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.
7 thoughts on “Guest Post: A QRP Labs QDX POTA Field Portable Report”
It’s a great transceiver, I have been using the low band one for the last year and have a high band that I plan on using for support your parks weekend.
Great report Conrad. Thanks.
This gave mo some ideas for POTA. I’m thinking just set this up and let it rip while working SSB or CW for POTA. I’m wondering how that would work out. I think my 705 would be okay with it. Would require two antenna setups though but that shouldn’t be too difficult.
The QDX is a fantastic radio. If you read Hans’ circuit description and how he architected the radio, then you will really get an understanding how such high performance from a small radio.
I’ve built two of them so far and it’s the only radio I use for FSK modes like FT8. With a wire vertical from the roof of my apartment building the QDX has achieved QRZ Awards for US States (WAS), World Continents (WAC), and 31 countries.
As this post above describes, the QDX does POTA. Here is my story of activating from a park bench on the edge of San Francisco bay at K-0819 https://w6csn.wordpress.com/2022/09/24/fort-point-national-historic-site/
The QDX went from a “toy that I had little interest in” to the radio with which the bulk of my QSOs have come in the past year.
I love this radio too! I built a v3-9v… but use the assembled 12v. I’m just getting into digital, but already I can say it performs fantastic. All my QRP Labs radios do.
In the field, I use an EFλ/2 40m, and I prefer using it vertical, high up in a tree.
When I eventually get into S/POTA, I’ll actively log.
Thanks for the input.
Thanks Conrad, I have a QDX being shipped to me now. Appreciate your report, it gives me a good idea as to how to proceed with set-up and operations. Will still be including CW as part of my QRP POTA activations but this will be part of it.
Were you not worried about smoking those output transistors with the >13V of the Battery?
Since I was so close to the rated output power and given the good antenna match, I wasn’t.