APRS packet system that normally operates 145.825 MHz has not been available. NOW is activated an ARISS UHF radio that had been in storage on the ISS, and it is now operational on 437.550 MHz. The packet system uses the same protocol as the VHF system. Operators using the system should adjust for increased Doppler shift at UHF. Kenwood TM-D710 to replace all Amateur Radio transceivers on board the ISS. The target date for delivery is late 2017 , hi !! 73 de IW2BSF - Rudy
This is true, but necessary. The replacement Kenwood radio is in the process of being tested, before it is sent up to the ISS. Until that happens, we are using the ISS packet system on 437.550 MHz, thanks to the UHF twin of the failed Ericsson VHF HT being pressed into service. All other voice or SSTV activity from the ISS on 2m will use the radio in the Russian part of the ISS. More stations, and more Internet gateways, are trying the 437.550 MHz ISS digipeater. The ariss.net web site shows more activity in the past couple of days, and - so far - the stations I have heard have had operators at the keyboard or keypad. Unattended beacons apparently haven't found their way from 145.825 MHz to 437.550 MHz. If stations aren't adjusting for Doppler, they may only be able to use the digipeater in the middle of the ISS passes, only for a couple of minutes of the 8- to 10-minute passes when the ISS is overhead. For those wanting to try working the ISS packet digipeater, it may be useful to program a series of memory channels in your radio that will compensate for Doppler: The 437.550 MHz frequency will see a change of about 9 kHz +/- due to the Doppler effect. To compensate for this, stations need to start receiving above the 437.550 MHz frequency, and transmitting below the 437.550 MHz frequency. These memory channels accomplish this. Stations will need to change channels as the passes progress, so they can decode the downlink and have the ISS hear their signals, as the ISS radio is fixed on 437.550 MHz. Stations using omnidirectional antennas on 145.825 MHz might see difficulties with omnidirectional antennas on 437.550 MHz. I have been using a Kenwood TH-D74A HT (it has a built-in TNC, like the older TH-D72 and TH-D7 HTs) with an Elk log periodic antenna to work these passes. I have made a few QSOs using APRS messages, which are handled by the Kenwood and Yaesu APRS-ready radios, along with software running on various platforms (i.e., UISS on Windows PCs). 73!
Thanks, I was wondering about the doppler shift and you cleared that up very well. I had it sorted out for the receive end but had not considered the transmit side, so thanks again.
Thanks! Since the ISS station stays on a single frequency, all Doppler adjustments have to be done by us on the ground. We have to adjust both receive and transmit frequencies, so everything appears to be on 437.550 MHz at the ISS. It takes some work, but with memory channels you don't have to mess with two VFOs or a combination of memory channels and VFOs. For those with software that can control the VFO(s) on a radio, and make the adjustments for Doppler, it can be a hands-off process. For everyone else, the 5-channel setup seems to be a good compromise. I'm able to get my APRS packets through the digipeater with just 5 watts and a directional antenna. Many of the stations I've heard on these ISS passes are also using an APRS-ready HT. I use APRS messages to make QSOs, and those can be loaded in advance with something like my location (city/state with grid locator), along with "RGR" or "QSL" responses that I'd send back to other stations. My position is transmitted in a beacon periodically, and I include text along with the location information. Good luck, and 73!
Thank you very much for your information. What is the baud rate of the digi? 1200 or 9600 Bd? Best 73 TA9J Ismail
I just got a kenwood tm710g but I need help setting up the aprs so that I can work the iss ? Any step by step simple terms on how to set this up? Tnx
You'll need to do a couple of things to make this work well - set up a group of memory channels that will compensate for Doppler as the ISS moves overhead, and use a different packet path than the WIDE1-1,WIDE2-x path used for terrestrial APRS networks. The ISS 70cm packet digipeater operates on 437.550 MHz, but the Doppler effect will make that frequency change up to 9 kHz +/- during a pass. This will affect both your transmit (uplink) and receive (downlink) frequency in different ways. The memory channels can be set using this chart: For 4 of the 5 memory channels, you will have to program separate receive and transmit frequencies. The third memory channel listed above can be done as a simplex frequency, with no offset or independent transmit frequency. You would start out on channel 1 in the chart above as the ISS rises from the horizon, and change channels every couple of minutes during the pass, ending up on channel 5 in the chart above as the ISS approaches the horizon near the end of the pass. The other thing I mentioned is the packet path. This is set in menu item 612. You would need to change the Packet Path Type to Others, and then enter ARISS as the packet path. There is no need to put in a call sign, as call signs used from the ISS can change. The manual on the CD-ROM that came with your radio explains this in more detail, or PDF copies of the manuals can be downloaded from Kenwood's web site. One thing you can transmit through the ISS digipeater is your position. The beacon settings in your radio are controlled by menu item 611. I normally use AUTO, and the Initial Interval time as 1 minute. You can manually transmit your position, in addition to what is covered by this menu item, but you don't want to transmit too often. With the passes that last up to 10 minutes, there's not a lot of time for others to get through if you are transmitting much more than in 1-minute intervals. When your position packets are retransmitted by the ISS, your radio will indicate that it heard your position through the call sign being used on the ISS. If a gateway station also picked up the retransmission, you can visit ariss.net to see your packets. You can also use aprs.fi - this site picks up traffic from both the terrestrial APRS networks and the space-borne digipeaters on 145.825 and 437.550 MHz. After you are seeing your position being retransmitted by the ISS, you can use the APRS messaging functions to send and receive messages with other stations on those passes. Most QSOs made through the space-borne digipeaters are similar to QSOs made through other satellites using FM or SSB - quick QSOs, typically exchanging call signs and grid locators. APRS messages can be seen by any type of station working these passes - a home station using a TNC and a simple terminal program, other home stations using software optimized for APRS like UISS, along with the APRS-ready radios made by Kenwood and Yaesu. I have been using the TH-D72A and TH-D74A HTs to work these passes for the past couple of years, most of time connected to a directional antenna (Elk Antennas handheld 2m/70cm log periodic), but on higher passes I have also used a long duckie antenna in place of the log periodic. With the move to 437.550 MHz, it takes some practice to be able to hear the ISS from the start of a pass until the end. Having to change frequencies is something we didn't have to deal with, when the ISS used 145.825 MHz until the radio failure last month. There is a small amount of Doppler at 2m when working satellites, but most radios can compensate for that without needing to change frequencies. Your mobile radio can transmit at power levels higher than my HTs, but with a good combination of antenna and coax this shouldn't be necessary. If you use an omnidirectional antenna, you may need to run higher power levels so enough of your signals make it to the ISS. If your antenna is an omnidirectional antenna with gain, it might have a radiation pattern that keeps most of your transmitted signals near the horizon. This may be good for working stations on the ground, or maybe the ISS when it is also near the horizon, but could cause problems when the ISS is higher in the sky. What will you use as an antenna with your radio for the ISS? You're welcome to also join discussions on the Satellite forum here on QRZ. There is a thread that has been going for a few weeks, discussing issues with the ISS digipeater since it moved from 2m to 70cm. Good luck, and 73!
[QUOTE="The 437.550 MHz frequency will see a change of about 9 kHz +/- due to the Doppler effect. To compensate for this, stations need to start receiving above the 437.550 MHz frequency, and transmitting below the 437.550 MHz frequency. These memory channels accomplish this. Stations will need to change channels as the passes progress, so they can decode the downlink and have the ISS hear their signals, as the ISS radio is fixed on 437.550 MHz. Stations using omnidirectional antennas on 145.825 MHz might see difficulties with omnidirectional antennas on 437.550 MHz. I have been using a Kenwood TH-D74A HT (it has a built-in TNC, like the older TH-D72 and TH-D7 HTs) with an Elk log periodic antenna to work these passes. I have made a few QSOs using APRS messages, which are handled by the Kenwood and Yaesu APRS-ready radios, along with software running on various platforms (i.e., UISS on Windows PCs)." 73![/QUOTE] I have been using a Kenwood TH-D72A with an Arrow Hand Held Yagi and trying to compensate for the Doppler Effect using the programmed memory channels I have set up in the rig. It is still difficult at times to hit the ISS digipeater for a couple of reasons. The first is cloud cover. I have noticed over the last few days, as a cold front with rain and snow came through the area, I would lose good signal strength from the ISS when it went "behind" cloud cover, and secondly polarization of my antenna came into play. A few times I have had to go horizontal to get a good signal while at other times I had to go to a vertical position with the Yagi. Needless to say trying to do that and manipulate the hand held radio with one hand while adjusting elevation, and polarization of the Yagi with the other hand is .... well .... trying (LoL). Though trying as it is I will keep plugging away and try to figure out how to do the contacts quicker and with less hassle. So if anyone does see my CQ - it is not from a beacon - it is me standing outside in the sun, rain, and snow acting like a nut and playing with Ham Radio much to the muse of my neighbors and family who are watching. 73 from Jerry W8LR EM79TM
