Category Archives: Projects

Powering a Ham Radio with USB Power Delivery

A while back, I built a cable to power 12V devices (in my case a Kenwood TH-D74 HT) using the QuickCharge standard available in some USB power adapters. This allowed me to use a USB charger to charge my HT rather than bringing a dedicated wall wart which helped save some space when I traveled. While my homemade cable was electrically simple and worked as expected, it was a bit clunky. Also, QuickCharge is largely being replaced by USB Power Delivery (USB-PD), and since my laptop chargers using USB-PD, I found that I could consolidate my charging needs further by getting an adapter that works with USB-PD. 

Of course, I’m not the first person to try to adapt USB-PD for other purposes, so I was able to find a few products that partially solved this problem. I quickly came across a line of small adapter boards that negotiate the USB-PD protocol and provide an adjustable or preset voltage based on the standard. These are available on Amazon (affiliate links on this page) but can also be found even cheaper on eBay if you’re willing to wait for shipping from China.

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Keeping Arrow Antenna Elements Tight with Loctite

I’m a big fan of the Arrow Antenna for satellite operations for its good performance and portability, but one issue that pops up is the constant need to tighten the elements. I leave my Arrow assembled in the back seat of my Honda Accord, so it loosens up on its own. This is annoying from a clanging noise perspective, but it also messes with the performance of the antenna and throws off the SWR.

In a discussion some time ago on Twitter, Mike, W8LID, suggested trying fully aluminum threaded rod as he noticed this eliminated the problem and lessens the weight of the antenna slightly. Apparently, the included threaded studs are zinc plated steel which doesn’t tighten nicely against the aluminum threaded inserts in the arrow shafts. McMaster-Carr sells this threaded rod (8-32), but I found it locally at a metal shop so I saved on shipping costs. You can use a hack saw to cut 2 1/4″ pieces and you’re good to go with some minor filing to clean up the ends.

The aluminum studs developed small bends which become big deflections at the end of the 2m elements!

For the past year or so, I used this setup and it did solve the loosening problem nicely, but I recently noticed the elements were looking bent and misaligned. It also was sometimes difficult to dissemble the antenna as the aluminum hardware was binding a bit too tight to get a good grip to loosen it. I’ve been thinking about switching back to the original studs for these reasons, but I was still concerned about the constantly loosening elements.

A couple weeks ago, Sean, KX9X, held a RoverCon on Zoom, which aimed to provide a forum for satellite operators to meet, talk roving, and have a good time. During this, R.J., WY7AA, who is well known for making awesome drilled out masts, mentioned a solution the to loosening elements problem: purple Loctite. Purple Loctite, or officially Loctite 222, is a low strength threadlocker, weaker than the more common blue Loctite. He suggested putting a dab of it on one side of the threads to lock in the stud into one side of the arrow shaft. This leaves the other side free to easily dissemble, but prevents them from loosening on their own. I ended up using off-brand threadlocker on my own (Permatex 24024). I’ll update this if I have any issues in the future, but I look forward to have a nice and snug Arrow Antenna again without the fragility of aluminum studs!

VUCC Circle Checker Script

As a relatively active rover for satellite operations, I’m often looking to check whether a new location will be within my “VUCC circle” and be eligible to count for my home station VUCC certificate. Rule six of the ARRL’s  VHF/UHF Century Club (VUCC) Award Rules states:

For VUCC awards on 50 through 1296 MHz and Satellite, all contacts must be made from locations no more than 200 km apart. For SHF awards, contacts must be made from a single location, defined as within a 300-meter diameter circle.

This means that I can use many operation positions, including those from different grids and parks from my Kansas State Parks POTA mission, and effectively double dip on these contacts as long as no two locations are more than 200km apart. Although it’s easy enough to manually measure distance between locations using the ruler tool on Google Maps, as your list of locations grows, that gets difficult. I decided to write a quick and dirty Python script that checks every combination of locations against one another to see if any are more than 200km apart.

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Raspberry Pi METAR Ticker Display

When I was still in graduate school a few years ago, my office was in the center of a building which meant no windows and no way to quickly see the weather outside. This motivated me to make a project that would display the current weather on my desk. Being a pilot, I thought using the local METAR would be nice because I could also use the VFR, MVFR, IFR, and LIFR as quick designations for the weather and whether I could go flying after I was done for the day.

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Arduino-Based Intervalometer for DSLR

Arduino-Based Camera Intervalometer

I originally made this intervalometer to photograph the 2017 total solar eclipse. I wanted to make a portable and simple intervalometer out of parts I had laying around. I had a small enclosure with a front panel cut out for a keypad, LED, and switch from an old project I didn’t finish, so that seemed like a good place to start. I used this with my Canon Rebel T6i, and it connects using the 2.5mm remote port on the DSLR body.

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Remote Display over USB for Kenwood TH-D74

Kenwood TH-D74 with Upward-Facing Display and Yaesu FT-817ND Chest Rig

Although I really like the Kenwood TH-D74 for its long list of features, being an HT, the user interface is not well suited to satellite operations. In particular, for linear satellites where I may need to continuously vary the tuning throughout the pass, it is tough to come up with a good mounting scheme on my chest rig so that the tuning knob is accessible and the screen is viewable. To try to solve this problem, I thought I could somehow build an upward facing display so I can mount the radio vertically and have access to the knobs and a good display. The photo above shows the final product for this project which is built around a Raspberry Pi Zero W and the USB interface the TH-D74 supports.

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Shorty Arrow Satellite Antenna

Shorty Arrow Antenna

After seeing a few people on Twitter with a a shortened Arrow Antenna for satellite operations (colloquially called a “Shorty Arrow”), I decided to try to build my own. Rather than three elements on 2m and seven elements on 70cm as with the regular Arrow Antenna, the shorty arrow has two elements on 2m and four elements on 70cm. This results in a more compact and lightweight antenna at the expense of gain, particularly on 70cm. In my experience, this limits the antennas use down near the horizon especially if you have foliage in the way, and it is definitely a bit more of a challenge to get into some sats. Still, I’ve made plenty of FM contacts using 5w radios and this antenna even on weekend passes. I particularly like using this setup when I travel somewhere via airplane as this is small enough to fit in a carry-on bag.

Since you’ll need the antenna elements anyway, I suggest you buy a full size Arrow if you don’t have one already and just share the elements between them. It also saves you having to bother with measuring and centering the holes you drill; just clamp the full sized Arrow to the shorty to drill like I describe below.

What you’ll need:
-2m driven element
-2m reflector element
-70cm driven element
-70cm reflector element
-70cm 1st director element
-70cm 2nd director element
approximately 2 feet of 3/4″ square aluminum tubing – I found four feet of this at Menards for around $10
-handgrip of some sort. I used a foam grip from a garden trowel I found at the dollar store

11/64″ drill bit
-hack saw
-metal file
-hand drill
-a couple clamps

The build process is actually really simple and doesn’t require any measuring:

  1. Remove all the antenna elements and the hand grip from the full size Arrow Antenna.
  2. Take the square aluminum tubing and clamp it flush against the Arrow Antenna. Make sure you don’t place the clamps over any holes.
  3. Use the Arrow Antenna as a drill guide by drilling through its element holes and into the square aluminum tubing with the 11/64″ drill bit. This allows you to easily drill with the same spacing as the original Arrow Antenna without have to measure and center the holes. Do not drill through the holes that are usually hidden behind the hand grip on the Arrow Antenna – these are tapped for a 1/4-20 tripod mount.
  4. Remove the clamps, rotate the tubing and Arrow Antenna so the blank side of the tubing aligns with the other band’s element holes on the Arrow Antenna, re-clamp, and drill the holes for the other band in the same way.
  5. Using the hacksaw, cut the excess length off the aluminum tubing.
  6. Use a metal file to round off the ends of the tubing and remove any burs around the holes.
  7. Slide the hand grip on your new Shorty Arrow Antenna and install the elements.
  8. Go work some sats!

USB Quick Charge 2.0 Adapter for 12V Non-Quick Charge-Enabled Devices

As I got interested in roving more for satellite operations, I was looking for ways to slim down the equipment I needed to carry, particularly on trips that require a flight. While packing one night, I noticed I had a Tronsmart WC2F USB power adapter that supports the Qualcomm Quick Charge 2.0 protocol. This is one of several protocols that let devices use higher voltages and currents over a standard USB A connector. There are a few versions, but in short, this protocol allows for the USB power adapter to supply 12V at 1.5A, among other less interesting voltages (to me anyway). This seemed like a perfect way to charge my 12V devices – my Kenwood TH-D74, Ailunce HD-1, and Yaesu FT-817ND – without having to bring along an additional wall wart.

After digging a bit, I found an article on Hackaday where someone made a custom power adapter using Digispark, a modified regulator, and some simple handshaking code. Going down into the comments, Sam Mallicoat mentions the handshake can simply be done with a couple resistors and a momentary switch. Even better, Horst Leykam replied that a regular old latching SPST could work instead of a momentary switch. Aha! Since I was trying to keep this compact, this seemed like a great option compared to adding a microcontroller to the system. My plan was to made a cable adapter with an in-line switch that contained the resistors. A USB A male connector on one end and 2.1mm barrel connector on the other would give me good compatibility with my devices.

12V Enable Circuit for USB QuickCharge 2.0

For the switch, I ended up buying a simple Leviton in-line lamp cord switch which is large enough to hold the resistors inside and can be found online or a hardware store. I unfortunately didn’t take photos at the time, and I admit it wasn’t pretty inside; I had to use some hot glue to keep wires where I wanted them and rip out the regular lamp cord contacts. But still, it was not too difficult of a project.  As this uses a SPST switch, the operation is as follows:


    1. Plug USB cable of adapter into Tronsmart
    2. Cycle the adapter switch to off (if it’s not off already)
    3. Switch adapter on
    4. Voila! After a moment, 12V will be coming out on the barrel connector

Note that this switch does not control power entirely; when the switch is in the off position and before cycling it, it will still be outputting 5V. This is likely not an issue for a 12V device, but of course, proceed at your own risk!

While I know my adapter could be prettier, I’ve been happy with it so far. I have 2.1mm y-splitter cable which allows me to charge two devices at a time, usually my D74 (with a small connector adapter) and HD-1 or D74 and 817ND. While it could actually run one of those devices at a time based on its current capability, the inexpensive switching regulator in the Tronsmart is expectedly noisy, so this really should only be used as a charger. Since the Tronsmart is a dual USB port charger, I can bring this adapter to charge my radios and iPhone or iPad all from the same outlet at the same time.