Showing posts with label aprs. Show all posts
Showing posts with label aprs. Show all posts

Saturday, January 26, 2019

Mobilinkd interface with TM-942A / Shack

A while back I bought the excellent Mobilinkd TNC - a device that interfaces amateur radio with smartphones and PCs via Bluetooth.  There are a ton of useful applications for this, not the least of which is being able to place my radio where I want it, and not be cable-tethered to it.  I've used the Mobilinkd TNC with a Kenwood TH-F6A as a mobile device, and that worked very well - I can leave my radio and the TNC in my backpack and type messages on my smartphone.  If I'm doing something mobile/portable like parade/race support, I put the radio/TNC and a battery pack up where it can get good reception and use my smartphone or PC as the interface - as long as I'm in Bluetooth range, I'm good. 

I've long been a fan of the old Kenwood TM-742A and TM-942A tri-band mobile radios.  I own several of them, and have become fairly well-versed in the art and science of repairing them.  I've always been curious about a somewhat unique feature of the radio, which is the Receive Data (RD) line on the microphone 8P8C connector - it's a direct feed of the receiver audio intended for packet radio that bypasses the final audio shaping/amplification stage, with a 100 mV pk-pk signal across a 10k load. 

I run a TM-942A (which is just a TM-742A with the 1.2 GHz band module in third slot) in my shack, which is interfaced to an MFJ-1263 microphone switch.  I thought it would be interesting to wire the Mobilinkd into the MFJ-1263 switch, so I could use the TM-942A for audio or APRS/packet at the flick of a switch.  The RD line makes this really simple to wire up.  Critical for APRS/packet applications, the RD line is tapped off before the squelch and CTCSS circuits - so I can monitor the audio for debug, or mute it as needed, without having to worry if the squelch and CTCSS settings are screwing with the RD line.  (Of course, this requires me to run DCD on the TNC software, otherwise it will never transmit while it sees the channel as "busy".)  Volume control also has no effect. 

I started off by ensuring that the MFJ-1263 was jumpered properly to bring the TM-942A connector out to the switch's front panel 8P8C jack without re-ordering the pins.  I put this onto the switch's A-side, and left my voice microphone on the B-side.  I had previously built a 3.5mm (1/8th inch) TRRS cable with breadboard pins soldered to the ends for my test kit.  I also have an 8P8C breakout board in my test kit.  Both pieces were jumpered together on a small breadboard.  Once I had the wiring confirmed, I made the cable permanent.  It might sound like overkill to proceed this way, but the TM-942A's microphone jack also has an 8 VDC (@ 100 mA) voltage source, and I wanted to make sure I wasn't injecting a voltage into my TNC. 

I'm really happy with this set up - I can use the Mobilinkd TNC at home, or take it mobile by simply unplugging the TRRS connector and USB power cable.  My Mobilinkd stays charged via USB when it's in the home configuration.  My only gripe is that the Receive Data line from the TM-742A is a fixed level which is slightly lower than the Mobilinkd's software wants to see, but it doesn't appear to be affecting decode on APRS. 

Tuesday, January 20, 2009

Looking forward...


With 2008 officially behind us I've spent the last few weeks (as I'm sure many did) contemplating where we've been and where we're going. There seems to be a pervasive sense of relief, some trepidation about what 2009 might bring, but also a growing sense of hope that we're leaving behind a lot of baggage and moving into a period of revitalization and renewal. I believe that it's human nature to think that the troubles of today are unusual, unprecedented, and thus we long for days of old when "life was simpler". The reality is that in each generation there occurs a crisis of some sort that must be addressed. As the saying goes, "This too shall pass". Fortune, bad or good, is a fleeting thing. Our forefathers struggled, we struggle, and I guarantee our children will struggle. In between these struggles are periods of great happiness, and periods relative calm which often pass by almost unnoticed. From an amateur radio perspective I think 2008 will be remembered as a period of struggle, and hopefully in hindsight will be seen as a time when things began to change.

Amateur radio struggled during 2008. We ended the year with the lowest number of sunspots since the early 1900's. The sun's been so quiet for so long that any time the sunspot number isn't zero, or the solar flux index climbs over 70, everyone gets excited. The quiet surface of our sun was echoed in many ways throughout amateur radio. At the 2008 Dayton Hamvention (and smaller events such as Pacificon 2008) equipment manufacturers offered almost nothing new. In some cases popular equipment such as the Kenwood TH-D7A APRS handheld was suddenly discontinued. (It's speculated that certain parts in the TH-D7A were not ROHS-compliant and Kenwood couldn't get drop-in replacements.) It's worth noting that two of the biggest product offerings of 2008 were the Icom's IC-7200 HF transceiver, and Yaesu's VX-8R quad-band APRS handheld. The IC-7200 has "new" features such as (drum roll please) a USB port for audio I/O and control! How innovative! (I'm being sarcastic.) The VX-8R was shown at Dayton in early 2008 but wasn't actually shipped to customers until mid-December. It contains cutting-edge features such as APRS - which works if you buy their "GPS-Mic" which is insanely large and quite expensive. How is it that my Blackberry Curve can feature a high-contrast LCD display, QWERTY keyboard, battery, multi-band voice/data radio and a GPS in a housing that fits in my hand, but Yaesu needs that much room just to house a microphone and GPS? To add insult to injury; I had an on-the-air QSO with KI6CRL once he finally received his VX-8R after several months on a waiting list -- and it turns out it's got a thermal problem where his transmit audio level drops to nothing as the radio gets hot. This is the hot (no pun intended) new product people waited almost a year to buy?

Perhaps the Japanese manufacturers simply observe that amateur radio is struggling to grab the attention of younger people and believe that it's therefore not capable of producing a good return on investment. I would say that this is both a correct and incorrect observation. It's correct that in its current state amateur radio is largely unattractive to younger people. It's incorrect in that it doesn't take into account the concept of "making a market"; more on this later.

Why are young people not getting into amateur radio? It's not because it's technically challenging; you need only look at the surging popularity of the Maker Movement to know that technical innovation is alive and well among the younger generation. The fact of the matter is that it's our own Luddite mindset that's at fault: It's hard to recruit younger people into a hobby where the equipment manufacturers have only just this year discovered that USB is a viable interface option! I once watched a guy at Ham Radio Outlet whine for five minutes about how hard it was to get RAM modules for his 486 laptop; and amazingly he was finding a sympathetic audience. (By the way this happened in 2006, not 1996.) I was once chastized in an online discussion group for promoting the proliferation of APRS iGates; devices that route packet radio traffic onto the Internet -- my detractor stated that he felt "anything which blurred the lines between ham radio and the Internet" was a bad idea. Finding ways to revitalize older technology with the most pervasive technical revolution since the telephone is a bad idea? Give (unto) me a break.

Even when amateurs use computing they often miss the point. Many people who use APRS are still using the DOS version. One of the most popular APRS applications is UI-View32; the author of which (G4IDE) has been dead for several years -- and specifically asked that upon his death the source-code be destroyed rather than be placed into the public domain as an Open-Source project. How about despite the fact that it's marketed as a stand-alone APRS/packet solution Kenwood continues to build its TM-D710A without a USB or even a PS/2 keyboard jack. Simply put: Amateur Radio can't reach a younger audience until it integrates modern technologies and embraces development/collaboration concepts such as Open Source that younger people associate with "good technology".

You might be saying, "So what? Who cares if we fail to attract and retain younger people into amateur radio?" The answer is simply; we stand to lose everything. The current mood in Washington DC is already somewhat negative towards the FCC; there have even been calls for Obama to dismantle the FCC and implement a new innovation-centric technology governance model. Amateur radio is nothing without our spectrum allocations, and given how we're not really using the spectrum we have it's likely that under the new FCC leadership we'll lose some spectrum in the coming years; someone's going to have to pay back that $700 billion bailout and spectrum leases can be auctioned off to raise cash. As time progresses the incoming FCC leadership is going to be increasingly younger, and likely resistant to the idea of leaving large swaths of potentially cash-generating spectrum in the hands of older amateurs who insist on using out-dated computing technology that increasingly doesn't integrate with modern systems.

So how can we solve this problem? How can amateurs help "make a market" and create a potential for vendors to recoup long-term return on their engineering investment? First and foremost we have got to actively embrace modern computing technology, Maker-style hardware re-purposing concepts, and an Open Source licensing model for software and firmware. This means that:
  • All amateur radios going forward should have USB ports, and if appropriate should support USB host-mode.
  • I should be able to plug my HF transceiver or my handheld into my laptop and control it or configure it over USB.
  • I should be able to plug a keyboard into my TNC-capable rig and type text without a computer.
  • Rather than a proprietary interface, and a proprietary configuration app, all amateur radios should contain an on-board web browser (just like a $30 Linksys router does) running from an embedded controller and an Ethernet jack. I should be able to connect the radio to my LAN, and ideally I should be able to plug in a USB Wi-Fi dongle and attach to the radio wirelessly.
  • The embedded controller should be some kind of standard (ARM-core, etc) and the operating system firmware should be Open Source and modifiable; picture OpenWRT or some variant.
We must start doing this now, or by the time we realize our mistake it will be too late. I firmly believe that a radical departure from our current mindset is the only way to move amateur radio forward.

Friday, September 19, 2008

Where's David?


Been a while since I posted. Most of the summer was spent doing various projects; some for pay and some for fun. One of my new interests is APRS - Automated Packet Reporting System. It started when a ham friend of mine decided to hike the John Muir Trail and wanted me to keep in touch with him and his girlfriend as they hiked. He carried a Kenwood TH-D7A(G) APRS handheld; so I decided that I would set up APRS to track him.

In the process of doing this I learned a lot about APRS and the mechanics of routing packets through RF. I set up an "I-Gate" which is a system that passes received RF packets into the APRS servers via the Internet. Turns out this was quite useful to some local hams that carried Kenwood TH-D7A(G) APRS handhelds which could not normally reach the mountain-top APRS repeaters aka "digipeaters". So now my station's running 24/7; not great for keeping the electric bill small but I guess that's why I have a 3 KW solar PV array on my roof, yeah?

In exploring APRS I learned that when it comes to digipeaters "more" is not necessarily equated to "better". RF packet is about passing packets to the target (or targets) with little (or ideally no) redundancy. For the most part we enjoy a great VHF environment here in the Bay Area; the Silicon Valley is ringed by mountain ranges which provide line-of-sight at nearly any time to at least one of the wide-area digipeaters. Any additional digipeaters are redundant and therefore create extra packet traffic. (The exception to this is of course low-level/low-power "fill-in digipeaters" designed to serve small pocket valleys, urban canyons, etc.) With a dense population and a lot of hams using APRS it's a constant battle to keep the 144.390 MHz APRS channel from becoming too crowded. I-Gates don't contribute to the crowding problem; that is if they're set up as receive-only I-Gates.

I'm having a good time with APRS; besides just being able to track locations I've also been exploring how it can be used for text communication; I had a nice QSO with YB2TJV in Indonesia recently. It's also proving useful to study VHF propogation in the area. I have no idea why my callsign was used by OH7LZB as an example in his blog post on the new I-Gate coverage function on aprs.fi; but I was flattered anyway!

I'll be hosting a forum on APRS at Pacificon 2008 which runs from October 17th - 19th in San Bruno, CA. My forum is scheduled for 8:00am Sunday the 19th; if you're in town please do come by and say hi!