Kessler Syndrome

Speculation on the effect of cascading space junk collisions on Amateur Radio.

“The Kessler Syndrome is a scenario proposed by NASA scientists Donald J. Kessler and Burton G. Cour-Palais in 1978. It describes a situation in which the density of objects in low Earth orbit (LEO) becomes so high due to space pollution that collisions between these objects cascade, exponentially increasing the amount of space debris over time.”

https://en.wikipedia.org/wiki/Kessler_syndrome

What if satellite communications were suddenly squeezed off. Internet, TV and Cellular telephone backbones choked or disconnected. Could it portend a fall-back to HF radio? How handy would Amateur radios become?

SpaceX recently had a satellite go silent then quickly drop several miles. It’s on an uncontrolled trajectory estimated to de-orbit (demise) in weeks. Analysis indicates it exploded. 

LeoLabs is a commercial group that tracks as many things in orbit as it can see with private space radar. They first estimated the debris at tens of shards. The guess has increased to some thousands.

https://platform.leolabs.space/visualization

Zoom in/out, turn the globe. Click on objects in the tool. It lists what they are.

Other experts offered the event didn’t seem like a spontaneous onboard failure, but almost certainly an impact. Perhaps an impact that ignited a fuel explosion propelling the apparatus into a decaying orbit. The speculation centers on the high degree of SpaceX orbiter reliability.

The visualization also shows debris regions. Precursors to an as yet narrowly avoided, Kessler Syndrome?

Question: How long after a Kessler Syndrome event would it be too dangerous for people to fly into space?

Answer*:

If a full Kessler event (a runaway chain reaction of collisions) occurred today, the answer depends entirely on how high the debris orbits earth. Space isn’t a single “room”; it’s a series of shells, and each shell has a different “cleaning cycle.”

Because there is no “janitor” in space, we rely on the Earth’s atmosphere to drag debris down. The higher the altitude, the thinner the air, and the longer the debris stays.

1. Low Earth Orbit (LEO) – Under 500 km

  • Safety Timeline: 1 to 10 years.
  • Context: This is where the International Space Station (ISS) and Starlink satellites live. Because there is still a tiny bit of atmosphere here, “drag” acts like a slow brake.
  • Result: In a Kessler event, this region would become a “death zone” almost instantly. However, within a decade, most of that specific debris would spiral down and burn up in the atmosphere, making it potentially safe for humans to fly through or inhabit again.

2. Mid-LEO – 600 km to 1,000 km

  • Safety Timeline: Decades to Centuries.
  • Context: This is the most dangerous “sweet spot” for Kessler Syndrome. It’s crowded with old weather satellites and rocket bodies, but the atmosphere is too thin to provide quick cleaning.
  • Result: Debris at 800 km can stay in orbit for over 100 years. If a full cascade happened here, this shell of space would be effectively closed to human life for multiple generations.

3. High Orbit – Above 1,000 km

  • Safety Timeline: Millennia (1,000+ years).
  • Context: At these heights, atmospheric drag is non-existent.
  • Result: Any debris created here is essentially permanent on a human timescale. A Kessler event at this altitude would create a “shell” around Earth that could remain lethal for thousands of years, potentially trapping humanity on the planet until we developed the technology to actively “harpoon” or laser-sweep millions of tiny fragments.

The “Hollywood” vs. Reality Factor

Contrary to the movie Gravity, a Kessler event doesn’t happen in 90 minutes. Experts describe it more like a “slow-motion train wreck.”

  • The First Days: You might lose 10% of satellites.
  • The Following Decades: The debris from those 10% hits others, creating more fragments. The “syndrome” is the period where the amount of junk is growing faster than the atmosphere can remove it.

Could we still leave Earth?

Even in a “full” Kessler scenario, humans could likely still launch through the debris to go to the Moon or Mars. A rocket only spends a few minutes passing through the danger zone. It’s like running across a busy highway—it’s incredibly risky and requires perfect timing, but you aren’t “stuck” forever. However, staying in orbit (like on a space station) would be impossible because you are a stationary target in a shooting gallery.

*Gemini AI

New 60m Amateur Band

The FCC allocated a new chunk of the 60m band to amateurs in the US.

The action opened 5351.5 – 5366.5 kHz (60 meters) to the amateur service on a secondary basis with a permitted power of 9.15 watts ERP.

The Commission also authorized amateurs to continue using four existing channels outside of the 5351.5 – 5366.5 kHz band centered on 5332, 5348, 5373, and 5405 kHz on a secondary basis with a permitted power of 100 watts ERP.

There are no antenna restrictions but antenna gain must be used to calculate ERP.

General class license holders and above will receive the new privileges 30 days after publication to the National Register.

FCC Announcement and Rules

Announcement in ARRL

DMR – FYI

Digital Mobile Radio – Internet linked Ham Radio.

As club members may be aware, there are no DMR VHF repeaters in the Coos County area. (At least to this editor’s knowledge.) If your HT has DMR mode, that mode is basically useless on the local air unless you have a friend and both radios are programmed correctly to use DMR.

However! DMR is a great way for Technician class operators to make contacts around the world. If you’re curious about DMR, it’s easy to jump in with nothing more than a web browser.

What is DMR? Well, as an amateur radio digital mode, the encoding improves weak signal reception. Also the packets are designed to be sent over IP networks (E.g the internet, VoIP.) On basic VHF/UHF FM radio, communication is “simplex” – one party talks at a time. DMR is duplex – allowing two simultaneous speakers. It’s done with TDM. Time Domain Multiplexing – just like analog telephones or POTs. “Plain old Telephone Service.”

“DMR (Digital Mobile Radio) in ham radio is a digital voice standard, adapted from commercial use, that allows two simultaneous conversations (time slots) on a single frequency, offers clearer audio, extended battery life, text messaging, GPS, and connects repeaters via the internet, providing enhanced features over traditional analog radio, primarily using Tier II for licensed users.” Wikipedia. (More about Tiers follow the link…)

https://en.wikipedia.org/wiki/Digital_mobile_radio

BrandMeister and TGIF DMR are carrier networks (requiring call sign login to chat) are the top DMR services. Users that login with their Call Sign and have registered for a DMR ID at RadioID.net with can converse on the DMR network.

Covering them both is a website where visitors can view the map and listen (only) to talk groups on either system – with out a call sign. See DMRMap.APP

https://dmrmap.app/#tg=3141&network=brandmeister

Brandmeister Talk Group 3141 (shown above) links the internet to the West Oregon DMR repeater network. Check out the “Happy Hour” Net at 5PM daily.

DMR is used on the amateur radio VHF and UHF bands, started by DMR-MARC around 2010. The FCC officially approved the use of DMR by amateurs in the US in 2014.

In amateur spaces, Coordinated DMR Identification Numbers are assigned and managed by RadioID Inc. Their coordinated database can be uploaded to DMR radios in order to display the name, call sign, and location of other operators.

Internet-linked systems allow users to communicate with other users around the world via connected repeaters, or DMR “hotspots.” Such systems are often based on the Raspberry Pi single-board computer.

There are currently more than 5,500 repeaters and 16,000 “hotspots” linked to the BrandMeister system worldwide.

As always! Let us know what you think. Comments and suggestions welcome. More information is available.

DMR Simplex

Yes, amateur radio DMR can operate transceiver to transceiver in a mode called simplex.

Here’s a breakdown:

Simplex Operation: In DMR simplex, two radios communicate directly with each other on the same frequency without the use of a repeater or an internet-connected hot spot. This is also sometimes referred to as “Direct Mode.”

Repeater/Network Operation: This is the most common way amateur DMR is used. A DMR repeater or personal hotspot links users to a wider network (often via the internet, like BrandMeister or Phoenix), allowing for local, regional, or even worldwide communication using Talk Groups. This is a form of duplex operation where the radio transmits on one frequency and receives on another.

Key Points for DMR Simplex:
Settings Required: Unlike simple analog FM simplex, DMR simplex requires both transceivers to have the same frequency, Color Code, and Talk Group ID programmed.

Color Code: A digital equivalent to a CTCSS/PL tone, used for system access.

Talk Group ID: Typically Talk Group 99 is designated for simplex use in amateur radio, though any shared Talk Group ID would technically work if all parties are programmed to it.

Range: As with any simplex mode, the range is limited by terrain, power output, and antenna efficiency—it’s strictly line-of-sight or slightly beyond.

TDMA: Even in simplex, DMR uses its Time-Division Multiple Access (TDMA) structure. On some radios, a transmission in simplex mode may use both time slots, while on others, it might only use one. However, the requirement is that both radios must be programmed to the same time slot (e.g., Slot 1 or Slot 2).

So, while DMR is famous for its wide-area networking through repeaters and hotspots, it absolutely maintains a direct, radio-to-radio simplex capability for local communication.

That is a great question. The DMR radio market is very active, especially for amateur radio operators. The radios available can generally be split into three main categories: Feature-Rich Handhelds (HTs), Budget-Friendly Handhelds, and Mobile Radios.

Here is a list of popular and well-regarded DMR-capable amateur radios across those categories:

📻 Popular Handheld Radios (HTs)

Handhelds are the most common entry point for DMR. They are portable and generally dual-band (VHF/UHF).

CategoryBrand/ModelKey Features/Notes
Feature-Rich/Best ValueAnyTone AT-D878UVII PlusWidely considered the most popular DMR handheld. Offers Dual-Band, Dual-Mode (Analog/DMR), built-in GPS, Bluetooth PTT, and supports a massive contact list (up to 500,000).
Alinco DJ-MD5XTGHighly capable DMR HT, often sharing similar internal firmware with Anytone. Available with GPS and APRS support.
Budget/Entry-LevelRadioddity GD-88Dual-Band, GPS/APRS, and is well-regarded for its cross-band repeat feature and large contact list capacity.
Retevis RT3S / TYT MD-UV380/390Very popular and affordable starting radios. They are often recommended for use with the OpenGD77 third-party firmware, which greatly enhances their features and usability for amateur radio.
Baofeng DM-1701One of the most budget-friendly DMR radios, also frequently upgraded with the OpenGD77 firmware for better performance.
Commercial BrandsMotorola XPR SeriesHigh-quality commercial radios (e.g., XPR 6550, XPR 7550) that are often available used. Known for superior build quality and audio, but often require commercial programming software (CPS) and may have limitations on channel/contact capacity for ham use.
Hytera PD SeriesCommercial-grade, known for ruggedness and reliability.

🚗 Popular Mobile Radios

Mobile radios are typically higher power (20W–50W) and designed for use in vehicles or as base stations.

Brand/ModelKey Features/Notes
AnyTone AT-D578UVIII PlusExtremely popular Dual-Band/Dual-Mode mobile radio. Features high power (50W), built-in GPS, Bluetooth, and often includes Full Duplex capability (allowing you to talk and listen simultaneously like a phone call on V/U).
Radioddity DB25-DA compact mini mobile radio, Dual-Band, Dual-Mode, with GPS/APRS support. A good option for smaller vehicles.
Retevis RT90A full-power (50W) dual-band DMR mobile radio with GPS and dual-mode functionality.
Motorola XPR 5550ePremium commercial mobile radio, often used in amateur radio for its quality, though it requires specific programming for ham use.

What to Consider When Choosing

  1. Codeplug Complexity: DMR radios require a “Codeplug” (the configuration file) to be programmed with channels, talkgroups, and contacts. Radios like the AnyTone 878UVII Plus are popular because their software is relatively well-documented and widely supported.
  2. GPS/APRS: Many amateur DMR radios now include built-in GPS to support APRS (Automatic Packet Reporting System) over the digital channel, allowing your location to be tracked.
  3. Firmware (OpenGD77): For certain budget radios (like TYT/Retevis), installing the OpenGD77 custom firmware is highly recommended by the ham community to unlock a vastly improved user experience and features.
  4. Analog/DMR (Dual-Mode): All radios listed above support both Analog FM and Digital DMR modes, which is essential for working both legacy FM repeaters and the digital network.

Do you have a specific budget or desired form factor (handheld or mobile) in mind that I could use to narrow down the best recommendation for you?

Coos County Radio Club Meeting time Snafu #2

Sorry everyone but please ignore the previous post about having the meeting on the December 18th. I had forgotten about the SWORA VE Test session that happens on the third Thursday of the month which many of us attend as VE’s.

I have once again re-scheduled the CCRC Club Meeting, this time to next Wedneday, December 10th at 5pm for social and 6pm meeting start. I am very sorry for the confusion and changes. I hope everyone can make it as choices for rescheduling is limited.

Gary N6BLU

CCRC Monthly Meeting Scheduling SNAFU. Rescheduled.

Hey y’all.

Per Gary N6BLU:

For reasons that can’t be altered having to do with the restaurant, the space we usually gather in is not available at our scheduled time.

Therefore our monthly dinner meeting is rescheduled for the evening of Thursday December 18th.

Again, the Monthly club meeting has been rescheduled.

IPv6 Block Reserve for Ham Radio

Link: Article In “The Register”

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