# The Analysis of Experimental Deployment of IGLUNA 2019 Trans-Ice Longwave System
## 2 Transmitting Antenna Design and Parameters  
The choice of the longwave system's frequency was based on an optimum between the antenna efficiency, ice penetration and spectrum availability, as the primary user/emission (analogue double-sided amplitude-modulated telephony with carrier-A3E, with effective isotropic radiated power (EIRP) of 50 kW from the _Radiokomuniakanti Stredisko_ (Radio Communication Centre, RKS) Topolna in Czech Republic) is almost not receivable in Switzerland; it was used under arrangements with the Swiss Federal Office of Communications (BAKOM). A sufficiently large loop antenna would have the length of at least quarter of the transmitted wavelength (for 270 kHz: approximately 278 m), providing high impedance and acceptable radiation efficiency at moderate total mass of the wire [4]--but with more complicated current distribution [10]. To mitigate the risk of antenna breakdown due to broken  
Figure 1: A schematic of the IGLUNA 2019 initial communication system. The HML (Horizontal Magnetic Loop) antennas were designed as both transmitting- and receiving antennas, as the receiving subsystem was to be operated continuously and simultaneously with the transmitting subsystem, the receiver would detect both the self-transmitted and incoming transmissions. wire and to reduce the DC resistance of the wire, a string of eight double-PVC-insulated wires was used (which also reduced the already-low for 270 kHz skin effect losses). Two 278-m-long loops were deployed--one on the surface of the glacier, forming a rectangle along the wide ski route, and one inside the Glacier Paradise, on the ice floor, closely to the ice walls, using corridors available to maximize the area enclosed by the loop (see Figure 2) below the rectangular-shaped surface antenna. Bearing similarities to other large antenna projects [6; 11; 12], the system effectively employed the available terrain conditions for the deployment of a large horizontally-polarized low-frequency radio communication inside the glacier and over large distances. On the surface of the glacier, the antenna was partially covered with gravy snow. As it crossed the ski route used also by snowcats, it was twice cut by the machine's tracks--the repairs kept the antenna operational, yet increased its DC resistance. Inside the glacier some parts of the antenna wire were flooded with drainage water which was constantly being removed from the melting glacier-the antenna remained undamaged despite the later freezing of the water. During the operation of the experiment--from 23 to 30 June 2019, with the 30 June as the day when the dismantling of the glacier-based system started, leaving only the surface system operational--every day the inductances and resistances of both antennas were measured. These values, presented on Figures 3-5, have been used to calculate the absolute values of the impedances of the antennas and their \(Q\) factors for 270 kHz (interpolations by linear functions between the values for adjacent days). The inductances of both antennas did not remain constant during the measurements-they have varied between the maximal and minimal values, most likely due to changes in the surface features of their 'cores' [6]--humans, vehicles, maintenance equipment, other IGLUNA experiments, electrical installations, etc.--the interpolation curves indicate the days when the surface antenna had been damaged by the snowcat's tracks (as it did not function as a one-loop coil, the inductance could not have been measured). Despite the fact that both antennas had different shapes and functioned in different conditions (shielded ice cave with approximately constant temperature of \(-5\)\({}^{\circ}\)C and no snow versus open space with gravy snow and severe temperature fluctuations, including its daily variations), their averaged inductances converge to a value between 0.45-0.46 mH. The resistances of the antennas (despite the temperature differences) remained nearly equal, with the value of 3.7 \(\Omega\).