![]() If there are good reasons to use mode VU, this can always be an option. If someone is planning a new cubesat mission, UV would be the preferred mode. Transmitters are more simple to build on VHF (but the difference is not that great.) The higher path loss on UHF is easily solved using more TX power on the ground side COTS antennas and transceivers are available for mode UV The downlink signal on VHF has less doppler shift so its easier to tune The downlink signal on VHF is better received than UHF (so friis formula is right!) The VHF amateur band satellite segment has primary status all over the world. VU mode is the recommended mode by the IARU. The IARU likes the UV mode (UHF up, VHF down), so coordination will be easier. There are numerous advantages of using UHF (2m) uplinks and VHF downlinks (70cm), the so-called mode UV. Separation between the TX output and RX input is the only reason to do this.īut this is an argument of the past, as many new components are around to provide good filtering. Please also consider that many teams don't have an RF specialist but rely on past designs which may not always be optimal. It seems to me it's just a copy and paste design habit of many new cubesat teams. The use of UHF downlinks is very strange indeed. Re: Choosing uplink and downlink frequencies for 1 kg sateli Within the satellite will not have that effect 3 x 144 = 432 MHz and transmitting on 2m is garanteed to induce additional noise into the 70cm receiver. One other really good reason to up on 2m and down on 70cm is that the bands are harmonically related ie. Some 2m and 70cm only satellites could be switched between 2up 70down or visa-versa which sets of freq's would be uplink and downlink at any given time, and that goes for many of the satellites. ![]() ![]() Through telecommand from the ground station the command team could switch between modes. Have a look here for a list of uplink and down link freq's of the AO40 satellite Some of the first satellites I was working through in during the 1980's we uplinked on 145MHz and downlinked on 28MHz We, Amateurs, have many different up uplink and down link freqs spread throughout our VHF, UHF and microwave bands You are just looking at a single example, there is much more variation than just that. ![]()
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