Digital Communications and Technology Net

The Digital Communications Net is an informal net that meets every Tuesday evening at 8:00pm on the SBARC Hub repeater network.

JT65 operating on 10m

JT65 operating on 10m

We discuss and operate all kinds of digital communications and special modes such as 2m/440 Yaesu System Fusion digital radios, mesh networking, as well as HF oriented modes like PSK31, JT65, FreeDV, SSTV, Olivia, DominoEx, the Winlink 2000 system and many others. We typically discuss and operate digital modes on HF but sometimes operate on VHF/UHF as well, so everyone gets a chance to participate regardless of your station equipment or license class.

Using a radio and your computer, you can send data, voice, pictures, documents, and even email over the air. We also discuss using the various digital mode software applications and explain how to install and use them.

Arduino and Raspberry Pi

Arduino and Raspberry Pi

We also discuss using microprocessors like the Arduino as well as small micro-computers like the Raspberry Pi. Both of these devices and similar development boards are fun to learn about, and are great for creating projects you can use with amateur radio.

If you are interested in digital communications or learning about working with microprocessors and micro-computers, we are happy to help you get set up and explain how things work.

The net is hosted by Brian – K6BPM and everyone is invited to check in. We hope to see you there!

You’ll find recordings of previous nets in the SBARC Audio Archives.

Please consider joining the SBARC Digital Modes and Digital Radio Discussion Group mailing list and participate in the group off the air! It’s easy to do. Just send a blank email to

For quick access to the programs we use for digital communications and other helpful resources, visit the link below…

Digital Communications Downloads and Resources

K6LCM LiFePO4 PowerBank Battery Box

The author’s battery box shown here at the K6TZ Museum of Doughnuts on a Saturday morning.

I experienced some disappointing results with a portable 12-volt jump-start lead-acid battery at Field Day this year. David, AC9AC, saved Field Day for me by bringing by his 30 amp-hour LiFePO4 battery to our operating location at Shoreline Park. Impressed with its capabilities, I decided to upgrade my portable power.

There are a number of vendors on Amazon and Ebay selling high-capacity LiFePO4 batteries at low prices. LiFePO4 batteries are impressive. Without going into too much detail, the main advantages are that they are up to 70% lighter than lead acid batteries, will continuously supply 13-14 volts under high-current draw conditions and can be completely discharged without damage. Most LiFePO4 batteries include a battery management system inside the sealed plastic battery itself, making them nearly a drop-in replacement for lead-acid applications. In fact, many new 12-volt chargers include special modes for optimally charging LiFePO4 cells.

If you search online, you’ll find many pre-made power stations. The problem is that most of them are designed with general consumers in mind. Your average power-hungry electronics guru mostly needs a 5-volt USB power connection and a 120-volt AC outlet. These premade power stations typically lack higher current connections such as Anderson Powerpole sockets. The designers of these pre-made power stations were probably thinking: “Who would want to draw 20-30 amps at 12 volts?” Hams would of course!

My requirements when designing the K6LCM PowerBank were that it would support typical 5-volt USB connections and a 12-volt DC cigarette lighter connection for running mobile chargers. But my design added two 12-volt DC Anderson Powerpole connections for supplying up to 30 amps of current to various rigs that are capable of transmitting up to 100 watts of RF.

Below are some photos of the build and a parts list. I mounted the binding posts inside the top compartment of the Harbor Freight ammo box as shown. Using 12 AWG wire, I connected the battery itself (using the blade fuse connector with a 30-amp fuse) and all of the power outlets to the positive and negative posts respectively. In addition to the fuse, the positive battery lead passes through the master switch on its way to the positive binding post. The only connection that does not pass through a binding post is the positive (7.5-amp fused) connection between the charging port on the back and the battery. Since I intend to use this setup as portable power, I won’t be running the charger and the radios at the same time. However, this 7.5-amp fuse protects the charger, just in case!

If you intended to use this PowerBank as an online battery backup in your shack, you could wire in your 13.8-volt, high-current shack supply instead of a battery charger and swap in a 30-amp fuse here as well. Consider the West Mountain Radio Epic PwrGate for this application.

Parts list:

The Hall Effect ammeter sensor is looped around the supply cable from the battery to the positive binding post and shows the current flow out from the battery.

Some newer Battery Tender chargers have settings for optimally charging LiFePO4 batteries. The volt meter doubles as two USB power ports. Connections from the various components to the battery are made through + / - binding posts. Be sure to install a 30-amp fuse on the main lead between the positive binding post and the battery. On this particular ammo box, the binding posts are concealed under the top compartment lid. High and low current 12-volt DC connections .An SAE connection for the Battery Tender charger is mounted on the back.

FM Simplex Node Frequencies in Santa Barbara


Over the past few months there has been a renewed interest in AllStarLink FM simplex nodes among our members. These low power devices allow users to connect to remote VoIP nodes and repeater systems using an internet connection and an HT. Most opt to buy or build a device on 70cm.

A couple years ago, during the initial DMR hotspot craze, SBARC expert consultant Matt W6XC identified a few frequencies around 431 MHz that were useful for digital hotspots like the OpenSpot and ZumSpot. HOWEVER, these frequencies are NOT appropriate for analog FM nodes. We must use a different part of the 70cm band for FM emissions.

Matt suggests the following options for low-power, analog FM usage:
440.000/445.000; 446.860/441.860; 446.880/441.880 may be used as pairs for a low-power duplex node or as separate simplex node frequencies. Please listen to these frequencies with low squelch settings and no CTCSS for a few days before permanently parking your node here to see if and how these frequencies are used. FM simplex nodes are best PL/CTCSS protected, especially if they are left connected to a system like K6TZ or WIN System.

Definitely avoid 446.000 altogether. This is the National Calling Frequency for 70cm. 446.500 and 446.520 are “General Simplex” frequencies. Others many want to use these for simplex QSOs or other itinerant purposes so please don’t park your node on any of these three frequencies. Also note that 432.000-439.999 MHz is allocated to weak signal, Amateur Television and digital emissions only. 440 is tough given the lack of simplex allocations. It’s a truly stuffed band!

Perhaps just as important as which frequency you choose for your node is setting the PL/CTCSS tones. In Santa Barbara and Ventura counties, DO NOT use 131.8 or 88.5 127.9 or 131.8 Hz as a tone for your node. Picking almost anything else will ensure that you don’t inadvertently open the receiver of a repeater on the same or nearby frequency.

If you are interested in these FM VoIP nodes, consider the ClearNode and SHARI projects.


Levi, K6LCM
K6TZ Trustee

November General Club Meeting: Tracking Transpacific Airliners

0:00 Pre-meeting chatter
26:30 Meeting Start and Intros
53:30 Tracking Transpacific Airliners Presentation Start
1:27:10 Questions & Answers

Meeting Presentation Slides (pdf)

Our November Club Meeting was host to our Board of Directors election as well as a presentation by Levi C. Maaia – K6LCM on using your ham equipment and/or computer or smartphone to listen in on transpacific airline traffic on the VHF and HF bands.

Hams aren’t the only ones using HF on a daily basis for reliable, long-distance communications. Airline pilots use HF frequencies from 2800 kHz to 22 MHz as their primary means of communication with shore stations during oceanic flights. These comms can be received by anyone with an HF SSB tuner and provide interesting data points for HF propagation. Aircraft are even sending PSK over HF! Levi showed us a tracking demonstration of a flight from Los Angeles (LAX) to Sydney (SYD) as well as pointed us toward some resources for tracking and listening in on our own, with or without a radio!

DMR QSOs from your Android

I just tried out a cool app for Android users …

DROID-Star lets users login to the Brandmeister DMR system using your DMR ID and presents an interface that is operationally similar to Echolink. You can connect to any TG and then use the on-screen PTT to have a QSO. Works decently well for a beta version. Despite the “D-Star” branding it is a DMR app. Haven’t figure that part out.

Download it from the Google Play App Store.

-Levi, K6LCM

Yaesu System Fusion-DMR (YSF2DMR) Cross-Mode Repeater

Over the past two years, there has been an explosion of interest in DMR amateur radio. Many SBARC members have been bitten by the DMR bug and they are chatting around the world on global Brandmeister talkgroups using hotspots and repeaters. While much of the attraction of DMR is the ability to work DX on a handheld transceiver, many local operators hang out on the local SBARC Brandmeister DMR Talkgroup (TG 31073).  In fact, every Tuesday night, the Digital Communications and Technology Net moves from 2m FM to TG 31073 at 21:00 Pacific Time.

If you aren’t on the air with DMR yet, not to worry.  You may be able to chat on TG 31073 with a radio you already own! K6TZ operates a multimode digital repeater at La Vigia on the Mesa in Santa Barbara. We have recently reconfigured this repeater to bridge traffic from Yaesu System Fusion radios to TG 31073 using a new protocol called YSF2DMR. If you have a newer Yaesu radio, you may be digital-ready right now. Many new Yaesu amateur radio models available support System Fusion and are capable of connecting to the K6TZ digital repeater in order to bridge from System Fusion to DMR and TG 31073.

Joining the local digital chatter on TG 31073 via System Fusion on the Santa Barbara South Coast is fairly straightforward. Just follow these steps:

  1. Obtain a DMR ID.
    If you have not already, click here to register your callsign with the DMR network and receive a unique DMR ID number. Your DMR ID is paired to your callsign on the DMR system and used to identify your transmissions. It takes a day or so to get a new DMR ID assigned and you only need to register once. Once you receive the confirmation email, keep it. You won’t need the number now using System Fusion but if you get bitten by the DMR bug in the future and want to explore further you will use this same DMR ID to configure a DMR radio.
  2. Set your amateur radio callsign in your System Fusion radio.
    Each radio model handles this differently. You must enter into your Yause radio the exact same callsign you registered to your DMR ID. The SBARC repeater will only bridge properly identified transmissions from System Fusion to DMR. So be sure you have input your callsign correctly and that you have received confirmation of your DMR ID registration by email before attempting to move on to the final step.
  3. Set your Yaesu System Fusion radio to the K6TZ digital repeater frequency pair.
    Tune 445.480- (negative offset) on your Yaesu System Fusion Radio.  Be sure you set the radio to transmit in Digital Narrow (DN) mode. Voice Wide (VW) and FM transmissions will not be bridged to DMR.

Hope to hear you on DMR/System Fusion. If this interests you and you want to learn more, join us every Tuesday night at 20:00 (8:00pm) on the K6TZ 146.79 FM repeater for the Digital Communications Net. Then QSY with us to DMR TG 31073 at 21:00 (9:00pm).


General Club Meeting – February 15, 2019

Last August our topic was DMR radio. Since then I have had a lot of requests for another DMR presentation, and since some new capabilities have become available, I thought this would be a good time. A lot of members have purchased DMR radios and would like to know more about their use and capabilities. A lot of our members have also purchased and Yaesu System Fusion radios as well. In fact, the Yaesu FTM400 mobile radio is probably the most popular general mobile radio in the Santa Barbara Area. There are probably 20 or more SBARC members with these radios but only use them for regular FM. Yaesu YSF radios are digital capable, but use a different digital protocol. Now it is easy to use your Yaesu YSF capable radios to communicate on DMR on the SBARC or other favorite talkgroup. At this meeting, we’ll show you how and do some demonstrations.

So bring your DMR radios and Yaesu YSF HT’s if you have one. And, bring your questions about this or DMR in general. SBARC is lucky enough to have their own dedicated talkgroup, and we need to utilize it more. With this new capability, hopefully we can get more members to come over and give digital a try.


SBARC General Club Meeting
Friday, September 21, 2018 at 7:30 PM
Goleta Union School District Board Room
401 North Fairview Avenue in Goleta

We hope to see you all at the meeting!

Post expires at 11:00pm on Friday February 15th, 2019 but will still be available in the archives.

ZUMspot Raspberry Pi Info and Setup

ZUMspot Raspberry Pi Info and Setup

Here’s some info on what it took for me to get my ZUMspot up and running, updated with new things I’ve learned recently.  This doc is a bit wordy but I’m hoping this will let you know what you need to successfully get your ZUMspot Rpi working using a Windows PC.  Don’t think the below is a lot of work – it’s really not.

I’m pretty impressed with this product which all in is about half the price of the SharkRF Openspot  but with built in Wi-Fi and the possibility of adding a display.  I found configuring the ZUMspot to be as easy as the Openspot and I’m not a Linux person.

Hardware Needs

  • ZUMspot Rpi ($80 + $10 shipping)
  • Raspberry Pi, either the Pi 3 Model B ($35) or the Pi Zero W ($10)
    • If you choose the Pi Zero W you may want additional accessories mentioned later
  • Micro SD card, 2GB or greater. (you likely already own this or <$10)
  • 5V power supply for the Pi with micro USB connector (you likely already own this)

 Software Needs

  •  Latest Pi-Star software image from the internet (free)
  • A windows tools to ‘burn’ the above image to your micro sd card (free)
  • A PC on your network to configure Pi-Star


Hardware Details

ZUMspot Rpizum

The ZUMspot Rpi is fully assembled and tested and comes with a short antenna.  It is purchased via email from Bruce Givens, VE2GZI (  Send him an email stating you’ll like to buy one and he’ll reply pretty quickly (for me in just a few hours).  He produces them in batches so you might be put on a waiting list.  He ships from NY and from the time I paid until it was in my hands was less than 1 business week.  Cost was $80 + $10 shipping.

He does offer a kit consisting of the ZUMspot Rpi + Rpi Zero W + 2×20 header + 4GB microsd card with Pi-Star already on it for $110 + $10 shipping but you can do better putting your own kit together.

Raspberry Pi

With the Raspberry Pi and you have 2 choices – the Pi Zero W, or the Pi 3 Model B.  Make sure you get exactly one of these part numbers.  The older version of each do not have built in Wi-Fi.


Raspberry Pi Zero W is the smallest, cheapest, and more power frugal of the two.  It only has Wi-Fi access (no wired Ethernet) and currently sells for $10 here (  It does not come with a 2×20 header which is needed to attach the ZumSpot and if you do not already have one lying around, Adafruit sells them here .

The Pi Zero W gets its small size by using smaller and fewer connectors.  There is only one micro USB port and the HDMI connector is mini.  Thankfully you no longer need to hook up a keyboard or monitor to set up the ZUMspot if you go with the Pi Zero W, but here are some OPTIONAL adapters to enable you to do so if you want to dabble deeper into using the Pi Zero W for some other project.

Rasberry Pi 3 Model B is larger because of the standard sized USB and HDMI connectors (which won’t matter in this application).  It also has a wired ethernet jack so if you require a wired connection, this is the Pi for you (it will do wireless also).  An added bonus is that the 2×20 header is already installed.  Other things that allow the Pi 3 Model B to command a higher price is more ram and a faster multi-coreprocessor – neither of which is much of an advantage to running a ZUMspot.

The Pi 3 Model B normally sells for $35 and is available from many vendors.

Micro SD card

I’m not going to be much help here.  I read that the Pi-Star image fit on a 2 GB Micro SD card and since I had a few lying around, of unknown speed, I went ahead and used what I had and it worked.  On Amazon the price of 2, 4, 8, 16 GB cards are nearly all the same.  See if you too already have one you can use or buy what you feel is a good value.  Note that Pi-Star normally does not write to the card except during configuration which explains why the speed is not a big issue.

5V Power Supply

Both Raspberry Pi’s take 5V power.  Current needs peak at <400mA for the Pi 3 Model B and <300mA for the Pi Zero W with steady state being about 100ma less than peak.  This can easily be handled with a cellphone power adapter with a micro USB connector commonly used with android devices.

For me I used a cellphone power adapter that takes a plug in USB cable and bought one of these cables with an in-line switch.  I hate plugging and unplugging the power connector from a Pi to reboot it and this makes life easier


Software Details – Preparing Your Memory Card


The heart of the system is the Raspberry Pi software Pi-Star.  It can be downloaded here  (you want the version with ‘RPi’ in the name.) I downloaded the .ZIP version as the burning tool in the next section can use the .ZIP directly.  Download the Pi-Star image to your machine.


Burning Image to Micro SD Card

Now you need to get this image onto your Micro SD card.  Since I’m using windows, I used Etcher which I found in a link here

Using Etcher is self explanatory.  Install and run it to burn your image to your micro-sd card. 2

Internet Configuration – Wi-Fi (Pi Zero B or Pi 3 Model B)

In this next step you’ll be creating a wireless configuration file so that when you boot up your ZUMspot it will automatically connect to your home network.  This is especially important if you use a Pi Zero W as later the Pi-Star software configuration is only performed in a web browser and the Zero has no wired ethernet.

  1. Open a web browser and navigate to
  2. Enter the SSID and password of your home Wi-Fi network into the boxes and click the Submit button.  A file will be created and downloaded to your pc.
  3. Find the file ‘wpa_supplicant.conf’ in your download folder and copy it into the root (top level) directory of the micro-sd card you prepared above.  In my example below, my micro-sd card is drive F: on my PC.wpa_supplicant

Internet Configuration – Wired Connection (Pi 3 Model B only)

  1. Connect an ethernet cable from your home network to the ethernet connector on the Pi3 Model B

That’s it!

Pi-Star Configuration

  1. Attach the ZUMspot RPi to your Raspberry Pi.  (if you are using the Pi Zero W, you should have already soldered the 2×20 header to the board).
  2. Connect power to the Pi and wait  ~ 2mins for the unit to fully boot up.
  3. Using Internet Explorer on a PC on your network (Chrome didn’t work for me), type into the address bar this address and hit return:


The following screen will come up*.


And after 10 seconds you should be prompted with a login.

(* if you cannot access the configuration page, you can type in the IP address of the Pi into the browser.  How do you know what IP address your Pi is?  One way is to log into your router and in the DHCP section for IP address requested, look for the name ‘Pi-Star’.  Another way is to connect a monitor to the HDMI port of your Pi and in the text scrolling by during bootup, the IP address of the Pi will be shown.)

  1. Enter the username ‘pi-star’ and password of ‘raspberry’ without quote. You will now see this configuration page.
    1. In the Radio/Modem Type: dropdown, choose ‘ZumSpot – Raspberry Pi Hat (GPIO)’ and then click on Apply Changes.


  1. Pi-Star will restart and after a bit, for whatever reason, you’ll get this warning.
    1. Click ‘OK’ and you will again be on the configuration page.


  1. Back to the configuration page under General Configuration, set these parameters
    1. In the Radio/Modem Type: dropdown, choose ‘ZumSpot – Raspberry Pi Hat (GPIO)’
    2. Enter your call sign in Node Callsign
    3. Enter your DMR ID in CCS7/DMR ID
    4. Enter your desired RF frequency in Radio Frequency
    5. Enter ‘USA for Country
    6. Choose ‘America/Los Angeles’ for System Time Zone


When complete, click on Apply Changes and wait for changes to be saved.

  1. In the DMR Configuration section, under the DMR Master pulldown, choose ‘BM_United_States_3101’ or 3102 or 3103, then click Apply Changes and wait for changes to be saved.


  1. You can set up more than one Wi-Fi access point (AP), or your first AP if you are using the Pi 3 Model B in wired Ethernet mode. By adding more than one AP, Pi-Star will automatically switch to another AP when the currently connected one goes away.
    1. Click on Configure Wi-Fi to proceed.8
    2. Click on Scan for Networks (10 secs) to survey your site. After a brief pause, a list of AP’s will be shown. Click Connect for the AP you wish to connect to.9
    3. After clicking Connect your choice will be added to the existing table with a blank box for the passphrase/security key. Enter the key and then click on Save (and connect) to save your settings.a

Misc Notes:

  • There are other ‘menus’ available in Pi-Star. You can get to the other menus by clicking on the menu name at the top of the screen.
    • The Dashboard menu shows last activity heard. The webpage updates live whenever there is activity.b
  • The Pi-Star ‘scans’ all the digital modes that are enabled on the configuration page, the LED on the ZUMspot showing which mode is active. Once Pi-Star figures out what mode is being requested, it stays on that mode until until there is no activity for 20 seconds before resuming the scan.  (the 20 seconds is configurable).  The default setting has D-Star and DMR enabled and I disabled D-Star as all I’m doing is DMR.
  • Power consumption in milliamps for the Pi Zero W is ~ 180mA, about twice that for the Pi 3 Model B.
  • I’ve seen that one can add a display to the Pi – I have yet to play with that. Not sure what it shows. In the Pi-Star configuration page, there is a section to enable this feature.
  • If you cannot find your Pi on your network, another way is if you have a monitor AND a keyboard attached to the Pi, you can log into it (username ‘pi-star’, password ‘raspberry’) and issue this command ‘sudo ifconfig’ (without the quotes).
  • I originally brought up my ZUMspot using a Pi 3 model B with a wired Ethernet connection – and glad I did. I didn’t know about how to configure the Wi-Fi from the Pi terminal itself at the time. Later did I find a snipped on how to do it and verified that it worked for this document.

73 & Good Luck,
Dave, AI6VX