Category Archives: Portable

Antennas, Guest Posts, Homebrew, How To, News, Portable, QRP

Sam builds a tiny tabletop HF antenna

October 30, 2022 Thomas Witherspoon 18 Comments

Many thanks to Sam Duwe (WN5C) who shares the following guest post:

A (surprisingly good) tabletop HF antenna

by Sam Duwe, WN5C

I recently built a tabletop QRP HF antenna for 17 and 20 meters, in the spirit of the Elecraft AX-1, so I could operate at lunchtime on the campus where I teach. My wants were something small, that would fit in my work bag, that didn’t require a tuner, and could work on a couple of different bands. But on a lark I decided to attempt a POTA activation at Lake Thunderbird State Park (K-2792) pairing this antenna with my Penntek TR-35 QRP CW transceiver. I figured I’d maybe get one or two QSOs and then switch to a long wire in a tree. But what happened amazed me.

I talked to seemingly everyone. Beginning at 9:00 AM September 26th I worked both 17 and 20 meters for an hour and a half and made 37 contacts from across the country. I even had a Swiss guy call me back on 17 but he faded before we could finish. This antenna, at least as a CW POTA activator, works. Granted conditions were very good, but I’ve replicated this multiple times in the past few weeks, just recently at a picnic table in the parking lot of the Route 66 Museum (K-8644) in Clinton, OK (there is quite a thrill in urban activations).

It has also reasonably low profile and very quick to setup and take down. It is also quite a conversation piece when I set it up at school. I elevated the counterpoise by attaching it to a nearby oak and an interested undergrad sheepishly asked if I was listening to the tree!

The build is pretty simple. Physically the antenna consists of a small painters pole from Walmart and an old tabletop camera tripod. I found a nut that fit the screw portion of the tripod and hot glued it into the orange connecting section of the pole. That way the tripod can then be screwed onto the pole. The RF parts of the antenna consist of a 38” telescoping whip that I scavenged from the rabbit ears antenna that came with my RTL-SDR. It connects using the original connector which was hot-glued into a hole I drilled into the top of the painters pole. I found similar small 3 or 4-foot whips from AliExpress for cheap and these would probably work fine.

I then soldered a long length of speaker wire that was wound into two coils: the top for 17 meters (24 turns) and the bottom for 20 meters (25 turns plus the former 24-turn coil). The speaker wire was the soldered to the center of a BNC connector which I hot glued and taped to the pole. I soldered a short piece of wire from the shield of the BNC for the counterpoise and added an automotive spade connector to attach to a 17-foot length of wire. I also included a switch between the coils and the BNC connector to select either just the top coil (17 meters) or both coils (20 meters) using solder, hot glue, and tape. I then covered my shame in silicone tape.

The most time-consuming aspect of the project was tuning the antenna. It required trial and error to first tune the number of turns on the 17-meter coil and then the 20-meters coil. I extended the counterpoise (for me it’s best when slightly elevated) and the telescoping whip. I performed the tuning with the whip not fully extended to give room to tune in the field. Using a nanoVNA was useful here, as was soldering a pin to the wire to poke through the wire at various parts of the coil to find the best SWR.

In use, the antenna can be affected by both body capacitance and how the counterpoise is situated, so I found that an in-line SWR meter was helpful in making sure all was well. Once set up it is easy to fine tune by just adjusting the whip length. 1.5:1 SWR is about how well I can tune on average. Obviously if you have a tuner you would just have to get it close.

There are a million variation on a small base-loaded vertical antenna, and you can definitely improve upon this design. And, besides the super well-built and elegant AX-1, QRP Guys sells an interesting looking kit, and there are some good 3D printed designs I might want to try out. But regardless how you go about it, it might be worth giving a tiny antenna a shot.

72, Sam WN5C

Antennas, How To, News, Portable, QRP, Videos

Jonathan demonstrates using a K7QO noise bridge and shares a 3D printed OM0ET loop mount

October 29, 2022 Thomas Witherspoon 6 Comments

Many thanks to Jonathan (KN6LFB) who shares the following in reply to my recent post about tuning mag loop antennas:

Hi Thomas,

I made a short video showing the use of a K7QO noise bridge from QRPguys to tune a mag loop antenna:

Also, inspired by your post, I dragged my OM0ET magloop up a mountain today for a POTA activation. I used a 3D printed tripod adapter of my own design that allows me to mount it on the collapsing legs from the Buddistick Pro. It makes the whole package a lot more manageable and light weight than carrying a camera tripod.

I had a successful activation of K-4454 on 20 meters, and thought you might enjoy some photos of the setup:

I’ve uploaded the design to Thingiverse at this address:

https://www.thingiverse.com/thing:5589250

73,
Jonathan KN6LFB

Wow! Thank you Jonathan. That short demonstration prompted me to order the K7QO noise bridge kit from QRPguys this morning. In fact, I plan to build this and keep it with my loop antenna as it’ll pair so nicely with my IC-705 and TX-500!

Thank you, also, for sharing those 3D files! I love that field setup at K-4454!

Articles, Field Reports, Guest Posts, News, Portable, POTA, QRP Radios

Mark’s first POTA activation with the Penntek TR-45L

October 28, 2022 Thomas Witherspoon 14 Comments

Many thanks to Mark (W8EWH) who shares the following field report:

An Afternoon POTA Activation with the PENNTEK TL-45L

by Mark (W8EWH)

I have a hard time resisting new QRP radios, and I have an equally hard time resisting getting outdoors when late October brings 70F (21C) temps to Michigan. Days like these are especially sweet given we saw the first snow here last week (no accumulation – but still…). For me there was no better way to enjoy this unexpected weather gift than with an early afternoon POTA activation with my newest QRP radio, the PENNTEK TL-45L.

The TL-45L is the latest radio from WA3RNC, joining the TR-35 and TR-25 in his online store. It’s a 5-band, 5-watt CW transceiver covering the 80, 40-, 30-, 20- and 17-meter bands. That in and of itself is not particularly noteworthy. But when you look at this radio, you’ll immediately see what makes it different.

The retro look for me is unlike anything I have seen in a modern QRP radio. It frankly looks like it was removed from an Apollo Command Module. From the front meter to every knob and switch, this radio just begs to be fiddled with. And each knob and switch serve a function that means no longer needing to dig through menu after menu to find where the narrow filter is switched in because of nearby QRM, or so I can slow down when my CQ POTA is responded to by a slower CW call.

The speaker is located on the (left) side of the radio, a feature many smaller QRP radios don’t have, though headphones can be used via a front mounted jack. The radio sounds great – I think the radio’s case provides a nice sound chamber.

The TR-45L comes with a couple of options, neither of which I chose to add to my order. One is a built-in rechargeable battery (5200 mAh), and the other an antenna tuner. I have plenty of batteries, and normally use resonant antennas.

With the Monday late morning temperature approaching 70 I packed the car with radio gear, and my wife, and we headed out to Island Lake State Recreation Area (POTA K-3315) to activate this park with the TR-45L for the first time. My wife is not a ham but often comes with me to POTA activations. While I set up, activate, and then pack up, she enjoys the outdoors with a magazine and crossword puzzle, and sometimes, like today, a light lunch. Usually, once the activation is complete, we’ll go for a hike on park trails.

Island Lake is about a 20-minute drive from my house. Its 4000 acres is a mix of open fields and hardwood forests surrounding Kent Lake and the Huron River. Today it was warm enough that someone was using a paddle board on the lake.

I have found a set of picnic shelters on elevated ground overlooking Kent Lake as a great place from which to activate. I worked North Pole Alaska from this location on 20M CW using my IC-705 with 10W into an EFHW last May.

Once at the shelter I set up my EFHW (KM4ACK kit) in a sloped configuration using a conveniently located mature tree and my throw line. It was roughly in an East/West orientation. Over the preceding weekend, I added PowerPole connectors to the provided power cord, and programed both internal CW keyer memory slots. These are activated using either dit or dah paddle when I toggle Play using the provided switch. Of course, I did a little POTA hunting using the home antenna to familiarize myself with the TR-45L’s operation. The learning curve is short with nothing hidden deep behind any menus.

With the radio and antenna ready to go, I set up HAMRS on my iPad, spotted myself on the POTA website, and started calling CQ POTA on 14.0615. Over the course of the next 35 minutes, I worked a total of 30 stations on 20M and 40M (most on 20M) at which point I basically ran out of hunters. Not bad for a weekday afternoon. I packed up and went on a couple mile hike with my wife.

The TR-45L is an absolute joy to use.

I forgot to put it in CW Narrow mode at first, and when nearby QRM popped up, I was able to add this in with the throw if one switch. QRM gone. (Note, this setting – wide vs. narrow filtering – must not be retained after the power is shut off or the battery is disconnected.)

It sounds wonderful. I used the side speaker the whole time as my wife doesn’t seem to mind, although the random guy who wandered in with a laptop to get some work done on a warm fall day decided to find somewhere else to work. There are front mounted jacks for headphones, paddles and a straight key. Even a rear mounted jack for an external speaker. The built-in speaker can be turned off and on via a toggle switch. The two CW memory slots are easy to fill using your paddle. The front meter can show power output or SWR based on toggle switch position, and you are alerted to high SWR via a front mounted red LED.

I waited a while to get this radio. Recent supply chain issues caused unexpected delays, but it’s available for order now in factory-built form and most definitely worth the wait. Kits will eventually be available. Check out all the TR-45L details here.

Mark Yergin

W8EWH

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

POTA in the Dark: Problem solving as the sun sets and the clock is ticking on my UTC day

October 27, 2022 Thomas Witherspoon 9 Comments

Have you ever had an activation that didn’t quite go to plan?

Yeah. Me too.

Truth is, it’s just the nature of field radio that things sometimes break, behave erratically, and/or some key component goes missing. When you’re lugging your gear around in a pack and deploying it outdoors in a wide variety of settings it’s a much less “controlled” environment than, say, in the shack.

When a problem arises, you have to work that problem in the field to get on the air and complete the activation.

If you watch my activation videos, you’ll note that I try to include everything in them–including mistakes and mishaps.

Mishaps that lead to a failed activation happen less frequently than they did when I first got started in the world of field radio. Over the years, I’ve refined my field kit and made sure I’ve got the right spare components and tools to solve minor issues I might encounter.

That said, I felt like my activation attempt of Lake James State Park on Wednesday, October 5, 2022 was a total comedy of errors. It seemed like an extra layer of complication presented itself each step along the way as I tried to activate that park.

Lake James State Park (K-2739)

The plan was to leave my home around 17:15 local, arrive at the park around 18:00, set up my Icom IC-703 Plus, pair it with a 40 meter end-fed half-wave, hop on the air and work stations until about 19:00 (23:00 UTC) at the latest, then pack up and continue driving another hour to my final destination.

Here’s how it actually played out…

I had all of my bags packed and ready to go at 17:15, but as I was ready to leave, I discovered a plumbing leak under our kitchen sink. It required immediate attention (obviously) so I grabbed my tools, pulled everything out from under the kitchen sink, found the leak, and sorted out the issue. Thankfully, I had some spare plumbing parts at the house. This only delayed my departure about 30 minutes.

I arrived at Lake James around 18:30 and had the entire park to myself.

My real goal at the park was to take the Icom IC-703 Plus out for a little fresh air. It had been ages since I put it on the air in the field. The last time I tried to use it in the field, the internal keyer was tripping up due to a little RF coming back to the radio from my end-fed half-wave. This is a known issue with the Icom IC-703–it’s more sensitive to RF than any other radio I own.

This time, I planned to eliminate the RF with the inline common mode choke built into my Chameleon 50′ cable.

I grabbed my throw line, MM0OPX EFHW and had the antenna deployed in record time.

You can’t tell from the photos because my iPhone does a great job with low-light, but the sun was setting quickly even as I set up the IC-703. I knew I’d be finishing the activation in the dark, but I had a headlamp handy so wasn’t concerned (again, never leave home without a headlamp!).

I turned on the ‘703 and the 40 meter band was chock-full of signals. A very good sign!

Then I switched the 703’s meter to the SWR setting and sent a couple of dits on an open frequency to confirm a low SWR.

The SWR was off the charts poor, pegging the SWR meter at 9:1 (or worse?).

What–?

Continue reading POTA in the Dark: Problem solving as the sun sets and the clock is ticking on my UTC day →

Morse Code, News, Portable, QRP, QRP Radios

When one KX1 is not enough. (For me, it seems.)

October 26, 2022 Thomas Witherspoon 27 Comments

If you’ve been following this site for long, you’ll know I’m a big fan of the Elecraft KX1 [understatement alert].

I owned one for the better part of a decade, then sold it to purchase a KX2 in 2016. I almost instantly regretted selling it.

In 2020 I purchased another KX1 for $300; like my previous one, it was a four band model, with ATU and paddles. In fact, it even came with a number of other accessories like a proper Pelican 1060 case.

I made dozens of POTA activations with this little KX1 and named her “Ruby” (because I tend to name radios that are a permanent part of my collection).

Trouble in paradise

In the summer of 2021, though, Ruby started exhibiting some issues. This was not completely unexpected because:

All KX1s started life as a kit. None were factory assembled and tested by Elecraft. Quality varies based on the original kit builder.
I believe Ruby is pushing 20 years old.

The main issue was, after turning on the power switch, the rig wouldn’t completely power up. Instead of the typical two clicks we KX1 owners are accustomed to hearing, I only heard one click and neither the display nor any of the functions worked.

This was an intermittent issue–the next day it might power up as it should. I continued operating and tried to find the issue myself, but my skills at doing repairs on radios is very limited.

I took Ruby to Dr. Vlado who traced the issue to a faulty encoder. I purchased a replacement encoder from Elecraft (along with a number of other spares) and Ruby was back on the air!

Back on the air for a while…

A couple months later, I discovered that power output would drop to nearly zero watts after about 20-25 minutes on the air. Basically, when the radio would get warm from operating, power output was affected.

Vlado traced the issue to a cold solder joint and repaired it (while also double checking other joints). Ruby worked perfectly for a few more activations…then once again the same issue with power output dropping reared its ugly head.

Right before we left for Canada this summer, Vlado found yet another cold solder joint and made the repair.

Once we were back home from Canada, I put Ruby back on the air. I did a lot of SOTA/POTA chasing from home and took her on a couple activations.

All was going well until a few weeks ago (you may see this in an upcoming activation video) when once again, power output took a nose dive after the radio warmed up from operating.

It appears old Ruby is just littered with cold solder joints.

I brought her home and decided that I would pull her completely apart this winter and re-solder every point on her board.

Parts radio hunt

Last year, I started hunting for a second KX1. I didn’t care if it was fully functioning because I was mainly searching for a parts radio.

The KX1 has become–and you’ll know this if you’ve been looking for one as well– as rare as hen’s teeth. When they do appear on the market, they command a premium.

In a full year, looking pretty steadily, I only found one reasonable deal on what sounded like a quality KX1. I contacted the seller and he told me that within the one hour his ad was published, he received 10 offers. He asked if I wanted to be put on the waiting list if all ten fell through.

“Okay, I guess?”

I blame the KX1 price increase on a few factors:

Elecraft discontinued the KX1 several years ago. No more are being made.
Others are looking for spare KX1s.
The CW renaissance we’re going through (truly an amazing thing!)
The popularity of POTA and SOTA
It is still a very unique and capable field radio
And quite possibly me, being so public about my love and admiration of the KX1 (where’s that foot of mine so I can shoot it?)

If you’ve been looking for a KX1, you’ve no doubt noticed the low supply and high prices.

Frankly, I’ve even felt a bit guilty looking for a second KX1 knowing how few there were on the market.

Then an opportunity

A few weeks ago, I was chatting with a friend and–long story short–I discovered that a mutual friend of ours would be willing to sell me his KX1.

It was a three band model with ATU and paddles.

He was the original builder and, in fact, this was the third KX1 he’d built. I know him and his soldering work; it’s top-shelf and professional.

I knew I’d likely never get an opportunity to be only the second owner of a KX1 and to actually know that the builder is one of the best out there.

He offered it to me for a fair price based on the current market. I didn’t want him to lose money by selling to me, so I agreed.

I’ve already taken the new KX1 on three activations and it’s performing flawlessly. In fact, I believe the built-in ATU is even doing a better job finding matches that the one in Ruby.

I still plan to work on Ruby this winter–it’ll make for a nice relaxing project some cold, snowy day. It’s the same process Vlado would have to go through (and he’d do it without hesitation) but I’d rather do it myself and save his time especially since it’ll be a bit tedious.

Oh yeah. The name for my new KX1?

Meet Ingrid!

Thank you for reading this post (which is arguably more of a confession and justification)! As always thank you for your support.

Antennas, News, Portable

Honing my mag loop tuning skills

October 25, 2022 Thomas Witherspoon 22 Comments

Yesterday, I posted the photo above on Twitter.

I couldn’t help it: I’m not an “Instagram Moment” kind of guy, but the fall leaf colors this year have simply been stellar. Any excuse.

Where was I? Oh yes…

Truth is, I was in the front yard practicing my loop tuning skills by hunting parks across 30, 20, and 17 meters.

The loop is the excellent Chameleon F-Loop 2.0 (which has since been replaced by Chameleon with the 3.0 version).

I’ve used this loop a few times in the field and even once from inside a large brick community building while doing an FT8 demo.

Loops are a brilliant solution when you have:

QRM from local noise sources,
limited space to deploy an antenna,
or need a very low-impact and small footprint antenna (very handy for those historic and archeological POTA sites).

The trade-off, of course, is that they have a high “Q”–meaning very, very narrow bandwidth. Basically, anytime you move frequency? Yeah, it’s time to re-tune.

The environment around a loop can also have a pretty significant impact on your ability to tune it as well. For example, metal support structure in a building, window frames, metal poles, vehicles–anything like this nearby can have an impact on your ability to tune a loop and obtain a low SWR.

It’s for this reason I use them so little in the field–where I live, wire antennas are so easy to deploy and use.

But sometimes loops are the perfect tool, so knowing how to efficiently and effectively use them is important.

The F-Loop packed

I thought I had posted an activation video using the F-Loop, but looking back I realize I have not.

Yesterday, I decided to pack the F-Loop in my larger Spec-Ops Brand T.H.E. Pack which can easily hold the entire loop, folding tripod, and antenna analyzer.

I always fully set up an antenna before packing it in a new pack just to make sure I’ve included all components. I used this as an excuse to improve my loop tuning skills by intentionally chasing POTA stations across the HF bands. I worked all of the stations I hunted (five, if memory serves).

Twice I obtained a brilliant match just by using my ear (listening for the HF band noise level to increase as I tuned the variable cap) and the rest of the time I turned to my RigExpert handheld analyzer to find a low SWR.

I’m looking forward to taking the F-Loop to the field soon just to see how well it performs. After my practice today, I do believe I’ll keep the antenna analyzer packed with the loop–it makes it so easy to find a good match.

I find the F-Loop a wee bit easier to tune than my W4OP loop. The W4OP loop is also a brilliant loop if you can find one–I recently gifted mine to a friend. Here’s my review from a few years ago.

I’ve used an AlexLoop once and was impressed as well. That’s another antenna I may review at some point.

Commercially-produced mag loops are pretty expensive though. I do plan to build a 20M mag loop antenna before end of year. They’re surprisingly easy to build if you have a good variable cap.

Curious how many of you regularly use mag loop antennas. If you do, what make and model? Or is your loop homebrewed? Please comment!

Field Reports, Guest Posts, News, Portable, POTA, QRP

Rich activates the very POTA-friendly Santa Fe Prairie State Nature Preserve (K-7839)

October 24, 2022 Thomas Witherspoon 2 Comments

Many thanks to Rich (KQ9L) for sharing the following field report:

Activating K-7839 with lessons learned from my last portable POTA activation

by Rich (KQ9L)

Here in Chicago, we have been blessed with unseasonably warm weather these past two days. I decided to build on my last successful POTA activation and apply some of the lessons I learned from that activation while working this one.

Close to my home is Park K-7839, the Santa Fe Prairie State Nature Preserve (K-7839) in Cook County, IL.

The preserve was established in 1997 and is staffed and maintained solely by volunteers. The park’s mission is to preserve a section of land for people to observe and admire the natural Illinois Prairie Landscape before it was altered by man.

The park itself is a thin sliver of land west of Chicago and is boarded by the Des Plaines River to the south and the rail yard / industrial park on the other there sides. If you look carefully in the second picture below, you can see some Sante Fe trains in the distance.

The park is easy to reach by car and right off the main park road are several picnic tables which I’m sure a ham in a wheel chair can easily access.

There are a number of features of the park which facilitate a POTA activation.

For example, in the picnic area, a Boy Scout Eagle Scout project resulted in the building of a 22ft flagpole. The flags are long gone, but the sturdy pole has been made available to hams for the hoisting of antennas. There are pulleys and easy tie down points to erect and inverted vee antenna.

To the east most section of the park is a lookout deck and at the east and west of the deck are trees with pulleys and lines permanently mounted. I’ve been told by the staff that the distance between the trees is a perfect fit for a 20m dipole. Continue reading Rich activates the very POTA-friendly Santa Fe Prairie State Nature Preserve (K-7839) →

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

An evening POTA activation with the Penntek TR-45L, a pileup, and buddy Steve

October 23, 2022 Thomas Witherspoon 14 Comments

Last month, my buddy Steve (VA3FLF/KM4FLF) was in North Carolina visiting family and we hoped to meet up in person at some point. Thing was, both of our schedules were pretty busy with various family activities and projects.

On Wednesday, September 21, 2022, we found an opening in the evening that coincided with a trip to do a little caregiving for my parents. We agreed to meet up at Lake Jame State Park (K-2739) which was on my way and also convenient to Steve.

Steve is also a fan of Parks On The Air, so why not fit in an activation? No better way to spend time with POTA family than at a POTA park, right? Right!

I arrived at the park around 18:30 local (22:30UTC) and set up MM0OPX’s 40 meter end-fed half-wave.

I only had one radio with me at the time: my prototype Penntek TR-45L.

At that point, the TR-45L had not yet been released and was in the very final stages of Beta testing. I was waiting on one more firmware update to bring the radio up to what would eventually be version 1.

Since I was still waiting on the final update that sorted out the CW message memory recording function (and boy did it–the final version is benchmark) I didn’t use message memories during this outing.

I offered Steve a hand at the TR-45L, but he claimed he wasn’t a heavy CW operator–he was interested in helping me with logging, though. How could I refuse that?

Continue reading An evening POTA activation with the Penntek TR-45L, a pileup, and buddy Steve →

Events, Field Reports, Hams, Morse Code, News, Portable, POTA, QRP, SOTA

W4G SOTA Fall Campout Recap

October 22, 2022 Thomas Witherspoon 7 Comments

As I noted last week, I participated in the W4G SOTA campout at Lake Winfield-Scott Campground in the Chattahoochee-Oconee National Forest in north Georgia.

In short? It was amazing!

I thought I’d share a few photos and memories…

Campsite and friends

These SOTA campouts typically involve an announcement via the W4 SOTA group then we all make individual reservations at the chosen campground. Since we’re not reserving the whole campground as a block, we tend to share our individual camping sites with others who might not have been able to reserve a spot.

At Lake Windfield Scott campground, the SOTA group did reserve one large group campsite, but only a couple months ago it was canceled by the park service due to a trail maintenance group that needed it.

Typically, I camp with my friend Monty, but he had other family plans that weekend.

When I found out my buddy Joshua (KO4AWH)–the fellow behind Tufteln products–needed a spot to pitch his tent, I offered up my site.

As you can see in the photo above, both of our tents fit on the tent pad with absolutely no extra room to spare. 🙂

It was such a pleasure getting to know Joshua. What a kindred spirit and super nice fellow.

KO4AWH (left) and K4SWL (right) on the summit of Black Mountain.

We ended up doing all of our SOTA activations together as you will see in upcoming activation videos and field reports.

Joshua is as pack and organization obsessed as I am. A proper pack nerd! I really enjoyed checking out his bags, cases and all of the brilliant accessories that are a part of his field kits.

He brought both an IC-705 and TX-500 along for the ride. He logs in the field using the HAMRS app (same one I do) but on an iPad Mini (see photo above) and I must admit that the size of the iPad mini is nearly ideal–much better than a phone for logging.

He also used the SDR-Control app to connect wirelessly with his IC-705 and operate digital modes.

Summits

We activated a total of three summits during the weekend (Big Cedar, Black Mountain, and Yonah Mountain). It would have been easy to activate six or more if that was the goal–the area is chock full of accessible summits.