SuperPacket

Purpose Built Amplifier for New Packet Radio

I love Tindie for the interesting electronic products that surface there such as 70cm Power Amplifier (PA) for New Packet Radio:

What makes it special?
It has high power RF switches, a VOX trigger and digital input switch. For the lowest packet error rate you should use the digital 3-5V line connected from the NPR and auto switch the PA.

...

As any experienced Amauteur Radio data communications geek knows, the transmit / receive turnaround time is a critical factor in the overall data rate of a data communications system. If you have to waste time waiting for the transmitter to be up to power, settled on frequency, you are wasting valuable channel time. Ditto for an external amplifier, unless you can signal it just as fast as the native transmitter, which is the "digital 3-5V line" the builder refers to.

New Packet Radio is a very interesting area of experimentation for me (I have several but haven't yet started experimenting). From their page:

NPR (New Packet Radio) is a custom radio protocol, designed to transport bidirectional IP trafic over 430MHz radio links (ham radio frequencies 420-450MHz). This protocol is optimized for "point to multipoint" topology, with the help of managed-TDMA.

Bitrate is 50 to 500kbps (net, effective bitrate), depending on the RF bandwidth chosen.

The radio modem is cheap (~80$) and home-made, with a 433MHz ISM module inside (flexible enough to be tuned over the whole 420-450MHz band). The modem is connected locally with Ethernet, therefore no specific software is needed on PC.

The modem is easy to build and reproduce.

You can add a DMR radio amplifier in order to achieve 20W radio power or more.

The main usage is an extension of HSMM - Hamnet - AREDN networks.

All the project is open-source : hardware, software, protocol specification.

...

Slightly bad news about this new amplifier - its power output of 38 dBm is 6.3 watts.

Worse news - apparently the builder has no plans to ship to the US.

More on New Packet Radio in the coming months, including my personal experimentation at N8GNJ.org.

Thanks for reading!

Steve Stroh N8GNJ
Bellingham, Washington, USA
2021-03-23

 

Good Thing There's Amateur Radio...

Police Report That White Supremacists are Attacking Cell Phone Towers

The goal is “to incite fear, disrupt essential services, and cause economic damage with the United States and abroad,” according to the report.

Anagha Srikanth, writing in TheHill.com, March 18, 2021

In more than one case, [white supremacists] succeeded in interrupting resources for law enforcement and emergency services personnel, according to the report, which lists several recent cases. One involved a neo-Nazi chat group whose “members strongly supported exploiting civil unrest in the United States by attacking the country’s infrastructure," The Intercept reported, while another was tied to the 5G conspiracy theory, which claims without evidence that the electromagnetic waves put out by 5G towers are harming peoples' immune systems and are responsible for the coronavirus pandemic.

...

What's alarming is how easy... if you understand how such systems work... it is to cause degradation and damage to such communications systems. We saw a vivid illustration on Christmas Day 2020 when an "RV bomb" in Nashville, TN was detonated in front of a regional AT&T network hub and disrupted communications over a wide region.

A second vulnerability is one that's already reported here - jamming Global Navigation Satellite Systems (GNSS). Signals from GNSS aren't just used for positioning. One of the signals available in GNSS systems is precision timing, which is used to synchronize multi-site wireless communications systems. The first generations of cellular communications systems used onsite precision timekeeping systems... which was expensive. As GNSS systems became more widespread, less expensive precision timekeeping systems were developed that used precision timing derived from GNSS.

Just like no one imagined that someone would detonate a RV full of explosives in front of an AT&T network hub... no one that decided to use GNSS-based precision timekeeping systems as a critical input to wireless communications systems imagined that the GNSS signals would be deliberately, maliciously interfered with.

Two decades ago, there were Federal Communications Commission (FCC) technical personnel in most states that could track down malicious interference within days at most. Now, there are a handful of FCC offices nationwide with that capability. Sometimes the FCC cannot be bothered to respond to malicious interference complaints.

Increasingly, Amateur Radio Operators are among the small pool of those with the skills to track down malicious interference to wireless communications systems. In fact, Amateur Radio Operators are probably the only group that practices those skills regularly, for fun, with their own equipment.

Good thing there's Amateur Radio... Yes?

Thanks for reading!

Steve Stroh N8GNJ
Bellingham, Washington, USA

 

About SuperPacket

This blog was started 2004-03-20 as "Advanced Digital Amateur Radio" - see my original description. I still like that name, but SuperPacket is a better, pithier description of what I want to write about in the big picture of (mostly US) Amateur Radio.

That's in contrast to what I should be writing about in my other Amateur Radio blog, N8GNJ.org, which is to discuss my personal experimentation in Amateur Radio.

Here's an update of the original description, adapted for 2021. It's incomplete - I'll be writing a "manifesto" for SuperPacket in the coming weeks. But this is the same description, minus the most dated bits.

Why? Here? Now?
This blog is something that I've hoped to find. My absolutely favorite reading in all of Amateur Radio was the late and very lamented Packet Radio Magazine, and Bdale Garbee's Bits In The Basement column in TAPR's Packet Status Register Newsletter (PSR). There's a dearth of discussion about "Advanced" Digital Amateur Radio, especially on the web, probably because much of the advancement in Amateur Packet Radio predates the web, and a lot of knowledge didn't get ported to the web. So... at some point... one is faced with "If it's to be, it's up to ME!"

"Advanced" First... a bit about what I mean about "Advanced" Digital Amateur Radio. I find it easiest to explain with a comparison. Connecting to a Packet Bulletin Board System (PBBS) via a Simplex or Digipeater Link @ 1200 baud doesn't meet my (admittedly subjective) definition of "Advanced". Connecting to a Linux system using TCP/IP via a full duplex bit regenerative repeater at 9600 baud or faster is "Advanced", in my opinion. Or, a more personal explanation is that the "Advanced" activities are sufficiently interesting and non-mundane that they continue to stimulate my personal interest in Amateur Radio.

Not So Advanced... That said... (warning - severe contradiction ahead...) I believe (it's been amply demonstrated to me) that there is tremendous value in "non-Advanced" or "trailing edge" Digital Amateur Radio systems - good old, boring, 1200 baud AFSK AX.25 connectivity beats no digital connectivity at all. Similarly, PBBS' have their use in the right situations (and general purpose message exchange isn't one of those right situations. Digipeaters have their place too; they're wonderfully simple, easy to construct and maintain, and if built and used with full understanding of their (numerous) limitations, they're a real boon to communications. So... despite the "Advanced" in the title (I had to call it something techy), expect to see coverage of plain old "boring" 1200 baud, AX.25, PBBS', Net/ROM (and its derivatives), digipeaters, etc.

Relevence of Amateur Radio What's "wrong" with Amateur Radio these days, in a nutshell, is that it's largely perceived as being irrelevant in this century. We have cell phones and Nextel pocket supercomputers, the Internet, and easy person-to-person International communications. At best, many (most?) Amateur Radio activities are, at best, trailing edge, if even relevant. At worst, many of Amateur Radio's activities are seen as irrelevant in this century. For the purposes of this introduction, I'll refrain from offering any examples, but "relevency" is a theme we'll touch upon regularly.

News and Reference The "news" portion will be this blog. I think that blogs are the most amazing and important tools we ordinary people have for conveying information to each other. This is especially important in Amateur Radio where so much information is "institutional knowledge" and we simply do not have a good channel for documenting the "Advanced" aspects of Digital Amateur Radio. When there is enough knowledge amassed here, perhaps a book is in order.

The "reference" portion will be a (static) web pages hosted on this blog.

Truth be told... there's far more going on in Advanced Digital Amateur Radio than most people realize; amazing software developments, interesting new hardware, and so much progress it's amazing at times. I'll be telling those stories here.

Thanks for reading!

Steve Stroh N8GNJ
Bellingham, Washington, USA

Repeater Coordination Does Not Exclude Other Use of the Repeater's Frequencies

(This was originally published on N8GNJ.org, and copied here; SuperPacket is now my "big picture of Amateur Radio" blog for articles like this - see About SuperPacket.)

In my earlier article The Puget Sound Amateur Radio TCP/IP Network (circa 1995) I said in passing:

The last bit regenerative 9600 bps repeater, on 146.98 MHz on Mt. Baldi fell victim to a "sneak attack" because its "coordination" with the Western Washington Amateur Repeater Association (WWARA) lapsed. The moment the coordination lapsed, WWARA gave the "coordination" for 146.98 to yet another "ego box" voice repeater. To this day, forcing the unique 146.98 9600 bps data repeater off the air is one of the stupidest things I've ever witnessed in Amateur Radio. For that reason I have a very dim view of the utility of "frequency coordination" for Amateur Radio in general, and the WWARA in particular.

The premise that "repeater coordination" is based upon is that (widely held) perception that portions of the Amateur Radio VHF / UHF bands are for the exclusive use of repeaters, and any other use of those portions of the Amateur Radio VHF / UHF bands is not allowed. It has happened that other use of a particular repeater's input or output frequencies have caused complaints to the "repeater coordination body" and sometimes escalated to a formal complaint to the Federal Communications Commission (FCC), mostly back decades ago when the FCC took Amateur Radio interference complaints seriously.

Even before the stupidity about "decoordinating" the unique Mt. Baldi 146.98 9600 bit-regent repeater, the "it's MY repeater frequency, dammit" attitude struck me as wrong. When I was learning about Amateur Radio, one of the tenets I was taught was that in operating, no Amateur Radio operator had a "right" or "claim" to a particular Amateur Radio frequency, and the "exclusivity" nature of repeater coordinations just seemed wrong. It's right there in the FCC rules - Part 97.101(b):

Each station licensee and each control operator must cooperate in selecting transmitting channels and in making the most effective use of the amateur service frequencies. No frequency will be assigned for the exclusive use of any station.

But that seems routinely ignored when "it's MY repeater frequency, dammit" is asserted.

In my opinion, the proper perspective of a "repeater coordination" is that it's a mild preference among equal peers - that all things being equal, this particular usage is preferred. No more than that.

Years afterward, I read an official opinion of the FCC that confirmed my perspective, that while coordinated repeaters are recognized as a "first among peers" designation if they have blessing from a "coordination body", that "coordination" does not extend to exclusive use of the frequencies the repeater is using, especially when the repeater is not in operation. I squirreled away that note... too well, apparently, because I could never find it again. I tried Google searches, to no avail, until a few days ago.

Kudos to the ARRL for keeping this sort of vital information online!

 http://www.arrl.org/news/fcc-dismisses-two-amateur-radio-related-petitions 

But, just in case... https://web.archive.org/web/20100527003357/http://www.arrl.org/news/fcc-dismisses-two-amateur-radio-related-petitions

FCC Dismisses Two Amateur Radio-Related Petitions

12/09/2009

On Wednesday, December 9, the Federal Communications Commission dismissed two separate Petitions for Rulemaking: One filed by Murray Green, K3BEQ, concerning the operation of repeater stations in the Amateur Service, and one filed by Glen Zook, K9STH, requesting amending Section 97.119(a) to change how often stations must identify themselves.

Murray Green, K3BEQ (DA 09-2559)

In his Petition, Green -- who filed his Petition on March 23, 2009 -- requested that the FCC amend Section 97.205(e) of its Rules "to prohibit a repeater station licensee or control operator from limiting the use of a repeater to only certain user stations, unless a user blatantly violates the Commission's Rules." Green argued that Section 97.205(e) -- which permits a repeater station licensee or control operator to limit the use of a repeater to certain user stations -- conflicts with Section 97.101(b) which states that no frequency is for the exclusive use of a particular amateur station, and each station's licensees must cooperate in selecting transmitting channels and in making the most effective use of the Amateur Service frequencies. In his Petition, Green argued that Section 97.205(e) permits "a pay for use policy in the Amateur Radio Service, enables user censorship and intimidation, breeds on the air inactivity by not using frequencies effectively and creates a negative public image."

In denying Green's Petition, the FCC concluded that Section 97.205(e) does not establish an exclusive assignment of a frequency to a repeater, saying that Green's contention that a coordinated closed repeater has "exclusive control of an Amateur Service frequency." The Commission noted that coordination is not required as a condition of operating a repeater: "Coordination does not and cannot result in assignment or establish control of an Amateur Service channel," the FCC said in its reply, "and nothing in the rules prohibits other amateur stations from using the channels for which a repeater has been coordinated when they are not being used by the repeater. Section 97.205(e) merely enables a repeater licensee or control operator to control the repeater so that he or she can ensure the repeater is properly operated as required by Section 97.105(a). Accordingly, there is no conflict between the rules, and no grounds for the Commission to propose to amend Section 97.105(a)."

The FCC advised Green that questions concerning the impact of the operational decisions of a repeater control operator, licensee or trustee -- such as limiting the repeater's use to certain stations -- should be addressed to the local frequency coordinator so that repeater problem can be "expeditiously dealt with at the local level by people with first-hand knowledge of the facts."

This phrase leapt out at me:

The Commission noted that coordination is not required as a condition of operating a repeater: "Coordination does not and cannot result in assignment or establish control of an Amateur Service channel," the FCC said in its reply, "and nothing in the rules prohibits other amateur stations from using the channels for which a repeater has been coordinated when they are not being used by the repeater.

Although this came too late to save the unique Mt. Baldi 146.98 9600 bit-regent repeater, it was something of a moral victory, at least to me. Armed with this, the fans and supporters of the unique Mt. Baldi 146.98 9600 bit-regent repeater could have argued that WWARA's new "coordination" of the "ego box" new 146.98 repeater was more of a gentle suggestion rather than effectively being "law of Amateur Radio in Western Washington".

Fast forward to 2021 and beyond. In my monitoring of the Amateur Radio VHF/UHF bands, the silence (unoccupied airtime) is deafening. Where is all the activity to justify the exclusion of every requested new "coordination" because "2 meters is full"?

I can also envision that based on this information, when a repeater is proposed for the 144-148 MHz band (2 meters) in Western Washington, instead of the WWARA essentially vetoing such a repeater ("2 meters is full. Go away.") that the new repeater "just do it". I think that especially applies to new data systems like the unique Mt. Baldi 146.98 9600 bit-regent repeater.

I've said that the entire function of Amateur Radio repeater coordination bodies should be, at most, a Wiki page where someone who wants to put up a repeater posts the basic information of the repeater:

• Latitude, Longtitude, and Height
• Relevant technical information - Frequency, Power, etc.
• Control operator's Amateur Radio callsign and name
• How to contact the control operator of the repeater.

That's it. Then, as the FCC suggests, any issues... can be "expeditiously dealt with at the local level by people with first-hand knowledge of the facts.

In a future post I'll discuss why all of the above is relevant - that new data modes such as VARA revive the discussion of using repeaters for data. Existing (voice) repeater owners are loathe to allow data usage of their (coordinated) existing "voice" repeaters, so those of us that want to use repeaters for data are just going to have to create new repeaters. For us "data first" enthusiasts, the situation K3BEQ describes with certain repeaters limiting usage for a select few users, we feel the same way about the exclusion of data. So, it's time to "route around those "voice only" repeaters. Likely they won't notice because their usage is so light.

The above is "cover" for putting up those new repeaters even though "2 meters is full".

There is now funding available to try interesting new things.

Thanks for reading!

Steve Stroh N8GNJ
Bellingham, Washington, USA

The Puget Sound Amateur Radio TCP/IP Network (Circa 1995)

(This was originally published on N8GNJ.org, and copied here; SuperPacket is now my "big picture of Amateur Radio" blog for articles like this - see About SuperPacket.)

 

This is the paper I wrote for the 1995 Digital Communications Conference. At the time I wrote this, the network was very active and it was the envy of the country for having not just one, but several 9600 bps bit-regenerative repeaters on the air, and running TCP/IP (Transmission Control Protocol / Internet Protocol) over them. I've cleaned this up for the blog format and removed out of date contact information.

Unfortunately, as time moved on, space on the US West NewVector cell sites became precious, and our sponsors in the US West NewVector Amateur Radio club moved on other companies and we had to remove the repeaters. The last bit regenerative 9600 bps repeater, on 146.98 MHz on Mt. Baldi fell victim to a "sneak attack" because its "coordination" with the Western Washington Amateur Repeater Association (WWARA) lapsed. The moment the coordination lapsed, WWARA gave the "coordination" for 146.98 to yet another "ego box" voice repeater. To this day, forcing the unique 146.98 9600 bps data repeater off the air is one of the stupidest things I've ever witnessed in Amateur Radio. For that reason I have a very dim view of the utility of "frequency coordination" for Amateur Radio in general, and the WWARA in particular.

I still have one of the UHF repeater systems from one of the US West NewVector sites in my shop. The UHF repeaters were rock-solid UHF Motorola Pulsars (if memory serves) which were the radios used for the old AT&T "Improved Mobile Phone Service", the precursor to cellular mobile telephony. Pulsars were a great choice because they were cheap (to them), well understood by the US West NewVector Amateur Radio Club members and thus easily modified for "flat audio" needed for 9600 bps Frequency Shift Keying (FSK), they were designed for long duty cycles (no fans needed) and they were designed for full duplex. The TNCs were MFJ-1270s with the TAPR 9600 bps modem with the bit-regent adapter. The computers were... whatever we could Frankenstein together in 1995. I remember going to a (then rare) computer surplus dealer called "Puter Parts to put together one computer on a tight budget. My personal station for accessing the Eastside repeater in Issaquah, WA was a Tekk 2 watt radio with an 11-element yagi pointed at the repeater, a Gracilis PackeTwin with a Kantronics 9600 bps modem, and sexy looking surplus industrial PC.

What was remarkable then, and has only now been achieved in the past five years or so with AREDN and HamWAN, is that this network was completely interoperable with the Internet. Unlike Packet Radio, the TCP/IP implementations we used (thank you KA9Q) were able to operate at 9600 bps, and we could send email from a user station on the network to an Internet email user, and vice versa. What made it work was that the router at the Internet Service Provider talked at "Internet speed" to other email hosts, and at "packet radio speed" to the network, and buffered between the two networks.

My experience with this network was formative for me. On the basis of "knowing" TCP/IP I was able to qualify for my first Network Administration job because it required knowledge of TCP/IP, which was then pretty rare. This article was the first major piece I wrote for publication. After this I wrote some articles for the TAPR Packet Status Register (PSR) newsletter, and (briefly) was the PSR Editor. Shortly after that, I began writing a column for Boardwatch Magazine about Wireless Internet Access, and thus began my writing career.

Abstract

The Puget Sound Amateur Radio TCP/IP Network (also known as WETNET, the Washington Experimenter’s Tcp/ip NETwork), centered in the Seattle, Washington metropolitan area, has built an extremely functional packet radio network based on TCP/IP networking and cellular RF techniques. The network encompasses more than eighteen separate Local Area Networks, an estimated 200 users, four 9600 baud bit regenerative repeaters, and a full time Internet gateway. This paper is intended to provide an overview of an operational Amateur Radio TCP/IP network.

A Frequently Asked Question is “Why TCP/IP? Can’t you do everything with regular packet radio that you can do with TCP/IP?” The answer is... somewhat, but not really. A key feature about Amateur Radio implementations of TCP/IP is that its various capabilities are built in- you don’t have to combine dissimilar systems to do mail forwarding, file transfers, provide Packet Bulletin Board System (PBBS) services, multi-connect chat sessions, multiple ports, etc.- “It’s (all) in there”. A typical TCP/IP station can do:

• file transfers (including binary files)
• keyboard to keyboard (chat, telnet)
• finger (display short text files)
• operate as a very capable Packet Bulletin Board System
• operate as a very capable Net/ROM, TheNET, Xl J node, etc.
• accept multiple connections from AX.25, Net/ROM, and other TCP/IP stations
• access multiple ports, including modem, RS-232, terminals, and Ethernet connections
• electronic mail
• automatic routing
• ping (test link integrity)
   

These operations are simultaneous, since the TCP/IP software is written to multitask. The capabilities outlined above are only a subset of TCP/IP’s capabilities.

Some Background on Amateur Radio TCP/IP

A complete discussion of all of the various TCP/IP utilities and capabilities is beyond the scope of this paper, but a few deserve some discussion. One of the most interesting capabilities of Amateur Radio TCP/IP is e-mail. Since each TCP/IP station can send and receive e-mail, there cannot be a “choke point” in the network for message traffic- each TCP/IP user has the ability to send e-mail to any other user from their station. This was a much appreciated feature after having been through “PBBS (Packet radio Bulletin Board System) Forwarding Battles”, where certain PBBS Sysops wouldn’t forward to other PBBS Sysops. With the added capability of a mailing list- being able to forward a single message to multiple recipients, e-mail made PBBS’, and their problems, almost irrelevant. TCP/IP users have the capability to participate in PBBS forwarding, and can “translate” PBBS messages to e-mail messages, and vice-versa.

Being able to add multiple ports easily is liberating. TCP/IP users can gateway between multiple ports, and this capability is used to provide redundant routes, and to provide network access to remote Local Area Networks whose users cannot access other parts of the network directly.

A TCP/IP station can effectively service AX.25 users by providing the capabilities of a PBBS, a network node, a “chat node” , and much more to AX.25 users.

Amateur Radio TCP/IP authors have traditionally (begun by Phil Karn KA9Q) made all source code, (written in C) freely available. If you want to add a new feature, or fix a bug, the source code is available, and several Puget Sound TCP/IP operators have made good use of this to add features and fix bugs, and contribute back to the code pool.

Network Operating System (NOS) was the name that KA9Q gave to his “second generation” of Amateur Radio TCP/IP software (the first was named NET). Since NOS was released, there have been numerous offshoots of NOS, including JNOS, TNOS (JNOS and TNOS were variants of NOS), and others In this paper, NOS is used interchangeably with the term “Amateur Radio TCP/IP Software”.

It is important to remember that “Amateur Radio” TCP/IP is completely interoperable with “commercial”, or “wired” TCP/IP. TCP/IP was enhanced to make use of Amateur Radio just as it was to make use of satellite links, other networking systems, and modems.

Typically, the Switches do not offer any “user functions” and only handle routing and other network functions. If a user function is enabled, it is typically routed to other systems in the network. This may change as the Switches are converted to Linux.

Several LANs have been formed by multi-ported stations that access a repeater and a 2m simplex frequency. Network users have gradually adopted the cellular telephone approach of using low power and a low RF profile, and thus are able to reuse frequencies.

Typically, the multi-ported station forms the center of a simplex LAN. Any stations joining the LAN are encouraged to be within good DCD (Data Carrier Detect) range of the other stations on the LAN. This keeps overall performance on the LAN reasonably high, despite the inevitable collisions and hidden transmitters resulting from simplex operation. 

The network is linked full time to the Internet through a Network Switch at the premises of one of the largest Internet Service Providers in the Seattle area. The primary use of the gateway is to allow participation in the global Converse Bridges. Amateur Radio TCP/IP users can also telnet, FTP (File Transfer Protocol), etc. to Internet hosts, as long as the user has a good connection to the network so the Internet system doesn’t time-out from long delays.

The group makes extensive use of subnetting- the third “octet” of the Amateur Radio TCPAP IP address is specific to a particular LAN. For example, 44.24.103 .xxx is an IP address for the 220 1200 baud repeater, and 44.24.101 .xxx is an IP address for the 147.60 simplex LAN. RIP (Routing Information Protocol) is used to propagate routes throughout the network.

Operational

A typical user station consists of a 386 PC using a Tekk KS-900 UHF radio with a beam, an AEA PK96 or MFJ1270 TNC with TAPR 9600 baud modem. The favored 2m 9600 baud radio is a modified GE MVP. The TCP/IP software of choice is the JNOS (WG7J). It is not uncommon to for the NOS PC to be configured as a “router” for other PC’s in the household via serial or Ethernet connections to a second PC running “commercial" TCP/IP software, often with a graphical user interface- Windows Winsock, OS/2 Warp, or Xwindows on Linux.

AX.25 users are welcome to connect to any TCP/IP station, both to browse around on that particular system or be routed to another system on the network. Some user stations and Switches actively encourage AX.25 and telnet connections by having numerous information files, binary files, and BBS areas available, . The group, at present, hasn’t placed a high priority on interconnection between AX.25 PBBS forwarding and Net/ROM -type networking. There is limited connectivity between local PBBS systems and TCP/IP users through a TCP/IP to PBBS gateway which transfers PBBS messages via e-mail. Personal PBBS messages are sent privately, and PBBS bulletins are sent via a mailing list.

Setup of TCP/IP for the first time has traditionally been a problem. The group has developed a JNOS setup disk, which includes all executable and configuration files necessary to get JNOS up and running. It includes a customized setup program which prompts the user for IP address, callsign, and other particulars, and then customizes the AUTOEXEC.NOS startup file, creates directories, and installs files as appropriate. From all accounts, the disk is working well in getting TCP/IP newcomers on the air.

The Puget Sound Amateur Radio TCP/IP Group

Early members of the group had been active in other area packet radio groups and had become bumed out from the formal duties of a group, such as holding office, constitutions, dues, newsletters, etc. A deliberate, conscious decision was made that this group would remain informal in order to concentrate on technical and other innovative lack-of- management techniques. When funding has been needed for repairs or new equipment, money is donated by members of the group. This arrangement has worked relatively well, but the group did recently decide to get “slightly less disorganized” by requestingvolunteers for Keeper of the Notes, Keeper of the List of Projects, and Keeper of the Shekels.

The group communicates primarily through a mailing list. Members of the group that wish to pose a question, comment on a previous posting, or share information send a single message to the list, and that message is automatically propagated. If a user’s connectivity is good, messages from the list can be delivered in minutes. Mailing list functions have been automated using Majordomo mailing list server software on a Linux system.

The group meets monthly on a weeknight evening. In keeping with its informal nature, meetings are “moderated” only to the point of “collision avoidance”. There is usually plenty to discuss, and formal presentations are rare. Any “burning issues” have typically been discussed on the mailing list prior to the meeting, and there are only a few “reports”. The group has a small advertisement in the local “Computer Paper” which draws in a few lapsed hams and technically curious non-hams.

An ongoing effort is to write effective documentation. Those involved in the documentation effort are enthusiastic about the potential of using the World Wide Web (WWW, or Web) to distribute information. Articles can be distributed as they are created, and updated individually. Web pages, being composed of ASCII text, can easily be distributed as e-mail, or printed from a Web browser. Using Web pages also enables other groups worldwide to easily access the group’s information. The group will support Web pages on the Internet gateway (typical graphically rich Web pages), and a well connected RF site in the network (primarily text Web pages). The group’s current Internet Web page is located at:

http://wetnet.wa.com/ (no longer online, was not saved into the Internet Archive)

Future goals and projects

• Enhancing the reliability of the overall network is a high priority
• Expand high speed TCP/IP links to other areas in the Pacific Northwest, especially Vancouver and Victoria, British Columbia and Portland, Oregon.
• Implement several 56 KBPS and higher links
• Replace NOS with Linux at all Network Switches
• Increased use of Linux and other TCP/IP capable systems
• Contribute to the forthcoming TAPR TCP/IP book
• Sponsor a TAPR Annual Meeting and/or an ARRL Digital Communication Conference Accommodate increased use of PC’s, Macs, Amigas, and Unix systems running their native implementations of TCP/IP
• Aggressively test and implement new radio-based routing techniques as they are developed

Conclusion

TCP/IP works very well for Amateur Radio networking. It has been a satisfying learning experience to get it running and keep it functioning. The results are well worth the effort expended.

The group would enjoy hearing from Amateur Radio TCP/IP users around the country and the globe that have implemented Internet access to their Amateur Radio Networks.

For those that are able, wouldn’t it be more interesting to use our “radio” computers to participate in mailing list discussions such as NOSBBS, NETSIG, and others? There is no reason not to if your system has adequate connectivity to the Internet.

References

Steve Stroh N8GNJ (old contact info removed) for questions on the Puget Sound Amateur Radio TCP/IP Group,

Ken Koster N7IPB (old contact info removed) for questions on the Puget Sound Amateur Radio TCP/IP Network,

Terry Conboy N6RY (old contact info removed) for questions on the US West NewVector Amateur Radio Group and the Cellular Base Station systems.

The most complete book on Amateur Radio TCP/IP is NOSintro, subtitled TCP/IP of Packet Radio, An introduction to the KA9Q Network Operating System by Ian Wade G3NRW, copyright 1992 by Dowermain Ltd., ISBN l-897649 00-2. NOSintro is available from the ARRL.

A good FTP site for downloading Amateur Radio TCP/IP software fi-om the Internet is:

ftp.ucsd.edu/hamradio/packet/tcpip (no longer online, was not saved into the Internet Archive)

The mailing list for Puget Sound Amateur Radio TCP/IP Network users is:

(old list email address removed)

My thanks to the users and builders of the Puget Sound Amateur Radio TCP/IP Network -  it’s not a network without users to use it. It’s been quite a ride, and we’re “finally having fun yet”. I’d especially like to thank (Ken Koster) N7IPB, (Bob Donnell) KD7NM (SK), (Ren Roderick) WA7QFR (now K7JB), (Don Werts) N7NKJ (SK), and (Peter Dahl) WA7FUS for inviting me into the group.

Amateur Radio Digital Communications (aka ampr.org / 44net)

(This was originally published on N8GNJ.org, and copied here; SuperPacket is now my "big picture of Amateur Radio" blog for articles like this - see About SuperPacket.)

Amateur Radio Digital Communications (ARDC) is a (now) confusing name for a 501(c)3 nonprofit organization whose primary mission is (now) philanthropic grantmaking. ARDC sold a portion of its 44.x.x.x Class A address space for a substantial profit, and invested the proceeds into an endowment. ARDC will continue to manage (and significantly improve) "ampr.org / 44net", which is the infrastructure involved in routing ARDC's remaining allocation of 44net addresses (44.0.0.0/9 and 44.128.0.0/10). With its endowment, ARDC can now make philanthropic grants of significant size and scope. See the list of ARDC's grants to date. 

Disclosure: I am a volunteer member of ARDC's Grants Advisory Committee (GAC). What follows is my personal perspective, and does not represent the views of ARDC.

Shortly after ARDC's announcement of its endowment and that it would begin grantmaking, I wrote the following article in 2019-08 about the potential of ARDC. I haven't published it until now. The mentions of Zero Retries refer to my newsletter which is still in development.

 

Amateur Radio Digital Corporation Creates Endowment for Angel Funding for Advanced Amateur Radio

 

(For those that aren’t familiar with venture capital terminology, the first, relatively small funding that a startup company receives, intended to be enough to prove out the company’s concept, is referred to as “Angel Funding”.) In July, 2019 (the exact date isn’t stated), a very significant development occurred for the Zero Retries Areas of Interest. I can’t summarize this development better than Amateur Radio Digital Communications (ARDC) did in their official announcement, reproduced below.

 

[I quoted a lot of background info about ARDC which is now all available on its website https://www.ampr.org. Thus I won't rehash anything already there (that was originally in my article).]

 

Wow. Just... Wow. Let’s let this sink in a bit. I for one am gobsmacked by this announcement, in a good way – I’m incredibly excited for what this will be for the future of Amateur Radio as a whole and especially the Zero Retries Areas of Interest.

 

[ARDC's late founder Brian Kantor WB6CYT] mentions in passing that they’re receiving “... a lot of vitriol, hate, and threats from small-minded hotheads.” I believe that. I’m really sorry that’s happening. If you feel as I do, considering dropping the folks at ARDC a note of encouragement and Thanks.

 

It’s my (strong) opinion that ARDC did a good thing in selling 44.192.0.0/10 and generating a pool of money for investing in Amateur Radio.. Again, they did a good thing... the right thing... and I believe they did it for the right reasons.

 

I’m excited that the ARDC board and their advisors have been “doing Internet” for a very long time. They get networking, they’ve been Amateur Radio operators for a very long time, and they can see the potential doing networking over Amateur Radio.

 

I’m also excited that the ARDC board has committed to funding “... a program of grants and scholarships that will serve to promote the art and science of digital communications including Amateur Radio” and “... apply for funding to support their projects, whether they be fundamental research, scholarships for education, design of new algorithms or technology, or the construction of Amateur facilities.” That... is... cool!!!

 

Note that ARDC is careful not to constrain themselves soley to Amateur Radio. As I’ll explore in Zero Retries, there’s an incredible amount of innovation adjacent, and relevant to Amateur Radio, that isn’t actually occurring within Amateur Radio. Just one example is the evolution of inexpensive Software Defined Receivers, epitomized by RTL-SDR.com. The creator of the unique RTL-SDR receivers certainly acknowledges innovative uses of his products with Amateur Radio... but by no means does he limit the uses of his products, or markets solely to Amateur Radio. I agree wholeheartedly with ARDC not to limit themselves to funding solely in relation to Amateur Radio.

 

Why does the emergence of an “investment fund” that understands Amateur Radio and “next generation” areas such as networking, (new) technology, facilities, etc. matter? I have a few stories to tell that are applicable.

 

Story 1: ARRL and TAPR DCC Student Paper Program

 

The first is about student paper presentations at the ARRL and TAPR Digital Communications Conference (DCC) in 1996 and 1997 (PDF). For those two years, a small grant (from the ARRL and TAPR, I think) created a program for university students to submit a paper that was relevant to “electronic communications” (I don’t think the subject was required to be about Amateur Radio, or radio communications, or even digital communications). The program was refereed. Although the DCC was not and is not an academic conference, the student paper program had the same rigor applied as for paper presentations at an academic conference. The papers were refereed by a committee of academics chaired by Greg Jones WD5IVD. The two best papers in each year were awarded a small stipend, and an all-expenses-paid trip to the DCC in 1996 and 1997. From my observations, the program was a success – there were a number of paper submissions, the four winning authors were thrilled to attend the DCC with all expenses paid, and the stipend was a nice bonus. But what was best for the students was that by formally presenting their paper at the DCC, they were able to claim credit on their CV as having presented a paper! That is a major accomplishment for a university student.

 

But, the program ran only for two years. While I don’t know exactly why the program wasn’t continued, here’s my speculation. After the first two years, Greg Jones (not yet Dr. Jones, if memory serves) couldn’t devote the time to managing the committee for a third year, and no one else stepped forward to do so. It takes a lot of time and energy manage a committee of academics to referee papers for a conference. Second, funding didn’t materialize to fund a third year of student paper presentations.

 

It might be that a small grant from ARDC might have enabled the continuation of the DCC Student Papers Program. The grant could have paid a small stipend to the academic committee to referee the submitted papers, and payment of the student’s travel expenses to the DCC to present their papers, and provide the students with a small stipend.

 

Amateur Radio needs more meaningful experiences like the DCC Student Papers Program, and it’s my hope that grants from ARDC can enable more experiences like it.

 

Story 2: ARISS Next Generation Radio Systems

 

Amateur Radio on the International Space Station (ARISS) is a tremendous success for Amateur Radio. Likely you’ve read the stories about the many grade school students who’ve actually talked, directly over Amateur Radio (usually, but not always) to astronaut Amateur Radio operators onboard the International Space Station (ISS). What you probably don’t know is that all of the Amateur Radio equipment onboard the ISS is not furnished by NASA or other country sponsors of the ISS. All Amateur Radio equipment on the ISS has to be furnished at no cost to NASA. That includes development of the equipment, testing, certification, training, and launch costs.

 

The original Amateur Radio equipment on the ISS, nearly since beginning operations, is old, inadequate, and in some cases, failed. The ARISS funding goal for new Amateur Radio systems is $150,000, of which only $33,000 has been raised to date.

 

ARISS is in critical need of an infrastructure update to ensure that programs like students talking to astronauts in space via amateur radio can continue. Through your donations ARISS seeks the following upgrades:
• Next Generation radio system will support easier radio mode transition, to enable new, exciting capabilities for hams, students and the general public including:

• New amateur radio communication and experimentation capabilities, including an enhanced voice repeater and updated digital packet radio (APRS) capabilities
• Slow Scan TV (picture up and downlinks) in both the US and Russian segments of ISS
• New multi-voltage power supply will support present and future radio capabilities and allow wireless experiments to be conducted

• ARISS needs to build 10 Next Generation Radio Systems to support our development, on-orbit operations, training and long-term maintenance. This includes units on-orbit (2 units--1 unit each in US and Russian segment), flight spares (2 units), training (3 units), testing (1 unit) and ground-based maintenance & troubleshooting (2 units).


All of that $150,000 is for actual expenses, not salaries, travel expenses, etc. The range of requirements for ISS hardware is astonishing, such as seamless operation on the US or Russian power systems (totally incompatible with each other), testing that failure of the systems won’t cause electrical damage, won’t outgas into the ISS atmosphere, maybe even endure vacuum conditions. $150,000 is a totally reasonable cost, especially when weighed against the vast goodwill that is generated from student contacts with the ISS.

 

And yet... they’re still $117,000 short – donations of only $33,000. I certainly don’t fault ARISS for that; I’ve met a few of the ARISS folks at Hamvention, and they’re incredibly hardworking. Time spent evangelizing for funds is time that’s not spent doing what ARISS is supposed to be about – getting the kids excited about space.

 

Thus, a grant from ARDC to ARISS to fully fund the ARISS Next Generation Radio Systems would make a huge difference to ARISS, and let them get on with the ARISS mission instead of worrying about fundraising.

 

Story 3: The Radios That Weren’t; Part 1

 

In 1997, a project was begun under the sponsorship of TAPR to build a Frequency Hopping Spread Spectrum (FHSS) Radio that was designed specifically for use by Amateur Radio operators in the 902-928 MHz band, available to hams in ITU Region 1. This would have been the first radio specifically for Amateur Radio use that employed spread spectrum technology, and it was intended to prove that spread spectrum technology was usable and useful in Amateur Radio. If spread spectrum could work for Amateur Radio in the 902-928 MHz band (which was also a band used for Industrial, Scientific, and Medical [ISM] devices, also known as “Part 15” devices), it could work in the other Amateur Radio VHF/UHF bands.

 

In 2002, the TAPR FHSS Radio project was discontinued. The reason, in a nutshell, is that radio frequency (RF) design is hard. It’s hard enough that those who are good at RF design are always in intensive demand. Despite heroic efforts by the FHSS Radio designers, the project stretched out over several years, long enough that the key components that were in the first design were obsoleted by the manufacturer. So, the team developed a second design for the FHSS Radio using different parts. It happened again! The parts for the second design were obsoleted by the manufacturer!

 

The problem seemed to be that the development stretched out over several years because the RF development was being done on a part-time basis. If funds had been available to hire a RF engineer that could focus on the design, and complete it within a few months, the design might have been able to be manufactured (at least one or two production runs) before the parts were obsoleted. If that had happened, we might well now be using FHSS or other methods of spread spectrum on Amateur Radio spectrum.

 

Story 4: The Radios That Weren’t; Part 2

 

A more recent example was the decision by NW Digital Radio in 2018 to formally discontinue their project for a software-defined transceiver for the 440-450 MHz band that they called the UDRX-440.

 

Disclaimer: I’ve had a number of private conversations about the UDRX-440 over the past years with some of the principals of NW Digital Radio, and it’s not my intent to betray any confidences. Thus, the following description of the UDRX-440 project will be very general.

 

The genesis of the UDRX-440 was a presentation and a resulting conversation at the 2010 ARRL and TAPR DCC in Vancouver, WA. The UDRX-440 as it came to be called was proposed to be a software-defined transceiver for the Amateur Radio 440-450 MHz band. It would have a 25 watt tramisit power, and its emission and reception characteristics would be defined by software. It would incorporate a powerful embedded computer which would manage the radio functions (such as transmit / receive channel), and also provide higher level functions such as data modems, and networking. The design for the UDRX-440 was originally hoped to be a relatively quick design process around an existing RF modem chipset, but that chipset was found to have profound limitations. Like with the TAPR FHSS Radio, the design was restarted using another chipset. From this point, the story of the UDRX-440 is much the same as the FHSS Radio; there just wasn’t time, or funds, available to devote focused, full-time effort (both RF hardware and supporting software) into getting the project completed in a reasonable amount of time to push a design into production.

 

I feel that the UDRX-440 would have been a profound step change in Amateur Radio, likely a larger impact to Amateur Radio than the emergence of the TAPR TNC-2 in 1985. Like the TAPR FHSS Radio, it would have enabled experimentation with spread spectrum techniques (FHSS at a minimum) in the popular 440-450 MHz band. If the UDRX-440 had become a product, it would likely have been followed by versions for the 222-225 MHz band, and likely the 144-148 MHz band. The UDRX’s 25 watts provided ample power to form up store-and-forward mesh networks between widely separated Amateur Radio stations to jointly experiment. It would have been able to operate at larger channel sizes such as 100 kHz, adequate to support 56 kbps and faster speeds. It would have enabled more advanced data modes such as incorporating Forward Error Correction (FEC), and much, much more. It was originally going to incorporate a proprietary single board computer running Linux, but with the overwhelming popularity of the Raspberry Pi series of computers use in Amateur Radio, the UDRX-440 was redesigned around the use of a Raspberry Pi.

 

In short, it was a very promising radio concept for us data geeks in Amateur Radio.

 

The UDRX-440 was formally discontinued in 2018. To date, there have been no announcements from NW Digital Radio about a successor to the UDRX-440.

 

Would a grant from ARDC to NW Digital Radio have made a difference in the development of the UDRX-440? And would that have been a good thing, a grant from a 501(c)(3) organization to a for-profit company? Yes, I think it would have made a difference and likely would have resulted in the UDRX-440 becoming a product. ARDC funding could have enabled the hiring of full time, focused RF design as well as hiring of full time, focused software. Consider that NW Digital Radio has demonstrated some history of contributing to open source, so if ARDC made that a requirement of a grant from them (with reasonable provisions for NW Digital Radio to make a profit, say a year of exclusivity before releasing the designs and software as open source), the Amateur Radio would have benefited from a released product and a “template” for other innovative designs based on the open source template of the UDRX-440.

 

Those are just four stories of how much difference “enlightened” investment on Amateur Radio projects could make. I am very much looking forward to what ARDC does with its “Angel Fund for Advanced Amateur Radio”.

 

I'm pleased that ARDC did fund Student Paper presentations at the TAPR DCC, and ARDC also helped fund the new radio system for the International Space Station. (I did suggest that they do so in private emails to some ARDC board members.)

 

In 2021, ARDC is going to be pretty busy.

 

ARDC released its 2020 Annual Report - https://www.ampr.org/wp-content/uploads/2020-ardc-annual-report-sm.pdf.

 

ARDC has rounded out its Grants Advisory Committee (GAC) and Technical Advisory Committee (TAC), as well as adding two board members - https://www.ampr.org/about/who-we-are/.

 

ARDC is now accepting applications for a Grants Manager - https://www.ampr.org/ardc-is-hiring-a-grants-manager/.

 

ARDC is now soliciting grant proposals - https://www.ampr.org/general-request-for-proposals-rfp-march-2020/

 

Lastly, ARDC's incredibly hard-working Executive Director is Rosy Wolfe KJ7RYV. If you appreciate what ARDC is doing, as I do, consider dropping her an email note with your thoughts.

 

Thanks for reading!

 

Steve N8GNJ

Bellingham, Washington, USA

 

 

Monitoring Satellite Navigation Signals for Interference

(This was originally published on N8GNJ.org, and copied here; SuperPacket is now my "big picture of Amateur Radio" blog for articles like this - see About SuperPacket.)

IEEE Spectrum published a 2021-03-03 article titled The Networks That Aim to Track GPS Interference Around the World.

(It's surprising that IEEE, despite its global membership and the worldwide audience of Spectrum, doesn't use the more accurate terminology of Global Navigation Satellite System (GNSS). It's been years now that other GNSS systems besides US Global Positioning System [GPS] have come online.)

That GNSS systems can, and do, get jammed is well-known to the audience of this blog. I knew that the US Federal Aviation Administration (FAA) monitors GPS and provides ground based and satellite based correction data. Of course, the US military monitors GNSS systems for potential jamming (including their own, to see how effective theirs is).

But I wasn't aware of several crowdsourced GNSS monitoring networks:

International GNSS Service (IGS)

OpenSky Network

This paragraph leapt out at me:

Another problem facing both these systems is the sparse distribution of sensors, says Todd Humphreys, Director of the Radionavigation Laboratory at UT Austin: “There are fewer than 3000 GPS reference stations with publicly-accessible data across the globe; these can be separated by hundreds of miles. Likewise, global coverage by ships and planes is still sparse enough to make detection challenging, and localization nearly impossible, except around ports and airports.” 

What if... Amateur Radio operators and others worldwide that were interested in wireless experimentation "crowdsourced" GNSS receiver data from an inexpensive GNSS receivers?

This sounds like yet another "fertile area of research" for Amateur Radio. Now that Amateur Radio Digital Communications (ARDC) has now issued their 2021 Request for Proposals (PDF), perhaps some enterprising grad student or wireless experimenter could create an organization such as Satellite Network Open Ground Station (SatNOGS) Project or Ham Radio Citizen Science Investigation (HamSCI) to create a website, infrastructure, and reference designs to create a open source hobbyist GNSS monitoring network.

Thanks for reading!

Steve N8GN
Bellingham, Washington, USA

Revisiting RadioMirror

(This was originally published on N8GNJ.org, and copied here; SuperPacket is now my "big picture of Amateur Radio" blog for articles like this - see About SuperPacket.)

The genesis of this idea was a discussion I overheard during a local radio club's (virtual - Zoom) meeting. The club wanted to implement a way to keep all members of their Emergency Communications (EMCOM) group up-to-date with a set of files - maps, lists of personnel, frequencies, etc. continuously updated so that when a communications emergency occurred and Internet connectivity was lost, all of the information they needed to respond would be up-to-date. The method they chose was an non-centralized Internet file replication system. I checked in with one of those who was named as one of the leads for implementing this idea, and he had not heard about the idea. I think the idea was a good one, but it requires installation of software and some sophistication to make it work, and perhaps the organizational skill to remember to keep the replicated files on a USB flash drive so that in a communications emergency, the USB flash drive (which hopefully doesn't get corrupted in a sudden power failure) can be taken with the up-to-date files and used in another system such as a laptop.

Update: A friend reminded me that the Pacsat Broadcast Protocol concept in 1990 predates (and is specified more rigorously) than RadioMirror. Thanks Larry!

Out of the deep recesses of my packet radio experience, I thought of a better way to accomplish this that didn't require Internet at all - RadioMirror. RadioMirror is a concept originated by John Hansen W2FS that's been around since the early days of packet radio. In a nutshell:

• A RadioMirror server broadcasts file blocks with checksums .
• Multiple RadioMirror clients receive broadcasted file blocks and (if the checksum is valid) reassemble the blocks into files.
• There is no handshake between the server and client.
• The RadioMirror server broadcasts blocks continuously. When the last block of the last file is transmitted, the RadioMirror server starts over.
• Any new or changed files are added to the RadioMirror server's queue, and they are transmitted.
• When a RadioMirror client receives all of the blocks (with valid checksums) of a file, the file is written to its received files queue.
• The RadioMirror client is responsible for (optionally) deleting, renaming, moving, or versioning files that the RadioMirror server is no longer transmitting.

Here is the original documentation: Thank goodness for Internet Archive's Wayback Machine!

General article explaining RadioMirror

One person's vision of RadioMirror usage

John's original article explaining the RadioMirror concept.

RadioMirror Technical Documentation

RadioMirror was created at a time when the dominant paradigm for packet radio was 1200 bps data rate and the method of getting a file was for each user that wanted the file to connect to a Bulletin Board System (BBS) and individually download the file. Doing so used up a huge amount of airtime sending the same file over and over. RadioMirror solved those issues by broadcasting files on a dedicated channel, freeing up the BBS channel for more user traffic.

To my knowlege, RadioMirror never caught on. I think it was an idea a bit ahead of its time, and the BBS paradigm was firmly entrenched in packet radio. In addition, not only did you have to dedicate a (then expensive) computer, Terminal Node Controller (TNC) and a radio, as a RadioMirror server, every RadioMirror client had to dedicate a (then expensive) computer, TNC, radio to receive RadioMirror files.

The brilliance of RadioMirror is that the files it broadcasts can be anything - images, maps, text files, codeplugs, spreadsheets... even HTML files.

I think RadioMirror could easily be reinvented to take advantage of the technology for current era.

• Computers are now cheap (for server and client). The Raspberry Pi 3+ is $35 and easily has sufficient compute power for RadioMirror server and client.
• Radios suitable for RadioMirror server are now inexpensive. Surplus land mobile radios are ideal - no fancy front panel needed, and are rugged enough for long duty cycles (continuous transmission).
• Radios suitable for RadioMirror clients are now very cheap. Either a inexpensive portable radio can be used, or a Software Defined Receiver dongle can be used.
• The TNC function that RadioMirror requires is now split between a simple audio Input/Output (I/O) interface (the modulator / demodulator in the TNC) and software such as Dire Wolf (the CPU and embedded software). I say "simple" audio I/O interface because there is no need for Push To Talk (PTT) hardware for the audio I/O interface, so the audio I/O interface can be nearly anything - as little as $8 (seach Amazon for "USB Sound Card".

What really elevates the potential of RadioMirror in this era are a combination of factors:

• There's a lot of shared information in Amateur Radio that is hard to keep in sync between individual Amateur Radio Operators. Two examples are Digital Mobile Radio (DMR) code plugs, and DMR ID/callsign tables as new Amateur Radio operators get on DMR with a new DMR ID. This is especially critical if DMR is to be used for EMCOM.
• FM repeaters now have ample unused airtime available, especially in the early morning hours.
• If a RadioMirror server is transmitting through a repeater, it can easily be scripted to only transmit during early morning hours.
• Direwolf can easily achieve speeds of 9600 bps Frequency Shift Keying (FSK), but it can also operate at 2400 and 4800 bps, which is universally usable with every radio using the microphone input and speaker output.
• Direwolf can be configured to use FX.25 - a variant of AX.25 that adds Forward Error Correction (FEC) while remaining compatible with AX.25. FX.25 wouldn't be needed if a repeater is used, but it would be highly useful if a RadioMirror server was not using a repeater.
• For example, a RadioMirror server could use Direwolf to transmit 4800 bps through a repeater. 
• For example, a RadioMirror client could also use Direwolf to receive the repeater's transmissions and be left on continuously. Voice transmissions on the repeater would be ignored (any decodes would fail the checksum).
• RadioMirror and the Raspberry Pi could be configured to save RadioMirror files to a plugged in USB flash drive. When an emergency occurs, grab the USB flash drive and go.
• Web browsers are now ubiquitous. Imagine if documentation such as a club's entire website, file directory, etc. could be distributed via RadioMirror as HTML. Just point the browser at file:///index.html in the RadioMirror client "received files" directory to view the documentation.

Lastly, to address those Amateur Radio operators who cringe in horror at the use of the word "broadcast" and immediately want to point out that "broadcasting" on Amateur Radio spectrum is prohibited... think about it. RadioMirror is a file transmission mechanicsm... just without the requirement of acknowlegements. If I wanted to transmit a series of files to another Amateur Radio operator, and that exchange took hours... that would not be considered broadcasting. RadioMirror just makes that same process much, much more efficient. Not to mention, Amateur Radio VHF / UHF spectrum has a lot... a lot... of unused channel time these days.

In summary, I consider "RadioMirror 2021" to be a "fertile area of research" for Amateur Radio.

Thanks for reading!
Steve N8GNJ in Bellingham, Washington, USA