P3D | Uplink Band (your transmitter) |
|||||||||||||||||
15m | 12m | V | U | L1 | L2 | S1 | S2 | C | ||||||||||
Down |
V | 167.13 | 170.84 | - |
581.575 | 1415.275 | 1414.35 | 2546.375 | 2592.475 | 5814.575 | ||||||||
U | 456.83 | 460.54 | 581.50 | - |
1704.975 | 1704.05 | 2836.075 | 2882.175 | 6104.275 | |||||||||
S1 | 2421.58 | 2425.29 | 2546.25 | 2836.025 | 3669.725 | 3668.80 | - | - | 8069.025 | |||||||||
S2 | 2422.58 | 2426.29 | 2547.25 | 2837.025 | 3670.725 | 3669.80 | - | - | 8070.025 | |||||||||
X | 10472.38 | 10476.09 | 10597.05 | 10886.825 | 11720.525 | 11719.60 | 12851.625 | 12897.725 | 16119.825 | |||||||||
K | 24069.38 | 24073.09 | 24194.05 | 24483.825 | 25317.525 | 25316.60 | 26448.625 | 26494.725 | 29716.825 |
See also Phase 3D Frequency Bands.
Tx = K - Rx
Suppose Phase 3D is in mode U/V, with an uplink on UHF (70cm or 435 MHz) and a downlink on VHF (2m or 145 MHz). This is the old favorite "Mode B". Suppose you hear a QSO on a downlink frequency of 145.890 MHz and wish to join in. In the "V" row of numbers, the number in the "U" column is 581.575. So you calculate 581.575 - 145.890 = 435.685 MHz, and set your transmitter to that frequency.
The calculation above ignores Doppler shift, the frequency shift caused by the motion of the satellite relative to each ground station. Doppler shift is proportional to frequency, and to the radial velocity of the satellite. Uplink Doppler is proportional to uplink frequency, and downlink Doppler is proportional to downlink frequency. Because the transponders are all inverting (Tx = C - Rx), the total Doppler shift you will observe in your receiver is proportional to the difference in frequency.
Doppler = (Rx - Tx) * Velocity/C
Much has been written about the best way to compensate for Doppler shift. Phase 3D's higher frequencies and the possibility of multiple simultaneous uplink bands translated into multiple simultaneous downlink bands make the problem more complex than ever before. For more on Doppler compensation, see The Radio Amateur's Satellite Handbook (purchase info) or read the One True Rule article.
The numbers shown in the chart are nominal, based on design and laboratory measurements. They will be revised after the spacecraft is launched and the oscillators have stabilized in the vacuum and thermal environment of P3D in space.
Conversion table supplied by Freddy de Guchteneire, ON6UG, of AMSAT-DL, via Lou McFadin, AMSAT P3D integration manager and P3D Laboratory manager, on 21 February 2000. Formatting and text by KB5MU.