Category Archives: QRP

Grab And Go, News, Portable, QRP, QRP Radios

The Elecraft KX1: Reunited and it feels so good.

11 Comments
The Elecraft KX1

A few weeks ago, I published a post about radios I’ve regretted selling or giving away.

Number one on that list was the Elecraft KX1.

Within a couple hours of posting that article, I had already purchased a KX1 I found on the QTH.com classifieds. It was, by any definition, an impulse purchase.

The seller, who lives about 2 hours from my QTH, described his KX1 as the full package: a complete 3 band (40/30/20M) KX1 with all of the items needed to get on the air (save batteries) in a Pelican 1060 Micro Case.

The KX1 I owned in the past was a four bander (80/40/30/20M) and I already double checked to make sure Elecraft still had a few of their 80/30 module kits available (they do!).  I do operate 80M in the field on occasion, but I really wanted the 80/30 module to get full use of the expanded HF receiver range which allows me to zero-beat broadcast stations and do a little SWLing while in the field.

The seller shipped the radio that same afternoon and I purchased it for $300 (plus shipping) based purely on his good word.

The KX1 package

I’ll admit, I was a bit nervous: I hadn’t asked all of the typical questions about dents/dings, if it smelled of cigarette smoke, and hadn’t even asked for photos. I just had a feeling it would all be good (but please, never follow my example here–I was drunk with excitement).

Here’s the photo I took after removing the Pelican case from the shipping box and opening it for the first time:

My jaw dropped.

The seller was right: everything I needed (and more!) was in the Pelican case with the KX1. Not only that, everything was labeled. An indication that the previous owner took pride in this little radio.

I don’t think the seller actually put this kit together. He bought it this way two years ago and I don’t think he ever even put it on the air based on his note to me. He sold the KX1 because he wasn’t using it.

I don’t know who the original owner was, but they did a fabulous job not only putting this field kit together, but also soldering/building the KX1. I hope the original owner reads this article sometime and steps forward.

You might note in the photo that there’s even a quick reference sheet, Morse Code reference sheet and QRP calling frequencies list attached to the Pelican’s lid inside. How clever!

I plan to replace the Morse Code sheet with a list of POTA and SOTA park/summit references and re-print the QRP calling frequencies sheet. But other than that, I’m leaving it all as-is. This might be the only time I’ve ever purchased a “package” transceiver and not modified it in some significant way.

Speaking of modifying: that 80/30 meter module? Glad I didn’t purchase one.

After putting the KX1 on a dummy load, I checked each band for output power. Band changes are made on the KX1 by pressing the “Band” button which cycles through the bands one-way. It started on 40 meters, then on to 30 meters, and 20 meters. All tested fine. Then I pressed the band button to return to 40 meters and the KX1 dived down to the 80 meter band!

Turns out, this is a four band KX1! Woo hoo! That saved me from having to purchase the $90 30/80M kit (although admittedly, I was looking forward to building it).

Photos

The only issue with the KX1 was that its paddles would only send “dit dah” from either side. I was able to fix this, though, by disassembling the paddles and fixing a short.

Although I’m currently in the process of testing the Icom IC-705, I’ve taken the KX1 along on a number of my park adventures and switched it out during band changes.

Indeed, my first two contacts were made using some nearly-depleted AA rechargeables on 30 meters: I worked a station in Iowa and one in Kansas with perhaps 1.5 watts of output power.

I’m super pleased to have the KX1 back in my field radio arsenal.

I name radios I plan to keep for the long-haul, so I dubbed this little KX1 “Ruby” after one of my favorite actresses, Barbara Stanwyck.

Look for Ruby and me on the air at a park or summit near you!

Field Reports, How To, Morse Code, News, Portable, POTA, QRP, SSB

Parks On The Air 101: Some real-time, real-life videos of a typical POTA activation using the Icom IC-705

8 Comments

On Monday (October 19, 2020) I received an inquiry from Dale (KI5ARH) only an hour or so before packing up my radio gear to activate Lake Norman State Park (K-2740).

Dale is interested in using his recently acquired Icom IC-705 to get involved with Parks On The Air (POTA) and play radio in the field.

What’s in my field kit

Dale was curious about all of the components of the field kit I use with the IC-705, so I made this video:

Equipment links:

Since I had already set up my phone to record the video above, I decided to make a couple more.

I thought there might be some value in making real-time videos showing what it’s like operating CW and SSB during a POTA activation.  The videos have no edits and haven’t been trimmed.  It’s as if the viewer were there at the activation sitting next to me at the picnic table.

Operating CW with the IC-705

After setting up my station, I first started on the 40M band in CW. I meant to start the camera rolling during tune-up, but forgot to hit record. The video begins after I’d made a few CW contacts, but shows what it’s like changing bands and relying on the Reverse Beacon Network (RBN) to pick me up then the POTA website to auto spot me.

Note: to be automatically spotted by the RBN, you must schedule your activation via the POTA website in advance, or have been already spotted by yourself or someone else, so the system will know to look for you.

My video cut off abruptly due to a low battery message. I had to give my iPhone a quick power charge to make the next video.

Operating SSB with the IC-705

After operating CW for a while, I plugged in the hand mic that ships with the IC-705 for a little SSB action. My main goal with this video was to show how I call CQ and use the voice keyer memories in order to manage the field “work flow” process.  I also speak to how important it is to either self-spot or have a friend spot you to the POTA network while operating phone.

I spent so much time setting up and running the camera, I wasn’t actually on the air for very long, but I easily managed to achieve a valid activation and had a lot of fun in the process.

I’m not a pro “YouTuber” as I say in one of my videos. I much prefer blogging my experiences rather than “vlogging,” I suppose.

Still, I think I’ll do a few more “real-time” videos of POTA activations and speak to the various techniques I use to activate parks. Since these videos aren’t edited for time, they may not appeal to the seasoned POTA activator or QRPer–that’s okay, though. My goal is primarily to assist first-time POTA activators.

Have you been activating Parks or Summits lately?  Do you have any advice or suggestions I failed to mention? Or do you have suggestions for future topics? Please comment!

Antennas, News, Portable, QRP, Reviews

MAT-TUNER mAT-705 woes

24 Comments

UPDATE: 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, I posted a review of the Mat-Tuner mAT-705 antenna tuner that is designed to pair with the new Icom IC-705 transceiver.

My initial assessment was very positive, but since then the shine has worn off. I’ll explain…

On Monday, I took the IC-705 and mAT-705 to the field for a little Parks On The Air (POTA) fun.

The Par EndFedz EFT-MTR triband (40/30/20M) antenna

Enroute to the site, I thought it would be a good test for the mAT-705 to attempt to tune the excellent EFT-MTR antenna (which is resonant on 40, 30, and 20 meters) on all bands above 40 meters.

After arriving on site, I very quickly deployed the EFT-MTR antenna using my throw line. I then hooked the EFT-MTR up to the mAT-705 ATU and connected the ATU to the IC-705.

After turning on the IC-705, I opened the menu screen and tried to engage the mAT-705 ATU. Unfortunately, the ‘705 didn’t recognize the tuner. I double-checked to make sure the control cable to the mAT-705 was secure–it was. After some head-scratching, I realized I must have left the ATU’s mechanical power switch in the “on” position while using it a few days prior.

This evidently depleted the mAT-705’s internal 9V battery. What a bummer!

I bragged about the mAT-705 in a previous post because, frankly, it is a very capable ATU–quickly finding matches from 160 to 6 meters on my random wire field antenna and horizontal loop antenna at home. It also has an incredibly sturdy aluminum enclosure.  It’s a very capable ATU in terms of quickly and efficiently finding matches and, superficially smacks of superb build quality.

Issues

But if I’m being honest, my love affaire with the mAT-705 ended Monday due to a number of discoveries.

9 volt batteries

The mAT-705 next to the IC-705

According to Mat-Tuner’s product description, the mAT-705:

“[I]s 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.”

Turns out, they mean it saves power only with the mechanical power switch turned “off.”

This, in turn, means that the user must remember each time they use the mAT-705 to flip the mAT-705 mechanical switch off.  If left in the “on” position by accident, even with no connection to the IC-705 and while not in use, it will deplete a 9V cell in a matter of a few days.

This is a significant issue, in my opinion, and is compounded by a few other design choices:

Complicated battery removal

There is no “easy access” to the mAT-705 battery. The user must use a supplied (standard) Allen wrench and unscrew the rear panel from the chassis.

As we mentioned in our previous post, Mat-Tuner actually has a procedure for opening the case and replacing the 9V battery in order to prevent the LED illuminators from falling out. I followed this procedure to the letter, yet the illuminators still fell out. They simply aren’t secured properly and would be very easy to lose if replacing a battery in the field.

The LED illuminators

Once open, you discover that the 9V battery’s holder is a piece of double-sided tape. Seriously:

The mAT-705’s 9V battery holder

In addition, the ATU board essentially “floats” in the chassis secured in slide-in slots. The problem is the back panel–which you pull to remove the board–is only secured to the ATU board with three wired solder points.

Even when I lay the board down carefully, gravity will bend those BNC connections.

I can’t imagine this holding up with multiple battery replacements.

No external power port

Given that battery removal will take a user at least 5 minutes, I find it a little surprising that there’s no external power port.

It would be no problem at all for me, if the 9V battery died, to simply hook the mAT-705 up to my portable DC distribution panel like I can do with other external ATUs. But since this isn’t an option, you’re simply out of luck in the field. Better carry spare 9V batteries!

Where the lack of an external power port is really an issue, though, is for mAT-705 users in the shack. If the IC-705 becomes one of your main radios, you’ll have to be very disciplined to turn it on and off each time you use it, else you’re going to be replacing a lot of 9V cells.

Command connection to the IC-705 is basic

It seems to me that if you build an antenna tuner specifically to pair with a radio via a dedicated control cable, the tuner could potentially:

  • derive power from the transceiver
  • or at least be told by the transceiver to turn completely off when not actively in use. Especially since once a match is found, it’s locked into position even if the mAT-705 has no power.

The mAT-705 can’t do either.

Is it a good ATU? Yes. But inside it could be better.

As I said above, my original review stands in terms of the mAT-705’s ability to match antennas, I think it’s brilliant.

But I can no longer recommend the mAT-705 until some of these design shortcomings are addressed.

I’ve never owned a portable ATU that required so much discipline from the user in order to preserve the battery. I’ve also never owned one that was so fragile internally. Most portable ATUs *only* turn on when finding a match and then either “sleep” or turn off when not in use.

And portable ATUs like the Elecraft T1, for example? Even have a convenient battery compartment for easy removal. (And, oh yeah, the T1 will run ages on a 9V!)

The Elecraft T1 ATU 9V battery compartment

To add insult to injury, it’s one thing to discover that your mAT-705 ATU eats 9V batteries if left on but not in use, but it’s quite something else to discover your $220 ATU’s 9V battery is held in with a piece of double-sided sticky tape.

How long could this possibly function if you’re replacing batteries frequently in the field?

My hope is that Mat-Tuner will sort out this design and re-introduce the mAT-705 to the market. I’ve heard so many positive things about other Mat-Tuner models which is why I wanted to try one out with the IC-705.

Mat-Tuner ATUs are sold by respected retailers in the ham radio world (like Vibroplex, who loaned this model for review) so I expect they’ll address these concerns in the coming months. I’ll certainly post all updates here on QRPer.

Until then, I have to recommend skipping the $220 mAT-705 and instead purchasing the excellent ($160 kit/$190 assembled) Elecraft T1.

Homebrew, Kits, News, QRP

Guest Post: Steve builds a DC30B QRP Transceiver

1 Comment

DC30B QRP Transceiver ProjectMany thanks to Steve (KZ4TN) who shares the following guest post:

DC30B QRP Transceiver Project

by Steve Allen, KZ4TN

I wanted to build a lightweight backpackable transceiver I could take hiking and camping. I chose the 30 meter band as it is specific to CW and the digital modes. I am also in the process of building Dave Benson’s (K1SWL) Phaser Digital Mode QRP Transceiver kit for the 30 meter band. Also, a 30 meter antenna is a bit smaller than one for 40 meters and the band is open most anytime of the day.

I sourced the DC30B transceiver kit, designed by Steve Weber KD1JV, from Pacific Antennas, http://www.qrpkits.com. It appears that they are now (10-11-20) only offering the kit for the 40 meter band. The following information can be used for the assembly of most any kit that lacks an enclosure.

Lately I have been finding extruded aluminum enclosures on Amazon.com and eBay.com. They come in many sizes and configurations. I like to use the versions with the split case which allows you to access the internal enclosure with the front and rear panels attached to the lower half of the enclosure. Most of these enclosures have a slot cut into the sides that allow a PCB to slide into the slots keeping it above the bottom of the enclosure without having to use standoffs. The one requirement for assembly is that the PCB needs to be attached to either the front or rear panel to hold it in place.

DC30B QRP Transceiver Project

As the enclosure is anodized, I didn’t want to rely on the enclosure for common ground. I used a piece of copper clad board that I cut to fit the slot width of the enclosure and attached it to the back panel. I was then able to mount the transceiver PCB to the copper clad board with standoffs. This basic platform of the enclosure with the copper clad PCB provides a good foundation for any number of projects. All you have to do is mount the wired PCB on the board, install the components on the front and rear panel, then wire it up.

DC30B QRP Transceiver Project

I wanted to have the choice of a few frequencies to operate on so I searched eBay for 30 meter crystals and found a source for 4 different popular frequencies. I installed a rotary switch on the front panel and added a small auxiliary PCB with two, 4 pin machined IC sockets. This allowed me to plug the crystals into the sockets. I wired the bottom of the socket PCB first using wire pairs stripped from computer ribbon cable leaving extra length. I marked the wires with dots to indicate which sockets each wire pair went to so I could solder them onto the rotary switch in the correct order. It was tight but I always work with optical magnification so I can see exactly what I’m doing. I have used this crystal switching method in the past with good success.

DC30B QRP Transceiver Project

DC30B QRP Transceiver ProjectThe rest of the assembly was straight forward. I find that most kits are well designed and documented, and if you take your time and follow the directions carefully all should go well. The two most common speed bumps seem to be soldering in the wrong component or bad soldering technique. I double check all component values and placements prior to soldering, and I always use optical magnification while working. I inspect each solder joint and look for good flow through in the plated through holes, and make sure there are no solder bridges.

DC30B QRP Transceiver Project

DC30B QRP Transceiver ProjectThe finished product. I bought a Dymo label maker and it works very well for projects like this. I love using these enclosures and they are a leap forward from the old folded aluminum clam shells I used in the past. I could stand on this without causing any damage. Power out is 1-3 watts depending on the DC power in. The receiver is sensitive and the ability to choose from four frequencies is a real plus.

73 de KZ4TN

Steve Allen
Elizabethton, TN

Wow, Steve! What a top-shelf job on this build! I’ll have to look for those aluminum enclosures as well. Beautiful little rig you’ve made there and I think it’s fantastic you’ve a few crystal frequency options! Thank you for sharing!

Morse Code, News, QRP

Eric’s DIY Cootie: “Levon”

1 Comment

Many thanks to Eric (WD8RIF) who writes:

Well, if K8RAT is going to tout Hermione, I guess I need to tout Levon.

My cootie/sideswiper was inspired by an article (http://sideswipernet.org/articles/w9ok-modernization.php) by W9LA about how hams in the 1930s might have constructed a cootie/sideswiper using a ceramic DPST knife switch. I didn’t have a ceramic DPST knife switch, but I did have a nice Leviton ceramic DPDT knife switch which I used as the basis for my cootie/sideswiper. Instead of using tape for the fingerpieces as described in the article, I used Fender guitar picks.

This cootie is the key I use most often for home-based operations.

While operating in the field, I usually use an inexpensive and lightweight Whiterook MK-33 single-lever paddle as a cootie key.

Levon is a handsome sideswiper, Eric! Thanks for sharing his story and your photo!

Thanks to both of you, I feel inspired to make my own “cootie” this winter. Perhaps I’ll try to find some historic context/inspiration as well!

Any other homebrew sideswipers, straight keys, or paddles you’d like to share? Please contact me and we’ll feature your creations!

I’ve got a very special one that’ll be featured later this week. Stay tuned!

Morse Code, Portable, POTA, QRP, QRP Radios, Reviews

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

7 Comments

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.

Antennas, News, POTA, QRP

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

8 Comments

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.

News, Portable, POTA, QRP

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

4 Comments

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!).

Kits, News, Product Announcements, QRP

An Introduction to the uSDX transceiver kit

10 Comments

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

QRP, Vintage

W9FKC’s suitcase portable

Leave a comment

Many thanks to Pete (WB9FLW), who writes:

Found this link on the Soldersmoke Blog this morning.

Click to access W9FKC.pdf

Interesting to compare this 70 year old Rig with your KX2 or KX3!

We’ve come a long way since then.

Indeed we have, Pete! But, man oh man! What a gorgeous vintage portable–absolutely beautiful vintage example of form following function!

Click here to download the PDF.