Steve K2GOG