Thx for posting. When you consider performance vs price point the QMX+ is amazing. Kudos to QRPLabs for the awesome design work on their products!
backyardcnc
Great presentation, I use smart phone apps (audio spectrum analyzer) to determine the 1kHz tone & 3 dB gain above noise floor as MDS.
73 vk2ihl
vkihl
As an owner of all 3 of these radios I approve of this message. Thanks for the cool content on comparisons. Fun to look at it. 73 om
Utahforrest
Thanks for the measurements! I just finished building a qrp-labs QMX+. The first component level kit i have built in over 20 Years. Seems to work well. Thanks again!
georgearthurrosaltalbot
Thanks for posting the test, John. I compared the FT-891 with the Penntek TR-35 using received signals from the antenna and they were quite similar in performance.
WBDTT
Thanks for the comparison. The availability of the narrow filters on the QMX really makes a difference in picking out really weak signals. Sometimes I go down to 150 Hz or below, play with the center frequency and the RIT and can pull something out that is not copyable on an of my small QRP rigs (KX1, MTR series, HB1B, etc.) That capability sets this rig apart from the others.
bryan
I did the same type of measurement on my QMX-low and QMX-high. TinySA, two Amazon-bought 50 Ohm attenuators of 41 dB (sticker says 40 dB), and adjust the internal variable attenuator in the TinySA. Each component is adding at least +/-1 dB of error, so the final results have a bit of error bar to them. But my results are pretty close to your results. Except that I don't see the dropoff on 12m and 10m on my QMX-high. They are about the same as 20m. On the other hand, for some bands, it matters greatly where in the band I measure. 20m and 15m have a behavior that at the low end of the band, say around xx.020 MHz, the MDS is like your table. But around xx.050 to xx.070, the MDS is about 10 dB worse. There is a noticeable rise in the noise floor as I tune up from the bottom of the band, with the peak noise right around the QRP calling frequencies (ugh). Since 20m is supported by both my rigs, I checked if this could be replicated on both rigs, and it can. I also have an older Rev 1 9-volt built QMX-low, and its 20m has the same behavior. So I wonder if this is a characteristic of the architecture. 73 de N9OHW
NOHW-xysw
Hello, on HF, at least up to 40 or up to 20 meters, it makes no sense to talk about receiver sensitivity: they all have more than enough sensitivity to receive natural noise and therefore useful signals, which must be higher in level than natural noise.
Anyone can do a simple test by disconnecting the antenna from the receiver (it should be connected to a non-inductive resistor with a value equal to the input impedance of the receiver, but here it makes little difference).
By turning up the volume, you hear a slight hiss; connecting the antenna, you receive signals but the noise increases a lot: with a more sensitive receiver, both noise and signals would only be stronger, but their ratio (signal-to-noise, which is what is needed for intelligibility) would remain the same.
From about VHF and upwards, the discussion is reversed and the sensitivity of the receiver (with the same noise produced) becomes decisive for the reception of the lowest signals. 73s
IKXOO--Paolo
I noticed you have a Hermes Lite 2 over there. Did you do this same test on the HL2? I am surprised how it compares to my FT-710, but it might be just a feeling. I've never done a proper test.
sadelta
I would love to have any one of these but the only one in my budget is the qmx +.
jbloodwo
I assume the FT-891 has a RF preamp running. Great performance from a kit, that's a fraction of the price of those others'. I wonder what the off frequency performance is like.
technishn
Meh, sensitivity is overrated (for HF). Dynamic range and receiver noise are so much more important for real-world operating, in my opinion. 🙂Thanks for the test though! 73s
ruhnet
For the cost differential and for the dangers involved in POTA and SOTA environments, I'd think the QMX+ is a winner. IMHO. aa7fo dit dit
