At Clearsky, we have longwire Beverage-style antennas at 45 degrees for longwave and lower shortwave work. We typically leave them unterminated, so they receive equally well in either “endfire” direction.
Since the radiation pattern is dependent on the length of the antenna relative to the frequency of interest, a simplified plot of the directional response of the “red” Beverage on the 2200 meter band, the 630 meter band, the 160 meter band, and the 80 meter band roughly looks like the following when plotted on a linearly concentric-in-dB chart.
To manage switching between these antennas, we designed and built a Beverage antenna switching device. It has automatic and manual modes, connects to our IoT WiFi, pulls UTC time from an ntp.org server, and rotates between four antennas at two-minute intervals to coincide with WSPR transmissions.
It is built around a 3.5-inch TFT display attached to an ESP32-Wroom microcontroller system, wired to a relay board, and uses an I2C expander to read the two “user interface” buttons and drive four double-pole, double-throw relays.
For receiving, we wired the entire station with 100-ohm differential CAT-6 cable. Impedance-control-wise, that system plays well with DPDT relays. (If that were to matter, but it doesn’t at the frequencies of interest.)
The case is 3D printed, 8 inches wide, and will go into a rackmount system. We have 8-inch, 10-inch, and 19-inch racks, all with standard 1U vertical offsets.
The top button allows for manual cycling between the four antennas. Pushing the top button activates the selected antenna indefinitely. Tapping the lower button switches the unit into automatic, 120-second rotation mode.
Leave a comment