Retevis RT73 Dual Band 20W DMR Mobile

Just before Christmas, I decided to splash out and purchase myself a new radio as a Christmas present. I really like DMR, and in particular, the way the Australian DMR+ network is structured.

The Network

Before getting onto the radio, let's talk about the Australian DMR+ network.

At the time of writing, there are 49 repeaters (including 2 WICEN only repeaters) on the VK DMR Network.

Map from https://vkdmr.vk2fly.com/repeaters.php

The VK network is structured in layers:

  • International TGs - User Activated (UA)

  • National TGs - 505 (VK Wide) triggers all repeaters on Time Slot (TS)2 and 5 (Nets) triggers all repeaters on Time Slot (TS) 1

  • State Based TGs 3801-3808 TS 1 triggers all the repeaters in that state but accessible outside the state as UA. A chat TG of 3809 and 3810 for WICEN is also available

  • Regional TG8 TS 1 is grouped into regional groups to allow regional communication

  • Local TG9 TS1 triggers only the repeater you are connected to.

  • Other DMR+ TGs are available as UA

For those that are not familiar with DMR as a digital mode - it uses Timeslots to share the same frequency. 

I regularly have TG 505 (all VK wide) on TS2 and TG 3801 (ACT) on TS1 as my two slots I am monitoring while I drive.

The Radio

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Originally this radio was released as the Kydera ​CDR-300UV. Through some magical process Retevis has taken them over and rebadged them as the RT73 and releasing their own CPS and own firmware almost weekly to correct the utter dogs breakfast that Kydera has released.

Overall impressions - this radio is tiny. This is my secondary mobile in the car with a the Kenwood TM-710 ARPS rig as the primary rig with the RT73 mounted using double sided tape on the horizontal position on the passenger side of the centre transmission cover with no issues.

I really wanted to use the roaming feature of this radio (load up a series of DMR repeaters and it finds the one with the best 'connection' [highest RSSI for the nerds] with the ability to auto search when the connection drops too low), however, the CPS does now allow importing of channels yet so I manually only entered a Simplex zone and a zone for my local repeater.

Negatives - the radio is fine - the downside is the CPS - it is basically being written on the run, a new version is released almost every 10-20 days. I surmise this will settle down when the bugs are ironed out.

Interesting quirks include the ability to choose 3 different audio options - speaker mic, radio front-facing speaker, or side audio plugs (Kenwood style?)

DIY 10ah 4s LifePo4 without a BMS V1.1

DIY 10ah 4s LifePo4 without a BMS V1.1

I had been toying with the idea of more power - either for longer operations or more power or even more devices which such as portable digital operations.

I could have gone the simple Zippy 8400mah blue brick that seems the next step up from my 4200 or.. there is the homebrew route.

Using headway 38120 lifepo 4 cells that are used in E-bikes, and some simple balance extension leads I made Big Bertha v1. 10AH 13.2v. This version does not have a Battery Management System (BMS) and for all intents and purposes, it is seen by balance chargers and even the little cell monitoring beepers that many use, like a big 4s pack.

Photo captions:

8486 - a partially built 4 cell pack comparing size with a 4200 zippy
8532 - I might have snapped up another 2x 4 cell lot on ebay that a company was getting rid of. The orange holders snap together giving the cells rigitiy
8577 - sitting on the bench testing connection to the balance charger - I took extension leads, clipped the socket end off and soldered ring terminals to the ends and connected to the negative of each cell, with one being positive - just the same as the zippy packs
8578 - v1 covered in packing foam, covered in light head shrink bags (x3)
8580 - testing my other balance charger to confirm 12v charging.

Possible improvements - increase the current handling of the load/charging cable for possible QRO operation of the 857.

Coming versions might will likely have a BMS going forward to auto cut off on low voltage.

Shopping list:

Cells, cell holders, bus bars : https://www.evworks.com.au/

The rest was either junk box or ebay

PortablePi - A RaspberryPi for Amateur radio Portable Operators

This project might be of interest to some SOTA operators.

I wanted to see if I could make a field companion Raspberry Pi for Data modes - I would never lug my laptop into the bush.

Hardware:

  • raspberry pi 3 with inbuilt wifi chip
  • USB GPS dongle
  • USB sound card
  • ZLP USB radio interface

Capability:

  • WSJT-X on RC1.9 for FT8 etc
  • Fldigi
  • Winlink using PAT - telnet only at this stage
  • APRS via Xastir and Direwolf
  • Logging using CQRLog - issues with database - working on that
  • GPS updates onboard time - needed for Data modes and logging as well as GPS for APRS

How do you use it?
Well when the Pi is near a wifi network it knows it connects when it is not - say on your favourite summit - it creates a hotspot allowing headless control by any VNC device - tablet, phone etc.

Some pictures:

Set on top of my 817

Set on top of my 817

Connected over VNC

Connected over VNC

Update: June 2018: http://wadeabout.com/blog/update-from-my-initial-testing-of-using-a-raspberry-pi-3-as-a-portable-option-for-amateur-radio-digital-modes

 

Wade
VK1MIC