KD0TLS: Comparing the Microsat TNC to the Mobilinkd TNC

  To some extent, this is an unfair comparison because the two devices are aimed at different niches. So, I'll state that at the outset, while pointing out that the comparison could be useful to an operator using one of the two and considering a change. 

 The Mobilinkd TNC4 is the only model currently available; the older (and less expensive) models are out of production permanently. At $150, the price point is virtually identical to what you would pay for a Microsat WX3in1 Plus 2.0 with shipping from Poland. In both cases, you would need to buy/make a cable to connect a radio to the device. 

 Strictly speaking, the TNC4 is a modem rather than a TNC. It must be connected over Bluetooth to another 'computer' (a smart-phone, tablet, laptop, etc.) to actually do anything useful. And that 'computer' must be running an APRS client (APRSDroid, YAAC, APRX, APRSIS32, UI-View, etc.) if you want to send or receive packets. 

 Mobilinkd Bluetooth issues

 Using Bluetooth (BT) is both a blessing and a curse for the TNC4. It eliminates the need for a cable to run into the computing device -- which in some cases, is not even practical. For example, I can just hop in my car and start up APRSDroid on my phone, and the TNC4 will instantly connect and start showing me traffic. The only cabling I need to fumble with is the USB power cable that keeps my phone charged, because BT and GPS draw more power than my phone would normally use. But Bluetooth has been the cause of the majority of issues I've had with the TNC4. As BT devices multiply, and as BT itself becomes more complex, connecting to the TNC4 becomes an irritating challenge more than a nifty convenience. With patience, these issues can be resolved, but support for BT issues is non-existent on the Mobilinkd forum. The 'support' tends to take an annoyed tone and assumes you are an idiot. Overall, Mobilinkd doesn't see this as their problem; it's seen as an issue with the device you are trying to connect to, rather than an issue with their product. 

 For example, I used various Mobilinkd models over the years on my KD0TLS-1 TX gateway. Then one day I noticed that the gateway had stopped functioning, with the issue being that the Mobilinkd TNC4 no longer connected to the tablet running the APRS client (and thus, the gateway). The TNC4 was paired, but did not connect. I was pointed to the instructions, which explained how to pair the device, but that wasn't the problem. Deleting and re-pairing the TNC4 did nothing to make it actually connect, and the 'support' became increasingly obtuse. After several months of frustration, I discovered that the solution was to delete and re-create the BT port on the APRSIS32 client. I still don't understand why that was necessary, because the new BT port was set up exactly the same as the old one. 

 Ultimately, it was the continuing issues with Bluetooth that prompted me to abandon the Mobilinkd devices on my home gateway, and limit my use to mobile operation only. Also, though Mobilinkd claims the TNC4 will work with iOS devices, I was unable to get mine to pair with someone's iPhone. 

 For others, I found that BT was also an annoyance but problems with the audio levels made the TNC4 unusable. In these cases, operators had connected the TNC4 to an HT, unaware that changing the volume level of the HT would alter the painstakingly-set input level to the TNC4. In practical terms, using the TNC4 requires a dedicated radio, because any adjustment of the radio's volume will render it incapable of receiving packets. One possible work-around is to use a radio that changes volume in steps, rather than one that is continuously variable. For example, The BaoFeng HTs operate this way. One must remember the volume step (e.g. 4) that the TNC4 was first set up to use, and that particular volume step must be be used when operating on APRS. 

 I should also note that changing between different radios will require a complete re-adjustment of both the TX and RX audio levels, and this process must be done through an Android  or Apple device only using the configuration app. Changing the TX audio level also requires a separate monitor radio, and the level of each of the two tones must be adjusted individually for best results. 

 So... using the Mobilinkd TNC4 requires a certain commitment. Any operator probably needs a dedicated radio where the volume never changes, an Android/iOS device to set the audio levels, and must consistently use the same device (phone, tablet, laptop, etc.) to connect to the TNC4 every time to avoid pairing/connection issues. 

 Advantages of the TNC4: 

• It's very small (about the size of a matchbox), and it can be easily strapped to an HT for portable operation. Mobilinkd even sells a Velcro strap for this purpose. 

• It's battery-powered, and the internal battery lasts two days on a full charge. This assumes, of course, that it remains paired continually for two days. If it's not paired, it uses about eight times the juice as it searches for another device. So, if you wander out of BT range with your paired phone, you'll want to turn the TNC4 off to save the battery life. It also charges with a USB cable, so no specialty/proprietary charger is needed. 

• Open-source software, so you can tweak and modify the device's to (in theory) make it function as a digipeater or operate on M17 packet mode. You are, of course, on your own when it comes to making these changes. 

• Uses BT to avoid cabling and connection compatibility issues. The radio and TNC4 can be placed out of reach (e.g. the trunk of a car), while the driver uses a smart-phone to send and receive packets. 

• The TNC4 can be configured to shut off when DC is no longer applied, and turn on when DC 5v is restored. This makes it great for vehicle use, as the device shuts down when you park your car, and turns on when you start it up. 

• Can operate with either a squelched or un-squelched radio. For un-squelched operation, the TNC4 can be set to detect digital signals. 

• Has a TXCO, which means it can (in theory) be used for 9600 bps operation. Whether the radio it is connected to can perform that task is the deeper question. In most cases, the answer is negative.

 Disadvantages of the TNC4: 

• Actual use is dramatically limited by the APRS client used. The TNC4 is just a modem. If you are using APRSDroid, you won't be able to create and maintain objects, bulletins, announcements, etc. for example. Beacon rate, comment text, and location are all determined by the client used, or the GPS on the 'computing device' the TNC4 is connected to over BT. There is no capacity to connect to an external GPS, for example.

• BT is painfully slow, making the TNC4 a poor choice for a gateway or digipeater -- unless it is the only one in the vicinity. Other infrastructure will beat it to the punch every time when gating/digipeating traffic. 

• No NTP time correction, unless that is done on the 'computing device' you connect to over BT. 

• No auto-level adjustment for audio levels. 

• Requires a separate 'computing device', which demands more battery power from that device for GPS, BT, or wi-fi. While the TNC4 may be able to operate for two days straight, that does little good if your 'computing device' runs out of power before that. 

• Basically designed for short-term operation, such a commute or field op. 

 Microsat WX3in1 Plus 2.0 

 The Microsat TNC is much larger than the Mobilinkd TNC4. It won't fit in your pocket, but it weighs virtually nothing. A Windows device is required for initial configuration, and a standard printer cable is used to connect it. The need for a Windows laptop/tablet is perhaps the biggest disadvantage of the Microsat TNC, though it only needs to be configured once. 

 Being completely self-contained with an embedded operating system, the Microsat TNC doesn't need a separate laptop, phone, tablet, etc. to start operating immediately after configuration. Once connected to a radio, it can act as a digipeater without the need for an internet connection. This is what makes it so nice for remote stations. An operator just needs to supply power for the radio and TNC, an antenna for the radio, and a cable to connect the radio to the TNC -- and a digipeater is born. 

 Since it's self-contained, the Microsat TNC, can send bulletins on regular intervals. If it has an internet connection, you can choose between -IS or RF transmission  (or both). It can also send STATUS text (over -IS or RF), create and maintain APRS objects (something APRSDroid can't do), and you can create beacon IDs at a set rate over RF or -IS (or both). 

 The Microsat TNC is geared for fixed-station use: a home APRS station, a digipeater, or a gateway. Adding an external GPS module ($50 plus shipping), and configuring the TNC to use GPS data rather than a fixed location, means that the Microsat TNC can also be used for mobile operation. It even has SmartBeaconing and Mic-E operation available to configure. 

 Another drawback is that the Microsat TNC uses ethernet for an internet connection. But there are many "wi-fi extenders" available that will allow you to plug the Microsat into it with CAT5 and use wi-fi to provide the internet connection. I bought this particular model, and I have no idea if it's the best or cheapest. It does, in fact, work. For field operation, a portable gateway could be set up using a mobile phone as a wi-fi hotspot, and it could also act as a "smart" digipeater. Another option would be to set up a gateway/digi in a garage, and use the home wi-fi to connect to the -IS. 

 I've used the Microsat TNC as a home gateway for a couple of months now, and it's been a delight. I ordered a Kenwood-style cable, and plugged the TNC into a PuXing PX-777 VHF monoband HT. The HT was powered by a "battery eliminator" for 24/7 use. The Microsat itself uses a typical wall-wart 12v supply, and draws very little current. Plugging the HT into an indoor antenna, and plugging the ethernet jack into my home router meant that I had an instant gateway/digi after the TNC was in initially configured. 

 Ethernet aside, the whole thing could have run on a solar panel connected to a 12v LiON battery for digipeater operation in emergencies. And the digipeater function can be configured to only kick in when the internet connection is lost (e.g. in a power outage when the router is down). 

 Perhaps best of all, the Microsat WX3in1 Plus 2.0 has auto-level for the audio. I had no level adjustments (unlike the Mobilinkd TNC4), and I changed the volume level on the HT in disbelief. To my complete surprise, the Microsat continued to operate the same as before. Neither RX nor TX required the slightest adjustments. 

 Issues with the Microsat TNC: 

 I did have three issues setting the TNC up, and they were all due to my own mistakes. 

• Setting the lat/long co-ordinates of my home station. I took the co-ordinates from aprs.fi, unaware that I had years ago set my aprs.fi account to show decimal degrees, rather than the "APRS format". This placed my station near Rockford. It took a close reading of the manual to see my mistake, and I simply re-configured the TNC with co-ordinates in the correct format. If you have an existing home station, the best bet is to look at the raw packets for that station to get the correct info. 

• Set the RX of the TNC to squelched operation, while leaving the HT un-squelched. This meant that the TNC believed the channel was always busy, and it would not TX. A simple change of the drop-down menu, and re-loading the config resolved the issue. 

• I was unable to pair the Bluetooth module at first, because I failed to read the instructions completely. Rather than a standard PIN (e.g. 1234), the BT module has a non-standard PIN placed on the label of the BT module near its connection to the TNC. Microsat support responded to my query the very next day, and I felt kind of stupid. 

 So... these were pretty minor issues, all in all. 

 Aside from adding your callsign, passcode, co-ordinates, N-path, and beacon text, the defaults are pretty good. I experimented with the beacon text fields, and discovered that I could send objects and maintain them at a set interval. Along with that, the beacon text allowed me to set up bulletins on a regular interval. It's even possible to send an APRS message on a fixed schedule (e.g. "Good morning!" to a friend or relative) every 24 hours. 

 Disadvantages of the Microsat TNC 

• No display. There are lights that flash to indicate a packet heard over RF, or a connection to the -IS server being made, or a properly-configured packet being detected, or a packet sent over RF. But there's no map, no display of raw packet traffic heard, and you can't view messages received. 

• No interface to send messages, and no notification of received messages. To be fair, this may be possible using some of the other functionality (e.g. simple server), but I have not puzzled that out yet. AFAICT, a second station would be needed for this kind of operation. 

• No internal battery. In addition, the 12vdc requirement means that 5vdc "power packs" can't be used. The TNC can actually be operated with a supply voltage between 9 and 16, however. 

• Ethernet jack means another solution is required to connect to wi-fi. Otherwise, placement is limited to areas of your home with an ethernet jack. 

• Embedded OS means little tinkering "under the hood' is possible, unlike open-source solutions. 

• Windows device needed to configure. 

• APRS only -- no "straight packet" or M17 mode. 

• No capability stats transmitted that describe how many stations have been heard, or how far away they are.

 Advantages of the Microsat TNC: 

• Allows native Mic-E, even if your radio doesn't support it. 

• Rock-solid reliability. No reboots for Windows updates, flaky BT connections, or a PC simply "freezing" after running for a week or so non-stop. It runs forever, basically.

• Great compatibility with weather stations, though an additional interface may be required in some cases. 

• A gateway can be configured to act as a digipeater-only station if the connection to the -IS servers goes down. Big EmComm selling point here. 

• Very flexible settings for most functions. It can operate as an RX-only gateway, a hybrid TX gateway/digi, or as a standalone digipeater. N-paths, beacon intervals, callsign filters, area filters, etc. 

• Can, in theory, operate using 9.6k. The radio itself is the real limiting factor, however, for this kind of operation. 

• No audio level adjustments needed. The radio can be easily swapped out between home, mobile, field, or portable operation seamlessly -- as long as the proper cable to the radio is at hand. 

• Has two mounting holes in the base for permanent attachment, but it's light enough that it could simply be taped on to a mast or other object for short-term use. 

• Excellent decoding ability, tested against transparent standards. No anecdotes or inflated assertions used to describe the capability of the unit. 

• If ethernet or wi-fi is used to connect to the servers, the Microsat TNC is fast enough to gate packets and confirm duplicates while the Mobilinkd's BT connection is still just thinking about it. The only real limitation is the speed (ping and latency) of your internet connection. 

• The Microsat has NTP ability to keep the clock accurate if the internet is available. A typical quartz clock varies 3-4 minutes a year, causing problems with digipeaters handling packets in the future or the past. In both cases, these packets will almost always be ignored by the network. This is most common with remote digipeaters. 

• No computer needed. It just works on its own.

 Summary 

 If you looking to set up a home digipeater/gateway, a solar-powered digi at a cabin, a field digi at an event (e.g. marathon or bike race), or just want a station to maintain repeater objects, bulletins, and announcements for the amateur community, the Microsat WX3in1 Plus 2.0 is the option you want to explore first. 

 If you want a simple mobile station that runs off your cell-phone and allows messaging, then the Mobilinkd TNC4 is the suitable choice -- if you don't swap radios frequently or change the volume level on a dedicated mobile rig.