Anatomy of a Field Radio Kit Part 1: Basic components and advantages of going QRP

The following review was first published in the June 2021 issue of The Spectrum Monitor magazine:


Part 1: Anatomy of a field radio kit

by Thomas (K4SWL)

Whether it’s the ARRL Field Day, Winter Field Day, a QRP contest, or, more likely, a Summits On The Air or Parks On The Air activation, I look for any and every excuse to hit the field with my radios.

Most of my on-air time is in the field. While I enjoy operating from the shack, I’ve discovered I especially enjoy operating in the great outdoors.

Besides being a fan of hiking, camping, and the great outdoors generally, I also am particularly fond of radio field gear. I like portable transceivers, portable antennas, battery packs, and all of the accessories that make field operation efficient and enjoyable.

I appreciate the emergency communications skills I’ve developed in the field, too. Should the need (or opportunity) arise, I now keep a complete field kit packed and ready to go at all times, and can even deploy all of it within just ten minutes. In my early days of ham radio operation, I might have easily spent thirty minutes setting the antenna, alone…especially on Field Day, with folks watching me struggle to untangle wires and cables, followed by the undoubtedly entertaining attempts I made to put a line into a tree to deploy the antenna. But after deploying a variety of antennas hundreds of times now, I find that––while I’m still not perfect––I finally have a bit of skill and the process of tossing up a line is becoming much swifter and smoother.

Confessions of a pack geek

The Red Oxx C-Ruck loaded and ready for the field!

If I’m being honest with myself, I admit: I also simply get a thrill out of kitting out my field packs, as well as organizing and tweaking them over time. Yes, (don’t judge me!) I actually like packing up my field gear.

I think my passion for organizing and packing gear goes back to a former career when I lived in the UK, Germany, and France, and was required to travel throughout Europe frequently. Originally inspired by travel guru Rick Steves, I’ve always appreciated the footloose feeling of having all of my travel gear in one lightweight pack. I don’t like checking in luggage, but love the freedom of grabbing my backpack and skipping the baggage claim carousels. And I also like knowing that, even though my gear is compact, it contains everything I need.

I’ve become something of a “less-is-more” traveller. Two years ago, for example, I traveled for one week using what Frontier Airlines classifies as a “personal carry-on.” My Tom Bihn Stowaway pack, which only measures 14.0″ (w) x 9.4″ (h) x 8.1″ (d), carried everything I needed for a conference, including my own presentation gear.

My Tom Bihn Stowaway personal carry on convertible pack with everything I needed for a one week trip including a conference.

Packing for that trip was great fun as it really challenged me to decide what was essential and what was not. My iPad doubled a computing and presentation device, for example, but I also packed a small flashlight and a mini first aid kit, which I felt were important. Of course, I also carried a small portable Shortwave/AM/FM radio and my Yaesu VX-3R handheld…also vital, as I can’t leave home without radios!

Getting started with a field kit

Putting together a field radio kit is so similar to packing for travel: you must first do an assessment of what you need, starting with the basics––then organize it, pack it, and test it.

In my world, this is a very deep topic. We’re going to break down this topic into two parts.

This article, Part 1, we’ll dive in:

  • first, going over the obvious components of a basic field radio kit;
  • second, discussing the benefits of going low-power (QRP) if that appeals

In Part 2, we will:

  • look at variations of kits based on activity, and finally
  • review what I consider the “golden rules” of a good field radio kit

The basics of a field radio kit

First, let’s go over the basics of your field kit, considering that that these primary components will dictate your bag, pack, or case size.

A transceiver

The lab599 Discovery TX-500

Since I’m a bit radio obsessed, I have a number of QRP transceivers I like to take to the field.  But if you have selected one transceiver you plan to dedicate to field work, or simply have only one transceiver, period, you can build a kit around it (and see my note below about “modular” kits). If budget allows, you might consider buying a radio specifically for field use, so it can always be packed and ready to go.

There are a number of transceivers on the market that are designed with field use in mind. Some are compact, power-stingy CW-only QRP transceivers that might only operate on three ham radio bands, while others are 100-watt general coverage transceivers that even have built-in antenna tuners––there’s a wide range of options.

Look for field-friendly, built-in options like:

  • CW and voice-memory keying;
  • SWR and power meter readings;
  • a battery voltage indicator;
  • low current consumption;
  • the ability to lower power to at least one watt;
  • an internal battery option; and
  • an internal antenna tuner option

And the more such options are already built into your field rig, obviously, the less separate accessories you’ll need to pack and keep track of in the field, which is a good thing.

The Elecraft KX2 has a built-in ATU, battery pack, and even attachable CW paddles!

Some of my favorite field-ready general-coverage transceivers currently in production are:

  • The Elecraft KX2 A full-featured, inclusive, and compact 80-10 meter transceiver that’s truly a “Swiss-army knife” of field operation (see November 2016 TSM review)
  • The Elecraft KX3 Benchmark performance, wide array of features, and compact design
  • The lab599 Discovery TX-500 Military-grade engineering, weatherproof, spectrum display, and benchmark current consumption for a general-coverage radio (see October 2020 TSM review)
  • Mission RGO One Top-notch performance, 50-watts out, and excellent audio (see November 2020 TSM review)
  • The Yaesu FT-817/818 Rugged chassis, 160-6 meters, VHF and UHF multi-mode, both BNC and PL-259 antenna inputs
  • The Xiegu X5105 Affordable, 160-6 meters, 5 watts output, built-in ATU, and built in rechargeable batttey
  • The Xiegu G90 Affordable, relatively compact rig with built-in ATU, color screen with spectrum/watefall, good audio, and 20 watts of output power (see August 2020 TSM review)
  • The Icom IC-705 Benchmark performance, a multitude of features, exchangeable battery packs, 160-6 meters, VHF and UHF multi-mode, D-Star, GPS, WiFi, Bluetooth (see February 2021 TSM review)
  • The Yaesu FT-891: Affordable relatively compact radio with detachable faceplate, 100 watts output, and excellent audio (see November 2017 TSM review)

And if you’re primarily a CW operator, you’ll have some incredibly compact radio options like the CW-only Mountain Topper MTR-3B or 4B, or the Elecraft KX1 (used).

An important side note for field contests: if you plan to use a field transceiver in an event like the ARRL Field Day and/or another popular radio contest, make sure you choose a transceiver that can handle tightly spaced signals in an RF-dense environment. This is not the time to pull out a lower-end radio with poor receiver specifications. Use Rob Sherwood’s receiver test data table as a guide.

An antenna––and a means to deploy/support it

The CHA LEFS sloper

This particular topic, alone, might warrant a three-part series of articles. So, to keep the scope of this article realistic, let’s just say that you should build or buy an antenna that can comfortably handle the wattage you’re pushing into it in all the modes that you operate, considering that some 100-watt SSB-rated antennas might melt or arc if you run 100 watts CW or FT8.

I would suggest you consider having at least one resonant antenna, like an end-fed half-wave (EFHW) that might cover 40 and 20 meters without the need of an antenna tuner to match the antenna impedance to your rig.

Some of my favorite portable antenna systems?

I’m a big fan of Chameleon Antenna for their ease of deployment and benchmark build quality. Their prices range from $145 for the Emcomm III random wire, to $550 for their MPAS 2.0 vertical antenna system. These prices are near the top of the market, but Chameleon antennas are all machined and produced in the US and the quality is second to none. These are antennas you might well pass along to the next generation, meaning, really heirloom-worthy kit!

Packtenna 9:1 UNUN Random Wire
The PackTenna 9:1 UNUN

PackTennas, likewise, are pricey for such a compact product, but they are also beautifully engineered, lightweight, and designed for heavy field use. PackTenna produces an EFHW, 9:1 UNUN random wire, and linked dipole models. They’re some of the most compact field antennas on the market that can still handle as much as 100 watts of power output.

My Wolf River Coils “TIA” vertical antenna

Wolf River Coils verticals are affordable, compact, and resonant––thus an ATU isn’t needed. It will take some time to learn how to adjust the coil during frequency changes, but they work amazingly well. I have the WRC Take It Along (TIA). Their antennas are designed to handle 100 watts SSB, 50 watts CW, or 20 watts digital.

The EFT Trail-Friendly

Vibroplex sells a number of compact field portable antennas and is the manufacturer of Par End Fedz offerings. I’m very fond of the EFT Trail-Friendly and the EFT-MTR.

The MFJ-1984LP EFHW packs a lot of performance for the price

MFJ Enterprises also has a few portable antennas in their catalog, and it’s very difficult to beat the price and performance of their antenna gear. I have their $50 EFHW antenna (the MFJ-1982LP) and love it.

The Elecraft AX1 attaches directly to the BNC port on the KX3 and KX2.

I’ve also had tremendous fun with the uber-compact Elecraft AX1 antenna. Unquestionably, it’s the most compact and quickest-to-deploy antenna I own. It’s designed to pair with the Elecraft KX2 and KX3 using the optional internal antenna tuner.

There are a number of other antenna manufacturers who cater to portable operators. For example––although I’ve not yet had the opportunity of testing their antennas––SOTAbeams is highly regarded among SOTA enthusiasts.

Short on cash? No worries; you can build your own! In fact, until 2016, I had never purchased a field antenna; I built all my own. EFHW antennas and random-wire antennas are no more than a carefully-wound coil, a female antenna connector, an enclosure or mounting plate, and some wire. Some of the most active field operators I know homebrew all of their antennas. It’s easy, affordable, and fun!

In fact, some antennas are no more than a bit of speaker wire matched with a good ATU.

A power source

A 3Ah Bioenno 12V LiFEPo4 powering my LD-11 transceiver

I’ll keep this point brief because we recently covered the topic of batteries in detail in our previous feature.

Make sure you choose a battery that is sized appropriately for your transceiver power output. I will say that I’m a huge fan of LiFePo4 rechargeable batteries for their voltage range, lightweight design, and longevity. Being primarily a QRPer, I typically use 3 to 4.5 amp hour batteries as they’ll carry me through as many as three or four activations without needing to be recharged. For longer field deployments, or when I’m powering my 100W KXPA100 amplifier, I’ll use my 15 aH Bioenno LiFePo4 pack.

I use my 15Ah Bioenno LiFePo4 pack for QRO transceivers

Again, check out our Portable Power Primer for a deep-dive into the world of portable power.

A key, mic, and/or computing device

It should go without saying that you need to pack these, but I have gone to the field with operators who forgot their key or mic and asked if I had a spare.

Keys are fairly universal, but keep in mind legacy transceivers often want a ¼” plug while newer rigs typically accept an ⅛” plug. Microphones, however, vary in port type and pin configuration based on the manufacturer and model. You could damage your mic or rig if you plug in a multi-pin mic that was designed for a different transceiver. Most mics that use a ⅛” plug are universal. Still, check before you plug it in if using an after-market or non-OEM mic.

Of course, choose a key, microphone, or boom headset that’s compact and rugged so that’ll be easy to pack and will stand the test of time.

I also always pack a set of inexpensive in-ear earphones. These can dramatically help with weak-signal interpretation.

Also, if you plan to operate a digital mode, you’ll likely need some sort of computing device. Even though I rarely operate digital modes in the field, I often pack my Microsoft Surface Go tablet in case I change my mind.

My Microsoft Surface Go tablet

In addition, I like logging directly to N3FJP’s Amateur Contact Log application directly in the field to save time submitting my logs later. Soon, I’ll be using the new HAMRS field log on my iPhone.

Speaking of logging…

A means of logging

I like compact notepads like Muji and Rite In The Rain for field use.

As simple as it is, it’s very important to take at least some paper and a pencil for logging your contacts. I like using small, pocket-sized Muji notebooks (affiliate link) for logging, and if the weather is even a little questionable, I’m a huge fan of getting my contacts down in Rite In The Rain mini notebooks (affiliate link) or notepads using a good old-fashioned pencil.

I like logging to paper and sometimes simultaneously logging to my Microsoft Surface Go. I have completed phone-only field activations where I only logged to my Surface Go tablet: in those cases, I snap a photo of my N3FJP call log, just in case something happens to my tablet between the field and the shack! Having endured enough technology failures, it gives me peace of mind to have at least one other backup.

Keep in mind that when you’re activating a park or summit, the folks calling you are relying on you to submit your logs to the appropriate programs so that they can get credit for working you. Many times, this might also help their awards for a state, county, or grid square. Always submit your logs after an activation even if you didn’t make enough contacts to validate the activation (POTA requires 10 contacts, SOTA requires 4 logged). It helps other folks out.

A pack or case

If you have a field radio kit, you’re going to need a means to organize and contain it for transport. There are at least three types of systems used for field kits.

A backpack or soft-sided case

My GoRuck BulletRuck is a brilliant SOTA pack

Since I enjoy the option of hiking with my radio gear, I love using backpacks. Although I’ll speak to this more next month in “Part 2,”, I choose quality packs that have at least one waterproof compartment and are comfortable to carry on long hikes. I also try to look for packs with Molle or some sort of external strapping so that I can attach portable antenna masts or even my hiking poles to the exterior of the pack.

A waterproof case or flight case

Ruggedized, weatherproof cases come in all sizes. This Pelican 1060 can house my entire KX1 radio kit.

Many field operators who want extra protection for their gear––especially when they don’t plan to hike or carry their gear long distances to the operating site––like hard-sided cases. I have built field radio kits in waterproof Pelican cases and appreciate knowing that I could drop my kit in a whitewater river, and it would likely survive the adventure unscathed. If you are one of these operators, look for quality watertight cases from brands like Pelican and Nanuk with interiors lined in pick foam padding that allows you to perfectly accommodate and safely protect your radio and accessories.

Portable ready-to-deploy cases

Although this option is almost outside the scope of this article, many emergency communications enthusiasts love having their gear loaded in rugged, portable––often rack-mounted and hard-sided––cases that they can simply open, hook to an antenna, and get right on the air. These systems are often the heaviest, least “portable,” and less suited for long distance hikes, but they’re often completely self-contained, with all of the components, including the power, hooked up and ready to go on a moment’s notice. While a system like this would be impractical for many Summits On The Air sites, it could be ideal for a park or island activation where you’re never that far from your vehicle.

Optional: Antenna cable

An ABR Industries RG-316 cable assembly

This doesn’t sound like an option, but it’s true.  I’ve often operated my Elecraft KX3, KX2, and KX1 without a feedline at all: I simply attached two wires to a BNC binding post, and connected that to the radio. It makes for a super-compact setup.

Even an 8-12 foot feedline can make it easier to configure your operating position in the field. If you want to keep the feedline as low-profile as possible,  especially if you’re operating QRP, consider investing in a quality RG-316 feedline terminated with the connector that fits your radio and antenna.

Optional: Antenna Tuner/Transmatch

A portable ATU with RF-sensing like the Elecraft T1 will give you an amazing amount of frequency agility. I’ve been known to use the T1 to tune my CHA Emcomm III random wire antenna on 160 meters..

Again, this topic could easily warrant a multi-part series of articles, but I’ll sum this one up in a nutshell: while I love (and even prefer) using resonant antennas that require no antenna tuner, I almost always carry a radio with a built-in ATU or an external portable ATU like the Elecraft T1 or ZM-2.

Why? Because an ATU will give you a certain amount of frequency agility or freedom. If I’m using an antenna that’s resonant on 40, 20, and 10 meters, but there’s a contest that day and the bands are incredibly crowded, I might use the ATU to find a match on 30 meters or 17 meters, thus finding a little refuge and space to operate. Also, sometimes antenna deployments aren’t ideal––due, for example, to site limitations such as dense vegetation that may alter the antenna deployment and thus its resonance. An ATU can at least keep your transceiver happy with the SWR when your resonant antenna might not be perfectly resonant.

But the main reason I carry it? A portable ATU gives you operational flexibility.

QRP or QRO?

I have operated QRO in the field with my KXPA100 amplifier on Field Day.

Its good to keep in mind that many of the station accessories listed above need to be matched to the output power of your transceiver and modes you use.

Many ham radio friendships have been placed in jeopardy over the question of either using QRP (low power) or QRO (high power) for field operations. This is a shame. Some operators have very strong opinions, but the truth is, there is no right or wrong answer.

In the spirit of full disclosure, I operate 97% of the time at QRP power levels––in my world, this means five watts or less. Personally, I enjoy the challenge of low-power operating.  But I also appreciate the portability QRP gear offers.

The wee Mountain Topper MTR-3B

Speaking pragmatically––and this fact really isn’t open to debate––QRP and lower-power transceivers and accessories tend to be more efficient, more compact, and lighter than their higher-power siblings.

Most of my QRP transceivers weigh anywhere from two to five times less than their 100-watt equivalents. If you’re operating mobile (from a vehicle or camper/caravan, for example), an eight to twelve pound difference might not be a big deal. But the moment you’re hiking several miles to a mountain summit, weight becomes an important factor.

QRP transceivers have modest power requirements: everything from battery, to antenna, and even to tuners, are smaller, lighter, and more compact.

When operating QRP, you don’t have to worry as much about RF coming back to the radio from, say, an end-fed antenna. If I’m pushing over 20 watts into an end-fed half wave or end-fed random wire, I’ll likely want an in-line RF choke to keep some of that energy from affecting my transceiver or giving me an RF “tingle” when I touch the radio chassis or my key. Too much RF coming back to the transceiver can also affect things like electronic CW keying. But at five watts? I don’t worry. This is almost a non-issue, unless your transceiver happens to be very RF-sensitive indeed.

And even though I’m predominantly a QRPer, I definitely do pack radios like the 50-watt Mission RGO One and occasionally my Elecraft KX3 and KXPA100 100-watt amplifier, especially for an event like Field Day where my club is operating at higher power. I simply size up my gear appropriately. Again, this is especially important with your antenna, feed line, ATU, and battery selections.

If you primarily activate parks and are never far from your vehicle, it’s quite easy to accommodate a 100 watt transceiver like an FT-891, for example. Of course, if you wish to operate low-power and save your battery, simply turn down the output power. If you plan to hike a lot with your gear, then get your mind around QRP!

Stay tuned for Part 2!

In Part 2 we’ll dig into some of the details, looking at different approaches to field radio kits and some guidance and suggestions based on my real-life experience (read: operating mistakes).

Click here to read Anatomy of a Field Radio Kit Part 2.


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15 thoughts on “Anatomy of a Field Radio Kit Part 1: Basic components and advantages of going QRP”

  1. Truly excellent article Thomas. Thank you!

    I suspect this one will be a reference article to which many of us will keep returning…

    Looking forward to part 2!

  2. A great read Thomas. You have a fabulous writing/presentation style. Clear and to the point. Looking forward to part 2.
    Cheers
    Andrew VK2FARR

  3. You guys seem to have the pick of the bunch in terms of batteries..I don’t believe the Bioenno batteries are available here in the UK. I was trying to find some source of power for the KX3 & 40w amp, for when Iam out /p, but need a little more “punch”.

    1. Maybe get some quality 18650’s from Fogstar( no it’s not an affiliate link!), a BMS and DIY it. M0 YZT, Doncaster.

  4. Is there any repair help for the Rock Mite. I need a chip replaced.
    and am toooo old to do it myself. (80).

  5. Great artical Thomas a lot of info but well presented and easy to follow and understand. For those in the UK like myself you can easily get hold of 16, 18, 22 and 25/26Ah 12V LiFePO4 batteries from most Golfing retailers which usually come with 12 gage T-bar to Powerpole cables wired to the common standard so perfect for all types of transceivers. Most can push 25A plus with no issues. I’m using an Eco-Worthy 30Ah LiFePO4 battery which is easily transportable and weighs a little over 3.2KG fitted with a Powerpole cable so I can hook up gear within seconds plus they are easy to charge with a 14.6V dedicated LiFePO4 charger at home. My next job is to look into portable LiFePO4 solar charging options.

  6. Hello Thomas K4SWL
    I’ve seen some of Your “Videologgs” on
    Your Youtube Channel and must express
    respect how You Do Your QSOs. Your CW
    is well articulated and distinct so there shouldn’t bee any problems for those who have morseprofishiancy(which I don’t!) to
    go threw QSOs with You! I wish I had that!
    KEEP UP YOUR GOOD PRACTICE!
    73s de Gunnar sm6oer 19 Aug 2021 >>\<

  7. Have you tried out KM4ACK’s efhw antenna kit? If so, I would love to see a review on it.

    I need to get busy and build mine. But today I think I will play with the speaker wire antenna that I built using your version as a guide.

  8. I’m really enjoying your articles and YouTube videos! I’m just getting started in the world of QRP. So many options! But like you I’m a backpack fanatic. House rule now is if a new pack comes in, one pack has to go out. Once I’m more confident in my code, I’ll very likely look hard at some of those CW only rights to go ultra-light.

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