Category Archives: FT4

Guest Post: A QRP Labs QDX POTA Field Portable Report

(Photo: QRP Labs)

Many thanks to Conrad (N2YCH) who shares the following field report:


QRP-Labs QDX Field Report

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.

Conrad packs the Elecraft KX3 and AX1 for a New York City POTA Rove

Many thanks to Conrad (N2YCH) who shares the following field report:


New York City Park Rove, December 30, 2022

Conrad Trautmann, N2YCH

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…

So now I’ve got a completely self contained POTA kit in a backpack that can be carried aboard a plane. Continue reading Conrad packs the Elecraft KX3 and AX1 for a New York City POTA Rove

FT4 digital mode now available in WSJT-X release candidate 5

(Source: Southgate ARC)

The new amateur radio digital mode FT4 is now available for download as part of WSJT-X Release Candidate 5 

You can download wsjtx-2.1.0-rc5-win64.exe (or for other O/S) from near the bottom of the page at 
http://physics.princeton.edu/pulsar/k1jt/wsjtx.html

FT4 Protocol document 
http://physics.princeton.edu/pulsar/k1jt/FT4_Protocol.pdf

See the WSJT Group at 
https://groups.io/g/WSJTX/

New digital mode: Joe Taylor (K1JT) has announced FT4

(Source: Southgate ARC)

Joe Taylor K1JT has announced a new digital mode, FT4, which is 2.5 times faster than FT8 

FT4 is an experimental digital mode designed specifically for radio contesting.  Like FT8, it uses fixed-length transmissions, structured messages with formats optimized for minimal QSOs, and strong forward error correction.  T/R sequences are 6 seconds long, so FT4 is 2.5 × faster than FT8 and about the same speed as RTTY for radio contesting.  

FT4 can work with signals 10 dB weaker than needed for RTTY, while using much less bandwidth.

FT4 message formats are the same as those in FT8 and encoded with the same (174,91) low-density parity check code.  Transmissions last for 4.48 s, compared to 12.64 s for FT8.  Modulation uses 4-tone frequency-shift keying at approximately 23.4 baud, with tones separated by the baud rate.  The occupied  bandwidth (that containing 99% of transmitted power) is 90 Hz

Further information on FT4 is at  
http://physics.princeton.edu/pulsar/k1jt/FT4_Protocol.pdf