Interim Findings of the HamSCI DASI2 HF Antenna Project

An ad hoc HamSCI DASI2 Antenna Group was tasked in late 2024 with evaluation of antenna options for the DASI2 grant. We present the the materials, methods, and criteria we have so far developed to accomplish this along with preliminary results.  Antenna systems under consideration include DXE-RSEAV-1FVI, N6GN SAS, LZ1AQ loop dipole, and others.  The materials include key elements already intended for use in the grant -- the RX888-SDR and software such as the KA9Q-Radio system, the KA9Q-Web spectrum display, WSPRDAEMON, and spot and noise reception reports to wspr.net, wsprdaemon.org, and pskreporter.  The methods leverage ITU noise figures, known broadcast station locations, significant recent improvements in the spectrum display, and analysis of the local site.  The criteria so far include antenna performance metrics, site evaluation, ease of deployment, support needs, and cost. This effort will enable us to provide good quality information, some of which we present, for selecting an appropriate antenna for the grant.  However, the effort to solve this particular task has also demonstrated the general utility of these tools and methods for the amateur radio community.  A view of the entire HF spectrum enable at-a-glance assessments that can help one more effectively identify and solve problems and optimize reception given the natural limitations of one's site.  One can see recognizable patterns suggesting local and propagated noise, overmodulation, aliasing, inadequate front-end gain, ground loops, and more.  One can compare two (or more) antennas or one antenna with itself at different sites or orientations, the effects of feed-line placement, interactions with nearby structures or foliage, and more.  These efforts will inform the choice of an antenna to use for the DASI2 grant but can prove immediately useful for all hams and scientists in understanding and optimizing their receiving systems.