Helical Antenna
Our custom ice RPM antenna is a custom "Normal mode" helical design see: [1]
"normal mode when the diameter and pitch of the helix is less than 0.1 Lambda"
for us that is clear - as our coils are very close together.
that ref also says trim the coils to tune resonance to the environment
ice has a dielectric constant of about 3.2 (we can measure it with the Radar gear at 50/100/200MHz)
173MHz radio has a wavelength of 1.73m in a vacuum,
151MHz wavelength in vacuum is 1.987m
in dielectric constant of ~3 wavelength of 173MHz radio becomes about 1m (1.15m at 151MHz) but in dry sediment? (30 would be wavelength of 32cm !?)
so a quarter lambda in ice is about 29cm at 151MHz
useful equation: c = wavelength x freq x sqrt(dielectric const)
so wavelength = c/(freq x sqrt(e))