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8

A summary of requirements: Licensing: Technician - very minimal requirements Equipment: Transceiver, Terminal Node Controller and terminal Transceiver - traditionally a VHF/UHF FM radio Terminal Node Controller - Partly a modem, partly an AX.25 layer manager Terminal - Any serial terminal will do, but most likely you will use a personal computer A ...


8

Coverage maps are a thing that is notoriously difficult to do right. There are some very complex programs (Radio Mobile is the one I know the most about) which can generate coverage maps if you're prepared to wade through the technical details and the quirks of the software. Unfortunately it's not as easy as drawing a circle of a certain size around each ...


8

That's a good question---and one that is heavily under debate currently. The FCC originally limited symbol rates as a way of limiting bandwidth for data modes indirectly (it made sense at the time). But now that there are more advanced modulations (like the various forms of phase shift keying) that can exceed the symbol rate limitations in less bandwidth ...


7

You could tune to 144.390 FM on a 2m rig and see if you can pick up some APRS. This would require some software to decode packets (such as arpx for Linux). Just make sure you're not setting yourself up as a Digipeater until you find out what the network structure is in your area and whether there is a requirement at all. National APRS frequencies: You ...


6

If you're used to dealing with protocols between chips, like UART, SPI and I2C, then APRS will feel quite strange. Whereas if you've been involved with CAN, Ethernet, USB at the low level, then APRS will seem quite familiar. It's not as simple as 1200Hz means 0, and 2200Hz means 1. There are two things which make it different, firstly bit-stuffing, and ...


6

Audio which sounds perfectly fine can be noisy or distorted (notably, by FM deemphasis) enough to prevent digital decoding. At a minimum, you should get rid of the microphone step and feed your audio directly into the demodulator program. You don't say what OS you're using, but I have had success demodulating APRS messages using multimon-ng. It can be set ...


5

Actually, current specifications encourage or require digipeaters to add their callsigns to the WIDEn-N path, since including callsigns greatly helps in finding and fixing all sorts of network issues (look for "traceable" in the page). WIDE1-1 is often replaced by the callsign of a dumb digipeater, WIDE2-1 is usually prepended by the callsign of a digipeater....


5

While 1200 baud packet radio uses AFSK with 1200 and 2200 tones, they don't correspond with digital 1's and 0's directly. It employs NRZI encoding as well as bit stuffing. Non-return to zero inverted (NRZI) means that a 0 is encoded as a change in tone, and a 1 is encoded as no change in tone. This depends on having an accurate clock on both ends. But even ...


5

If by "packet radio" you mean the common AX.25 kind used by APRS for example, you can probably forget about it. Otherwise you'll need to use HF, and also find an appropriate mode since there's nothing quite like packet on HF which works reasonably well. A VHF or higher direct link will be difficult. The radio horizon in miles of an antenna at height h feet ...


5

I've put together something that is conceptually similar to @user3486184's comment, but without actually using chroot. I'm taking advantage of SystemD to manage both direwolf and the subsequent kissattach command necessary to activate an ax.25 interface. I created the following Systemd template unit and installed it into /etc/systemd/system/direwolf@....


4

A Technician Class license or better is required. What equipment you need very much depends on the solution or solutions you pursue. There exist well-baked schemes for creating relatively long distance vhf/uhf ham-radio-exclusive networks where radios are used to tie stations together over short range, and then many hops are used to pass traffic across ...


4

As far as I know, none of that series "speaks" APRS by itself, so you'd need your external controller to generated the AFSK tones. Whilst it's possible to generate AFSK at such low rates with an arduino or the like – wouldn't a simple "proper" computer like a raspberry pi or so not be the better choice here? You could basically run any ham software for ...


4

In absence of a clear indication of what Amateur Radio band is being targeted here, an answer for the 13 cm band: You can use 802.11g/OFDM with a 20MHz bandwidth on 2400-2450 MHz Amateur band. You could even modify existing/consumer Wifi equipment to do so. This would give you a (theoretical) 54 Mbits/sec throughput. Obviously you need to check that you ...


3

In the end I used 'amodem' ( see https://github.com/romanz/amodem ). After a few calibration steps, I could get decent I/O rates - considering the nature of the medium. Compression of archives is necessary, and may be considered unethical. But the compression algorithms (e.g. 7zip, xz) are public, and anyone paying attention can read the data. Rates of >=...


3

The easiest way now is to get the Btech APRS-K2 Cable: it allows you to receive and send audio to the radio with a single cable. You can use it with the aprs.fi app or with a variety of software from a computer.


3

I think you're barking up the wrong tree preparing for the possible dystopian future. If the internet is unavailable, short-term or long-term, generally the need is to communicate as widely as circumstances allow to get emergency messages in and out. In times like that, I'd think that you'd want to be able to talk to anybody who can still get on the air. ...


3

IMAP is a protocol for transferring email, nothing more, nothing less. It typically uses TCP/IP as the underlying protocol, but it could be routed over something else (like packet radio). If you wanted to, you could configure TCP/IP over AX.25 but I don't know if anyone else is doing it, so you'd probably need to run your own mailserver on the other end as ...


3

I didn't see anything in the manual that would indicate the MFJ 1270B would support packet BBS natively. You would need some external hardware to do that. You can find a scan of the manual online here: http://www.repeater-builder.com/mfj/pdfs/mfj-1270b-tnc-manual.pdf According to that doc, the STA LED "is normally low and goes high only when this TNC has ...


3

The Colorado Council of Amateur Radio Clubs (CCARC) 2 Meter Frequency Use Plan states that 144.900 - 145.100 MHZ should be used for Packet communications. 144.390 MHZ is also used Nationwide for APRS. Colorado Council of Amateur Radio Clubs (CCARC) 2 Meter Frequency Use Plan - 144.000 through 148.000 MHz Frequency (MHz) Usage 144.000 - 144....


3

The APRS system and protocol itself doesn't track iGate type or frequency. There is a list of active iGates, but there is no frequency information for them, or for the packets they receive. Further no one appears to maintain a database of such stations. However those that have used it indicate that the coverage is good enough that you really don't need to ...


3

Xastir isn't bad at all but I recently encountered something called YAAC (Yet Another APRS Client). On it's site it states the following: YAAC can be used as a stand-alone APRS client, an APRS RF-Internet gateway (I-Gate), or as a AX.25 digipeater. It supports 16 different data reporting views as delivered, and can be extended with user-written "...


3

Assuming that you have: correctly connected your Baofeng to the TNC installed the AX25-tools and AX25-apps configured /etc/ax25/axports with your call and the baud rate attached the serial port to the AX.25 system using kissattach then you may first want to listen for AX25 traffic on that frequency by typing: sudo axlisten –a Finally, you can connect to ...


2

RX audio: The FT-7900R has separate audio outputs for RX audio on the DIN connector for 1200 and 9600, so those can be simply wired to the two separate KPC-9612+ ports. PTT: The PTT line has a little voltage provided by the radio, and the TNC's PTT pin grounds that pin to transmit. You can directly wire both TNC port PTTs to the radio, and it'll transmit ...


2

Karl Medcalf, WK5M, of Kantronics, has published a paper titled Multi-Drop KISS operation for ARRL CNC v10 conference (San Jose, California, 1991). That document was distributed as a PostScript file, at some point a copy was in the source code of the Linux ax25-tools, in the doc directory. It seemed a bit hard to find an URL for the file now, so I ran it ...


2

Have a look at the IARU Region 2 Band Plan. Most of the frequencies marked "all modes" or "DM" (digital mode) may be used for packet radio, although there does not seem to be a single designated packet calling frequency. Normally a packet radio frequency is coordinated between operators in the area, since one frequency can be shared by several TNCs. In ...


2

Just a suggestion, but have you considered the possibility of it being an SSTV transmission? I would download an SSTV decoder and run it through that, using various encoding methods (e.g. Robot32, PD180, etc.) and see what you get.


2

145.010 was the "primary" packet frequency in the 90's Lee N4TCW


2

I recommend against using the modern inexpensive HT radios for packet, especially if you are buying the equipment on purpose for that application. You'd be much better off with 30 year old used ham radio mobile gear, with more power, more selective receiver, more predictable operation, easier UI, and less RF into your digital equipment, easier connections, ...


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