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

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useful equation: c = wavelength x freq x sqrt(dielectric const)

so wavelength = c/(freq x sqrt(e))