August 2, 2025
QDX installed in its case with the battery and USB power supply.
The QRP-Labs QDX is a five band, five watt, digital mode HF transceiver. It’s highly efficient, easy
to operate, and configurable for bands from 2200 meter through 4 meter. As usual, Hans has created a
very clever bit of kit for the homebrew-minded ham.
For my QDX build I added a rechargeable LiPo battery pack, charge circuit, and a USB power supply. I
packed the build into an inexpensive extruded aluminum enclosure that I
sloppily machined for access to the various connectors. The result is a very lightweight and nearly
self contained digital rig that can be operated with nothing more than my iPhone and a simple wire
antenna.
Nearly every radio project needs a low pass filter at some point, the QRP-Labs LPF kit is a quick
and easy build that can knock out harmonics for nearly any low power HF radio. This is a compact,
modular kit implementing a 7-element low pass filter which can handle 10 watts safely. Variants are
available for bands from 2200m through 1.25m.
The kit was developed by Hans Summers, G0UPL. With Tor F.I Anderson, SM6FWF, contributing the 2m and
1.25m variants. I’m using these filters as the final filtering stage of a 10-band POTA rig I’m
building around the HackRF One.
March 28, 2024
The completed QRP-Labs Ultimate Relay Switched LPF board.
The QRP-Labs Ultimate Relay Switched LPF Kit was developed by Hans Summers, G0UPL, as an extension
to the Ultimate 3 and Ultimate 3S transceivers. It allows
switching between six different Low Pass Filters (LPFs) and so operating the transceiver on six
different bands instead of one.
I’ve used these relay-switched filter boards in several projects now and I’ve been surprised at how
easily they can be adapted to uses beyond their design. The build below shows an unconventional use
for the kit – switching multiple filter arrays from a single MCU pin. This is a part of a 10-band
POTA rig I’m building around the HackRF One.
For details on the kit and more conventional uses of it check out
QRP-Labs.com.
