Creating content again

I once had a site that I used for collecting information around radios and communications. I’m now recreating it here. Please stay tuned as the old articles will likely start showing up once I have had a chance to go through all the old information and figure out what’s still good and what’s old and crusty.

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SWL Logs for the week of 2021-01-02

2021-01-03 – 19:45 – Radio National da Amazonia – 11910kHz DRM

A very good music program in Poruguese broadcast using DRM (Mode B) from Parque do Rodeador, Braslia, Brasil. Heard via SDR in Santa Domingo, Dominican Republic. Nearby AM signal was causing some dropouts. Adjusting receive frequency up 0.12 kHz seemed to help. SINPO 54555

Recording of Radio National da Amazonia on 2021-01-03 on 11910kHz DRM
Recording of Radio National da Amazonia on 2021-01-03 on 11910kHz DRM

2021-01-03 – 20:50 – China Radio International – 6020kHz

A personal favorite of mine, Chinese music via AM. This program was destined to the Polish-speaking community of Europe although heard very well in Mardshegy, Hungary. There did seem to be some sort of TTY signal near the carrier that caused some interference but did not take away from the overall experience. SINPO 54555

Recording of China Radio International on 2021-01-03 on 6020kHz

2021-01-05 – 14:14 – Denge Welat – 11540kHz

Music program. Lost signal at 14:30. SINPO 35433 in Wien, Austria.

2021-01-05 – 14:40 – All India Radio – 11560kHz

Music program with what appears to be news mixed in. According to documentation I can find online, this is being transmitted from Bengaluru. SINPO 45544 in Wien, Austria.

2021-01-05 – 16:30 – China Radio International – 5970kHz

Music program with news in German. SINPO 55555 in Lutsk, Ukraine.

2021-01-05 – 16:46 – China Radio International – 6040kHz

Singing music program. Not my favorite but it was a nice program. SINPO 55555 in Lutsk, Ukraine.

2021-01-05 – 17:00 – Radio New Zealand Pacific – 9780kHz DRM

Supposed to be DRM to the Pacific Islands but I’m not getting a full lock on the signal using any of the SDRs on the [New Zealand] island. Signal looks strong with no adjacent signals. Did hear a blip of audio at the top second.

2021-01-05 – 17:10 – Radio New Zealand Pacific – 9780kHz DRM

Music and Apollo 13 BBC story. Finally found the audio! No joy using SDR in Brisbane (no signal at all) but a great signal in Hawaii (AI6VN/KH6 using 75m Beverage antenna). DRM Mode B. Really enjoy the text being sent along with the audio:

16:50 - 18:35 9780kHz
18:36 - 19:58 11690kHz

SINPO 55555 in Hawaii

2021-01-05 – 20:13 – China Radio International – 6020kHz

Traditional Chinese music. Another day of great traditional music (with Polish introductions). Tried a receiver in Poland but transmission is noisy there. Signal is very clear in Fuzesabony, Hungary. SINPO 55555.

2021-01-05 – 20:58 – Tech Note

49m band is quite crowded at his hour. Seeing 6010, 6020, and 6030 all in use simultaneously (including a DRM signal!). All signals seem to be clean and no problem with selectivity on the receiver.

2021-01-05 – 21:00 – Radio Romania International – 6030kHz DRM

French program. Tried a receiver in Hungary but SNR is too low. Showing 17.7dB in Buchen, Germany (DM7RM). SINPO 55555.

2021-01-06 – 02:30 – WRMI – 9395kHz

60s, 70s, and 80s music program. Great signal in Alexandria, Virginia. SINPO 55555.

2021-01-07 – 20:00 – China Radio International – 6020kHz

I’m really starting to like this music program beamed to Europe from China. Traditional Chinese music with very good signals. Receiver used today was a KiwiSDR in Maroshegy, Hungary. SINPO 44544.

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Starting my GridMaster after a long hiatus from the birds

Map of the United States showing grids worked using amateur satellites.
Grids worked by satellite within a 200 km circle of Newport News, Virginia.

It’s been a while since I’ve been active on the birds. So long that when I started adding my grids to the Grid Master map many of them are from paper cards! I mean, who does that now days?! Going through those cards, though, brought back a lot of good memories from the past including cobbling together gear to work AO-16 back when it spontaneously came back to life and standing in the parking lot at Dowdy-Ficklen Stadium at East Carolina University waiting for AO-51, SO-50, and AO-27 to come by. Ahh, yes, the good times.

Here we are at the beginning of December, 2020, at 8.81% of the grids filled. We’ll see what it looks like in a month.

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On the air from Charleston, SC (EM92, FM02, and FM04)

We stayed in quarantine for much of November to make the trip down to Charleston to see family we haven’t seen in more than a year. It was a small affair but good for the soul. What else is good for the soul? Satellite passes!

While in town, I tried to work every good SO-50 and ISS pass that came overhead (AO-91 still eludes me for some reason, I can’t hear myself on the downlink). Since I have been off the birds for so long, I think I made most every mistake a rookie could make. But, in less time than it takes to tie my shoe, I had corrected my problems and put stations in the log. I even roved over to Folly Beach to activate a not-quite-rare-but-still-needed grid (FM02) which is also an IOTA contact! Of course it was raining at the time and there were issues.

Eric holding an arrow antenna and portable radio
Umm, Daddy, I think the satellite is over there.

We also stopped on our way back north to snag an ISS pass in FM04. I was hoping it would be in FM15 but we didn’t leave in time and Lumberton, not Wilson, was where we crossed paths with the bird. For those of you needing FM15 and FM16, I will very likely be back “home” later in December and will be happy to give out FM15 and rove over to FM16.

This is really the first time I have been back on the birds in many years. Sure, I’ve picked up my antenna and made a few contacts here and there but I haven’t really been active during the past ten years or so. I do love anything to do with portable operations so this obviously works well for me. We’ll see if it sticks this time.

Thanks to K4KDR, WI7P, KG4AKV, N8URE, N5BO/R, N4THC, N9KT, N3CRT, and N1RCN for answering my calls. I’ve got you in the logs and you should have already received a QSL via LoTW if you do such things. If I can find my QSL cards, I shall have something in the mail to you as well.

73 for now.

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Coastal Linking Network: A thought experiment in replicating the Coastal Linking System for data.

John, KE4TZN, and I were discussing the idea of replicating the Coastal Linking System in DMR. The difference being that the existing network uses audio linking where DMR, and other digital modes, use an IP-based network for routing the links.

IP networks, not to be confused with Internet-connected networks, switch data between networks without degrading the quality of the data. Switching audio, however, results in degrading audio quality and, thus, cannot be repeated indefinitely.

The existing network

Generally speaking, the existing network uses a core analog voice repeater and other analog voice repeaters use a separate radio, a link radio, to route the repeater’s audio to that core repeater. This allows users of a repeater to send their audio across their local repeater, across the link radio, to the core repeater. The core repeater then repeats that audio to any other link radio that is listening which would then direct the audio to its repeater. This is a traditional star network. This type of network has several advantages and disadvantages, including a big disadvantage of the core repeater being a single point of failure.

One benefit of the existing links, that will become apparent shortly, is using a frequency of 440MHz and a bandwidth of 15kHz.

Replicating the network

The first plan was to try to replicate the existing star network layout.

The network has connections from Columbia to:

  • Ahoskie
  • Bath
  • Buxton
  • Elizabeth City
  • Englehard
  • Greenville
  • Hertford
  • Williamston

All sites could be connected to Columbia except Buxton and Greenville. Buxton, being a high priority when hurricanes threaten, absolutely needs a good connection back to the mainland. Greenville is also a target city as there are resources there that would be good to link to, including the regional trauma center.

Because we don’t have to worry about degrading our audio (it’s all data after all), we can daisy-chain links together to create paths to more distant locations. Buxton, not reachable directly from Columbia, becomes connected via the Englehard site. Greenville also joins the network but through Williamston.

A bonus to using a routed network is we’re no longer required to stick with that star configuration. You’ll notice a lot of links (lines) on the map that don’t connect back to the Columbia site. These links not only relieve the stress on the Columbia site handling all of the traffic on the network but also provides alternate routes for the traffic to flow. In an IP network, these links are constantly being weighed to determine the lowest cost path for moving data from one point to another. If data is moving between Buxton and Bodie Island, two hops, there is no reason to send it via Columbia (three hops). However, if one of the links between Buxton and Bodie Island is congested or has failed, the data can flow through Englehard and Columbia to route around the issue. These changes in routing happen automatically.

Headaches with the design

The difference between amateur radio, and basically any other radio service, is that amateur radio systems (and networks are no different) are generally built where it can be built where commercial and public safety systems are built to satisfy a specific need. If you were to overlay the North Carolina Highway Patrol’s microwave network on top of what I have laid out you would see that we aren’t using half the sites they use. You’ll also see that they use multiple altitudes and frequencies at each site to make sure their statewide network stays up and operational. They have a slightly larger budget that I (we) do.

Another issue is that all of these links are currently setup with 5GHz in mind. There are other bands available to amateur radio operators including a nice, quiet piece of spectrum in the 3GHz area that could be used. Using other bands might improve bandwidth and throughput.

The Greenville site being used in this model is actually the NC Highway Patrol tower that we currently don’t have permission to use. Of course we don’t have permission to hang any of this new gear on any tower so why not shoot for the Moon and ask for it all, right?

The frequencies we’re talking about using attenuate significantly in air. Add moisture and we’re talking about the possibility of a link dropping. Hopefully any link degradation would likely mean a reduction in available bandwidth and not a complete link failure.

The last issue I had was trying to remove the star configuration, and somewhat failed to do. I ended up with two segments of the network that still need the Columbia site to connect to each other. The two segments generally break down to the “Beach” sites (Bodie Island, Buxton, Chicamacomico, Englehard, and Ocracoke) and the mainland sites.

So I have a network, now what am I supposed to do with it?

Well, the original idea was to have an independent network that would replicate the Coastal Linking System but for DMR. We can easily connect our DMR repeaters to this network and use it for backhaul to connect them to a regional c-Bridge-like device that would provide the connectivity to all repeaters on the network and also route traffic off the network to other DMR networks (Brandmeister, DMRVA, etc) to get access to outside networks. The required bandwidth for DMR is miniscule compared to the bandwidth that will be available on the links.

It would also be possible for DMR users that have their own hotspot devices to connect them directly to the c-Bridge-like device over the IP network and get access to the repeaters in the region.

There are also ways to connect analog repeaters together using this isolated IP-network. AllStar is one system that allows you to create your own network with their software, thus linking analog repeaters across the IP network.

APRS can also be used over the IP network. If all the IGates in the region were connected with an APRS server that was on the network, any messages and position reports could be routed to all other users that were also connected to the network (either on the IP network or in the area of the IGate that was).

Servers supporting email, webpages, keyboard and video chat, and file exchanges can also be put on the network much like packet radio BBSs used to be setup. Heck, if you wanted to stand up BBSs for users to connect to using traditional packet radio, the BBSs could connect to each other over the IP network and send and receive messages and bulletins using telnet.

The idea is, it’s all just data. The network doesn’t really care what the data is, it just wants to know where it’s going.

How do users connect?

So far we’ve only been talking about building the wide area network (WAN) that connects towns and cities together. This is not the network that users, or even servers and devices, interface with.

A simple view of a LAN in Greenville.

To do that, we’ll need to build out a local area network (LAN) or, maybe even a metropolitan area network (MAN) that will handle data going between users and between users and local resources.

In the image we see the city of Greenville with a light blue sector shaded in representing a LAN. We also see some example links established within that sector representing the Brody School of Medicine building, Pitt Community College, and a ham radio operator’s home. The idea of the LAN is that anywhere in that blue area you should be able to connect to the local network and use it to connect to whatever resources you may need whether that be a web server, a file server, or a chat room. And that server may be located in a server room at Brody, in someone’s home that is on the LAN, or on a server in Buxton.

LAN bandwidth can be much greater, supporting many more users, than that of the WAN so it would be best to have certain resources replicated locally wherever many users will be accessing the information. The WAN can be used to synchronize data between servers where speed isn’t a factor leaving a faster experience for the user.

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