------------------------------------------------------------------------- ISS FREQUENCY BAND PLANNING: Draft 10 Dec 2002 ------------------------------------------------------------------------ WB4APR and WF1F As more equipment and operating modes are carried to ISS, there needs to be a planning document to assure an ordered approach to frequency coordination. That is, in the long run we should not be using the same band for simultaneous uplink and downlink or we end up with de-sense of our own systems. Currently the ISS antennas installed for Phase 2 support multiple bands of: HF, 145 MHz, 435 MHz, 1296 MHz, and 2400 MHz. RECOMMENDED BAND PLAN: 2400 MHz Downlinks 1200 MHz Uplinks 435 MHz Uplinks 145 MHz Downlinks 29 MHz Either, but usually uplinks based on crew's license class 21 MHz Either, depending on crew license class 14 MHz Eitehr, depending on crew license class DETAIL DESCRIPTIONS: 2400 MHz Band: The S-Band or 2400 MHz should be a downlink band primarily because there are hundreds of amateur satellite users that have invested in this band for receving the weak signal downlink from our largest and most complex amateur satellite, AO-40. Receiving down-converters are readily available as surplus from comercial microwave Distribution Systems at very low cost. 1200 MHz Band: The L-Band is available according to the ITU regulations as a worldwide uplink band only. 435-437 MHz: The UHF Band from 435 to 437 MHz should be the primary uplink band. This is because UHF uplink stations can use directional gain antennas to make up for the 9 dB path loss penalty of UHF. Further, UHF is the uplink band for AO-40. UHF Uplinks must avoid the high end of the band (437 MHz) because it is the 3rd harmonic of the 2m band downlinks. 145.8 to 145.999 MHz: The 2 meter band should be used for downlinks. This is the primary school contact, crew communications and outreach mission objective to reach minimal stations at schools or newcomers to amateur radio. There are many reasons for using 2 meters as the primary downlink band: a) Two meters offers a 9 dB advantage over UHF or higher bands for reception to an OMNI antenna. b) The coax loss for receiving stations is one/third less on 2m c) Simple low cost stations are less expensive on 2m d) Receiving antennas are easy to build and quite forgiving in design e) No tracking, Doppler tuning, nor Antenna pointing is required f) The Doppler is minimal and can be received without tuning g) 2m is the ideal out-reach band. Further Recommendations for ARISS Systems Design: * All 2m downlinks should use 3 KHz deviation to keep the signal within the typical ground station narrowband IF passband with minimal tuning. Most modern radios use 12.5 KHz IF's. * UHF Uplink receivers that are not full duplex (Packet) should have wideband (40 Khz) uplink passbands to allow for ground station uplinks to be receivable with no distortion during the central 70% of a satellite pass including almost 10 KHz of Doppler. * Uplink Receivers should not be overly sensitive (vulnerable to intermod), but should assure a good link budget from a ground user with about a 50W EIRP. (A mobile, or a 5W HT with handheld Beam). * Full Duplex UHF receivers should remain narrowband to filter out those uplink stations that are not paying attention to Doppler. RECOMMENDED ARISS FREQUENCIES: Phase 1: Operation with the Ericsson radios in the FGB: 144.49 Voice Uplink, Region 3 145.20 Voice Uplink, Region 1 145.800 Multi-use downlink 145.990 Packet Uplink 14X.XXX Unpublished School and Crew uplink frequencies Phase 1.5: The two Ericsson radios should be operated as a pair for the crew to listen to the UHF uplink and talk on the VHF downlink. Enough sidetone should pass through so that downlink listeners can hear themselves in the uplink. (see note below)... Phase 2: After installation of new equipment in the Service Module: 145.800 Voice Downlink, FM 436.250 Voice Uplink 145.815 SSTV Downlink, FM 436.300 SSTV Uplink 145.830 UI Digipeating, 1200 baud 436.350 UI Digipeating uplink 145,845 reserved (future after AO-27) 436.400 reserved future ISS 145.860 PSK-31 Downlink, FM 29.120 LSB uplink 145.990 Packet BBS downlink 436.500 Packet BBS uplink 1200 MHz Reserved for future uplinks 2400 MHz Reserved for future downlinks NOTE-1: This band plan suggests that all future space UI digipeaters move up 5 KHz to center on 145.830 instead of 145.825 in order to change the wasted 10 Khz guard band into a useful ISS downlink channel. (PCsat splits the difference (145.8275) in anticipation of this move). NOTE-2: Because there is a 4 fold improvement in throughput at 9600 baud, BBS operation should move to 9600 baud when the equipment permits. Conversly, UI-digipeating gains hardly anything at 9600 baud because of the relatively long TX delays associated with each and every packet. UI digipeating should remain at 1200 baud because it has a 7 dB performance advantage over 9600 baud in typical stock radios. NOTE-3: The close 15 KHz spacing of the contiguous ARISS downlinks from 145.800 to 145.86 is not as problematic as may first appear: - Any single user sees the same doppler on all 4 channels - Signal strengths from all four will be at comparable weak signal levels - All being equal, any adjacnet splatter is well below the FM threshold - All modern radios use 15 or 12.5 KHz filters - All modern radios can tune in 5 KHz steps both in the USA and Europe - This is unlike terrestrial problems with 15 KHz spacing where one station may be 20 miles from one repeater and have a neighbor on the adjacnet channel causing splatter (he is 60 dB stronger!) BANDWIDTHS: The following packet transmit bandwidths were measured on the 3 radios readily available to me in the lab: RADIO -10dB BW -20dB BW Comments ----- -------- -------- ----------------------------------------------- D700 10 KHz 15 KHz Factory set 3.5 KHz deviation Modulation levels D7 12.5 KHz 16 KHz Factgory set 3.5 KHz deviation Modulation levels DJS11 15 KHz 20 KHz External TNC blasting the MIC jack w full audio ISS? 9 KHz 13 KHz Presumed bandwidth of a 3 KHz deviated ISS XMTR Thus, with a 3 KHz deviation on packet, there will be no spill over even of packet between 15 KHz channels. Radio design has come a long way in the past 40 years since the first Oscar and we need to better allocate our limited bandwidth on 2m. GRAPHICAL 2m BAND PLAN SUGGESTION: See a graphical depiction of the 2m band plan: http://www.ew.usna.edu/~bruninga/iss-aprs/bandplan.jpg ACTION REQUIRED: As soon as the UHF equipment ON ISS and planned for ISS in the near future is activated, every effort should be made to operate cross band with 2m for all downlinks and UHF for all uplinks. ERICSSON UHF: It may appear that this obsoletes the two Ericsson radios because they are both simplex radios. BUT, this is not the case, The astronaut simply listens to the Headset on the UHF radio and TALKS on the VHF radio. Both can be connected to the same FGB antenna with a simple $39 VHF/UHF diplexer. The antenna is not optimum for UHF, but then the users on the ground have 50 Watts and gain antennas that yield at least 10 dB advantage to UHF uplinks. ERICSSON FULL DUPLEX REPEATER: Adding a rubber band around the transmitting VHF HT PTT and holding the Mic near the UHF speaker further becomes a Crossband Repeater (as long as the VHF radio doesn't overheat)... (Of course a VOX PTT circuit being assembled for the SSTV experiment can do this job perfectly if the right cables are prepared in advance).. See the idea at: http://www.ew.usna.edu/~bruninga/iss-aprs/ARISSu-v.jpg CONCLUSION: These issues are critical and timely. PCsat2 is stuck in the middle. If ARISS continues with simplex on 2m and simplex SSTV on UHF, there is NO band we can operate on without interference. and no other modes can operate simultaneoully on ARISS. But if we act NOW to have a plan in place, not only can PCsat2 be designed not to inteerfere, but it can be designed to operate mode B as well and fully complement ARISS operations. Either way, PCsat2 must know what frequencies are planned and what modes, over what time frame, so that it can be designed properly. I ask ARISS technical committee's consideration of this proposal. de WB4APR, BOb