Many thanks to Adam (BD6CR) who shares the following guest post about his latest project:
From Open Source Project ADX to Kit ADX-S
by Adam (BD6CR)
BD6CR @ CRKits.COM
Original Design: WB2CBA
Modification and Kitting: BD6CR
I knew Barb, WB2CBA from his uSDX design a few years ago and I introduced both DL2MAN and his designs in my blog. So, when I came across the ADX – Arduino Digital Xcvr a few months ago, I immediately ordered both the ADX (through hole) and the ADX UNO (surface mount) PCB samples.
I started building the ADX UNO and put it in a dental floss case and made a few contacts on park bench. However, the soldering is too much for my eyesight. So, I turned back to the ADX because I don’t need to solder any SMD parts, since both the M328P and SI5351 are module based. I could build the project in 3 hours and it worked the first time.
However, I felt unsatisfied with the strong BCI since the CD2003 radio receiver chip was connected as a direct conversion receiver. JE1RAV mentioned in his QP-7C modification project that he tried JA9TTT’s idea to build a superhet SSB receiver with the TA2003 or CD2003, so I tried and it worked very well. I have decided to name the new circuit as ADX-S, where S stands for Superhet.
I shared the great news with Barb and he encouraged me to carry the flag to make it a kit, since my design D4D was his first digital radio and he loved it.
My hardware modification can be outlined in this schematic. I have added an FL1, PFB455JR ceramic filter by Murata and a C25 coupling capacitor from CLK2 of SI5351 module. The RX audio comes from pin 11 instead of pin 4.
Field Report :POTA Activation K-0228, Stuart B. McKinney National Wildlife Refuge, Great Meadows Unit
by Conrad (N2YCH)
January 21, 2023
Parks On the Air’s Support Your Parks weekend event for winter 2023 is the third full weekend in January and I found myself without my Jeep. I sold my ten-year-old Jeep Wrangler and my new Jeep wasn’t due to be delivered until the following week, leaving me without my “POTA activation vehicle”. I ended up borrowing my XYL’s MINI Countryman to activate K-0228, but let’s face it, a MINI is not a Jeep. It didn’t have all of my “stuff” in it. I needed to get creative about what to bring along with me that would fit easily in the MINI, yet work well enough to activate the park.
I started with my backpack kit which contains an Elecraft KX3, battery, Signalink and computer (for FT8 and logging).
It includes everything I need to transmit and it’s easy to toss in the car. I just needed to decide on what antenna to use. Since it’s winter here in Connecticut and pretty cold outside, this would be an “in-the-car” activation and without the Jeep, my antenna options were limited. I could have brought my Sotabeams Tac-Mini which could fly my PackTenna EFHW up about 20’. However, anchoring the mast would be a challenge in the cold weather. In the end, I decided to bring my Buddipole tripod and nested mast, which are compact and fit in a small bag which fit right in the passenger seat. Continue reading MINI Portable: Conrad’s POTA field report from Stuart B. McKinney National Wildlife Refuge→
K-1716, Silver Sands State Park, Milford, Connecticut
January 13, 2023
By: Conrad Trautmann, N2YCH
A digital mode multiband transceiver for $69? Yes! QRP Labs has the QDX kit available for $69 US. Add $20 if you would like a very nice black anodized aluminum case to mount it in and if you want it assembled and tested add another $45. Visit the QRP Labs web site for all of the details (QDX 4-band 5W Digi transceiver (qrp-labs.com)
How well can a $69 digital transceiver work? Read on…
I ordered my QDX kit back in May 2022. It arrived in June, I assembled it and ran some tests at home. It worked well on FT8 into my home antennas. It interfaces nicely with WSJT-X and I liked the idea of using a low power transceiver to band hop on WSPR. My QDX is an early four band version, which does 20, 30, 40 & 80 meters. I set it to band hop on all four bands not remembering that my multiband offset center fed dipole is not resonant on 30 meters. Since the QDX does not have a tuner, it didn’t like the higher reflected power of a two minute long WSPR transmission into a bad load and smoke resulted. I was fortunate that the failure was isolated to the RF power amplifier transistors and replacing those got me running again. This was my own fault, not the transceiver. Now, it band hops on 20, 40 and 80 meters with no issues, I eliminated 30 meters from the hop schedule.
I share this important story at the beginning of my field report as a warning to anyone considering using a QDX to be very careful when connecting an antenna to it. Since the QDX does not have an internal antenna tuner, you either need a resonant antenna or must use an external tuner to provide a 50 ohm load with low SWR to the QDX. The QRP Labs groups.io site has a number of posts from users with different tuner suggestions.
Now comes the fun part. I visited Silver Sands State Park, K-1716, located on Long Island sound in Milford, CT on January 13, 2023 in the afternoon. While it was Friday the 13th, I had nothing but good luck. Knowing I would be running QRP power, I decided to use what I consider to be my best 20 meter antenna. It’s a modified version of a Buddipole, which I call my “no coil” Buddipole dipole. I use a Buddipole VersaTee mounted to a WILL-BURT Hurry Up mast, which is a push up mast that extends to about 25’ high. The dipole consists of two Buddipole 32” accessory arms, one for each side of the VersaTee and two MFJ 17’ telescoping whips, extended to just about 17.5’. This provides a very broad bandwidth and low SWR on 20 meters. See the screen shot of my antenna sweep from the RigExpert analyzer below.
Here’s a photo of the antenna in the air.
The temperature on this January day was a mild 55 degrees so I was able to set up my equipment in the back of my Jeep. Here’s everything I needed to do the activation. Since the antenna is resonant, I did not use a tuner.
My iPhone gives you an idea of just how big the QDX is, which is sitting just to the right of it. There are only three connections needed, the antenna cable, a 12V power cable and the USB cable. I was using my Bioenno 9ah battery for power. I brought the Bird Model 43 with a 25 watt element in it to monitor the output power and also to measure the reflected power, which barely even nudged the meter. It was effectively zero watts reflected. In the photo above, I was in a transmit cycle and you can see the power meter just a touch above 5 watts. On the computer, you can see a mini pile-up of six hunters in the queue. One thing to note about the QDX is that you can’t adjust the power by lowering the PWR slider in WSJT-X. It’s recommended to leave that at maximum. The way to adjust output power is to adjust the power supply voltage. In this case, the Bioenno had a full charge, so the radio was running full power.
I began the activation without spotting myself, just to see who’d hear me. Here’s a map of the pskreporter showing my spots.
I eventually spotted myself so hunters would know what park I was at. I was amazed that during my activation, I never ran dry or had to call CQ POTA, there was a steady stream of hunters the entire time. The QDX does a fine job receiving, here’s a screenshot of WSJT-X including the waterfall to show what it was receiving.
So, how did the $69 radio do? In a one hour and 17 minute activation, I completed 46 FT8 QSO’s. Here’s my coverage map.
I managed to complete three park to park QSO’s, too. One park called me and I called the other two who heard me and answered. I use JTAlert which helps me keep track of the order of who called. I always try to answer the hunters in the order they called me. I’ve set up a Directed CQ alert in JTAlert for anyone calling “CQ POTA” which helps me to see who else is at a park while I’m activating. If I’m able to contact them, I use the POTA spot list to include their park number in the SIG_INFO field of my log, which is N3FJP. N3FJP is handy to use since I start a new log for each activation and I’ve configured it to upload to LOTW and QRZ when I’m done for the day.
Another thing worth noting is that there is no speaker on the QDX. I’m one of those digital operators who actually listens to the cycles while I’m on the air. It provides a certain cadence to hear each cycle go by so you know what to be looking at or clicking on and when. With no sound coming out of the QDX, it forces you to find that cadence by looking at the computer screen. For me, it means watching the receive audio levels and the progress bar to see if I’m transmitting or receiving. The QDX does have a single red LED on the front panel that will flash during transmit cycles, which is also a helpful indicator.
I’d say the results shown here speak for themselves. I had a steady stream of hunters, I had just one or two QSO’s that needed a second RR73 to confirm and the coverage was as good as most activations I’ve done with more expensive radios and more power. Despite the self-inflicted hiccup I experienced at the beginning, I’d say that If you’re looking to try activating digital for Parks On The Air or even for your home, the QDX certainly works very well and provides a lot of value for the money.
After being bitten by the Parks On The Air (POTA) bug, I became an activator in early 2022. I was hooked. Digital, and specifically FT8 & FT4, is the mode I prefer. A lot of experimentation ensued until I was able to refine my POTA setup to an Icom IC-7300 powered by a Bioenno 20ah battery mounted in a four rack unit Gator case and a Buddipole dipole antenna on a push up mast.
As a radio broadcast engineer by trade, I was very focused on maximizing performance and coverage and after much refinement and trying different things, I feel like my POTA kit performs well. I’ve made contacts as far away as Indonesia, Japan and Israel using the POTA setup in a park… so mission accomplished.
The POTA kit above is not something I can easily take with me on a business trip however, especially by air, so I turned my sites to a Xiegu G90 and various end fed half wave antennas and fiberglass masts and more Buddipole parts to pack into my carry-on luggage. Now I could activate parks wherever I could fly to and I’ve completed successful activations in Wisconsin and Georgia.
Still, I needed to pack a second bag and check the luggage to do these trips. What I really wanted was something I could carry on the plane with me.
I knew I had to change my point of view on what I could achieve using a portable kit. A small radio and antenna wasn’t going to get me contacts in Indonesia, but I could transmit far enough to have someone hear me and get my ten contacts to activate a park. Researching my options online constantly brought me to videos and blog posts here on QRPer.com. Thomas loves his Elecraft KX2 and in a few field report videos he demonstrates an Elecraft AX1 antenna connected directly to the radio for some fast CW POTA activations. This setup was appealing because of the size and he always has a successful activation.
I researched the Elecraft options and the KX3 seemed like the right radio for my digital activations. It has a DATA mode, it can run split operation, it’s got a wideband filter setting and while Elecraft only recommends 5 watts for data modes, it can do up to 10 watts. I managed to find and purchase one gently used on eBay.
I installed the Pro Audio Engineering Kx32 aftermarket heat sink to be sure I protected the final output transistors from overheating and use a Signalink model USB SLUSBKX3 as a sound card interface to the computer. The Signalink can key the radio using the audio keying feature, but I chose to use the Elecraft KXUSB cable to use CAT control and let WSJT-X key it instead. It also allows WSJT-X to read and control the radio’s frequency for easy band changes. I have a Bioenno BLF-1209A 9Ah battery to run it rather than use the internal batteries and I haven’t come close to running the battery out on an activation yet.
Then I bought the Elecraft AX1 antenna with the 40 meter AXE1 optional antenna extender and the AXT1 tripod adapter. It is tiny. There’s really no other way to describe it. It’s a little, baby antenna. Fully extended, it is about four feet tall. I was highly skeptical of how this might perform given its size. I’m using a 25’ Buddipole RG-58 A/U 50 ohm MILSPEC-17 cable terminated to BNC connectors to get the antenna away from my computer because I’ve found that RF and USB do not play well together. I typically try to get the antenna situated in a nearby spot, with a little distance between it and the computer. I bought the Maxpedition Fatty Pocket Organizer Thomas suggested on QRPer.com and a little Amazon Basics Lightweight Mini Tripod.
The AX1, the adapter and tripod all fit in the organizer with room to spare and it fits into a backpack with the radio, battery, cables and my Lenovo Thinkpad 3 laptop. I’m also able to fit in the the Bioenno battery and laptop chargers. At the urging of my XYL, I also have a printed copy of my license in the backpack, too. I haven’t had to show it to anyone yet, but I’m ready, just in case. The backpack is a Mindshift model 18L, designed for photographers, but is easily adapted to contain all of the components I need for a portable activation. Here’s a photo…
Many thanks to Scott (KK4Z) who shares the following post from his blog KK4Z.com:
The Maiden Voyage of the Radio Flyer
by Scott (KK4Z)
When I was young, it was a simpler time. All you needed was a pen knife, cap gun, your dog, and a Radio Flyer red wagon to put your stuff in. The world was your oyster and adventure was right around the corner. Even though I am much older now, and my horizons have expanded; adventure is still right around the corner. It was fitting that my new camper is also a Flyer. I thought it fitting to name my camper the Radio Flyer, big boy’s red wagon.
For my first adventure, I chose to go to the Stephen C. Foster State Park located within the Okefenokee Swamp. It’s about a 6-hour drive from my home QTH. Getting off of the interstate at Valdosta; it’s about a 45-mile drive down a highway that is largely uninhabited. For a man who likes his solitude, I felt alone. I pulled into Fargo, GA for gas, and then it was another 18 miles of desolation to the park. The first gate was entering the refuge. Then another lonely stretch to the park entrance.
The park was quiet with several different species of Owl providing commentary. The park never got noisy while I was there. I liked it. The campsite was rustic and nice. In short order I was set up and ready to go.
One of the things I like about the camper is its simplicity. The interior is open and spacious. there is enough room for me and my gear plus I can sit comfortably. The AC and heater work well. The galley is all I need. I added a microwave that fits on the storage shelf. Continue reading Scott takes the Radio Flyer on a maiden voyage→
QRP POTA Activation During the CQ World Wide Contest
by Joshua (KO4AWH)
I had an opportunity to activate Fort Yargo State Park (K-2177) during the CQ WW DX contest.
Fort Yargo is my local park, about 30 minutes away. The park features a great playground for the kids to play on and many tall trees which are perfect for deploying a wire antenna. There really is not much more I could ask for in a POTA location. Even the noise floor is very low, about S0, so I typically turn on the pre-amp which brings it up to S2-S3 on my Discovery TX-500.
This was very much a last minute plan. I knew the contest was going on which may present some difficulty activating QRP. I knew I would not be calling CQ on 20m where I normally activate and hunting stations could be difficult but likely doable.
There was a bit of rain at the house in the morning, then a promise of drizzle the rest of the day. Not too sure what I would find at the park, but hopefully the rain would hold off and I could get the activation in using the TX-500 without too much worry about it getting wet. I threw in a picnic blanket with a water barrier that promised a bit of protection from the rain if needed it.
I have a go-box setup with my TX-500 and IC-705, as well as several antennas, an ATU, and all cabling and power needed to run FT8 either on my Raspberry PI4 with the TX-500, or on my iPad through the IC-705.
I was taking my wife’s vehicle as she had the car seats needed for the 3 kiddos that were coming along. So, I had to be sure I had everything I needed. There are quite a few additional radio items I keep in the back of my car that I would not have available. But everything should be in the go-box, right?
After a bit of mist and some rain on the drive over, I planned to setup the TX-500 knowing it would get a bit wet. I tossed the throw line in the tree and pulled up my Tufteln EFHW QRP cut for 20m. In retrospect I probably should have pulled up the EFRW for a bit more band agility.
I tuned around for a few minutes.
Yup, there was not a single free place across 20 meters where I could start calling CQ in the clear. In fact, the stations I listened to for more than a few seconds had someone else start calling right on top of them. 20 meters was indeed crazy.
I’ve recently discovered QRP FT8, which I’ve been working with my Icom IC-705. I run with an end-fed sloper that runs out of my 2nd floor shack window using a 49:1 unun and a length of RG-58. I’m also using an Emtech ZM-2 tuner between the antenna and the radio when needed.
The set up works really nicely, except for the way FT8 heats up and overtaxes the radio after a while. Searching around a bit, I’ve found just the right solution for that issue. The AC Infinity MULTIFAN S1 USB-powered table fan.
It’s basically just a 3-inch square fan like you’d find in a computer or some other electronic devices, with rubber “feet” attached. It can stand upright or lay flat depending on your need. it’s stated purpose is to cool or ventilate routers, game consoles, audio equipment, etc.
The AC Infinity MULTIFAN S1 includes a speed control switch and an inline USB socket to daisy-chain other devices. One caveat with the inline socket: because it’s placed in the line between the fan and the speed control switch, the switch must be set to high speed else the socket won’t have adequate power for the attached device.
All I do is plug the fan into a USB socket and place it at the rear of the radio, sans battery, to keep it cool. I have it set up to blow onto the radio. Obviously I need to power the radio with an external source when the battery isn’t attached. I’ve not tried to use the fan with the battery attached, but I don’t think it would help much. The ventilation slots next to the battery compartment don’t seem wide enough to let much air in. Continue reading How Joe keeps his Icom IC-705 cool during long FT8 sessions→
I recently finished my Phaser digital mode QRP transceiver kit and have had a hankerin’ to take it portable, and today was the day.
Temps were in the upper 60s with clear blue sky. About fifteen minutes from home is the Watauga Point Recreation Area on Watauga Lake in Carter County, Tennessee. It’s a day use area and is not an official POTA site, though it is in the Cherokee National Forest, which is. I opted to not make this a POTA activation as it was more of a first time “proof of concept” trip.
The Phaser is a small digital mode transceiver designed by Dave Benson, K1SWL with the enclosure the design of AA0ZZ, Craig Johnson. Phasers were available for most all of the HF bands, put out between 3 to 5 watts, and in addition to FT8, have the ability to program a second frequency to operation other digital modes such as PSK-31. They were sold and supported through Midnight Design Solutions, but unfortunately are no longer being offered. Occasionally I see them coming up for sale on the QRZ.com swapmeet forum.
In addition to the Phaser, I brought an FT-891, an LDG Z-11Pro 2 tuner, a netbook computer, and two batteries; a small AGM for the Phaser and a deep cycle lead acid power pack for the FT-891. I brought my W2LI magnetic loop antenna and a homebrew “NorCal Doublet” that sets up as an inverted V on a 20 ft kite pole as a backup antenna. The whole kit (excluding the batteries) fits in two wooden ammunition crates which make it really easy to drive, set up, and operate.
One note on using the W2LI mag loop. You need to first tune the antenna using the radio and listen for an increase in the background noise level. Using the Phaser while connected to my computer made that not possible. If I had brought a small set of earphones I could have plugged them into the audio out jack on the Phaser and tuned for max background noise. So, instead I connected FT-891 to the loop and used it to tune the antenna to 30 meters. Next time bring earphones.
After about fifteen minutes I had the station set up. The waterfall on WJST-X showed that the Phaser was receiving transmissions but no displayed text. Unfortunately I had neglected to synchronize the computer clock before I left the house. The netbook is pretty old and the internal battery needs to be replaced. What to do? First I tried to manually sync the clock to WWV but Windows 10 won’t let you set the seconds in the clock to 00. As I had cell service I figured I could use my cell phone as a hotspot. Never having set it up before I have to say that it was pretty easy. Thank you 21st century tech! This allowed me to sync the internal netbook clock, but it also let me log contacts on QRZ.com, and check my propagation on PSK Reporter.
The Phaser puts out around 3.5 watts, so I didn’t respond to a CQ that was less than -5 dB. While PSK Reporter showed reception of my signal up and down the East coast, contacts were scarce. I seemed to have a window open up into New England as I worked PA, MA, and CT. I was right in the middle of my fifth contact when the computer battery died so that was it. WSJT-X reported these stations on the +dB side for reception but my signal strength was always reported at < -10 dB.
The 30 Meter band was up and down with band conditions being reported as only Fair on the Solar-Terrestrial Data report on QRZ, and at one point for about a half hour there were no signals displayed on the waterfall.
With a loop antenna on a tripod and 3.5 watts I can’t complain. I’m thinking of building an RF amplifier to boost the output up to 10 watts which should help. My next step is to load WSJT-X on my tablet and see how portable of a kit I can assemble. As FT8 was designed as a weak signal mode, it’s perfect for QRP portable operating.
Thomas, Adam of CR Kits is now taking orders for his FT8 Transceiver Kit and the price is very reasonable.
From Adam at CR Kits:
FT8 transceiver kit
Folks, I start to take email order now. The introductory price is 39 USD for kit including shipping to worldwide. As in the introductory period, you will get audio cable options for free. The earliest possible shipment date is now improved to May 13.
You can directly PayPal to [email protected] and let me know 40m or 20m (80m not ready yet). I will ship based on the sequence of receiving your payment. I may delay shipment for one week or two due to workload.
This is the spec so far:
Summary: Crystal controlled single frequency DSB transceiver for 20m (14.074MHz), 40m (7.074MHz) or 80m (3.573MHz), other frequencies could be added per requestPower supply: 10-14V DC regulated power supply or battery pack, 12V is recommended, center positive, reverse polarity protection availableCurrent consumption in RX: about 15mA at 12VCurrent consumption in TX: about 300mA at 12VRF output: about 1W for 40m band at 12V, and a bit less for 20m bandSpurious suppression: no worse than -50dBcAntenna connector: BNC connector, 50 ohmAudio in connector: 3.5mm mono, at least 600mV to activate VOX, connects to headphone connector at PC sound card, no dedicated PTT connector is requiredAudio out connector: 3.5mm mono, connects to microphone connector at PC sound cardAmber LED: TX statusGreen LED: RX statusFrequency accuracy: -600 Hz ~ + 200 HzFrequency stability: Okay for FT8 mode per test. If the optional heater resistor R20* is added, after warm up, long term frequency stability in 10 min will be improved at the cost of acceptable short term frequency stability sacrifice in 30 sec. Thanks, Adam
Adam BD6CR of CR Kits is getting close to releasing the FT8 DSB Transceiver. Below is some preliminary information:
D4D: A simple QRP transceiver for FT8
Adam Rong, BD6CR
D4D stands for DSB transceiver for Digital modes. It is a Double Sided Band transceiver kit designed for digital modes, especially for FT8. If have chance to try FT8, you will be amazed by the strong decoding capability offered by the communication protocol, digital signal processing and software. I still remember clearly a YouTube video by W6LG who communicated with bulbs. I started to think how much the transceiver could be simplified if you have a moderate antenna like a full sized dipole or EFHW.
A DSB transceiver is much simpler than a usual SSB transceiver, however it was never used for FT8 as far as I know. I did some experiments on my Choc perf board. I started with a direct conversion receiver for FT8 and it worked okay. Then I made a DSB transmitter and the transmitted signal can be decoded. By referring to the designs of AA7EE, VK3YE and ZL2BMI, I combined them using only one NE602 and a PTT switch and it gave me success to make a few FT8 QSO’s.
Personally I really enjoyed it because a manual PTT switch will save power consumption and circuit complexity, but you will need to well sync with computer, although it was not really a problem for me. Per request from a few hams, I found a VOX control circuit and modify the hold time to be compatible with FT8, and I put them together and made a few improvements on the signal purity and frequency stability, and it became our D4D. Do we have to worry about the unwanted Lower Side Band? Maybe, but for a transmitter of 1-watt, it is not really a big problem. Is it just a toy for a transmitter of 1-watt and only half of the power will be effective? Not really, as I can easily make a few QSO’s as far as 1500 miles range for 40-meter band.
Here is the brief specifications I have measured (subject to change without notice):
Summary: Crystal controlled single frequency DSB transceiver for 20m (14.074MHz), 40m (7.074MHz) or 80m (3.573MHz), other frequencies could be added per request Power supply: 10-14V DC regulated power supply or battery pack, 12V is recommended, center positive, reverse polarity protection available Current consumption in RX: 15mA Current consumption in TX: about 260mA(?) at 12V, and about 300mA at 13.8V RF output: about 1W for 20m band at 12V, a bit more for lower bands like 40m and 80m Spurious suppression: no worse than -50dBc Antenna connector: BNC connector, 50 ohm Audio in connector: 3.5mm mono, at least 600mV to activate VOX, connects to headphone connector at PC sound card, no dedicated PTT connector is required Audio out connector: 3.5mm mono, connects to microphone connector at PC sound card Amber LED: TX status Green LED: RX status Frequency stability: Okay for FT8 mode per test. If the optional heater resistor R20* is added, after warm up of about 3 min, long term frequency stability in 10 min will be improved at the cost of acceptable short term frequency stability sacrifice in 30 sec.
Let us briefly go through the circuit: The input audio will activate the VOX circuit of D2 (1N4148), Q5 (2N3906), Q6 (2N3904), Q7 (2N3904) and Relay. The relay is a DPDT type and controls both antenna and power supply. The LPF consists of L2, L3 and surrounding capacitors, and it is switched to either transmitter output or receiver input. The power supply is polarity protected by D1 (1N5817) and switched to either receiver circuit or transmitter circuit. The receiver circuit is only for audio amplifier consists of Q1 (2N3904) and optional heater resistor R20*, while the transmitter circuit is for RX muter Q8 (2N3904), TX driver Q3 (2N3904) and TX final Q4 (BD139). X1 is a filter in the receiver front end to help eliminate strong broadcast interference, and X2 is the crystal for the built-in oscillator in U1 (NE602). U2 (78L05) is the 5V regulator for U1, and Q2 (2N3904) is a buffer amplifier in the TX chain.
Thanks for sharing this, Pete! What a simple transceiver concept!