51TNC, review of this multipurpose APRS TNC


2014 12 11 13 46 16


Hi, today I will be doing a very short review about the mystical 51TNC APRS-box which is made in China.   Just add ingredients such as proper data-cable + HT/Rig and you can  turn it into iGate/Digipeater/Tracker or even WX-Station.  

51TNC-box comes with the following set: 

  • 51TNC-box
  • PSU (without the adapter thought)
  • TTL to USB serial Interface
  • RJ45 network-cable
  • Yaesu/Kenwood compatible 6-pin data cable
  • 51TNC-box should also be equipped with bluetooth (for ie aprsdroid), but my model was lacking it! (damn ebay seller) 

Different usage profiles: (link to bigger picture HERE)



2014 12 30 09 23 05

Ive been mostly testing and using it as iGate so got no experience on the Digipeater Side. However I have verified it works nicely on both RX/TX. My current setup is SainSonic GT3MK2 handheld, proper  data-cable from taobao-seller, and the TNC-box.  You can track me on:   http://aprs.fi/#!call=a%2FOH2FXD-10&timerange=3600&tail=3600

PEOPLE having problem to startup program check that you have atleast .NET framework 4.0 installed! This is depency I noticed just a while ago!

Configuration is done via TCP/IP API and this time I need to say that the software provided is actually quite usable.  Here is some screenshots for the application itself. Please bear in mind that default IP is so you need to configure your LAN / routing for that network too 🙂

Screenshot 2014 12 12 21 20 43

Screenshot 2014 12 12 21 20 51

Screenshot 2014 12 30 10 53 25

Screenshot 2014 12 12 21 21 07


Screenshot 2014 12 12 21 21 15

Screenshot 2014 12 12 21 21 23

Screenshot 2014 12 12 21 21 38

Screenshot 2014 12 12 21 21 44


  • software is ok, its even in english and works quite good
  • box is easy to configure
  • price/quality/usability 


  • bluetooth module missing (ebay sellers fault) , not needing it anyway on own projects
  • cabling (yaesu/kenwood cable) was a bit loose, not good quality
  • missing psu-adapter
Few notices after longer use:
  • when you have SQL open on HT it wont TX (not manual or automatic), my friend oh6elf pointed out that it is important to tune audio level not too high. Im using 16ch kenwood VHF HT now as RX and it is a bit less than “nine a clock”.  You can test this yourself by sending RF test on Beacon page, tune your HT volume until TXD light wont anymore light up when you try to send a packet. When it does not lit anymore tune volume a bit down and repeat. Thanks “ELF” for support 🙂 


Original Site I got my inspiration:


Software you will need:


Taobao-Seller for the 51TNC box and wouxun/baofeng/kenwood data-cable:




Taobao-agent site Im using:



Original manual: (in chinese):




I noticed that app needs atleast MS .NET Framework 4.0 installed. Try with that and report back to me if possible!
I have mailed to developer and requested more data about the device: howto aquire newer firmware, and howto update it (serial cable included in box should do it).
I have also requested would there be DNS addition to the TCP/IP settings in the future.  



Hear you in the APRS-NET! 73 de OH2FXD-7/9/10  




PS. Here is more pictures for the item if anyone interested ^__^

2014 12 11 13 46 23

2014 12 11 13 46 35


2014 12 11 13 46 44

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2014 12 11 13 50 22

2014 12 11 13 50 49



39 thoughts on “51TNC, review of this multipurpose APRS TNC”

  1. Does anybody have documentation for this unit? How do I connect a LCD, a weather station to it? What does the internal jumper? I cannot find the documentation even is Chinese. Please help! Thanks!

    1. There is some chinese doc on the internet for gps/weather station pinout. I can check it next week.
      For LCD or internal jumper no idea… product is ok but english and even chinese documentation are the worse 🙂

  2. Hi there,

    I have the bluetooth unit but I can’t get the software installed/running? What do I need to install extra to get the APRS51TNC application to start?

    1. I have no idea, my app on virtualbox is still running fine. Youre not the only one reporting this odd behaviour.
      Is it related to antivirus or some windows update package? Im running Win7pro 64bit.

    2. I noticed that app needs atleast MS .NET Framework 4.0 installed. Try with that and report back to me if possible!

      73 de OH2FXD

  3. I bought ant51 from Aliexpress in late summer and I had problems to get it running. I think in newer versions you do not have to worry about IP address, you just just plug your computer and ant51 unit in same router and hit connect and then read after that you put your own data and hit write.
    I am using Win 7 64 bit.
    73 de OH2FDO

    ps. many thanks for OH2FXD for the info

    1. TNX Tapani. If anyone has newer config software I would appreciate it alot. Im also waiting reply from the developer for some nfo/improvements.
      73 de OH2FXD

  4. Did you get any response from the developer BH4DTV in the meanwhile? My ANT51 quits working last week. I couldn’t find the issue yet but I wonder if some has the hex-File of the newest firmware. Mine is 290141215 but I know that there is at least 20150808 out there. I want to ask the developer also if he can change the SmartBeaconing function a little bit that there will also a Paket be generated when your speed goes down to zero for at least 30 s. Maybe you can share the e-mail address of the developer with me.

    vy 73 de Stephan, DG1BGS

      1. I got your e-mail and asked my girlfriend who is chinese to translate my questions. Hopefully he will answere her. I will let you know as soon as we got any response.

  5. Hi Folks, I have two of them running in the APRS network in LU, the old ones are FW 2014, but last week I get two new ones to expand the network and the FW is very new, from 2016, Any idea where I can get any description, changes and new conf sw?. 73 de Claudio Lu7DW

      1. Last year I asked my chinese girlfriend to write an e-mail to BH4DTV to asked for the newest firmware and also how to upload it to the tracker but he never respond to this e-mail. To be honest, I gave it up. But anyway, after I changed a transistor my tracker came back to live again.

    1. New FW date is 20160307, old one is 20140316… I don´t know what are the diferences, improvement, not information at all… I use the old SW to configure and look that is working in same way .. If you want to see on APRS.fi.. OLD FW is LU2EP-10 new FW is LU4AA-10

  6. Is there any router configuration that needs to be done? I’ve been fiddling with this forever, cant even get a successful login.

    1. Hi Jeffrey, The ANT51 has an IP by default and DGW is or do you need to login on APRS.fi page? BR Claudio LU7DW

      1. Maybe its the APRS.fi page thats not logging in. Under server status on the first tab, its always said “Server Status 2 Linked Server, unknown”.
        Perhaps my captcha is wrong? i”ve been getting that from http://apps.magicbug.co.uk/passcode/
        Maybe thats my issue.

  7. Forgot to add, under Data Monitoring,
    “server link start…
    SERVER TCP/IP Link Outtime!”
    For some reason its just not connecting.

    1. I had to exchange the IP addresses in the Network tap and put only the IP addresses of servers which equals to my country, e.g. . You can find a list of available servers at http://www.aprs2.net/serverstats.php .I also checked the options “Server automatically rotate” and “Restart connection timeout 2” and unchecked “Always use Server A” just in the hope that at least one server is available.

  8. Could not get the software running on my W10 laptop or my trusty old XP machine.

    Any advice hints or newer config software?

    I installed NET 4 on the XP machine but it made no difference…

    Steve VK2ARS

    1. No sorry, these chinese applications can be pain in the ***. 😐 Do you get any error message or is possible your AV (antivirus) application blocking it to start?

  9. Hello

    I search the software to run the TNC51 under windows xp.I have tried several downloads, I have “vshost files” I do not understand.


    Sebastien – F4GQK

  10. Hello, how is it possible to reset the TNC?
    Just short the Reset Pads on the PCB and power on?
    I’ve lost the IP settings.

  11. I have net51 device
    this is the tnc-x device that I tested and can not communicate with
    Where can I download new software for this.

    1. yes, its been 2 years since blog post was released and Ive dropped “dropbox” since that. You can still find the app from the google or via other hobbyists.

  12. Does anyone have a copy of the 51tnc setup software?
    Our club has the hardware but no software:-(

    I have downloaded a zip file containing vshost files but they won’t run on my pc. I’m not sure how to use the vshost files. Can anyone help or point me in the right direction?

    1. Hi! I recently buy one of this 51tnc from Aliexpress. It´s a bit hard to make the software run. It doen´t work on Win10. Neither on windows 8.1 (at least for me). But I realice that It work on windows xp. So, I had to do this:
      – Get a copy of windows XP (SP3)
      – Download an install Oracle VirtualBox
      – Install Windows XP on a virtual machine
      – Inside winxp, install Framework .NET 4.0 (downloaded from: http://netframework4.net/download-net-framework-4-0-full/)
      – Copy the software for 51TNC to windows XP
      – From the directory “OCX Files” copy MSCOMM32.OCX,mswinsck.ocx and tabctl32.ocx to the c:/windows/system32 (on windows xp)
      – register each of the OCX files on your XP. Go to start, run and then: regsvr32 Starrmscomm32.ocx, regsvr32 TABCTL32.OCX and regsvr32 mswinsck.OCX
      Now try to run “APRS 51TNC SETUP _ENGLISH_20140701.exe”

      Hope it works to you. (Sorry for my english)
      Jorge – LU7HEP

  13. Hi, As listed in the seller specs (and confirmed in your pictures), the 51TNC uses the CML FX604 chip – a V.23 modem – which doesn’t generate the same mark/space tones as AX.25 (CML FX614, Bell 202, for packet/APRS). In the FX604 and FX614 datasheets, the FSK modulator and demodulator mark/space tones are outside the min/max operating characteristics. Not too far out, but still out of range. And if it does work, it must be working only by virtue of component tolerances that barely make it through the filters. It’s a real shame as it looks otherwise ideal. I would order a 51TNC today if I hadn’t noticed that. Can anyone confirm I’m understanding this right? Has anyone noticed how performance is in terms of dropped packets vs other TNCs?

    Paul m0set

    1. Hi Paul, I cannot answer to your question (goes a bit too deep in technical part) but have you checked something newer product from china ie. AVRT7+ (plus version). I have such box after net51tnc and in my opinion its great! 🙂

  14. Thanks for getting back so soon, oh2fxd, much appreciated. I had a look at the AVRT7+ manual, which shows it has FX602 chips which receive the correct Bell 202 mark/space tones – definitely a good sign. Never heard of it before. AVRT7+ seems a really neat integrated box, you got me interested – I like the idea of an igate now also!

    I was interested in the bluetooth 51TNC because I thought it could use it to work plain old AX.25 packet – do you happen to know if the 51TNC can do that? (even in KISS mode?)

    Paul m0set

    1. Hi Paul, unfortunately its been few years since I setupped mine and I only used it as igate. For AVRT7 plus you can contact me via mycallsign@gmail if you want to know for example where did I ordered my unit. Compared to net51tnc box there is few major positive things: ARVRT7+ supports DNS! (yeah amazing), and it has integrated VHF receiver which removes the need for external mobile radio/ht. Also depending on the place where you order the unit you get nice LCD screen a accessory which shows the last heard packet, callsign, bearing and distance.

      I havent writed on this blog for a while but next project will be related to “remote igate” with following setup: avrt7plus, 4g wifi dongle, solar panel +battery and some waterpoof boxes. Stay tuned 🙂

      73 de OH2FXD

  15. I got old net51tnc unit from my brother and issues to start the confing app on windows7 64bit. Here is the steps to get it working:

    Under the application folder there is folder called OCX.
    – Copy ocx files under c:\windows\syswow64
    – Open CMD with admin rights (startbutton -> type cmd-> open cmd with right mouse click “run as admin”)
    – find your way to c:\windows\syswow64
    – run regsvr32.exe to those 3 files you just copied ie. regsvr32.exe mscomm.ocx

    – Also remember to install NET4.0 framework.

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