The downlink frequency question is one that is constantly under discussion. The biggest problem is that everyone wants to be on 2 meters. Not everyone worldwide can transmit on 70 cm plus the Doppler is harder to correct for newbies in the that band. The other constraint (as you mentioned) is hardware. Depending on what mode is active, the current hardware may only support having one radio on at a time and thus just one mode. Currently, the D700 is the ONLY radio that does SSTV, Packet or Crossband Repeater options so only one of those modes can be active at a time. The Ericsson VHF is presently only able to support voice operations. Also, if the Kenwood D700 is on 2 meters, the Ericsson VHF radio cannot be used. It is possible to move SSTV (or packet) to 70 cm and allow voice (not the crossband repeater though) on 2 meters but that would mean silence on 145.80 about 90% of the time (depending on the crew).
ISS currently has an assigned worldwide downlink on 145.80 and a world wide uplink on 145.99 (digital). In addition, Region 1 uses 145.20 (voice) for an uplink but Region 2 and 3 use 144.49 (voice) due to differences in regional band planning. I guess everyone could use the 145.99 world uplink for everything but the crew would have issues listening to all the interference from digital stations that operate unattended.
Some operations have been conducted on 70 cm such as the uplink for the crossband repeater and some up/down voice contacts. As additional bands and modes are added, hopefully we can allocate specific frequencies for those so that simultaneous operations can take place.
Regarding Columbus, the antennas were not able to be designed for replacement so if they break, no fixing will be possible. I believe the same is true for the antennas used for the Ericsson amateur radio system located in the Functional Cargo Block (FGB).
The reason I posted my reply to the SAREX reflector is because it was created to discuss manned spaceflight amateur radio topics.
Kenneth - N5VHO
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Felim Doyle M3HIM Sent: Friday, August 04, 2006 8:49 AM To: [email protected]; Frank H. Bauer Subject: Re: [amsat-bb] ISS SSTV
I think it was fairly well understood that this is an experimental SSTV transmission from the ISS and that the downlink frequency is temporary. I was not aware of the conflict between the international 145.800MHz 'all mode' ISS downlink frequency and repeater services in Russia, having assumed it was chosen for its worldwide availability, but now appreciate that there is great on-going co-operation to make this a unique frequency for ISS-to-earth communication. Another great facet of Amateur Radio. Perhaps someone can explain the uplink diversity.
My concern is that putting voice, packet and SSTV all on one downlink frequency is rather restrictive. I realise that, at present, equipment is a limiting factor and that there is not enough kit to have all of the various modes in use at once but this may change over time so we should be thinking ahead and considering other frequencies or even bands (e.g. SSTV on 70cm). In the meantime, we can only look forward to the launch of the Columbus module with its additional ARISS facilities, including ATV (shame there are no windows in the module), and feel secure in the knowledge that this is one satellite that we can fix in flight should the need arise.
That said, I was disappointed to find out yesterday, listening to the EVA, that it takes two years to get an engineer out to fix a computer on the external truss. :-( And that Ivan Ivanovic (SuitSat-1) guy isn't much use either! [http://en.wikipedia.org/wiki/Ivan_Ivanovich]
73 de
Félim M3HIM IO91ot Aylesbury, Buckinghamshire, UK ----- Original Message ----- From: "Frank H. Bauer" [email protected] To: [email protected] Sent: Friday, August 04, 2006 12:55 PM Subject: [amsat-bb] ISS SSTV
All,
The ARISS team does not plan to use the 144.49 downlink for SSTV for the long term.
The ARISS team fully understands the Region 1 band allocations and wishes to abide by them. It should be noted that amateur satellite
communications
are allowed by ITU rules in the 144-146 segment. The reason that we have different uplinks in different regions is that the three ITU regions do
not
have consistent frequency allocations per mode. As an international team, ARISS and many ham radio entities worked hard to clear as many systems (repeaters, APRS, etc) from the lower edge of the AMSAT Satellite band segment (145.80-146) as possible. This enabled ARISS to have a dedicated downlink on 2 meters 145.80.
Our Russian team members were running some initial tests on SSTV last weekend. They utilized 144.49 for these initial tests because they wanted to do a full checkout of the SSTV downlink and there are still a few repeaters on 145.80 in Russia. These tests were successful. We
appreciate
the amateur community's patience on this while our Russian colleagues were running these tests. Based on these initial tests, the ARISS international team has been working on some procedures for long-term use
of
SSTV. This includes the use of SSTV on the 145.80 international downlink. As we get closer to final checkout of the system, you will see these changes made.
Thanks for all your interest in ARISS. We are looking forward to some exciting times as SSTV images once again beam down from space!!
73, Frank Bauer, KA3HDO ARISS International Chairman
Message: 12 Date: Wed, 2 Aug 2006 16:07:55 +0100 From: =?iso-8859-1?Q?F=E9lim_Doyle_M3HIM?= [email protected]Subject: Re: [amsat-bb] ISS SSTV
The 144.490MHz frequency being used on the ISS for the SSTV downlink is
not
a valid satellite or SSTV frequency in Region 1 as it is just at the top
of
the CW Beacon segment of the 2m band. So, if the ISS crew are on the ball, they should not have SSTV on when passing over the UK. However, they did have it on during one or more passes at the weekend when I was in the
GB4FUN
bus at the AMSAT-UK Colloquium. We failed to capture a picture despite having a crystal clear signal and correctly decoding the CW
identification.
It was possibly because the software was not set up for the correct mode (i.e. not Robot 36).
There may be other opportunities over the coming days/weeks but, as I say, strictly speaking it should not be running over Region 1.
73 de
Félim M3HIM IO91ot Aylesbury, Buckinghamshire, UK
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