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====== Link Budget ======

$P_{RX} = P_{TX} – L_{TX} + G_{TX} – L_{free space} – L_{misc. propagation} - L_{polarisation} + G_{RX} – L_{RX}$

Polarisation loss from heal can be calculated. It might also be worth working out losses due to heal and aerial directivity.

===== Free space loss =====

<file>
Distance (km)	Distance (nautical miles)	Frequency (MHz)		Loss (dB)	Fresnel r (m)
1		0.54				434			-85.2		13.1
1		0.54				869			-91.2		9.3
10		5.40				434			-105.2		41.6
10		5.40				869			-111.2		29.4
20		10.80				434			-111.2		58.8
20		10.80				869			-117.2		41.5
30		16.20				434			-114.7		72.0
30		16.20				869			-120.8		50.9
40		21.60				434			-117.2		83.1
40		21.60				869			-123.3		58.7
50		27.00				434			-119.2		92.9
50		27.00				869			-125.2		65.7
60		32.40				434			-120.8		101.8
60		32.40				869			-126.8		71.9

</file>

===== Bibliography =====

  * [[https://www.internetsociety.org/wp-content/uploads/2017/10/Link-Budget-Calculation.pdf]]
  * [[https://www.erau.ee/et/ultraluehilained/78-uncategorised/477-vhf-uhf-microwave-radio-propagation-a-primer-for-digital-experimenters]]