Have you ever regretted selling a radio? I have. More than once.

The Elecraft KX1

I’ve been a ham radio operator since 1997. In the first decade of my amateur radio life, I only owned three HF radios (Icom IC-735, Yaesu FT-817, and a Ten-Tec OMNI VI+).

As I got into writing, blogging, and evaluating/testing radios, that number increased. Quite often, radios are only in my shack for a short period of time as I alpha/beta test and/or review production run units.

I try not to get attached to radios because I know they’re often only temporarily in the shack.

Over the years, there have been a few radios I’ve sold for…let’s say “pragmatic” reasons. It’s very rare that I purchase a radio with the intention of keeping it only to find that I want to sell it shortly thereafter. More likely than not, I sell because the radio is redundant (how many field radios does one need–?) or because I’m raising money to make a larger purchase.

Here’s a short list of transceivers I regret selling/trading:

Elecraft KX1

I sold my Elecraft KX1 in 2016 in order to help purchase my Elecraft KX2. It was a solid decision. The KX2 has become my favorite field radio (here’s my review) and was SO much more versatile than the KX1. Still: I really miss the KX1. I loved how bare-bones it was, I loved the top-mounted controls and the fact I often operated it while simply holding it in my hands. The controls were super easy to use even with gloves on in the winter. Plus, it was “cute” in a boxy Elecraft sort of way. If I ever find a deal on another one, I might grab it!

Elecraft K2

I’ve owned both the Elecraft K2/10 and K2/100. Funny story: I acquired a K2/10 in 2008 or so and absolutely loved the radio. After I purchased my KX3 in 2013, however, it was rarely used and sat on my shelf as a “back-up” radio. Eventually, I decided to sell it and did so with ease. Within a week of selling it, a local ham posted on our club email list that he was selling a K2/100 in an SK sale. He wasn’t sure of all of the upgrades, but knew it was a K2/100. The price was very low, but there were no takers after a few days, so I bought it. I used the K2/100 for a few years and it served as a back-up 100 watt radio. I eventually sold it, though, to purchase a KXPA100 used. Now, of course, I do miss that radio. In truth, I’ll likely never purchase one again, because I own so many other transceivers–and the KXPA100 is truly a genius compliment to the KX2 and KX3–but I do have an affinity for that fine rig.

Index Labs QRP++

QRP+ ad from the Dec 1995 issue of QST. Source: WD8RIF

My buddy Eric (WD8RIF) is to blame for this radio. He owned an Index Labs QRP+ for years. He loved operating it in the field and at home. It was the first QRP radio I ever saw in action (at this particular field event). More than 10 years ago, I happened upon a great deal on a QRP++ and instantly bought it. It was SO much fun to operate—super simple, yet had pretty much every feature you’d want in a basic transceiver. I sold it because, frankly, performance was sub-par especially if you ever planned to use it in an RF-dense environment. The receiver front end would simply fall apart, for example, during contests or events like Field Day. Otherwise, it was a pretty sensitive radio. It was incredibly portable and had that awfully “cute” cube form factor. Another fear I had was availability of replacement parts. Index Labs was no longer in business and there were quite a few obsolete parts in the radio. Perhaps it’s a stretch to say I “regret” selling it because, in truth I don’t. But when I see them at hamfests, I’m still tempted to grab one if for no other reasons than nostalgia.

Yaesu FT-817

I purchased an ‘817 shortly after they were introduced in…what…2000? At the time, there wasn’t a radio like it on the market: it was the most compact full-featured HF/VHF/UHF radio in the amateur radio world. Back then, I was living in the UK and travelling all over Europe. I purchased the FT-817 with the idea that I could play radio while, say, working in Hagen, Munich, Chartres, Berlin, Torino, Pescara, or any of the other fabulous sites I regularly visited. I did pack the FT-817 on a number of occasions but since I’m a one-bag traveller, it was scrutinized to some degree at most airports—especially post-9/11. Also, my first production run model blew its finals within the first two years of ownership (a common problem that was addressed by Yaesu shortly after that production run).

I had the finals replaced by Burghardt Amateur Center but rarely used the FT-817 after that. Truth was, I found the radio’s front panel to be too compact and the embedded menus really frustrated me. But back then, I wasn’t as much of a field op as I am now and I could really appreciate a compact, affordable radio that also sports VHF/UHF operation—especially for SOTA activations. Plus, few transceivers have enjoyed a product life like the FT-817/818 which is now pushing 20 years on the market. While the 817/818 lacks a number of features I’ve grown to love (like memory keying) I do believe I may purchase an FT-818 next time they go on sale. In the end, I miss the rig.

How about you? Any regrets?

Please feel free to comment with any radios you regret selling, trading, or giving away over the years and tell us why you miss it! Inquiring minds want to know!

Operating the Icom IC-705 QRP transceiver in CW with full break-in QSK

Readers have been asking me about operating the new Icom IC-705 in CW; specifically if the T/R relay is noisy and how full break-in QSK sounds.

Here’s a quick video that should answer a few of those questions:

I made this video yesterday while testing the new mAT-705 ATU.

Please comment if you have other IC-705 questions.

Icom IC-705: Reviewing the Mat-Tuner mAT-705 in the field

UPDATE: My review of the mAT-705 ATU below is accurate as of its original posting. Since this review, however, I’ve discovered some design issues that prevent me from continuing to recommend it. Click here for details.

UPDATE 2: Mat-Tuner released the latest updated and upgraded version of the mAT-705 in December 2020. It’s called the mAT-705Plus. Click here to read my initial review of the mAT-705Plus. Note that the following article pertains to the original mAT-705 which is no no longer being produced, but still available for sale (at time of posting) both new and used.

Last week, Vibroplex sent me their new Mat-Tuner mAT-705 external ATU on loan to evaluate with my recently acquired Icom IC-705.

Here’s some info about the mAT-705 from Vibroplex’s product page:

The new mAT-705 antenna tuner is designed specifically for use with the new Icom IC-705 QRP transceiver. Connect the mAT-705 directly to the TUNER jack on the IC-705 with the included cable and control the antenna tuner directly from the front panel of the radio or use RF-sensing to actuate the tuner when changing bands. 1.8-54 MHz, 5-1500 ohms matching range, 16000 user memories recalling previous used settings internal to the tuner when returning to an earlier used frequency.

The tuner is powered by an internal standard 9 volt alkaline battery. Power saving technology inside the tuner allows the use of the unit for months without replacement. No battery power is consumed by the unit when powered off.

Yesterday, I stopped by South Mountains State Game Land (K-6952) to give the mAT-705 some field time. Up to this point, I had not used the tuner other than tuning to the 80 and 40 meter bands from home (mainly to make sure it worked before hitting the field).

To really give the mAT-705 a workout, I deployed my CHA Emcomm III Portable random wire antenna. The Emcomm III is the only field antenna in my arsenal that covers 160 meters – 6 meters–an exceptionally wide frequency range.

What I like about this particular POTA site is the open parking area which allows me to configure the Emcomm III a number of ways.

The Emcomm III, being a wire antenna, is incredibly stealthy. Since you can’t see it in the photo above, I’ve marked up the configuration below (click to enlarge):

I’m guessing the apex of the antenna was easily 45′ high.

Activating

I started my activation on the 80 meter band.

After working a few stations on 80 meters, I decided to test the mAT-Tuner over a fairly wide frequency range before calling CQ on the 40 meter band.

Here’s a short video:

POTA Hunters: look for me on the 160 meter band this fall and winter! I’m so impressed how well it matched the Emcomm III on 160.

 

Indeed, I am very pleased with how quickly and efficiently the mAT-705 found matches on every band I tested.

In terms of form factor, the mAT-705 is quite compact, but a little longer in length than I had anticipated. Honestly, though, there’s nothing here to complain about.

The enclosure/chassis is incredibly strong. I’m willing to bet you could accidentally drive over it with your car and it would survive in tact.

The mAT is powered by an alkaline 9V battery. Vibroplex expects that this battery will last for months under normal use.

Note that there is a specific procedure for replacing the battery in order to protect the LED “illuminators” that are press-fit to the board.:

  1. Remove the case by removing the 4 rear 2mm allen screws.
  2. Turn the tuner upside down and shake it a little to get the PCB to slide out of the case enough to grab.
  3. Carefully grasp the PCB sides and slide the board out slowly.

Update: I’ve followed the procedure above and still had an issue with the illuminators falling out. They really need to be secured better. I was able to re-insert them and close the ATU, but when you open the mAT-705 to change the battery, be in a space where you can capture both of them if they fall out.

Any mAT-705 negatives?

Not really, but I do feel the price is a little steep at $219.95–but then again the mAT-705 seems to do the job and do it well. I have to assume the TBA Icom AH-705 ATU will cost at least as much. I’m okay with paying at the top end of the market if I’m getting a quality product and this certainly seems like one.

I like the fact that the mAT-705 integrates perfectly with the IC-705 via the control cable and that I don’t have to worry about protecting it at all in my backpack. It’ll also take the IC-705 through the entire HF spectrum and even up to 6 meters.

 

I plan to continue using the mAT-705 for a while and even test it on severely non-resonant antennas just to see how far I can push it for a match.

Stay tuned! (See what I did there–?)

Many thanks to Vibroplex, again, for lending me this mAT-705 for review and evaluation.

Click here to check out the mAT-705 at Vibroplex.

Hiking to a POTA “two-fer” site from home

I feel pretty lucky that my QTH borders tens of thousands of acres of protected lands: a watershed, Pisgah National Forest, and Pisgah Game Land WRC. Our family enjoys hiking, so we often venture into the forest around our house  and explore the ridge lines, peaks, and views.

This year, while exploring all of the public lands available to activate in the Parks On The Air (POTA) program, I realized there were no less than two sites within a 30-35 minute hike of my home! Quite literally, in my back yard.

In fact, there’s a large area where two POTA entities overlap–Pisgah National Forest and Pisgah Game Land–giving me the opportunity to activate both sites simultaneously as a “two-fer.”

If it’s so close, you may wonder why I haven’t activated it yet–? Well, by the time I realized the park boundary overlap was within hiking distance of the house, we were well into spring, thus the forest was lush with vegetation and the hike to the site requires proper trail-blazing with an elevation change of 600′ (183M). It’s a much easier hike in fall and winter when you can actually see where you’re going through the trees.

Still: Saturday morning, the weather was so perfect for hiking I floated the idea by my teenage daughter, Geneva: “I’ve got a hankering to hike up the mountain today and do a POTA activation.” She replied, “I’ll need to pack my daypack and take the HT.” She was eager to see if she could communicate back to the house simplex with her mom and sis with her new FT-60R handheld.

My wife gave me her blessing, so I packed my trusty Red Oxx C-Ruck with my Elecraft KX2 kit, CHA Emcomm III Portable antenna, water, snacks, logbook and tablet, and used the ruck top flap to secure my three leg folding stool.

Pisgah Game Land WRC (K-6937) & Pisgah National Forest (K-4510)

We arrived at a suitable site about 40 minutes after leaving the QTH. My Garmin GPS and topo maps confirmed we were well within park boundaries. I found a rock outcropping and set up my station.

Even though the area was pretty dense with trees, Rhododendrons, and Mountain Laurel, I had no difficulty deploying the Emcomm III Portable antenna using my throw line.

That’s not a flying squirrel, it’s the winder/balun of the Emcomm III.

The Elecraft KX2 had no trouble at all matching the Emcomm III on all bands.

Even though Geneva was busy communicating with her sister (back at “Mission Control” via simplex) on the FT-60R, she actively logged all of my contact on the Surface Go tablet using N3FJP’s excellent contact log.

I quickly logged eleven contacts on 80 and 40 meters and my daughter suggested we cut the activation a bit short to take in more hiking.

We both wanted to follow a trail we found and see if it lead to the Blue Ridge Parkway.

Hazel has that “Seriously? You want to continue hiking?” look.

I packed up the station and hit the trail!

It turned out to be a good 45 minute trek along a ridge line increasing our elevation about 1,000′ (305M) ASL compared with home. The trail to the BRP was what I would call a moderately difficult trail (much easier than trail-blazing up the mountain!).

In the end, we found the Blue Ridge Parkway and the trail head to ascend Lane Pinnacle which is an excellent SOTA site. We decided to save Lane for another day this fall/winter with a very early departure from home.

Neva also discovered she could easily chat with her sister back at the QTH via 2 meter simplex at the parkway. This means I can definitely chat with the family back home when I eventually make that Lane Pinnacle SOTA activation.

The hike back to the POTA site was mostly downhill so only took about 40 minutes. I then veered off the path to trail-blaze our way back to the house. I did get a little off course which added about 25 minutes (!!) to our descent and requiring us to mitigate the steepest part of the ridge. Next time, I’ll pay more attention to my GPS map (although, in the winter, it’ll be much easier).

Still, it was a very enjoyable hike and certainly one of the more challenging I’ve been on in ages mainly due to the steep part at the end.

All-in-all: I discovered that there are no less than three POTA sites and one SOTA site within hiking distance of the QTH. The best part, by far, was the father/daughter time. Geneva is always up for an adventure (including currently studying for her General class license!).

Alex builds a simple sideswiper

Many thanks to Alex (W3AVP) who shares this photos of his homemade cootie/sideswiper originally posted on the POTA Faxcebook page. Alex notes:

I didn’t want to lug my Begali key to the parks so I made my own using the plans from KA8VIT. Worked great! I had a little QRP key but my fat fingers would make so many mistakes. The DIY aspect of this hobby is extremely entertaining!

And I bet your “cootie” serves you well in the field! I love the simple design and the fact it even has an adjustable action. At the end of the day, keys are merely switches so are perfect for homebrewing!

If you have a sideswiper/cootie or any other key you’ve built and would like to share it here on QRPer, contact me (K4SWL at QRPer.com).

Thanks for sharing, Alex!

642 Miles Per Watt with the new Icom IC-705 QRP transceiver

Thursday, I set out to test how long the Icom IC-705 could operate during a Parks On The Air (POTA) activation with one fully-charged Icom BP-272 Li-ion battery pack. This, following my listening endurance test.

I knew conditions were pretty terrible Thursday in terms of propagation, but that didn’t really matter. I intended to call “CQ POTA” in CW until the ‘705 finally shut down due to low voltage. In my head, I imagined this wouldn’t take much longer than 1.5 to 2 hours and during that time, despite propagation, surely I’d work 10 stations to validate the activation, right–?

Sandy Mush Game Lands (K-6949)

I picked Sandy Mush Game Lands as my test site. Since I’d been there before, I knew there were ample trees to hang the Vibroplex EFT-MTR end-fed antenna, and I knew I’d likely be the only one in the parking area as this site is secluded and this was not a designated hunting day.

The Vibroplex/End-Fedz EFT-MTR antenna

Setup at the site was pretty straight-forward. I quickly deployed the EFT-MTR antenna–using my arborist throw line–in a “V” shape hanging over a high tree branch.

I picked the EFT-MTR because it’s resonant on my three favorite POTA bands: 40, 30, and 20 meters. Note that the IC-705 does not have an internal ATU.

Although I have an mAT-705 external ATU on loan to test, I didn’t take it to this first activation–I wanted to keep the set up simple for testing battery endurance.

On the Air

I started calling CQ at 16:30 UTC on the 40 meter band and set the IC-705 to beacon mode call “CQ POTA K4SWL.” No replies for 10 minutes. At that point, I discovered the POTA spots website was down for a scheduled upgrade (I have impeccable timing!), so I posted my spot on the POTA Facebook page.

Then my buddy Mike (K8RAT) sent a text message stating that the Reverse Beacon Network (RBN) had spotted me, but with a very low signal report. Hmmm….why would that be?

Turns out, I still had the IC-705 power level set to “0” watts (this story might sound familiar). Doh!

Note to IC-705 owners: zero watts is not zero watts!

I turned up the power to 5 watts (the max the IC-705 will achieve on a 7.4V battery pack) and was greeted by an instant CW pile-up.

What a blast! I started on 40 meters in CW, but eventually worked both 40 and 20 meters in SSB and CW. I then lowered the antenna, removed the SMA cap on the EFT-MTR coil, and worked 30 meters CW for the remainder of my time.

I logged my first contact at 16:28, my last at 18:18 UTC. So 1 hour 50 minutes of near constant operating.

Remaining battery capacity after 1:50 of operating.

The IC-705 battery pack was still going strong and had about 40% capacity left, but I simply ran out of time as I needed to run an errand in town, so had to shut down the radio and pack up.

I must admit: the IC-705 is doing a much better job managing battery usage than I would have expected. I’m guessing I could have operated for 3 hours or so at 5 watts without needing to recharge the BP-272 1880 mAh Li-ion battery pack.

I do believe I’ll invest in the larger BP-307 battery pack which has a capacity of 3100 mAh. It’s a pricey battery, though, at $130 US.

How does the IC-705’s battery endurance compare with the Elecraft KX2? I’m not sure yet, but I’m guessing the KX2 will have even better longevity as its current drain is less than half that of the IC-705. The KX2 will operate at 10 watts output for about 1 hour 15 minutes with the internal battery pack, before decreasing to 5 watts output. I’ve never tried a battery endurance test with the KX2 at only 5 watts.

Of course, with an external 12 volt battery, the IC-705 will pump out a full 10 watts of power as well.

Five watts and a wire–wow!

The biggest surprise of the day?

I worked stations from Oregon, and Saskatchewan to the Azores…in single sideband!

Here’s a map of my contacts–red signal paths are SSB, CW in green (click to enlarge):

This was one activation where 5 watts SSB actually snagged more DX than CW. Great fun!

While I’d like to think it was a little IC-705 “mojo” on its first field outing, in truth it had everything to do with the EFT-MTR antenna and what must have been a moment of propagation stability.

This was also my maiden voyage with the CW Morse Single Lever paddle. CW Morse sent this paddle, along with their double lever paddle and a selection of straight keys, for me to evaluate. If you’ve been considering an affordable, portable single-lever paddle, this is a brilliant one. I really enjoyed using it and the action is very easy to adjust.

I’m already regretting the decision to send it to my buddy Eric (WD8RIF) for a proper evaluation. (Just kidding, Eric! (Maybe.)) He only uses a single lever paddle for his numerous field radio adventures.

Eric will give this single-lever paddle a proper workout and give us a full report.

I must admit, I had a lot of fun with the IC-705/EFT-MTR antenna combo.

Of course, I’ll be taking the IC-705 to the field a lot in the coming weeks.

IC-705 Questions?

Feel free to comment and ask any questions you may have about the IC-705. I’ll do my best to answer them.

The new Portable Operations Challenge this weekend!

(Source: Southgate ARC)

Portable Operations Challenge

The final rules for the FMH Portable Operations Challenge are now posted on the POC webpage at foxmikehotel.com/challenge/. N1MM+ users, need to select FMHPOC as the contest and VKContest Logger users just POC.

The organisers wish all other contests taking place this weekend success and lots of fun – the bands will be busy again and we’re hoping propagation plays along.

We hope many amateurs give this new-style contest a go whether from a home QTH station or out portable.

Ed DD5LP

Proud ham family…

Apologies in advance, but I need to brag a bit…

This weekend, both of my middle school-aged daughters passed their amateur radio exams with colors flying. Volunteers with the WCARS VEC were kind enough to meet us at a local park to conduct the test in a covered picnic area.

At the test site I was more nervous than my girls were, but I really had nothing to fear. Both were hitting a 95% pass rate on practice exams in advance.

Even though the girls have obviously learned a bit about radio through osmosis in this household, they did all of the exam prep on their own. Funny story: I remember allowing them both to send CW to my buddies K8RAT and WD8RIF on my lap when they were maybe 2 years old? Of course, they had no idea what they were sending, but they loved playing with the “clicky thing” (my paddles). I think WD8RIF actually copied their code to paper. 🙂 

I purchased both of them an FT-60R handheld radio from Universal Radio. I think these HTs should serve them well for many years to come!

I know one of my daughters is already chomping at the bit to pass her General now.

Anyway, thanks for letting me brag a bit here. I’m certainly a proud papa!

POTA Portable, Picnic, Paddles, and Unpredictable Propagation

Practicing left hand lunching, right hand keying/logging!

It seems like lately I’ve had to work hard to log 10-15 contacts during my Parks On The Air (POTA) activations.  Propagation has been so flaky, I use every trick in the book to snag at least my ten contacts for a valid activation: change antenna configuration, run up to 40-50 watts output, employ both CW and SSB, have friends spot me on the network, and try every band possible (typically from 80-17).

Note that the majority of my activations are proper QRP and rarely do I spend longer than 60 to 90 minutes actually on the air. Indeed, many of my activations are only 60 minutes long including set-up and take-down. That may seem short to most POTA folks, but that’s what works in my schedule and family life: quick hits. It’s one of the reasons I’m not more active in Summits On The Air (SOTA)–I need more time for those sites as they’re not as accessible as our numerous POTA entities.

Still, our local star has been misbehaving, and I had not planned to do an activation on Sunday (September 28) because I saw the propagation forecast and it was rather discouraging (A index 26, SW 505, Bz -2).

From home that morning, I chased a few parks but found it challenging to hear most of them. QSB was incredibly deep–strong stations gone in an instant.

Still, my wife suggested we take a picnic to one of our favorite local spots and how could I possibly visit a park without activating it? Right–?

Zebulon B. Vance Birthplace (K-6856)

What we, as a family, love about this site is the large covered picnic area and historic log cabins. Also, the site receives very few visitors on Sundays when the main museum is closed.

Each time we visit the Vance site, we bring my MSR liquid fuel stove and make lunch/dinner.

I set up the stove, got lunch started and my wife took over food prep.

Knowing propagation was unstable, I opted for more than QRP power this time–at least, at first–so I chose the Mission RGO One transceiver (capable of 55 W output) and CHA Emcomm III Portable antenna for this activation.

I deployed the Emcomm III in a sloping configuration with the end of the 73′ radiator high in a nearby (dead) tree and the counterpoise on the ground. I also suspended the winder/balun from the corner of one of the shelter’s rafter’s with paracord.

Since it’s difficult to see a wire antenna in photos, I’ve labeled the components in the following image (click to enlarge):

I didn’t know if this configuration would prove useful, but I knew it would be better than attempting this activation with my Wolf River Coils TIA vertical antenna.

I hopped on the air starting on 80M CW (at the request of my buddy WD8RIF), worked him and three stations in rapid succession. After a few minutes of silence, I moved up to the 40 meter band and worked 16 stations. I then moved to 30 meters and worked 11 stations.

I was working more stations than I would have ever guessed beforehand.

Since I only had about 10 minutes to spare after working 30 meters, I decided to plug in the microphone and work some park-to-park contacts. While I always intend to hunt for other parks while I’m in the field, more times than not, I don’t have the luxury of an Internet connection to check the POTA spots page like I did at Vance on Sunday.

I worked 5 parks: 3 in SSB and 2 in CW.

Speaking of CW, this was my first field activation using CW Morse Double Paddles.

CW Morse recently surprised me by sending a few of their products to evaluate in the field (guessing they saw my previous post asking about keys–?).

I must say, I really love the CW Morse double paddles. They’re fully (and easily) adjustable, the action is responsive and smooth, and with the base, they’re incredibly stable on a hard surface. I highly recommend them.

At a setting like we had at Vance, I love the heavy base plate, but if I planned to hike into a site, I believe I’d remove the base to save on weight.

Unpredictable Propagation?

Perhaps there was a brief window of stability between solar events and I was able to take advantage of that while I was on the air? I’m not sure.

I never expected to log 37 contacts in the space of a little over an hour (with some of that time being off the air to help with picnic prep). Not on that Sunday when the solar numbers were in the dumps.

I’d like to believe it was a combination of things:

  • A large wire field antenna with decent gain and the ability to work multiple bands
  • 40 watts of power (at first, I backed down to QRP on 30 meters)
  • Using CW for 34 of the 37 contacts
  • Perhaps unintentionally good timing

All I know is, I had a blast! It’s hard to beat a combination of good radio, good food, good scenery, and good weather!

I suppose this was also a lesson in simply hitting the field and ignoring the propagation.

Or as Rear Admiral David G. Farragut once famously said, “Damn the torpedoes, full speed ahead!”

An Introduction to the uSDX transceiver kit

Many thanks to Pete (WB9FLW) who shares the following article by Bob (KD8CGH) regarding the uSDX transceiver kit.

I reached out to Bob who has kindly given me permission to share his article on QRPer:


An Introduction to the uSDX

by Bob Benedict (KD8CGH)

There is a new open source, home brew multi band, multi mode QRP transceiver that grew out of the QRP Labs QCX. Through some serious wizardry  it retains an efficient class E RF amplifier for SSB and digital modes. It crams impressive SDR capabilities into an Arduino.

This has an interesting international development process conducted on  https://groups.io/g/ucx/topics with contributions by many, including the usual gang of suspects: Hans Summers G0UPL, Guido Ten Dolle PE1NN, Barbaros Asuroglu WB2CBA , Manuel Klaerig DL2MAN, Kees Talen K5BCQ, Allison Parent KB1GMX, Jean-Marie T’Jaeckx ON7EN, Ashhar Farhan VU2ESE,  and Miguel Angelo Bartie PY2OHH. I apologize to the many others whose names I didn’t list. A summary is in the WIKI https://groups.io/g/ucx/wiki.

The basic work uSDX appears to have been accomplished by Guido Ten Dolle PE1NNZ. It uses pulse width modulation of the PA supply voltage to transmit  modes other than CW while retaining class E efficiency and uses a direct conversion SDR receiver.

The basic idea behind Class E nonlinear amplifiers is that transistors have little loss when they are switched fully on or off. The losses occur when devices are limiting power flow in linear amplifiers. The idea behind a Class E amplifier is to use transistors in a switching mode to generate a square wave to drive a resonant circuit to generate RF power.

This method is used in the popular QCX QRP CW transceiver kit line developed by Hans Summers and sold through QRP Labs  https://qrp-labs.com/.  More than 10,000 of these great transceiver kits have been sold (I built one). There is a good discussion of the circuit and particularly of the class E amplifier in the excellent QCX documentation https://www.qrp-labs.com/images/qcx/assembly_A4-Rev-5e.pdf.

The QCX was the base for the QCX-SSB which starts with a QCX and modified the circuit and software to add SSB capabilities. The wizardry that  Guido accomplished uses pulse width modulation of the PA supply voltage to control the amplifier in an Envelope Elimination and Restoration (EER) technique  https://core.ac.uk/download/pdf/148657773.pdf. To generate SSB a DSP algorithm samples the  audio input and performs a Hilbert transformation to determine the phase and amplitude of the complex signal.  The phase changes are transformed into temporary frequency changes which are sent  to the  clock generator. This result in phase changes on the SSB carrier signal and delivers a SSB-signal with the opposite side-band components is attenuated.

On the receive side a direct conversion SDR receiver is used with the I and Q signal digitized and all further processing carrying out digitally. Attenuators are included to help not overload the ADC range.  Documentation is at  https://github.com/threeme3/QCX-SSB .  In addition to a good description of the theory and hardware mod there is also a good description of the software command menu.

From there development took off in several directions. One is by Barbaros Asuroglu WB2CBA  and Antrak that uses through hole components (mostly) and replaceable band boards that  hold the low pass filter and band dependent class E amplifier components (an inductor and capacitor). Barb also includes boards designed to be a case top and bottom, battery pack and a PA.

Another development track by Manuel Klaerig DL2MAN uses SMT components in a stacked board layout and has a relay switched band pass board https://groups.io/g/ucx/message/1596  and  https://groups.io/g/ucx/files/DL2MAN uSDX-Sandwich Files. A new revision has been released that uses serial resonance class E amp design and easier to obtain relays, https://groups.io/g/ucx/files/DL2MAN uSDX-Sandwich Files with new Serial Resonance Class E Multiband Circuit .

Other development streams include one by Kees Talen K5BCQ https://groups.io/g/ucx/files/K5BCQ uSDX Board Schematics and Jean-Marie T’Jaeckx ON7EN https://groups.io/g/ucx/files/QCXV4.zip.

I built the variant designed by Barbaros Asuroglu WB2CBA   and I’m pleased with it’s performance. I ordered 10 main boards and 40 LP filter band boards PCBs from PCBWAY, but now you can also purchase single boards sets from https://shop.offline.systems/.

I also designed and 3D printed a case for the transceiver and a small box to carry band boards. Info at https://www.thingiverse.com/thing:4582865 and at https://www.thingiverse.com/thing:4587868 and also in the files section https://groups.io/g/ucx/files/3D printed case for Barb WB2CBA V1.02.

In an example of hams collaborating at its finest, Hans Summers  announced on 9/11/2020 that his new QCX mini product, a QCX in a smaller package,  will include a daughter board that can be used to give the QCX mini a uSDX like SSB capability. The QCX mini has the same circuit as the QCX but uses SMD components packaged it into a two board stack that is less than half the volume of the original QCX. The mod is unsupported by QRP-LABS but may be supported by the uSDX group.

http://qrp-labs.com/qcxmini.html 

More information at https://groups.io/g/ucx/topics and don’t forget the WIKI https://groups.io/g/ucx/wiki.

73

Bob,  KD8CGH


Many thanks again, Bob, for sharing this excellent uSDX introduction. Thanks again for the tip, Pete!

Pete also notes that there is a very active uSDX experimenters discussion group on Groups.io with over 100 members: https://groups.io/g/ucx

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