Tag Archives: Mountain Topper MTR-3B

Antennas, Guest Posts, How To, News, QRP

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

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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 Radio Kits, Guest Posts, News, QRP

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

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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

Field Reports, News, Portable, POTA, QRP, QRP Radios

Getting To Know You Series: The Mountain Topper MTR-3B — My thoughts, notes, and a POTA activation!

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I’m very fortunate in that in the past few years I’ve accumulated a number of QRP radios that I use in rotation when I do park and summit activations.

I’m often asked for advice on choosing radios, and as I’ve mentioned in the past, I feel like the decision is a very personal one–everything is based on an operator’s own particular preferences.

Over the years, I’ve written formal reviews about most of the field radios in my collection. In those reviews, I try to take a wide angle view of a radio–to see how it might appeal to a number of types of operators. I highlight the pros and cons, but I don’t focus on my own particular take because, again, my style of operating might not match that of readers. I try to present the full picture as clearly as I can and let the reader decide.

The Getting To Know You series gives me an opportunity to highlight one radio at a time and showcase what I love about it and why it’s a part of my permanent radio collection. After we spend a bit of time talking about the radio, we’ll do a park or summit activation with it!

The Mountain Topper MTR-3B

The fourth radio in my Getting To Know You series is the Mountain Topper MTR-3B by LnR Precision.

And, spoiler alert: I think the MTR-3B is one of the most ingenious little QRP transceivers ever made.

In truth, all of the Mountain Topper series radios are outstanding if you’re a CW operator and into truly portable, ultra-lightweight, field radio activities.

Steve Weber (KD1JV), the designer behind the ATS and Mountain Topper series, created a brilliant platform that has only been improved upon over time.

I’ve only ever operated the MTR-3B and MTR-4B. That said, I’d love to add a high band MTR-5B to my field radio collection someday.

The Mountain Topper MTR-4B V2. Read the review here.

I recently reviewed the MTR-4B (see photo above) and I absolutely love it, but in truth? I prefer the more compact MTR-3B simply because it’s rare that I operate 80 meters in the field and I like the even more compact from factor of the 3B. It’s literally the size of a pack of playing cards.

That said, I wish the 3B had some of the later model MTR-4B upgrades like easy-access sidetone adjustments and power/SWR metering, but I still prefer the MTR-3B.

What? A second MTR-3B?

Confession time: last month, a good friend and QRPer.com patron/supporter offered to sell me his MTR-3B for a very fair market price. He could have put this on eBay or in ham classifieds and surely commanded a much higher price, but he knows how much I love this radio and offered his never used MTR-3B to me.

It didn’t take long for me to accept his offer–like quicker than the blink of an eye quick.

I’ve been looking for a second MTR-3B because 1.) these radios are no longer manufactured and 2.) if something happened to my one and only MTR-3B, I would sob uncontrollably.

I should state here that I blame my buddy, Vince (VE6LK), for introducing the “Two is one, one is none” slogan. Over time, I’ve convinced myself to keep two copies of my favorite radios such as the KX1, FT-817, and MTR-3B.

Vince, by the way, is a card-carrying, certified enabler!

Holmes Educational State Forest (K-4856)

On Friday, August 25, 2023, I made my way to Holmes Educational State Forest to play a little POTA with the MTR-3B.

The site was very quiet. The new school year had just started,  so it was too early for school field trips at the park.

I had my pick of spots to set up, so I chose a new-to-me picnic table. Continue reading Getting To Know You Series: The Mountain Topper MTR-3B — My thoughts, notes, and a POTA activation! →

Field Reports, Morse Code, News, Portable, POTA, QRP, Videos

Mountain Topper MTR-3B: A quick POTA activation before leaving camp!

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View from Yonah Mountain the previous day.

As I mentioned in previous field reports, the W4G SOTA Campout was amazing fun this year.  I enjoyed hanging with Joshua (KO4AWH) as we activated a total of three summits and a few parks–plus it was great meeting so many fellow SOTA activators at the Saturday evening potluck!

On Sunday morning, October 16, 2022, it was time to pack up the campsite and hit the road.

Although I was a little pressed for time, I decided to fit in one more activation as Joshua packed up his tent and before we took down the 40 meter Tufteln end-fed half-wave.

Chattahoochee-Oconee National Forest (K-4473)

Fortunately, our campsite was within Chattahoochee-Oconee National Forest and since all I needed to do was to connect my rig to our campsite antenna, setup took all of two minutes.

I pulled out the Mountain MTR-3B for this activation. It had been quite some time since I used this wee radio because I had only recently finished a review of the MTR-4B V2 (look for that review on QRPer.com very soon).

The MTR-3B is now permanently at-the-ready inside my MTR-3B ultra portable field kit, but since there was already an antenna and key in place, I only needed the radio, power cord, logging items, and battery.

Continue reading Mountain Topper MTR-3B: A quick POTA activation before leaving camp! →

Comparisons, QRP Radios

Photos: Comparing sizes of the Mountain Topper MTR-4B, MTR-3B, and Elecraft KX1

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After sharing a few photos by request comparing the size of the  Mountain Topper MTR-3B, MTR-4B, and Elecraft KX2 yesterday, I took a few pmore photos by request comparing those same radios with the Elecraft KX1.

I decided to simply post these on QRPer.com in case they could also be of help to someone else:

Mountain Topper MTR-3B v Elecraft KX1

Mountain Topper MTR-4B v Elecraft KX1

Elecraft KX1 v KX2

News, QRP Radios

Photos: Comparing sizes of the Mountain Topper MTR-4B, MTR-3B, and Elecraft KX2

10 Comments

A reader/subscriber just asked for photos comparing the size of the  Mountain Topper MTR-3B and MTR-4B. I know they were also curious how the MTR-4B might compare in size with the Elecraft KX2. Of course, one can look up the actual sizes, but sometimes a photo adds more context.

I decided to simply post these on QRPer.com in case they could also be of help to someone else:

Mountain Topper MTR-4B vs MTR-3B

Mountain Topper MTR-4B vs Elecraft KX2

How To, News, QRP Radios

Why does the Mountain Topper MTR-4B (& 3B) have three separate band switches?

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A question I’ve received several times since sharing my last field activation with the MTR-4B is “why do Mountain Topper radios have three individual band switches–?”

That’s a great question and the answer is actually in the product manual.

The following comes from the MTR-3B manual but also applies to the MTR-4B (save the 4B has four band positions instead of three):

The band is selected by three, three position slide switches. For proper operation, all three switches must be in the same
column[…]. It’s easy to get into the habit of flipping each switch in sequence from the top down.

The top switch tells the processor which band to operate on and connects the Receiver input filter to the first mixer. The
middle switch connects the transmitter low pass filter output to the antenna and connects the antenna to the receiver
input filter. The bottom switch connects the output of the transmitter PA to the low pass filter.

The manual is correct: it’s easy to get in the habit of sliding all three switches with band changes. It becomes second nature in very short order.

It’s easy to tell that all of the switches are in the correct position as well because without all three switches selected, the receiver sounds deaf and audio muted. With them in position, the receiver sounds “alive.”  (That said, the noise floor is so low on these radios, it’s quite possible you might think they’re not engaged properly if there aren’t many signals on the band!) Of course, it’s very easily to visually inspect the switches and confirm they’re in the correct position.

Side note: On the Mountain Topper series, each band switch is an independent mechanical switch. On the Venus SW-3B (which was no doubt inspired by the Mountain Topper) the two band switches are bound together as one:

You can’t tell from looking at the photo above, but if you slide the top switch, you’re also sliding the bottom switch: the two switches are only one mechanical piece. An interesting design choice!

Side Note: The (now discontinued) Mountain Topper MTR-5B had a more complex series of six switches. Here are the instructions for it along with a drawing from the MTR-5B manual:

I hope this helps clarify how/why the Mountain Topper series uses multiple switches for band changes!

Field Reports, Morse Code, News, Portable, POTA, QRP

“The Elecraft AX1 antenna is just a dummy load!” Really? Let’s test that!

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Like a lot of QRPers, I love a good challenge.

Maybe it’s just in the nature of those of us who love QRP.

We get a small thrill out of seeing what we can accomplish with less.

AX1 Doubts?

On the morning of February 7, 2022, I received an email from a subscriber in South Carolina who had placed an order for a new Elecraft KX2 and an AX1 antenna package.  He picked this particular combination because he wanted the most simple and easy-to-set-up field radio system for impromptu CW POTA activations and a little random QRP fun.

He mentioned that, at his age, mobility is a bit of an issue and even though he knew a wire antenna would be more effective, deploying it while walking on uneven ground just wasn’t in the cards. The AX1 was a much more manageable and packable system. Plus, as he said, “I’m not going out to work DX. I just want to play and have fun.”

Only a week after placing his order, he was having buyer’s remorse which prompted his message.

He explained that he had exchanged emails with a friend in his radio club who told him he’d made a foolish mistake and that the AX1 was completely ineffective as an antenna and would only lead to disappointment. His friend said [direct quote here], “I owned [an AX1] for a month and was never able to make a single contact. It is really good at being a dummy load and nothing more! This thing shouldn’t be marketed as an antenna. It doesn’t work.”

I pointed out that I’ve used the AX1 numerous times in the field and have yet to be disappointed.

Before I used the AX1, I too, was very skeptical but after actually using it (instead of simply theorizing about it) I found it’s one of my most valuable antennas for a quick and fruitful activation. I pointed him to this playlist that includes all of my AX1 activations on YouTube. In all of these activation, I’ve limited myself to 5 watts as well even though the antenna can handle a full 10 or 15 watts from the KX2 or KX3.

I told him I’d been planning to pair the AX1 with my Mountain Topper MTR-3B and, it turned out, that very day a small window of opportunity opened in the afternoon. I told him we could both see how the AX1 might perform with three watts of power, especially since he’d planned to use 10 watts with his KX2.

As I’ve mentioned in the past, my motto is less theory, more practice!

We’d put the “dummy load theory” to the test! Continue reading “The Elecraft AX1 antenna is just a dummy load!” Really? Let’s test that! →

Field Reports, Morse Code, News, Portable, POTA, QRP

Amazing Fun with 3 Watts: Pairing the MTR-3B, T1, Speaker Wire, and a 9V LiFePo4 battery at South Mountains

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I’ve been spending more time with my Mountain Topper MTR-3B (“Tuppence”) recently and have been thoroughly enjoying this little radio’s companionship.

Since I made a dedicated ultra-compact field kit for the MTR-3B, it has also been even easier to toss it in my backpack and take it on little field adventures. The field kit is truly a grab-and-go and even includes a throw line and weight.

On Friday, January 28, 2022, after a total of six individual park activations during the previous two days (a POTA RaDAR run and my first 2020 Antenna Challenge activation) driving back to the QTH I thought, “surely I can skip doing an activation today.”

That quickly turned into, “Wait a minute…I’ve got enough time to fit in both an activation and a hike!”

So I made a quick detour off of I-40 to visit the Clear Creek access of South Mountains State Park.

South Mountains State Park (K-2753)

I pulled into an empty parking area; not really a surprise on an early Friday afternoon. In addition, I figured many were out grabbing bread and milk since winter weather was in the forecast.

I decided to do my activation first, then pack up and take the full kit on a hike. Continue reading Amazing Fun with 3 Watts: Pairing the MTR-3B, T1, Speaker Wire, and a 9V LiFePo4 battery at South Mountains →

Field Radio Kits, Field Reports, Morse Code, News, Portable, POTA, QRP

POTA RaDAR Run Final Activation: Testing the new MTR-3B field kit at Tuttle Educational State Forest

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On January 26, 2022, I fit in multiple park activations in one day as a RaDAR (Rapid Deployment Amateur Radio) run. My hope was to activate four or five sites between 14:00 – 21:30 UTC.

Here are the field reports and videos of my first four activations:

The next park in my run (#5) was Tuttle Educational State Forest and it was the final park in this modest RaDAR run!

I packed up the gear at Johns River Game Land in a matter of three minutes, popped it all in the car, then drove 8 minutes to nearby Tuttle Educational State Forest which, at this point, almost feels like a home away from home.

Tuttle Educational State Forest (K-4861)

As I pulled into the Tuttle parking lot, I found my buddy Max (W4GZ) activating the park from his truck. It was no surprise finding Max here since I had just worked him Park-To-Park (P2P) from Johns River next door.

Max delivered some precious cargo: some more of his mom’s homemade QRP pickles!

“Them’s QRP pickles!”

Max continued to activate Tuttle from his truck while I set up my station. Continue reading POTA RaDAR Run Final Activation: Testing the new MTR-3B field kit at Tuttle Educational State Forest →