Category Archives: Public Service

J-Pole antennas for SAR

Image of fibreglass mast with two VHF j-pole antennas affixed.

Fiberglass mast with two VHF j-pole antennas affixed.

I recently started working with Calvert K9 Search, a local SAR team that specializes in using dogs to search for people.  In an effort to improve communications between the command post (base) and teams in the field I embarked on a mission to find a simple solution to the problem of limited comms.

There were several requirements that prevented the use of a repeater (added complexity, weight, setup time), using a higher power base station (may damage dog collar transmitters and GPSr receivers1 and only amplifies one side of the communication), or a portable tower (see repeater above).

The solution was happened upon almost by accident and the improvements were immediately noticeable.  Digging through the back of my car I came up with a VHF j-pole and fiberglass expandable pole to put it up in the air.  A few adapters later and we were on the air!

The performance improvement was immediate!  Suddenly communications were possible at a much further distance and, when connected to the Garmin Astro 320, dog collars could be received from a much further distance away.

Anyone who has examined the efficiency of a “rubber duck” antenna will know that these stock antennas aren’t great and that almost anything is better.  Stepping up to a j-pole antenna is a significant improvement and then putting that antenna up in the air has a lot of wow-factor to a non-radio person.

Image of collapsed fibreglass pole, used as mast, straps, and two VHF j-pole antennas rolled up and ready for deployment.

Two VHF antennas, straps, and mast ready for activation.

With the tests complete I built two j-pole antennas: one centered on 155.160MHz, our primary operational frequency, and one centered on the average of all the MURS frequencies.  The latter is used as a receive-only antenna for the dog collars and hangs below the VHF “ops” antenna.  Both of these antennas are hung onto a fiberglass expandable pole that holds the antennas up in the air around 20 feet or so.  This pole can be attached to a fence post, command trailer, tent pole, or laid into a tree branch to keep it upright.

The most expensive part of the project was the LMR-240 feedline2 that we used.  The antennas were made out of 300-ohm ladderline with shrink wrap at each end to help keep the elements out.  The pole is actually made for pulling cable and wires and is made by  It’s really strong but isn’t crush resistant so you have to be careful not to step on it when it’s laying on the ground.

For about the price of a good commercial antenna we were able to get a working antenna system that is completely portable/pack-able and lightweight and takes only a few minutes to setup and take down.  It also doesn’t take up much space for storage meaning it fits into the existing infrastructure without having to make changes.

We’ve deployed this antenna system several times this spring and summer and have noted improvements over a variety of terrain.  This project would have cost around $350 for parts if not for donations of parts and pieces along the way.


1. Calvert K9 Search uses the Garmin Astro 320 GPSr units that, when coupled with the dog collars, allow the user to track the location of the dogs on the screen.  These units are very sensitive to RF energy and the manufacturer recommends not using any more than 5 watts near these devices. (Although they don’t specify what frequency band they are most sensitive, the units use MURS for communicating between the dog collars and receiver units so I’m assuming VHF is the most sensitive.)
2. LMR-240 feedline was utilized as it was small, lightweight, and reasonably low-loss at VHF frequencies.

Managing resources during Public Service events using APRS

Picture of Mark Freeze shadowing Zoe during 2016 Raleigh Tour de Cure

Mark, WD4KSE, shadowing Zoe during the 2016 Raleigh Tour de Cure. – photo by MotoPhotoMe.

Over the weekend I helped support the American Diabetes Association‘s Raleigh Tour de Cure – a two-day charity bicycle ride that allows riders to choose between 80 and 100-mile courses each day.  I’ve been supporting this ride for many years, and, thankfully, we’ve been using the same route for the last few years which makes it easier to come up with a communications plan each year.

Over the years I’ve watched other people’s techniques for managing resources.  One guy kept his notes on a knee board and used some sort of shorthand notation that no one could figure out during the brief glances we were allowed.  In years past I’ve enjoyed using a small whiteboard to keep track of where my Support and Gear (SAG) vehicles were.  This year, however, I decided to do something a little different.

The Goal

2016 Raleigh Tour de Cure course map with rest stop objects.

Raleigh Tour de Cure course map with rest stop objects.

The goal of my madness is to make sure I had SAG vehicles “patrolling” between rest stops where we knew bicyclists were located.  The Raleigh Tour de Cure has six rest stops with those doing 100 miles doing a loop that takes them back through rest stops five and six before heading to the finish.  Altogether, there are eight segments of race course that need to be covered.  Each SAG is assigned a segment to run in a particular direction.  In this way, it is hoped that a SAG will go past a certain point every ten to fifteen minutes (we don’t want a rider to have to wait a long time for a SAG).  Luckily not all eight segments are occupied at the same time which reduces the overall need.  This year we managed to do it with five SAGs, one doctor, one motorcycle SAG (who also had a photographer riding backwards taking pictures of the riders for MotoPhotoMe), and two shadows.  We could have used more but this is a great crew, and everyone worked together as a team flawlessly.

Past Management Tool

Like I pointed out earlier, I used to use a whiteboard to keep track of who was where and to make assignments when a SAG made it to their next rest stop.  My chart looked something like this:

 RS  | SAG
S->1 | 1↑, 2↓, Last Rider
1->2 | 3↓
2->3 | 4↓, First Rider

This means that between the Start and Rest Stop 1 I have SAGs 1 (running backwards from 1 to the Start) and 2 (running forwards from the Start to 1), between Rest Stops 1 and 2 I have SAG 3, and between Rest Stops 2 and 3 I have SAG 4.  I try to stagger SAGs going between the same rest stops to add patrol coverage.  When SAG 1 reaches Rest Stop 1 the expectation is that they will call me on the radio and let me know they’ve arrived.  I will then give them a new assignment (it could be patrolling back towards the Start line or moving on to Rest Stop 2).  A whiteboard makes it easy to make these updates and keep everything in order.

The benefits of using such a system is that it’s simple and easy to manage, allows a quick look to see your needs for coverage, and allows you to make other notes (e.g. who has already had lunch, special assignments, where is the lead and last riders).  The drawback is that there is no record keeping with this system.  You can’t go back and see who was where when.  Keeping up with this information would require a completely separate form and would likely slow you down.  Also, because all this information lives locally on a whiteboard there is no way to share this information with anyone else if, for example, you need to step away from the radio for a few minutes.

Using APRS to manage the resources

This year I decided to use my APRS client, Xastir, to manage my resources.  Some of the SAGs ran APRS trackers (thanks to the Raleigh Amateur Radio Society (RARS) for letting us use their trackers!) in their vehicles which meant I didn’t have to update their locations and I always knew where they were.  The other resources I had I simply used objects on the map to track where they were located (approximately) and moved those objects when they provided an update.  It looked something like this:

APRS map showing SAG objects

APRS map showing SAG objects in motion between rest stops.

I could also put requests for service on the map (e.g. bicyclists that had contacted us via phone or SMS to say they needed assistance) and be reasonably sure I was sending the closest SAG to them.

Because I was the only consumer of this data (this year) none of the objects I created were actually sent over the air or to the Internet.  I could have easily shared this information over the air or the Internet to others and I hope to do so in the future.

Oh, I should point out that one of the SAGs, Moto 1, used APRSDroid on his cellphone to provide his location.  This was problematic as there were many places along the route that didn’t have any cellular connectivity much less sufficient data connectivity.

We also didn’t have sufficient APRS infrastructure to cover the entire route.  This was mostly remedied by the addition of a tactical digipeater.  I’m hoping to establish a new permanent digipeater along the route in the future.

What other benefits can APRS bring to the table?

Beyond keeping track of everyone’s location, either in semi-real-time or by moving objects around the map, APRS can provide information sharing to other stations that need to know what’s happening.  By pushing objects to the network, one can inform all participants of resources and needs (this requires some sort of display to consume this information).  Also, the voice frequency can be kept clear of routine requests by using the text messaging capabilities of APRS.

Record keeping can be done in a not-so-detailed way by having the APRS client record all traffic to disk.  This means that every movement, addition or deletion of an object, and every message would be recorded.  While not as detailed as formal messages, or even keeping a detailed log, it does provide some tracking that, if needed, might be helpful.


Using APRS to manage public service events could prove to be helpful.  It doesn’t necessarily require buy-in from everyone involved but would benefit from others participating.  I didn’t go into all the features that APRS could bring to the table but, rather, touched on the ones that I felt were important.  I’m hoping to extend this article in the coming months to bring more thoughts on the subject.


I’d like to thank the volunteer hams that came out and participated in this two-day event:

  • Photo of Doctor Playford roaming the rest stops.

    Doctor Playford, KM4NWC, roaming the rest stops.

    John Snellen, AI4RT – SAG 1 (RARS Public Service Coordinator)

  • Wallace Smith, KJ4UKV – SAG 2
  • David Krum, NW3U – SAG 3
  • Joe Sheets, KJ4LZM – SAG 4
  • Bruce Buck, KC4UQN – SAG 5
  • Tom Byrum, N3TCB – Moto 1
  • Lubov Byrum, N3BOV – Photo 1
  • Dr. Scott Playford, KM4NWC – Doc
  • Bill Cole, KG4CXY – “Jim” (founder of Carolina Helping Hams)
  • Mark Freeze, WD4KSE – “Zoe”


  • Yes, I realize all the maps used in this article don’t contain roads and such.  While this information was available to me I really didn’t need it as I had the route and rest stop data staring at me.  If I needed the road-level maps they were just a couple of clicks away.
  • The APRS network frequency, 144.390MHz, is quite busy and I wonder if building a separate network on a different frequency would benefit the event.  Think ALOHA.
Photo of SAG vehicle at finish line


Apps for Ham Radio Networks

You’ve built your mesh or 802.11 network to support your activity.  Now what?  Unfortunately, most client software doesn’t support peer-to-peer activities.  You have to have a server acting as the central repository and distribution point for your data.  Sounds complicated…

It can be daunting to make these resources available but it doesn’t have to be.  If you are already running a Linux-based operating system (sorry, Windows users but Microsoft will want you to pay an arm and a leg for what I’m getting ready to suggest and Microsoft software can’t do much of what I’m going to suggest, either) then you’re already most of the way to having your own server.  Most, if not all, of this software is already available in your distribution’s software repository for easy installation.

There are core software being used on the Internet, today, for moving data around.  Using the tools that most people are familiar with help make the overall network successful.  Obviously the first question should be “what are you trying to accomplish?”.  Setting up a camera on the network and sharing that data across the network is easy, mostly because the camera likely already includes its own webserver.  But how can you bring the rest of the tools into play to make your network even more useful?


Email is fairly ubiquitous and everyone seems to know how it works.  There are three protocols you should be familiar with when dealing with email: smtp, pop3, and imap.  These are the services that handle routing and delivery of your mail.


Simple Mail Transfer Protocol (SMTP) is an Internet standard for routing messages between email servers.  When you send an email, today, your client connects to an SMTP server and sends the message.  The SMTP server, after receiving the message from you, attempts to figure out how to deliver the message to the distant email server.  If the message is being kept locally (i.e. the recipient is on the same server as where you delivered the message) then the message is filed for delivery when the recipient queries the server.

Postfix LogoAn often-used SMTP program is postfix.  It requires a little configuration but basically “just works”.  Postfix will handle receipt of mail and delivery to the mailserver where your recipient is without further action from the user.


Post Office Protocol version 3 (POP3) and Internet Message Access Protocol (IMAP) are on the message delivery side of the house.  These are the protocols that allow a user to query the email server for mail.

POP3 basically forces a user to collect their mail and then delete it from the server.  By doing so, once downloaded, the user has the only copy of the message and the server is freed of the responsibility (and storage space) for handling the message.

IMAP, on the other hand, allows the user to download a copy of the message but, until deleted, the message remains on the server.  This allows the user to utilize multiple clients, with sorting into folders, and have that organization synchronized among all the user’s client software.

The Dovecot logoDovecot handles delivery of messages to clients using POP3 and IMAP.  Again, the software requires a bit of configuration but generally just works.

Web Server

Have a website you want to publish on your network?  Want to use a program to share files and other information?  You’ll need a webserver!

Apache Feather Logo.svgApache’s http server, commonly known as httpd, is very easy to setup and use.  Once installed, the server looks for files in your web folder (/var/www/html) and waits for a request from a client.

Want to share files and other information?


OwnCloud is a suite of client-server software that creates a file hosting service and also allows management and sharing of calendar information, contacts, and more.  Because it’s far more efficient to share files using the http protocol, compared to email, and because files can be managed and synchronized among many computers through shares, using OwnCloud to manage files is far superior than using email.

Instant Messaging

Instant Messaging (IM) is an efficient and simple way of communicating short messages to other users in real time.  Some protocols allow peer-to-peer communications but usually a server is needed to facilitate the communications.

XMPP logoJabber, instant messaging software based on Extensible Messaging and Presence Protocol (XMPP) protocol, allows users to communicate between each other either person-to-person or in a chatroom where multiple people can participate.

Voice Communications (VoIP)

Using the session initiation protocol (SIP), one can handle VoIP “calls” over the network.  This can be between VoIP phones or between AT conversion boxes linking analog repeaters.  Unless you know exactly what phones are where, and your system isn’t growing, you likely don’t need a server.  But, if you plan on expanding your network and wish to have dynamic routing (phone numbers) then you’ll likely need a centralized server.

File:Asterisk Logo.svgAsterisk is a great private branch exchange (PBX) server allowing telephones to connect with each other.  Connections between the server and the clients are generally done using SIP whereas connections between Asterisk servers use Inter-Asterisk eXchange (IAX).

Connecting LANs

All of this information has been presented absent the network management infrastructure that helps make communications between easier.  Handling data on a single local area network (LAN) doesn’t necessarily require this kind of infrastructure but utilizing tools like DHCP, DNS, and others can be helpful.

Summary Conclusion

As you’ve seen, once you’ve built your network there are a few more challenges to making your network work for you.  This, however, doesn’t need to be an impediment and with just a little work you can make your network truly work for you.  You also don’t need any fancy hardware, either, as these tools can easily work on a laptop connected to the network for easy deployment.

All the suggested software is free and open source software (FOSS) which allows anyone to deploy the software for free (and allows you to make changes to the software if needed).

Upcoming public service events

Bill, KG4CXY, just sent out this year’s big public service events.  If you are interested in these or other events in eastern North Carolina please visit

Goin’ Coastal Bike Ride – May 5th
The first annual running of the Goin’ Coastal bike ride to benefit the Coastal Land Trust will be held in New Bern. A 30K, 70K, and 100K course is planned.  This one goes way into the boonies of the Eastern coast, and we envision needing about 15 ham volunteers for shadows, SAGs, net control, rest stops and a variety of other assignments.ere are the upcoming events for Spring 2012:
Time: 7:00am – 5:00pm
See the CHH web page to volunteer.

Tour de Cure – June 2nd & 3rd
Time again for the 200 mile/2 day Tour de Cure to benefit the American Diabetes Association.  One of our largest events of the year – and we can never have too many volunteers for this event.
Time: 7:00am – 5:00pm Saturday and Sunday
See the CHH web page to volunteer.

Ride Without Limits – Sept 15th & 16th
June 11, 2011 – Saturday – Pittsboro, NC
The 5th annual Ride without limits to benefit Easter Seals/United Cerebral Palsy.  A 200 mile/2 day Bike run that starts and finishes at Camp Royale in Pittsboro.  Again, we can never have too many volunteers for this event.
Time: 7:00am – 5:00pm Saturday and Sunday
See the CHH web page to volunteer.