Category Archives: QRPp

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Guest Post: Lake Thunderbird (K-2792) with a homebrew transmitter!

May 31, 2023 Thomas Witherspoon 16 Comments

Activating (sort of) Lake Thunderbird (K-2792) with a homebrew transmitter

Sam Duwe WN5C

When I dove into radio a couple years ago a few sub-hobbies caught my attention: QRP, portable ops, CW, and homebrew. Of course, these all fit nicely together, but in my mind there was a huge leap between soldering an unun and a building a radio. But why not try? What’s the worst that could happen by melting solder and then sitting at a picnic table? This is how I built a simple transmitter and kind of activated a park.

The Michigan Mighty Mite

Nearly everyone has heard about the Michigan Mighty Mite (MMM), a QRPp transmitter popularized by the Solder Smoke blog. There are countless YouTube videos and posts across the internet. It’s very simple: a single transistor, a variable cap, a coil, a crystal and some resistors and a cap. Supposedly one can get up to half a watt of output (I couldn’t). But with a small purchase from Mouser one can oscillate. That seemed pretty cool.

I hadn’t touched an iron until I started playing radio. But I’ve been drawn to homebrew projects. I built a regenerative receiver last year which was very rewarding. I’ve also put together kits (a QCX mini and a TR-35). But my dream has always been to construct a transmitter/receiver combo, or a transceiver. I thought a good place to start was the MMM.

I built the transmitter based on the common schematic for the 40-meter band. The MMM is crystal controlled but I opted to solder in a socket and buy a handful of crystals, so I have the luxury of operating on 7056, 7040, and 7030 kHz. I made a few other improvements, too. The first was to build a low pass filter to attenuate harmonics. Second, although I haven’t finished it yet, the switch on the right will be to choose between multiple crystals. And third, I added a BNC jack to connect a receiver, with a transmit switch. When not in use the transmitter will dump into a dummy load. This receiver switching idea was lifted from the design of the MMM that QRP Guys produces.

When I tested the transmitter at home the best I could get with my charged Bioenno 3 Ah battery was about 300 mW output. The filter is reducing things somewhat, but maybe I need to look into a different transistor or rewind the coil. But I was able to get a 339 signal report from Illinois (no sked) in the midst of distance lightning crashes, so I had a little confidence going forwards. School is out for me this summer, so I decided to head to the park. Continue reading Guest Post: Lake Thunderbird (K-2792) with a homebrew transmitter! →

CW, Field Reports, News, Portable, POTA, QRP, QRPp

QRPp POTA: How many hunters can I possibly log with only 100 milliwatts–?

April 7, 2023 Thomas Witherspoon 6 Comments

As I walked out the door on the morning of Tuesday, March 21, 2023, I grabbed my Elecraft KX2, MM0OPX 40 meter end-fed half-wave, and a key I hadn’t yet taken to the field: my Bamakey TP-III!

I had a full day of errands, appointments, and carting my daughters to/from school, but I also had a good 90 minute window to play radio!

As I’ve mentioned previously, the Vance Birthplace (K-6856) is incredibly convenient this particular school term. I pass by it twice a week, and I feel incredibly fortunate because it’s a wonderful POTA site with POTA-friendly staff. They all know me quite well there at this point.

The Vance site is a small park and the only negative (from the point of view of a POTA activator) is if you have poor timing, you might arrive only to find that a large school group has taken over the site. This is especially a concern on weekdays during school hours–in other words, the time I usually activate Vance.

I pulled into the Vance site that morning and there were no vehicles there other than park staff. A good sign so far!

The only appropriate spot to activate at Vance (if you operate a portable HF station) is in or near the picnic shelter. The rest of the site is where visitors wonder through the old homestead and take guided tours.

I never set up my station in the middle of park activities or in a viewshed.

At the end of the day, we represent all Parks On The Air activators and the amateur radio community at large when we’re in public spaces. The last thing we want to do is detract from others’ park experience.

Before pulling any gear out of the car, I walked into the visitor center and asked the park staff for permission to set up in the picnic shelter. I always do this because if a school or tour group is scheduled to visit the site that day, they almost always need the picnic shelter and have it reserved.

Fortunately, no one had scheduled the picnic shelter, so the park ranger told me, “It’s all yours! Have fun!”

Proper POTA Flea Power!

I like shaking up each new activation in some small way so that it’s not a carbon copy of any previous activation.

Since, like most POTA activators, I visit the same local parks the bulk of the time, it adds a little extra challenge and fun to try different gear combinations, experiment with new antennas, or even (as in this case) try different power settings–! Continue reading QRPp POTA: How many hunters can I possibly log with only 100 milliwatts–? →

CW, Field Reports, News, Portable, POTA, QRP, QRPp, Videos

QRPp: Activate a park with ⅒ of a watt–? I had to at least try!

January 1, 2023 Thomas Witherspoon 33 Comments

In my last published field report, you might recall that I successfully activated a park using 500 milliwatts or ½ of a watt. I was so surprised by the results of using this QRPp power level I immediately made plans to push the power level even lower during my next activation.

Let’s face it, I was drunk with a lack of power!

QRPp

After my last field report, there were quite a few questions about the term QRPp and what it means. To be honest, I’m not sure if there’s an “official” definition, but here’s what is widely accepted as QRP power categories:

QRP: 5 watts to 1 watt (for some contest 10 watts = SSB QRP)
QRPp: Less than 1 watt to 100 mw
QRPpp: Less than 100mw

I don’t own a field radio that allows me to lower the output power to QRPpp levels. In fact, few of my radios actually allow me to lower power below one watt.

My Elecraft radios, however, do allow me to lower power output to as low as 0.1 watts or 100 milliwatts.

The plan

On Wednesday, December 7, 2022, my travel schedule shifted and it opened up the entire afternoon to play radio.

A rarity indeed!

It was very rainy and foggy that day and I didn’t have my ENO rain fly with me, so I decided to visit a park with a good picnic shelter to keep me, an my gear, nice and dry.

Fort Dobbs State Historic Site (K-6839)

I had four park options with covered picnic shelters within a 45 minute drive. I decided that I would try to activate Fort Dobbs State Historic (since it had been a couple months since I’d visited) and Lake Norman State Park would be my back-up plan.

Fort Dobbs is a small park, so I called in advanced and asked for permission to do the activation and also asked if their picnic shelter was reserved.

The rangers there know me, so the phone call was pretty quick–no need to explain POTA nor my motivations. They told me that on rainy/foggy December days they have so few guests that I was welcome to use the picnic shelter or even the entire park if I wished (perhaps an ideal time to erect a Rhombic antenna–okay, just kidding!).

The Dobbs park rangers an volunteers are the best!

Setting up

On the way to the site, I decided that I would deploy my MM0OPX end-fed half-wave I’d cut for 40 meters.

I needed to make the most of my 100 milliwatts, so I figured the MM0OPX EFHW would be the best antenna for the job. Continue reading QRPp: Activate a park with ⅒ of a watt–? I had to at least try! →

CW, Field Reports, News, Portable, POTA, QRP, QRP Radios, QRPp, Videos

POTA with 500 milliwatts CW and 10 watts SSB using the Elecraft KX2 and PackTenna Random Wire combo

December 30, 2022 Thomas Witherspoon 17 Comments

I’d like to start this field report with a side story. I’ll keep this reader anonymous since I haven’t asked for permission to post his story (although I’m certain he wouldn’t mind!):

A QRP Christmas Gift

Yesterday, I was contacted by a reader who had just received an amazing gift.

On Christmas morning, his wife presented him with a tiny wrapped box and inside there was a small note:

“Get yourself a great field radio. You have Carte Blanche!”

What an amazing gift…right–?! She literally said Carte Blanche!

Evidently, she is familiar with my YouTube channel (poor thing) because he often watches my activation videos on their living room TV. [Between us, I’m a bit surprised she still loves him after subjecting her to my videos.]

She told him, “Run your choice by Thomas before ordering.”

The funny bit? He approached me with this very question in November as he plotted a 2023 radio purchase. He couldn’t decide between the Icom IC-705 and the Elecraft KX2.

He wrote yesterday to tell me that he placed an order for a new Elecraft KX2 with all the trimmings; Elecraft’s KX2 “Shack-In-A-Box” package plus a set of KXPD2 paddles.

The KX2 is back-ordered due to parts availability, so he won’t receive his unit for several months, most likely.

Based on his operating style, I think he chose wisely. The IC-705 is a benchmark field radio, but he was looking for something that he could pair with a random wire antenna (the ‘705 lacks an internal ATU) and that would be easy to use on SOTA activations. He’s new to CW as well and loved the fact that the KXPD2 paddles attach to the front of the KX2.

Why do I mention this story? Because it’s not only fresh on my mind, but it’s the same radio and antenna I used during an activation on Thursday, December 1, 2022.

Tuttle Educational State Forest (K-4861)

As I pulled into Tuttle’s parking area that day I had a tried-and-true field radio kit pairing in my pack: my Elecraft KX2 and PackTenna 9:1 Random Wire antenna.

As I mention at the start of my activation video (see below), with the Elecraft KX2 and a random wire, I could easily activate all of the summits, parks, and islands I desire. It’s such an effective, flexible, and portable combo.

QRPp

To shake things up, I decided to knock the output power of the KX2 down to one half of one watt–500 milliwatts–at least for the CW portion of my activation.