Tag Archives: Mountain Topper MTR-3B

New Mountain Topper MTR-3B Details

by Matt (W6CSN)

The Mountaintopper MTR-3B is a popular QRP portable HF transceiver that has a bit of “cult-ish” mystique about it. The radio seems to hit the sweet spot of size, weight, performance and capability desired by so many portable operators.

While I have operated the MTR-4B, and quite like it, I have yet to get my hands on the much vaunted 3B. Hopefully that’s about to change as LNR Precision has released details and pricing for the next iteration of this legendary radio.

LNR website showing the new MTR-3B “Curahee”

You can check the specs for yourself on the LNR Precision web site. What piques my interest is that the band plan adds 15 meters at the expense of 30 meter coverage and the integrated touch keyer eliminates the need to pack a set of paddles.

Things that I am wondering out loud:

  • Does plugging in paddles disable the touch sensors?
  • Can the frequency display be configured to show MHz?
  • What is the receive current draw?
  • How many “R”s in “Curahee”?

Perhaps the announced pre-release of the user manual will answer these questions.

What do you all think of what we’ve seen of this new Mountaintopper so far?

72 de W6CSN

KH1 to the Rescue! A postcard field report from Pisgah National Forest.

On Friday afternoon (August 16, 2024), after dropping off one daughter at her volunteer job and the other at Shakespeare class, my wife and I had about 90 minutes of free time before the next scheduled activity.

We opted to visit the Sycamore Flats Picnic Area in Pisgah National Forest (US-4510) so that I could fit in a POTA activation while my wife caught up on a project she’d been working on.

The picnic area was bustling with activity–the busiest I’d seen it in a while. No doubt, everyone was out enjoying the beautiful weather and the last hurrah before many local kids head back to school. Nevertheless, we found a nice picnic table to set up and play radio.

I did not have all of my camera gear with me, so opted not to film this activation with my phone.

Since there’d be no video, it meant that I could operate with earphones and a minimal amount of extra gear. It’s nice to do this every so often!

On the way out the door, earlier that day, I grabbed my Mountain Topper MTR-3B field kit. The goal was to put it on the air since it had been a few months since I last used it. I like rotating out radios regularly so I don’t forget nuances of operating them while in the field.

The previous day, I also charged the two Li-Ion rechargeable batteries [affiliate link] that are stored in the MTR-3B Pelican case. At least I thought I charged them!

When I checked the batteries, they were both completely dead. Turns out, the USB charging station I’d connected them to the previous day was not plugged into an AC outlet. Doh!

This presented a little problem because the only other battery I had in my GR1 rucksack was a 3Ah LiFePo4 battery which likely pushed about 13.2VDC. The MTR-3B doesn’t care for voltages much higher than 12VDC–at least, if you are higher than 12V, you need to make darn sure you’ve got a great SWR match.

I was a bit bummed because I hadn’t packed a backup radio in the GR1 and I wasn’t driving the Subaru which has a Venus SW3B headrest field kit.

Hang on…

Then it hit me…I’ve got my EDC (Everyday Carry) radio with me: the Elecraft KH1! Woo hoo!

I went back to the car and grabbed my Trakke EDC bag.

Then pulled out the KH1 packed in my Tufteln-modified Pelican Micro M40 watertight case.

It is such a luxury to have a small, lightweight, and versatile radio always at the ready in the backpack I carry with me everywhere.

Since I’d already deployed my K6ARK 40 meter counterpoise-less end-fed half-wave [affiliate link], this was the antenna I connected to the KH1.

I also grabbed the Bamakey TP-III from my GR1 pack and the 3×5 Rite in the Rain Pad and Zebra mechanical pencil [again, affiliate links] from the MTR-3B kit (don’t worry, I returned these to their respective kits post-activation!).

I had announced this activation on the POTA website, so hypothetically, the RBN should auto-spot me.

I turned on the KH1, moved to the 20 meter band, and was tuning around looking for a clear frequency when I heard a station calling CQ POTA. Continue reading KH1 to the Rescue! A postcard field report from Pisgah National Forest.

Deep Dive: My Mountain Topper MTR-3B Watertight SOTA Field Kit

Last week, in response to a reader’s question here on QRPer.com, I was reminded that I hadn’t yet made a video specifically about my Mountain Topper MTR-3B SOTA field kit.

Yesterday, I made a short video (see below) where I show what I pack in my MTR-3B field kit and why I choose to house it in a Pelican 1060 case.

First, let’s look at a list of the gear, then I’ll talk about what went into my choices, and I’ll link to the video.

Gear:

Note: All Amazon, CW Morse, ABR, Chelegance, eBay, and Radioddity links are affiliate links that support QRPer.com at no cost to you.

Self-Contained Watertight Field Kit:

Optional Gear for SOTA/POTA:

Design Choices

Here’s the philosophy behind my design choices in this kit:

Pelican 1060 Case

I chose to house this field kit in a Pelican 1060 Micro Case even though, at one pound, it weighs more than the typical pouch I also use for small field radios. The Pelican, however, protects the entire radio kit as it’s fully watertight and crush-proof. If I trip while fording a creek or fall and land on my pack, the Mountain Topper will be safe. Yes, there’s a mass/weight cost, but I feel it’s very minimal for the protection it offers.

Counterpoise-less End-Fed Half-Wave

When I build the K6ARK EFHW antenna kit for my MTR-3B, I chose to make it without a counterpoise. Even though the antenna would be more efficient with a dedicated counterpoise and less prone to the effects of body capacitance, I feel like the benefits of this design outweigh the compromises. For one thing, leaving off the counterpoise saves space inside the Pelican case. In addition, by designing the antenna to attach directly to the MTR-3B’s BNC port, there’s no need to include a feedline, thus saving quite a bit of space.

So far, I’ve been very impressed with how forgiving this antenna has been and, most importantly, with how well it has performed.

N6ARA SWR Meter

I include the N6ARA MiniSWR  in my field kit to give me some peace of mind if my antenna deployment is compromised (for example, if the trees on a summit are too small, etc.). Since my MTR-3B version has no built-in SWR metering, I feel this is a meaningful addition tot he kit.

Throw Line and Weight

At least 90% of the summits and parks I activate here in western North Carolina have trees. To me, no field kit is truly sufficient unless I include a throw line and weight. I find that the Marlow KF1050 Excel 2mm Throwline is small, lightweight, and effective—-25 meters is enough to deploy any wire antenna I’d carry on a SOTA activation.

Many SOTA ops use a small sack that they place stones in to act as a throw weight for their line. This is very clever because you don’t have to pack in that extra 8 ounces on the roundtrip hike. Still, I like the convenience of a throw weight that’s designed to glide through tree branches with ease–especially if the tree is dense. If I were to do a multi-day SOTA backpacking trip, I’d probably use an empty throw sack instead of a dedicated weight.

Rechargeable 9 Volt Battery Packs

I love these 9V rechargeable batteries. It’s hard to believe that the MTR-3B can complete 2-3 typically SOTA activations on one charge! Then again, the MTR-3B uses something like 18ma in receive? That’s crazy low current consumption. These batteries are super lightweight and the particular brand I use has never produced any RFI (I’ve read that some others can). What’s best is that I can recharge these easy via a USB-C cable.

The MTR-3B will operate on nine volts, which yields three watts of output power.

Helinox Chair and Kneeboard

Yes, these are luxury items. I know many SOTA ops who are quite happy to sit on the ground and balance their radio on their leg. Perhaps it’s my age, but I don’t like doing this anymore because my legs tend to fall asleep and I lose feeling in them if not careful.

My Helinox Zero chair weighs 1 lbs 2 oz (509 g). I feel like it’s weight and mass well-spent. Since I record activation videos, the chair also gives me a much better position for my camera angle (bonus!).

My Tufteln/N0RNM kneeboard is an essential part of my SOTA kit. I never leave without it. The chair and kneeboard combo gives me the flexibility to set up anywhere, anytime. I love it.

Video

Here’s a video showing the breakdown of my Mountain Topper MTR-3B SOTA field kit:

Click here to view on YouTube.

Thank you!

 

Thank you for reading my field kit post and watching the video! I hope you enjoyed it.

As always, I’d also 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 not a requirement, as my content will always be free, I really appreciate the support.

If you’d like to see loads more field kits, check out our field radio kit gallery!

Thanks for spending part of your day with me!
Cheers & 72,
Thomas (K4SWL)

Did you know there’s a new MTR-3B in the works–?

A reader reached out to me this morning asking about the Mountain Topper MTR-3B. It reminded me of a teaser LnR Precision posted earlier this month in an MTR-4B update on their website. Here’s what they said:

Update: 4/1/23: We do not have MTR4 V2.3 available for purchase now but will be releasing more for purchase on May 1, 2024.

Apologies on the delay but we needed more time to get parts that are in short supply and fabricate. This will be the only and last offering of the MTR4b V2.3 radios as we are shifting focus on a redesigned and re-engineered version of the popular MTR3B!

It is our hope to have these out in Fall of 2024 if possible, but no guarantees.

I’m very excited about this news! I own two MTR-3Bs and absolutely love this model. When I checked in with LnR a couple of years ago, they said they had no plans to produce the MTR-3B again. They must have noticed the strong customer demand.

I assume the new model might incorporate some of the upgrades found on the MTR-4B, like an SWR and Power Output meter and a more accessible sidetone control. We’ll have to wait and see!

LnR is a small “mom-and-pop” company, so we’ll need to be patient as they introduce the new MTR-3B. I’m sure they’ll struggle to keep up with demand. I, for one, am eager to see this super-compact transceiver back on the market.

Field Radio Kit Gallery: N7KOM’s Pocket HF Go Kit

I couldn’t believe my eyes when I saw it or held it – just how small this kit is. Tim (N7KOM) and I met up in December 2023 when I was on a trip in the Pacific Northwest and he and I stopped for a lunchtime activation.

Tim’s ENTIRE kit for mountain-top activating less his mast and the 9V battery seen in the background. It’s a stark comparison to my KX3 Go-Kit.

His kit is super light and small. I’ll let Tim take up the description from here:


A Pocket HF Go Kit.

by Tim (N7KOM)

There are few pleasures in life more satisfying than making QSOs on a thin wire tuned for a half wave.

One of my favorite radios is the classic MTR3B. At 9.8cm x 6.5cm x 2.4cm it is truly a pocket radio. Everything I need to get on the air fits into an Amazon external Harddrive case. Here’s a breakdown with weight measurements:

  • MTR-3B – 126 g
  • 9V Li-Poly USB-C rechargeable battery + power plug – 29 g
  • K6ARK 3D printed paddle and 3.5mm cable – 22 g
  • Earbuds + external volume control knob – 26 g
  • Trapped EFHW on an RCA connector (matching the radio’s connector) tuned for 20m/30m/40m. 28-32 ga wire on a 3d printed winder. – 42 g
N7KOM’s ultra-lightweight HF Kit

As is, it weighs a total of 323 grams or 0.7 lbs. Add in a lightweight 9 foot mast from ali-express and I have everything I need to make contacts. I could even string the wire on some bushes or the ground if I was really in a pinch.

Other notes

I could reduce the weight and packability further by using shorter cables on the earbuds/volume control as well as the paddle cable.

The antenna winder is a K6ARK 3D printed winder printed at around 70% size.

A 41 g external speaker may also be added to the kit, but it does not fit in the HDD case and must be carried separately.

Here is a video tour of the kit on YouTube:


So there you have it folks -323g of portable HF kit everything included! Check out Tim’s YouTube page or his Microlight QRP Traps on Etsy for your next QRP outing.

Tim’s field kit is now featured on our Field Kit Gallery page. If you would like to share your field kit with the QRPer community, read this post

[Please note that Amazon affiliate links support QRPer.com at no cost to you. Thank you!]

Video: Comparing the Elecraft KH1 with Mountain Topper Series QRP Transceivers

A couple weeks ago, I posted a video where I compared the Elecraft KH1 and KX2;I mentioned that it was the most requested comparison I’d received after I started taking the Elecraft KH1 to the field.

The second most requested KH1 comparison focused on various Mountain Topper series models: the MTR-3B, MTR-4B and MTR-5B.

That’s what we’ll take a look at in the comparison video below!

Basic KH1 ($550)

So when folks have asked me how the KH1 compares with a Mountain Topper, I think of the basic KH1 ($550 US) package, not the ($1100 US) “Edgewood” package like I have.

Why?

Without the Edgewood package, the KH1 lacks the internal ATU, coils for the whip antenna, internal battery, internal battery charger, logging tray, whip antenna, counterpoise, case, and attachable paddles.

In short, the basic KH1 is a 5 band CW-only radio, much like Mountain Topper series radios–in fact, a lot like my 5 band Mountain Topper!

This is why, in my video below, I base the comparison on the basic KH1 package which includes the KH1, power cord, USB cable, and manual only.

Video

I should note that this video primarily focuses on making a purchase decision–it’s not a receiver comparison or in-depth reviews:

Click here to view on YouTube.

A few notes…

The video above contains a lot more detail, but at the end of the day, you can’t make a “bad” choice here. All of these are fantastic radios for someone who enjoys ultra-light operating.

The Elecraft KH1 is more a more feature-rich transceiver; it has adjustable filters, attenuation, CW encode/decode, mini pan/scan, general coverage, SWR/power meter, more message memories, internal logging options (soon), user upgradable firmware, an internal speaker, and much, much more. On top of that, the KH1 can be upgraded to become a complete shack-in-a-box radio with internal battery, charger, ATU, attachable whip antenna, and attachable paddles.

That said, even thought the Mountain Topper radios are spartan in terms of features compared with the Elecraft KH1, they get the job done effectively. Their feature set is laser-focused on providing a SOTA activator everything they need in order to complete an activation and not a lot else. They will also operate effectively on the smallest of batteries and consume a mere 20-17 mA in receive–proper battery misers! For more of my thoughts of the Mountain Topper, check out my MTR-4B review and my “Getting To Know You” report on the MTR-3B.

Again, you can’t go wrong with a Mountain Topper or a KH1: they’re both made by fantastic companies and have a loyal customer base for good reasons.

Price

The Elecraft KH1 base model (40, 30, 20, 17, and 15 Meters) is $550, the complete, fully-loaded, “Edgewood” package is $1,100. They are currently on backorder, but Elecraft does note that they intend to start shipping again mid-January 2024. Click here for the latest news about lead times.

The Mountain Topper MTR-4B V2.

The LnR Precision MTR-4B (80, 40, 30, and 20 Meters) is the latest Mountain Topper radio and the current model at time of publishing. You can purchase these new for $369 US. LnR Precision builds roughy 25 per month when they have the parts. You will need to follow LnR closely in order to be updated when a production run is shipping. Each time units are offered, they’re snatched up in a matter of hours. You can find used Mountain Toppers out there, but pricing tends to be within 10-20% of the new price.

Thank you

I hope you enjoyed this little comparison video and that it might help you make a purchase decision.

Of course, I’d also 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.

As I mentioned before, the Patreon platform connected to Vimeo make it possible for me to share videos that are not only 100% ad-free, but also downloadable for offline viewing. The Vimeo account also serves as a third backup for my video files.

Thanks for spending part of your day with me!

Cheers & 72,

Thomas (K4SWL)

Field Radio Kit Gallery: Bob’s MTR-3B Bug-Out Go-Kit

Many thanks to Bob (K4RLC) 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


MTR-3B Bug-Out Go-Kit

by Bob (K4RLC)

I wanted to build a lightweight Bug Out Go Kit around the incredible Mountain Topper MTR-3B LCD model.

Bass Pro Shop sold a tackle box that seemed perfectly for this. I took a Bear Grylls Scout Knife and cut/customized the partitions as needed. The Elecraft AX 1 antenna and tripod mount, and a flexible tripod fit perfectly.

Counterpoise consists of three 13 ft BNTECHNO 22 AWG silicon wires, attached with a Mueller 55 alligator clip to the tripod mount.

The CW Morse Outdoor Pocket Paddle (and cable) fit into another section. For audio, use either generic ear buds or the rechargeable cell phone speaker with PChero volume adjustment cable.

For power, rechargeable Li-Ion 9 volt batteries use a USB connection, so no separate charger is needed. I keep this in the car.

It’s a great set up for POTA and lightweight enough to throw into a backpack for the steepest SOTA climb. The MTR-3B, the size of a deck of playing cards and not weighing much more, is an awesome QRP rig that’s still a keeper, if you can find one.

Equipment List:

Field Report with N5FY: Checking out the new N6ARA MiniSWR (and a sweet 9V battery) at Don Carter State Park!

I am catching up with field reports and videos from last month and, I must admit, it’s fun reliving these activations.

October was such a busy month, it’s all been a bit of a blur.

Because I have a second Thanksgiving meal to prepare this morning for my wife’s family, I need to keep this report short–which won’t be easy because there’s a lot to unpack here– so we’re going to attempt do another Postcard Field Report!

Postcard Report from Don Carter State Park (K-2171)

I mentioned in a previous post that I participated in the W4 SOTA campout last month. .

Part of the fun  of the campout was hanging with my good friend Joshua (N5FY) whom many of you know from his amazing Tufteln antennas and accessories.

On the morning of Friday, October 13, 2023, Joshua and I activated Rocky Mountain (W4G/NG-011), a beautiful 10 point summit along the Appalachian Trail.

That afternoon, we met with Joshua’s family briefly, then planned to head to a pub in Clayton, Georgia, where a number of the W4 SOTA campers were gathering.

Joshua determined we had just enough time to pop by Don Carter State Park (K-2171) for a quick POTA activation and still make it to Clayton in time. As a bonus, Don Carter SP has a number of covered picnic shelters, making set up in the dry quite easy (it was raining at the time).

For this activation, I used my Mountain Topper MTR-3B field kit that I had used during my SOTA activation on Rocky Mountain. In fact, it was the only radio kit I brought with me for activations that day.

Joshua lent me his Tufteln 40/20 meter linked EFHW antenna (we only used the 20 meter portion of it) and I also got to use a few other accessories that were still very new to me:

N6ARA MiniSWR Meter

One was my friend Ara’s latest creation, the MiniSWR meter. Ara (N6ARA) kindly sent me this production unit to test (at no cost to me) earlier in October.

I was very excited about this particular product because a few of my QRP radios lack a built-in SWR meter (my MTR-3B, MTR-5B, TR-35, and SW-3B to name a few). Ara’s MiniSWR meter is so tiny, it’s easy to carry even in my MTR-3B SOTA kit that’s built into a Pelican 1060 waterproof case. (If you’d like more details, I’ll be adding this MTR-3B kit to the Radio Field Kit Gallery soon).

The MiniSWR in action earlier that day on Rocky Mountain.

As with all of Ara’s products, the MiniSWR works brilliantly, is very affordable, and is available as a kit or pre-assembled. Check it out at N6ARA.com!

Rechargeable 9V Batteries

Another new-to-me product was this USB-C rechargeable 9V battery originally recommended by Adam (K6ARK).

Being honest here: this battery sort of blows my mind!

When paired with super efficient QRP radios like my MTR-3B (which uses something like 18mA in receive), one charge will take me through as many as two or three full SOTA/POTA activations!

These batteries are insanely affordable too. You can buy two for $15 and change at Amazon.

When I purchased these, I also bought two 3S packs in a Prime Day deal. These 9V batteries work so well, though, I’ve yet to add PowerPoles to the new 3S packs. I prefer the size and ease of use of these 9V cells.

Set up

Joshua helped me set up in short order. We deployed the 20M EFHW next to the picnic shelter and Joshua kindly lent me his OSMO 2 Action Camera and Anker SoundCore Mini speaker so I could make a video of this impromptu activation. Continue reading Field Report with N5FY: Checking out the new N6ARA MiniSWR (and a sweet 9V battery) at Don Carter State Park!

The Best Mountain Topper Antenna: How to build lightweight, in-line links

Many thanks to Dick (K7ULM) who shares the following guest post:


The Best Mountain Topper Antenna

(And a modification that makes it a little better)

by Dick (K7ULM)

When I decided to pursue HF radio, I had already decided to learn Morse Code.  Since learning code on my own wasn’t working, I enrolled in CW Academy classes.   Nearly everyone that I met in the CW Academy classes, plus my Elmer, were all involved in QRP portable ops as well.  A common theme among them all was using efficient, lightweight, easy to deploy antennas.

New to ham radio, QRP, and antennas.  I started to research antennas that fit that set of criteria.  Of course, I stumbled onto K6ARK, Adam Kimmerly’s YouTube video on building an ultralight 40m EFHW.  I accumulated the parts and built an EFHW for 40m.  After tuning the antenna for the lowest SWR, I connected it to a KX3 and contacted hams in Long Island, NY and Atlanta, GA with 12watts using SSB.  I was hooked on QRP and Adam’s antenna design.

When the instructor in my CW Academy class asked what goals each of us had for ham radio, I realized that I had no real goals.  So, I told the group that I wanted to assemble a portable QRP kit that weighed under one pound, and I wanted to operate portable CW from my elk hunting camp in the fall.  The sub-one pound HF kit was inspired by SOTA guru and legend, Fred Mass, KT5X.   I ordered an MTR-3B (Mountain Topper 3b – a QRP CW transceiver), which arrived 2 days before I left for elk camp.  The sub one pound HF kit had become reality.

At elk camp, I was a little distressed that I couldn’t work 30m with the EFHW, but 20m and 40m were a great combination.  Three nights later I was laying on a cot in a canvas wall tent in elk camp scanning the bands and trying to decode signals as I found them.  I heard one signal calling CQ for a long time and decided to try to answer him with my very limited CW skills.  I was able to get the minimum information to make an official QSO.  Looking up the contact’s information on QRZ, I found that it was Lloyd, KH6LC in Keaau, HI, 3000+ miles from elk camp.  Hawaii worked on 5 watts.  I was totally hooked on QRP and CW.

The only problem with the 40m EFHW, is that it doesn’t tune up easily on 30m.  Adam’s 40m EFHW design is excellent, and I wanted to stay with his build design, so I concluded that I needed to put a 30m link in mine EFHW to cover 40m, 30m and 20m without the use of a tuner.   My first effort on building a 30m link worked well but it was heavy and rigid which made it hard to store.  Eventually I created a design for the link that met my goals.

How to build lightweight links

My goals for a link on a lightweight EFHW are that it needs to be lightweight and flexible for easy storage.  It should also be relatively clean in design to minimize the chance of hanging up in trees and bushes while deploying and retrieving the antenna.

The materials for the link design that are currently working the best for me are as follows:

  • Attwood 3/32” tactical cord.
  • Heat shrink tube.
  • Superglue.  Gel type is the least messy.

2mm bullet connectors, or a more solid connection, red knife disconnects from Aircraft Spruce and Specialties Co. https://www.aircraftspruce.com/catalog/elpages/knifedisc.php

The knife disconnects idea is from Charlie Brown of Red Summit RF.  They are worth looking into.  They are my current choice of connector although the bullet connectors are working OK.

The installation of this link is fairly simple.

The first step is to tune a 30m section of wire on your preferred transformer.  The narrow 30m band will normally be well below 1.5:1 across the entire band, which is awesome.  I have found that it is about 32’ 7” of wire for my deployment style and soil conditions.  Your mileage will vary.  You can cut this into an existing antenna but, plan on adding a piece of wire to the end of the antenna to retune it for 20m and 40m.  For an existing antenna, measure the overall length from the transformer to the end of the antenna prior to cutting in the link.  You will use this measurement to restore the overall length of the antenna for the 40m EFHW.

Step two is to cut two pieces of heat shrink tube that will fit over your selected antenna wire and the 3/32” cord.  Slide one piece of tube onto the newly tuned 30m wire and the other onto the wire that will be tuned for the final 40m EFHW.  I use 26ga Polysteath wire.

Step three, cut two pieces of shrink tube to cover the solder joint of the wire connectors and slide one piece of tubing on both wires.

Step four, solder the connectors onto the 30m and 40m wire sections.  When cool, slide the shrink tube onto the solder joint and shrink.

Step five, cut about 6.5” of cord and melt the ends of the cord.  Mark the center of the cord so you can center it on the connectors.  Center the cord on the connectors and slide the shrink tube over one end of the cord.  Leave the final location of the shrink tube exposed for glue.  Put a couple of drops of superglue on that area, slide the shrink tube into its final placement and shrink in place.

Step six, slide the shrink tube onto the other side of the cord and leave a little room to put glue on the cord as was done on the first end.  For strain relief on the connection, it is best to put some slack in the wire, so the full load of the antenna is placed on the cord and not on the connection.  The easiest way I have found to do this is to disconnect the connectors and overlap them by ¼” or so prior to shrinking the second shrink tube into place.  Once everything is ready, put a couple of drops of superglue on the cord, slide the tube into place and shrink.

When you reconnect the connectors, there should be a bit of slack in the wire that prevents any pull on the connectors while the antenna is deployed.  At this point restore the full original length of your antenna for add a new section of wire and tune for 40m and 20m as desired.

With K6ARK’s ingenious EFHW design and a 30m link, you can have a fantastic antenna matched to the MTR3B that is, tuned for resonance on 40m, 30m, and 20m, easy to deploy and weights under 2oz.  If you add one of Adam’s 3D printed paddles, a couple of 500mAHr LiPo batteries, and earphones your complete HF kit will be about 12oz.  Add a Carbon 6 mast and your total kit come in at a mere 23.7oz.  WINNING! 

For those operators who are fortunate enough to own an MTR4B, an 80m removable extension can be added to the 40m EFHW using a similar technique.  On the 40m EFHW, prior to installing the connector, a piece of the cordage can be folded back on itself to create a loop and slid through a piece of shrink tube.  This loop works as a good connection point for your guy lines while deploying the 40m antenna by itself and a place to tie on the 80m extension when needed.

For the 80m section, a single 5” length of cord will be connected to the wire to tie with superglue and shrink tube.  Solder the connector onto the 80m section before securing the cord.  The cord on the 80m extension is to tie the antenna sections together in a manner to provide strain relief for the couplers.  A cord loop can be put on the far end of the 80m section using this technique after it is tuned.

This is my vote for the best Mountain Topper portable easy to deploy antenna, or for any QRP radio without an ATU.  IMHO.

Field Kit Gallery: N8PEM’s MTR-3 Portable Field Radio Kit

Many thanks to Chris (N8PEM) 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, check out this post.


MTR-3 Field Kit Build by N8PEM

Ham radio is a hobby best enjoyed in community with others.

Ever since I began operating QRP portable a few years back I had admired the Mountain Toppers.  Granted my Elecraft KX2 is a perfect daily driver.  I’ve been lucky to have that as my sole portable QRP rig for some time.  That didn’t stop me from dreaming of an ultralight QRP portable kit centered on an MTR3.  High resale prices and scarcity made it a purchase I had long put on the back burner.  But then one day I saw my good friend Julia, KF8JBB, while walking my dog in the park.  So I stopped to chat.

Figure 1:  Antenna Design

Like many of us, Julia is an avid QRP and CW enthusiast.  She has numerous QRP and SWL radios.  Life is also pretty busy for her.  She doesn’t get out to operate as much as she would like.  As we chatted on that warm August evening, she offered to gift me her MTR3.  For her, it was time to move that rig on to a good home so it would get it’s proper use.  But the shrewd negotiator in me knew to never accept a first offer.  I countered.  I’d take the MTR3 off her hands if she let me build her a QRP portable antenna in return (later I also threw in a built N6ARA TinySWR kit for good measure).  She accepted.  The next day she dropped off the rig.  The fun of outfitting an ultralight (UL) QRP kit began.

I quickly determined that I wanted to build a trapped 20/30/40 meter EFHW antenna to match the three bands on the Mountain Topper.  I prefer end feds, and I wanted the challenge of building traps for the first time.  Keeping in mind I wanted an UL kit, I could also leave the coax at home with an end fed.  I had read that a trapped EFHW can be shorter than a standard EFHW due to the inductance of the traps.  This appealed to me as I knew from experience that getting a 40-ish foot antenna up in the air is much easier than a 60-ish foot antenna.  It took nearly six weeks to research, procure parts and build out this antenna, partly due to the fact I had to build this antenna twice.

My first attempt at this antenna build wasn’t good.  I couldn’t get SWR better than about 1.8:1 on any band.  I hadn’t tested every component at every step of the build.  Thus, I had a hard time determining what went wrong.  I used 100 and 150 pF capacitors for the traps which proved to have marginal shortening effects.  I needed more turns on the toroids!  I decided to do more research and start over.

Thanks to advice and blogs from folks like Dan AI6XG and Fred KT5X, I settled on a different, better design of the trapped EFHW.  I ordered more parts.  Switched out to 15 and 33 pF capacitors.  I took my time to build and test this antenna in a step by step manner.  The results were much better the second time around.  Overall 45 feet 8 inches long and weighing two ounces.  SWR better than 1.5 to 1 on all three bands.

I had the idea to place a TinySWR kit in line between the RCA plug and the end fed matching unit.  I know there are SWR kits which can be installed within the radio, but I didn’t want to modify the MTR3 in any way.  The stock design is sublime.  I also built a back-up emergency antenna into the design.  If for some reason I have a trap fail, I installed a bullet connector right before the first trap.  Thus, I can disconnect the 30 and 40 meter portions of the antenna and  have a basic resonant 20M EFHW.  These thoughtful touches seemed to perfect the antenna.

Photo 1:  Completed miniSWR, matching unit, 30m trap, and 20m quick disconnect

I tried to be thoughtful with the other choices in my kit as well.  At 3.5 ounces and the size of a bag of coffee, the LowePro CS40 padded case proved to be ideal.  I found it cheapest from a UK-based eBay seller.  I made my flight deck out of the steel housing from an old external CD Drive.  I measured, cut and filed the edges.  It’s perfectly sized for loose Rite in the Rain paper, lightweight and thin.  A metal flight deck also can hold the magnetic base of my CW paddles.  When it came to the battery, I decided to go with a RC airplane LiPo battery.  Fuzzy math told me that the 650 mAh would give me more than enough operating time.  Once complete, I was happy to find the entire kit weighed in at just 18 ounces, not counting a throw weight or collapsable mast.

Photo 2:  The completed MTR3 kit

My first activation with this kit was September 21st.  I wasn’t sure how well I would do.  Band conditions weren’t the best the previous two days.  I went to my favorite spot, Bunker Hill (W8O/SE-009) located within Great Seal State Park (K-1954) in south central Ohio.  It’s a short 20 minute hike to the high point on what was a partly cloudy 70 degree Thursday morning.  I set the antenna up in a sloper configuration, gave my dog Togo some treats, ate half my sandwich, took a sip of coffee, and pulled up the POTA and SOTA spotting pages.

In just over an hour I had made 54 QSOs covering all 3 bands.  The MTR3 combined with the trapped 20/30/40 EFHW worked flawlessly.  It was an absolute joy to operate.

Photo 3:  First activation complete

That joy came from the sublime kit for sure.  But enjoyment also came from the community carried within the kit itself.  The MTR3 from Julia KF8JBB.  The paddle and wire winder designs from Adam K6ARK. The MiniSWR Kit from Ara N6ARA.  The Trap PCB boards from Tim N7KOM.  The toroids, capacitors, and antenna advice from Dan AI6XG.  The blog post from Fred KT5X.  The 3D printing from my nephew Colin.  Even the RigExpert I bought from Glen W1ND this Spring was integral.  This kit is an homage to that community.

Figure 2:  First Activation QSO Map

If you made it to the end, thanks for reading!  I hope it was interesting and helpful.

TU 73 EE,

Chris N8PEM

Radio Kit

Antenna Build