23cm/33cm Geosynchronous APRS digipeater satellite idea

Discussion in 'Ham Radio Discussions' started by KH2SR, Sep 6, 2016.

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  1. KH2SR

    KH2SR Ham Member QRZ Page

    Utilizing APRS via the ISS and the various other satellites on the 2 meter band is really cool and useful for those times when out of range of land based digipeaters and internet gates.

    Unfortunately the 2 meter and 70cm bands have one problem in common when it comes to pedestrian portable satellite APRS operations. They both require directional antennas that are bulky, difficult to walk with and take considerable time to setup.

    There is a device called the SPOT GPS Tracker. It operates on 1,600mhz runs on 2 AA batteries and only puts out 0.4 watts with an integrated directional patch antenna which transmits to geosynchronous satellites. All of this fits into a compact handheld device that easily fits in your pocket.

    Why cant ham radio operators have the same thing on the 23cm & 33cm ham bands with 5 watt hand held APRS transceivers?

    I think the next APRS satellite should be geosynchronous and contain an experimental 23cm & 33cm digipeater with 23cm / 33cm uplink frequencies and a 2m downlink frequency to utilize the preexisting terrestrial based APRS internet gate receiver network.

    Thoughts anyone?

    73!

    James - KH2SR
     
  2. KC4YLV

    KC4YLV Ham Member QRZ Page

    Money.
    If you can find us the funding to put most of the link budget in space, like NOAA/US Mil, we can!

    A GPS seatellite is rated at 25.6 watts continuous power output and is the size of a VW Beetle, and has solar panels the size of RVs. The GPS network cost $12 billion to deploy, and its ongoing costs average $2 million dollars a day. I think the NOAA APT satellites are rated somewhere around 850 watts ERP.

    Average low earth orbit ham satellite costs 50-200k including launch and has a 100 mW to 500 mW transmitter in a 10x10x10 (10x10x30 if you're well-heeled) cm chassis.

    Edit: We *do* have a geosynchronous (but not geostationary) bird in the works for the western hemisphere; it will be 5ghz uplink, 10ghz down and you'll need about a 1 meter dish or so. Support AMSAT! This one is going to be very expensive. Probably launching in the next 2-3 years
     
    Last edited: Sep 6, 2016
  3. W6RZ

    W6RZ Premium Subscriber QRZ Page

    Just a note, there is no allocation for amateur radio satellites (either uplink or downlink) in the 33cm band.
     
  4. KH2SR

    KH2SR Ham Member QRZ Page

  5. KH2SR

    KH2SR Ham Member QRZ Page

  6. KH2SR

    KH2SR Ham Member QRZ Page

    Maybe there should be an allocation for amateur radio satellites in the 33cm band.

    Rules and band plans are not set in stone and can be changed.
     
  7. W3WN

    W3WN Ham Member QRZ Page

    Interesting idea. Should be doable. Once we get the infrastructure in place.

    If memory serves, most if not all Amateur satellites are in polar orbits. For this idea to work, we'd need a geostationary bird or three. As has already been noted, one is in the works.
     
  8. KC4YLV

    KC4YLV Ham Member QRZ Page

    33cm doesn't even exist as a ham band outside of Region 2. I'm not really sure what the benefit of embarking on a long running campaign to:

    1: legalize 33cm worldwide
    2: convince satellite ops to use it
    3: convince manufacturers to start engineering and releasing 33cm equipment

    would bring to the table. Do you have some specific technical points in mind as to why this would be worthwhile? I mean, as a satellite nerd, I can say "Yeah, that'd be neat". But i don't know if it'd be worth it.
     
  9. W6RZ

    W6RZ Premium Subscriber QRZ Page

    Non-starter. It's a popular cell-phone band in ITU Regions 1 and 3.
     
  10. KH2SR

    KH2SR Ham Member QRZ Page

    So maybe 33cm isn't the best choice. but 23cm should work fine with a geostationary satellite.

    The reasoning behind my idea is that a 23cm HT could transmit APRS to the satellite with a very small directional antenna that could fit in your pocket and be easily deployed instead of an inconvenient 3 element yagi or 2 element cubical quad for the 2 meter band that has to be carried in a backpack when not in use and takes. and with the 23cm band there have been several models of handheld ham radios that have been produced over the years.

    One of the newest which is still being made is the Alinco DJ-G7T.

    Discontinued models that can still be found on the used market include:

    Icom IC-T81A
    Icom IC-12GAT

    Icom IC-12G
    Icom IC-Δ1A
    Kenwood TH-55AT
    Yaesu FT-911

    So since those manufacturers have made 23cm HT's in the past then its very possible they might create new models if there there was enough interest.

    Plus there are lots of used 1200mhz motorola hand held radios that hams have been converting for years. All these radios would be capable of transmitting APRS to a geo sync satellite when combined with a TNC and a very compact directional antenna.

    Not to mention SDR radios that could easily accomplish the task. I even just heard back from the maker of the Tracksoar micro APRS transmitter and he tells me that the 2nd generation model will be frequency agile and possibly cover these bands. https://www.tracksoar.com

    The main point is making satellite APRS usable for operating pedestrian portable with a radio and antenna that fit in your pocket.

    All it would take would be for the next generation of APRS/Dstar HT's from Yaesu, Kenwood, and Icom to include the 23cm band. And until that happens we could be using pre-existing 23cm HT's paired with a compact TNC or software based TNC smartphone app such as Pocket Packet or APRS Pro.

    My main point is "If owners of the SPOT GPS Tracker and Delorme InReach can transmit their position data to a geosynchronous satellite using 0.4 watts on 1600mhz without any training or passing an FCC test then whats holding back the much more technically inclined ham radio community from doing the same with 5 watts on 1200mhz, with better radios, better antennas, and better skill set?

    There are already several large ham radio groups that dedicate their time to putting satellites in orbit. Why not put up something in geo sync orbit that would be very effective at making satellite APRS communications fit in a shirt pocket.

    This would allow an APRS user to send an emergency message without the need to take 20 minutes to set up his radio, directional antenna, and then try to keep the antenna aimed at the ISS or NO-84 APRS digipeaters during their short 10 minute overhead pass which only happens a couple times a day. What are the odds that one of those satellites will be over head when they are needed? Such as during an emergency.

    This is why we need 23cm APRS digipeater satellites in geo sync orbit. It's the next logical step in the evolution of this technology.

    73!

    James - KH2SR



     

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