(Skip to the bottom for BOM and how to build)

Thingiverse Link: https://www.thingiverse.com/thing:4750435

Original Reddit Post: https://www.reddit.com/r/amateurradio/comments/hyeuvt/weekend_project_a_portable_20m_hexbeam/

After being frustrated with 3 element beams and towers during field days past, I wanted to build something that gives me most of the benefits of a beam, but fits in a hatchback and can be setup by myself.

After finding some inspiration online, I bought 6 13′ Shakespeare TPS13 fishing poles and fired up my 3d printer.

The center core fits on the top section of an MGS mast with 2 nylon set screws to hold it in place. 3 bolts with wingnuts clamp the rods into place.

I even added a choke/1:1 unun inside at the feedpoint to minimize external parts

After the core and poles are assembled, wire guides go on the outside of the poles. Shock cord is added between the open poles to act as a tensioner/shock absorber.

Right now I just have a 20m element cut, but intend to add 10 and 6 (maybe 15 and 17 too)

Balun – https://www.fair-rite.com/product/toroids-5943002721/ or 5943001601 or 2643803802, Connector AMP 083-878, Screwposts 111-2223-001, RG-316

6x Shakespeare TSP13 or B&M BW4

  • Qty 2(per wire element): Locking Spade Connectors 8007K56
  • Qty 3: Wingnuts 92001A321
  • Qty 3: Pan Head Screw 90604A541
  • Qty 3: Fender Washers 91525A129
  • Qty 2: Plastic Screw 94564A310

Sized to mount on MGS Mk-4-Ext Mast, but any 1.5″ OD mast should work.

With the current popularity of air core magnetic loop antennas in amateur radio, I thought it would be nice to build another uncommon type. Instead of having a large loop with air in the middle (or core) of the antenna, this antenna uses a ferrite, not entirely dissimilar to those clips that come on USB cables, as a way to minimize physical size while maximizing the RF energy that flows through it.

The ARRL’s Antenna Book mentions this style of antenna, but only gives about a paragraph and references to the “Antenna Compendium Volume 1” and a reference to DeMaw’s text “Ferromagnetic-Core Design & Application Handbook”

Online, Ferrite Rod Antenna information is mostly about receive-only antennas, both for direction finding and shortwave listening. This particular antenna’s trick, thanks to the sizable ferrite, is the ability to transmit.

Granted it is only capable of handling about 20 watts, for a portable QRP rig it is pretty great. Especially with digital modes. Not to mention, that like a normal air core magnetic loop, it has great e-field noise rejection for urban environments.

With the capacitor I have and 10 turns on the LC tank circuit, it is able to tune from below 1.8 MHz up to 17 MHz. Tuning is an experience. When turning the knob, the human body de-tunes the whole circuit, so one has to adjust, move away and check, adjust, move away and check, repeat… Since it has such a high Q, there will be a lot of repeats getting it center on where you want it.

As for the parts it is fairly simple.

  • The ferrite rod itself.
    • This one is from a custom batch a friend of mine commissioned about a dozen years ago. (If interested, I recommend Stormwise Ferrite Rods, no affiliation, I’ve just had good luck with their products on several other projects, including a stack of rods for transmitting 100W)
  • A Vacuum Variable Capacitor
    • This one is a used Jennings 7-1000pF that only gets down to about 80pF
  • Wire for completing the LC Tank Circuit
    • I used some cheap Litz wire from eBay I had laying around. Its effects at this frequency aren’t as important, but with how soft it is it coils well.
  • Coax or wire for the ‘primary’ winding
    • I used a two turn Faraday coupler. Two turns because it gave me a 50 ohm match. A BNC to banana post adapter could work in a pinch too (and what I started with…)
  • Structure to hold it all together
    • I 3D printed some quick shapes with undyed filament, because plastics make it possible

I picked up a LulzBot Mini this week.  The printer’s specs and price point finally pushed me into getting one.  It requires a computer with USB to be able to drive it (there is no screen or SD slot.)  I rather like this because it means the interface can be what I want. After using it enough with my laptop that I was confident in taking the next step, I went looking around for smaller systems.

I had an Arndale Octa with Linaro laying about being unused.  The Octa is a really interesting board that I originally got for playing around with OpenCL and USB 3 on an ARM Cortex-A15. While it only has 1 USB port, it has a lot more computing power than the Pis that are usually used.  I followed the guide to install OctoPrint on Raspian (since it is similar enough to a generic Debian install,) but when all was told, I plugged the printer in, connected to the web interface, went to select the serial port….and nothing.

Here it turns out the bog standard Linaro builds don’t include the CDC-ACM module.

No problem, it’s easy enough to build a kernel module.

First find the kernel version you’re using with the command “uname -r”

I was on 3.15, which is fairly recent, so I went straight to the Linux kernel repo on github and found the folder that contained the module of interest.

Make a new folder on the Arndale and wget cdc-acm.c cdc-acm.m from the repo.  Then create a Makefile that contains:

obj-m += cdc-acm.o
make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules
make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean

(Cut and paste may make things fail.  If you get errors in the next step, just type it out)

Make sure you have the needed packages to build from apt (they were already on mine)

apt-get install linux-headers-$(uname -r) build-essential

Then you should just be able to type “make” and things should go.  Once it’s done there should be a cdc-acm.ko in the folder. Try to use “sudo insmod cdc-acm.ko” and the printer should show up!

This winter I replaced the light bar with something a little slicker.

2 Rigid Industries Dually D2’s in the driving configuration.  I built two mirror image bars that share the center hood release mount bolt and then go to the radiator support bolts just below the headlights.  The LEDs only fit toward the center, but it makes a better pattern this way.

More pictures once this fog finally lifts.


I’ve been working at quite a few rallies now, and one of the biggest things that a radio volunteer gets to do is listen.  When people listen long enough they start to think they know it all and can do a better job.  After Rally West Virginia I’ve kind of reached that point and humbly want to start compiling information into a more complete resource.  This is the start of that.

So, where to begin…..


Every rally that I have worked relies on the 2 meter amateur radio band for its communication.  Communication that is vital to both the safety of everyone involved and the logistics of running a rally.  The radio communications are usually directed by one individual called ‘Net’ that is typically located at the rally HQ.  Now there are lots of exceptions to both of those things, but I will cover that later.  The volunteers give information to Net who then disseminates it to the proper individual.  For example the 0 car will radio to Net from the finish that the course is clear and suitable for competition.  Then Net radios the stage captain, gets his assessment, then radios the start control and tells start that the stage is hot and to begin competition.

Order in this structure is absolutely critical for a smoothly functioning rally.  If one point needs to communicate with another point they either have Net transfer the information or ask to speak directly.

Most rallies also work through devices called repeaters.  Instead of each radio talking to every other radio, they communicate to a completely independent device on top of a nearby tower.  This device then repeats the information back out immediately, hence the name.  This allows for a much longer range and lets a spread out rally all work as one.

Like I said earlier, there are exceptions to all of these.  At NEFR for example each stage is run as it’s own self-contained unit.  Radios communicate using Simplex, where each radio just talks to each radio and works without a repeater.  In this case the Stage Captain or someone near the Stage Captain should be functioning as Net.

This leads us to hardware.  Almost all of use have gotten into rally due to hardware, but typically it’s automotive hardware and once a ralliest has his technicians license he doesn’t care anymore.

The absolute best mobile communication setup that one can have is a 75 watt 2 meter radio (like the Yaesu FT-2900) connected to a drilled NMO mount on the roof with a clean ground equipped with either a 1/4 wave antenna or a 5/8 wave antenna.  The quarter wave has 0 dBi of gain while the 5/8 has about 3 dBi.  The way to understand what this means is to imagine the radio being put out of the antenna as a donut.  The more gain it has the flatter the donut.  A flatter donut pushes more out the sides while having less height.  So a 1/4 wave is better for a more mountainous region.  For a general way to figure which is better if the target is over 45 degrees above/below you the 1/4 wave will be better.  If 60 degrees the 1/4 wave will be significantly better.

It should be noted that both of these antennas need a ground plane.  The roof of the car (or the trunk for those less willing) when tied in correctly acts as a ground plane.  It actually becomes part of the antenna allowing the maximum amount of signal to get out.

If one doesn’t want to drill, and use one of the many magnetic options a 1/2 wave antenna becomes needed.  The half wave doesn’t need to be coupled to the roof as a ground plane.  For maximum performance here the antenna’s whip has to be cut to ideal length.  This is called tuning, and a poorly tuned antenna can be the difference between putting out 20 watts or 65.  This is best done by someone who has the right tools and has done it before.

Another option is the HT or hand-held transceiver. These are mostly limited to 5 watts, and are great for listening and control working especially with a nearby repeater.  Some rallies can be conducted entirely with HTs, but there are not many.

Congratulations, you just read through Rally Radio 101.  I’ll think of more and add it later including radios in course cars, how to absolutely positively make sure your signal gets there, and additional means of propagation that should be employed by rallies.  If I made a mistake anywhere please comment or email me.

The problem causing the slow load times was reverse DNS look-ups throughout the server.  I had set /etc/resolv.conf to use Cablevisions DNS and they were not responding properly so I changed it to use OpenDNS’s 4.2.2.x addresses.  Everything seems happier now.

Virtualization is a buzzword right now, but it has a very remote audience.  For the one job I work they have 4 different servers doing things.  One hosts the inventory system, one the web system, one does backups, and I have no idea what the last one does (I think it’s for ghetto VPN. I don’t touch it.)

This historically has been a very windows-centric setup.  Every computer there runs XP.  Every upgrade cycle is the same thing.  New hardware, XP, then figured out how the old software was setup.  Being a fan of new things, I decided to just virtualize the machines for this cycle.

First I wanted to use a hypervisor.  It’s a natural choice.  One can waste as little resources as possible.   I grabbed a copy of OpenSUSE and ran it with Xen and everything was dandy until I realized the processor didn’t have support for full-virtualization.  Porting the existing Windows systems would be impossible.

I was told to get away from Linux, which I guess makes sense since these are critical apps and the owner needs to know how to troubleshoot.  So I looked into my old buddy VMWare.  I first started using VMWare when I got an old PPC mac and I could experiment more with my PC.

VMWare’s converter took the 2 windows installs I wanted to port, and in about 5 hours had the machines virtualized and ready to go.  Knowing as little as I did I first tried to use VMWware player to host them, but that wasn’t quite sitting right.  I did a facepalm.jpg and moved to VMWare server.

The virtualization system has been running for about 3 months now without a problem.  The data rack has almost nothing left in it and things are dandy.

Recently I started hosting from his location with a bunch of used IBM 300’s I picked up.  These have Ubuntu 8.10 on them and run great for the price, but I think they don’t fit his deployment goals as much, so I may be virtualizing them in the near future.

I now have 3 fully functional domains.  This is probably the longest span that I’ve ever had Linux running on a machine.  There’s no content, so loading potential is unknown, but that’s another bridge to hang from…

Linux is only free if your time is worthless.

The NTFS partition on my HTPC/Server thing shit the bed.

I formatted the primary drive.  It’s all openSUSE all the time now.  I still have the storage drives isolated because I have no trust in linux as a file server due to windows interaction.  NTFS support and SAMBA are sore spots to me, I know they work 97% now, but I have a habit of dragging out that last 3.

Where is this incoherent rant going?  MythTV!  This is now my 4th attempt at Myth.  It’s name really fits.  I think I almost have it at this point.  I have the IR controller working to change channels on the shitty Comcast box, I have the capture cards seemingly working.  Tonight after work I can test it to see if they work together.  I currently have the backend running without any verbose errors.  I have no idea if it works or not.  It simply haunts me with the ever present:

AutoExpire: CalcParams(): Max required Free Space: 0.0 GB w/freq: 15 min

I think if I can make it record shows I’m through the woods.  Then I have to worry about scheduling and the transcoding, but I think they are minor.

Oh, and I have to figure out a way to get it to pass the RAF (Roomate acceptance factor.)  Back in the Windows Media Center days the 360 did a great job of it.  I’m hoping to leverage UPnP for viewing, but live TV is also required.  I may have to break down and get an extra cable box.

I wonder if the A180 will actually work.

Now I need content for SitA…