My new MTR-3B Ultra-Compact Field Kit built in a Tom Bihn HLT2

I’m a bit obsessed with field radio kits (understatement alert).

If you don’t believe me, check out this episode of the Ham Radio Workbench podcast where they graciously allowed me to geek out about radio packs for a good two hours.

I should also note that I write, in detail, about my packing philosophy in this Anatomy of a Field Radio kit series.

There’s no cure for my pack obsession. I’m constantly in a state of assembling and testing the most efficient kits I can conjure up.

Since I rotate a fair amount of radios in my activations, the majority of my kits are modular; meaning, components like antennas, ATU’s, batteries, log/pen, and cables are packed in their own small pouches/pack. Before embarking on an activation, I simply assemble the components in a backpack along with the radio/s I might use that day. Over the years, I’ve developed a certain workflow with this process that ensures I don’t forget components or pack the wrong ones.

But by far, my favorite type of kit are those that are fully self-contained–proper grab-and-go kits that have everything I need inside to, for example, activate a summit.

Self-Contained Kits

Fully self-contained kits are reserved for the radios I use in the field most because, frankly, they’re stingy resource hogs: they  don’t share components with my other radios or kits.

They strictly adhere to field kit Golden Rule #1: Don’t borrow from one kit to feed another.

There are a couple reasons for this:

  1. To be properly self-contained, they need at least one of everything. If I “borrow” an adapter from my KX2 kit and forget to return it, I may find myself in the field unable to connect my antenna to my radio. (Lesson learned at the School of Hard Knocks during a 2016 NPOTA activation.)
  2. Fully self-contained kits have more possible fail points if an item is missing. To save weight and space, these kits have less spares than my modular packs do. Often, there’s only one key, one cable assembly, one log book, one battery, etc. Remove one item and you’re staring at a not-so-ideal situation.

(Again, more details about this in my field kit series.)

Until last week, I only had three fully self-contained kits: one for my QRP Labs QCX-Mini, one for my Elecraft KX2, and one for my Lab599 Discovery TX-500.

I purchased a radio in 2020 with one goal in mind: building a fully self-contained field kit for it. It’s a super compact radio and I wanted its kit to be as compact and lightweight as possible.

Enter the LNR Precision MTR-3B

If you’re not familiar, the MTR-3B is a super compact and lightweight three band, CW-only transceiver. It measures 3.85” X 2.5” X 0.9” and weighs a mere 4.8 oz. It’s the smallest, lightest weight transceiver I’ve ever owned.

The MTR-3B is a bit of a legend in the world of SOTA (Summits On The Air).

Thing is, the MTR-3B is a trimmed-down, purpose-built radio with only the essentials. It’s designed around activating summits and parks, so contains features like three programmable CW memory messages, but lacks things like a volume control, SWR meter, and rotary encoder (tuning knob).

When you start to add essential accessories to the MTR-3B, it can bulk it out a bit.

Antenna deployment

I love seeing how other operators design their field kits and there’s certainly no shortage of MTR-3B compact kit examples on the internet and YouTube. I’ve learned a lot from others’ experience.

Many, however, omit one item that I wanted to be included in my field kit pouch/pack: a means to deploy my antenna.

Here in the mountains of North Carolina, I’m lucky that even our tallest summits have trees (albeit short trees) that I can use to hang wire antennas. Not all of our summits have trees within the activation zone, mind you, but most do. This gives me the freedom of leaving telescoping poles and other self-supporting antenna suspension systems at home.

In the past, I carried some very compact fishing line and a small weight in order to deploy my antennas, but after discovering arborist throw lines–which can be reused hundreds of times–I haven’t used fishing line since.

Traditional arborist throw line is made of 3.175 mm polyethylene line which is (by design) quite bulky.

Marlow 2mm throw line.

Recently, however, Mike (W4MAF) introduced me to Marlow 2mm throw line which is much less bulky. Since then, I’ve bought four 50M reels of the stuff. If you want more detail, check out this recent field report and especially the activation video where I demonstrate it.

The Marlow line opened to door for me to include full throw lines in compact kits, including one for the MTR-3B.

A little Christmas money provided the perfect excuse to purchase a new pouch for the MTR-3B that I knew in advance would fit the bill.

The Tom Bihn Handy Little Thing (HLT) Size 2

I’ve been a customer of Seattle-based, Tom Bihn, for many years. Along with Red Oxx, they make some of the highest quality travel and field packs on the market in my humble opinion. If you’ve been reading my field reports, you’ve no doubt seen reference to their large travel tray which I use very heavily in my modular field kits.

A few years ago, Tom Bihn designed a new EDC (everyday carry) pouch called the Handy Little Thing (HLT).

I purchased a larger “Size 2” (see above/below) from the very first production batch and have been using it ever since in my main EDC pack.

In fact, the HLT2 has become one of my most useful pouches. Someday, I might do a short video showing how I pack it out. In the meantime, check out this video from Tom Bihn demonstrating how it could be used for EDC.

When I purchased my HLT2, I also bought a smaller HLT1 (see above/below) for my wife who quickly turned it into a super portable and super organized water color field kit.

My first HTL2 was made of Black 210 Ballistic Nylon. For the MTR-3B field kit, I decided to go for a higher visibility Solaris 200 Halcyon material.

Let’s take a look inside…

My MTR-3B fully self-contained compact field kit!

Keep in mind this is a first draft of the MTR-3B field kit. I’ll tidy it up and slowly cut down on some of its bulk over time.

As-is, it completely meets my requirements and warms this pack geek’s heart even as I took these photos on a fresh layer of snow.

The pouch/pack:

  • Tom Bihn Handy Little Thing (HLT) Size 2. This little guy retails for $70, but keep in mind that it’s designed and made in the USA. It also carries a lifetime warranty from a company that offers best-in-class customer service.

Inside, I’ve the following items:

  • A 5′ DC power cord. I like extra length to offer up a bit of flexibility for op position in the field. I also have a super short 9V alkaline battery connector (not pictured).
  • Sennheiser earphones (circa 1999) with an analog in-line volume control.
  • A prototype PackTenna 40M linked EFHW antenna. I’m testing this for buddy George (KJ6VU).
  • Koh-I-Noor .9 mm Mechanical Pencil
  • Muji A6 Notepad (hidden in the open pocket behind the mesh pocket
  • N0SA SOTA paddles (hidden in the upper left zippered pocket–and no, this particular model is no longer available)


In the main interior mesh pocket:

In the exterior pocket:

  • 25 meters of Marlow KF1050 Excel 2mm Throwline, and an 8 oz Weaver throw weight. After a lot of experimenting, I find that 25 meters is an adequate amount of throw line for 90% of my antenna deployments. It’s certainly more than enough for mountain summits where trees tend to be short and for parks where there are so many trees to choose from.
  • A Bioenno 3 aH (9V) LiFePo Battery (Model BLF-0903W). I’ll admit it: this battery is bulkier than I’d like, but it does fit perfectly in the exterior pocket. I’m currently debating the purchase of a 1200 mAh pack 3S LiPo pack which is much smaller, but would require the purchase of a balanced charger. That and having had experience with LiPo thermal runaway in the past, I’m hesitant to go this route. I might just take the mass hit and stay with the LiFePo4.

The really cool thing about this pack is that even without having refined it, it’s already super compact, lightweight, and fully self-contained. I’ve tested it in the field and it works brilliantly.

This pack is so compact, I can keep it under the driver’s seat of my car or truck.

At the last minute, I can slip it into my EDC pack or airline carry-on and I know that I have a full field radio kit ready for radio adventures.

It’s always ready for some field action! The only thing it needs to hop on the air is a willing operator and I’m that guy!

How about you?

Are you obsessed with super-compact, self-contained field radio kits? I’d love to hear your comments and suggestions or even share photos and descriptions of your kit here on QRPer.com!

Thank you!

I’d like to send a special thanks to those of you who have been supporting the site and channel through Patreon and the Coffee Fund. While certainly not a requirement as my content will always be free, I really appreciate the support.

Patreon and Coffee Fund contributors help fund my radio purchases, experiments, and travels. I’m incredibly grateful and honored for your support which makes posts like this one possible.

I hope you get an opportunity to play radio in the coming days!

Cheers & 73,

Thomas (K4SWL)

12 thoughts on “My new MTR-3B Ultra-Compact Field Kit built in a Tom Bihn HLT2”

  1. What a wonderful article, thank you. Many thoughts to ponder over. I as a new QRP op, gathering my gear. your suggestions are my motivation to carry on.

    73
    Wb8yxf

  2. Tom, what do you do to tame down the 13.2v Bioenno to the power limitations of the MTR3B? Some of my most memorable contacts have been with the MTR3B and I would not want to be without it.

    1. Looks like he uses the 9V size with this kit.

      On my MTR I have a power lead that puts a few silicon diodes in line to drop the voltage. I believe I use 3 of them.

    2. Hi, Dick,

      So I don’t use a 12V Bioenno battery. Mine is their 9V 3Ah battery. Works a charm! I’m fine with reduced power knowing I’m not damaging the finals.

      Cheers,
      Thomas

      1. Very good Tom, thanks. Will pass that on to a friend. Have you tested the acutual output power with that battery?

  3. Very interesting article Thomas!

    I have similarly created a micro kit for my MTR3b using two CaseLogic hard drive cases – one for the MTR3b, palm micro key, headphones and power lead, the second contains 2x 9v Li-ion batteries and a Wonderwand Wonderloop (mini mag loop).

    Lightweight, highly portable and not dependent on trees! Using the mini mag-loop that the Wonderloop is, allows for use in locations that a wire can’t – sure signal strengths will never be as good, but it works in places that otherwise you wouldn’t.

    Richard M0RGM

    1. Excellent! Richard, I would most welcome a little write up with photos if you cared to share your kit with us! 🙂 I love seeing how others’ pack their field kits. I learn so much this way.

      Cheers & 73,
      Thomas
      K4SWL / M0CYI

  4. I have a similar kit that I built using an old first aid bag, around the same size with my MTR3b. I have an american Morse paddle, feed line and a PAR EF trail friendly antenna. I have throw rope( string really) and pray that I can find a rock to use for weight. This is my backpacking kit, so every oz saved is an oz not felt. 😉

    I also keep mine in the truck.

    Now I’m gonna have to look up that bag.

    Thanks for the ideas

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