Field Radio Kit Gallery: KD0FNR’s Rockmite 20 and Tuna Topper

Many thanks to Hamilton (KD0FNR) who shares the following article about his portable field radio kit which will be featured on our Field Kit Gallery page. If you would like to share your field kit with the QRPer community, read this post.


Rockmite 20 and Tuna Topper Pack QRP Punch

by Hamilton (KD0FNR)

Our ham radio field kit—in my mind—revolves around simplicity. I’ll walk you through a lot of details, because we have a blast with the field kit and I love talking about it. At the end of the day, it’s a kit radio and amplifier housed in a couple of cans with lengths of wire we bought at a hardware store for an antenna, a cell phone power brick, and a keyer glued together out of video game switches and an old battery case. We’ve thrown the kit into cloth shopping bags and backpacks with equal measures of success. We once patched an antenna connection using washi tape.

OK, I said ‘our’ and ‘we’, but who are we? I’m the dad of three kids—one of whom recently passed her Technician radio exam, KO6BTY—who are 12, 11, and 8 years old. Right now, they’re rarely on the radio—of course, that’s about to change—they help with most aspects of our radio outings.

Which brings up the question, what do our radio outings look like? Our outings are pretty equally divided between, camping and day trips. Our entire family has enjoyed camping—and done a lot of it—since long before I got back into ham radio. Each of the kids went on their first camping trip when they were a few weeks old.  Our camping trips range from local, public transit enabled outings—we take the bus to Pantol Campground, across the Golden Gate Bridge from San Francisco where there are two POTAs readily available: Mt. Tamalpais State Park and  Muir Woods. We also take multi-day/week trips: I grew up in New Mexico, so the kids and I frequently find ourselves back there activating or attempting to activate sites like Villa Nueva State Park, Organ Mountains National Monument, and Cibola National Forest, among others. These are the outings that have led to large-ish battery selections you’ll see below.

Our day trips are quick runs along various local bus, train, and ferry lines with a hike tacked on the end. Within the peninsula that encloses San Francisco, we have several POTA locations and two easily reachable SOTA locations. We pretty frequently bus to a spot, and then spend a few hours hanging out in a nice park getting some radio time.

Having said all of that, you might have guessed that our kit would be optimized for easy travel. You’d be right. Now, finally, let’s talk about the kit!

Radio Details:

All of our equipment is home-built. It’s evolved over the last year-and-a-half into he tidy kit you see above. Finally having a ‘typical’ kit picture is actually what inspired this article.

Equipment List:

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  • Rockmite 20
  • Tuna Topper
  • One 20 ounce can Dole Pineapple Slices (emptied—see support crew; and cleaned)
  • Two RJ-45 breakout boards
  • One spool butcher’s twine (two if you’re feeling bougie)
  • One Imuto power brick that supplies 15 V when funneled through:
  • One Adafruit USB Type C Power Delivery Dummy Breakout – I2C or Fixed – HUSB238
  • Two banana jack sockets (plus a few more for spares)
  • Forty feet 12 gauge insulated/stranded wire
  • Twenty-five feet (or so) RJ-45 Ethernet cable (scavenged from the parts bin at our local maker space)
  • One antenna launcher (scavenged from available fallen tree limbs onsite)
  • One donut Bag from your favorite donut store
  • One roll of washi tape

The Rockmite is a rock-locked radio with two available frequencies that are 500 Hz apart from each other. That makes our antenna design really simple; we’ve got a dipole that’s trimmed to be resonant at 14057.5 kHz. Project TouCans puts out a QRP maximum 5 Watts. Our field kit has evolved to that 5 Watts though. We started out with the Flying Rockmite at 250 mW, then we made a power bump to 750 mW, and then with the addition of a Tuna Topper amplifier and a lot of experimenting we finally achieved a QRP maximum 5 Watts output power.

The QRPp Rockmites–having so little power combined with lots of somewhat confusing reading about antenna matchers and coaxial cable and baluns–led to the original Flying Rockmite. “Do you know what makes you not have to discuss feed lines?” I reasoned, “Not having a feedline.” And so, the RockMite was inserted into the dipole. I brought the keyer controls down to me and sent the power up along an Ethernet cable.

Earlier this year, while listening to Ham Radio Work Bench, it finally occurred to me not to clip off the Ethernet connectors, and our rig wound up with a really nice home-built keyer that was written up in Sprat this summer, more about that in just a moment.

The addition of a Tuna Topper amplifier was the icing on our QRP cake, so to speak. That made the rig louder which made POTAs much, much easier. But where to put the amp? I mean, the rig’s in the antenna. Can the amp go up there too? Yes! And thus, was born Project TouCans. The RockMite and the Tuna Topper are housed in a pineapple can. The Tuna can that shipped with the amplifier is used as an enclosure and antenna mount.

But what’s the donut bag for you ask? It’s serves as a rain cover, a necessary accessory here in San Francisco where fog and drizzle are common.

Keyer:

The rig’s keyer is also homebrew. It was written up in the Summer 2023 issue of Sprat (the journal of the GQRP club.)

The rig (the flying Rockmite back then) needs batteries… 8 of them… AAs. The rig needed dit, dah,  and keyer programming switches. Also, thanks to the aforementioned decision to not clip the end off the Ethernet cable, the keyer now needed an RJ-45 breakout bug. How to combine all of these thing? By doing plastic dead-bug construction SuperGlue style!

Here’s the result:

Support Crew

My support crew, the 12, 11, and 8 year-olds who call me Dad, are very instrumental in our outings to the outer reaches as they carry the bulk of our extra equipment: tents, sleeping bags, camp stoves, and what have you.

One thing you’ll need to keep in mind about support crews is that odd traditions tend to build up around them. For example, the support crew and I are obligated to go out for sushi and ice cream any time we make a QSO with Japan.

They also frequently help out with radio engineering.

Due to the camping nature of many of our outings, we use the following additional equipment for the support crew and myself:

  • Two North Face 20 degree sleeping bags (ours are the discontinued youth Aleutian 20; this one is similar)
  • Two Kelty 0 degree sleeping bags (this one looks about the same but without the geese)
  • One Marmot Tungsten 3 tent for the crew
  • One Kelty Outfitter Pro 2 tent for me
  • One Osprey 38 liter pack
  • One Osprey 50 liter pack
  • One Osprey 75 liter pack
  • One Kelty RedCloud 6650 cubic inch pack

You might wonder why there’s so much cold weather equipment. Well, sometimes your support crew, (the 8 year-old in this case), insists that you camp towards the snow.

And I’ll leave you with a few more optional accessories that can make your POTA experience a bit more of a luxury.

For more information, check out Hamilton’s Project TouCans page!

8 thoughts on “Field Radio Kit Gallery: KD0FNR’s Rockmite 20 and Tuna Topper”

  1. A brilliant exposé on the clever hacking behind the mysterious and elusive KD0FNR ham radio signal. Made somewhat less elusive now with the bump to a full gallon of QRP!

    1. Hey Matt!

      I’ve had a lot of fun chasing you around SF parks! I’m hoping I’m going to get out to more local parks and summits more often in the new year. Our two rigs in the Bay area make a really good arguemnt for why ground wave on 20 meters isn’t a great mode 🙂 I frequently know you’re only two miles away, but we’re both at 229.

  2. Hamilton,
    Perfect timing for this post – I just got you on 20m CW from NM 🙂 I could not get through with QRP, so I had to crank it up all the way to 50W to work you. Thanks so much for describing your very interesting setup. It’s always nice to know what is used on the other end of a QSO.

    Thanks again and good luck for keeping the SF fog out of your rig.

    Karl Heinz – K5KHK

    1. Hi Karl!
      Thanks for the NM to NY QSO! The day before KO6BTY were further north near Mountainair and the fog shield became a frost shield 🙂
      Our received signal reports to the East were weaker right about then than later in the day as well.

  3. I had a Rockmite once, sold at HamFest. It is a very nice way to get into QRP, but most are sold with rock bound frequency of 14.023 MHz. I got crystals on ebay to move up to 14.055 (need 2 xtals, one for xmt and one for rcvr). The rig has built in keyer so is great for CW. Just need to learn the menu and how to get to them.

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