The ground station complexity for using the linear satellites is a real issue, especially for anyone trying to rove or use a handheld antenna. I've always found the suggestion to use two FT-817s strapped to your neck very awkward (and pricey).
I'm starting to think of what would be needed for a handheld-size linear satellite transceiver. It would have to do SSB on UHF and VHF, and the Doppler correction could probably be handled by a phone app which would also provide visual tracking. I know it's a bit more complicated than FM, but at least you wouldn't need much power. Having separate U/V and V/U versions would be even easier. It could be a fun project.
-Stephen, N8URE
On 05/08/20 11:42, Stephen DeVience via AMSAT-BB wrote:
The ground station complexity for using the linear satellites is a real issue, especially for anyone trying to rove or use a handheld antenna. I've always found the suggestion to use two FT-817s strapped to your neck very awkward (and pricey).
On the downlink (RX), one can use a very cheap SDR dongle such as:
Here's a demo from Drew (KO4MA) at Hamvention 2018:
https://www.youtube.com/watch?v=hBZvWCKxjcM
He's using a FUNcube dongle (not sure if Pro+ or not, but ~$155 for the Pro+), but the same could be done with an RTL-SDR dongle ($35):
https://www.rtl-sdr.com/buy-rtl-sdr-dvb-t-dongles/
Gqrx, the software "receiver" already runs on a cheap Raspberry Pi 3:
https://gqrx.dk/download/gqrx-sdr-for-the-raspberry-pi
Your choice of transmitter includes an existing multi-band radio, or one of many SDRs with transmit capability (assuming that one appropriately filters the output before amplification).
I'm starting to think of what would be needed for a handheld-size linear satellite transceiver. It would have to do SSB on UHF and VHF, and the Doppler correction could probably be handled by a phone app which would also provide visual tracking.
Well, if it were an _open_ digital voice format (down with AMBE!) with error-correcting codes, one might create such a transceiver quite easily, using highly-integrated modem ICs already on the market.
Someone might already be thinking about this.
--- Zach N0ZGO
On 05/08/20 12:56, Zach Metzinger via AMSAT-BB wrote:
On the downlink (RX), one can use a very cheap SDR dongle such as:
Non-linear thought processes during editing strikes again! Here are the FUNCube Dongle URLs:
http://www.funcubedongle.com/?page_id=1073
http://funcubedongle.3dcartstores.com/checkout.asp
--- Zach N0ZGO
That's me, not Drew!
It was the FUNcube Dongle Pro+. Unfortunately, the FUNCube Dongle, despite decent filtering, still struggles in environments like Dayton. In normal conditions, it performs very well for this purpose. N8
Some form of integrated, small, full duplex VHF/UHF transceiver is definitely the holy grail of linear satellite operations. I'd love a KX2 or KX3 sized VHF/UHF full-duplex all-mode transceiver. Sadly, the maximum sales figures for something like that are probably measured in the hundreds, which makes it tough to justify commercially.
73,
Paul, N8HM
On Fri, May 8, 2020 at 1:57 PM Zach Metzinger via AMSAT-BB < [email protected]> wrote:
On 05/08/20 11:42, Stephen DeVience via AMSAT-BB wrote:
The ground station complexity for using the linear satellites is a real issue, especially for anyone trying to rove or use a handheld antenna.
I've
always found the suggestion to use two FT-817s strapped to your neck very awkward (and pricey).
On the downlink (RX), one can use a very cheap SDR dongle such as:
Here's a demo from Drew (KO4MA) at Hamvention 2018:
https://www.youtube.com/watch?v=hBZvWCKxjcM
He's using a FUNcube dongle (not sure if Pro+ or not, but ~$155 for the Pro+), but the same could be done with an RTL-SDR dongle ($35):
https://www.rtl-sdr.com/buy-rtl-sdr-dvb-t-dongles/
Gqrx, the software "receiver" already runs on a cheap Raspberry Pi 3:
https://gqrx.dk/download/gqrx-sdr-for-the-raspberry-pi
Your choice of transmitter includes an existing multi-band radio, or one of many SDRs with transmit capability (assuming that one appropriately filters the output before amplification).
I'm starting to think of what would be needed for a handheld-size linear satellite transceiver. It would have to do SSB on UHF and VHF, and the Doppler correction could probably be handled by a phone app which would also provide visual tracking.
Well, if it were an _open_ digital voice format (down with AMBE!) with error-correcting codes, one might create such a transceiver quite easily, using highly-integrated modem ICs already on the market.
Someone might already be thinking about this.
--- Zach N0ZGO
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On 05/08/20 13:03, Paul Stoetzer wrote:
That's me, not Drew!
Doh! I'm sorry, Paul. I've got that problem with putting names to faces, and we've even met in person a few times. :-)
--- Zach N0ZGO
You guys beat me to the punch on the replies......got distracted by a work thing from the fun stuff.....
My inputs on the challenges for the Linear GS setup.....also trying to highlight potential technical solutions that might enable solutions to the operational issues being discussed (I have no dog in that particular race):
1. 100% agree with all that DIY/Open designs and demos for low complexity, low cost GS solutions would be great! 2. Major challenge right now is a Handheld that transmits on sideband.....there are few that receive sideband and can transmit NBFM. Kenwood TH-F6A pops into mind (because I have one). It wasn't cheap as far as handhelds go, but I believe cheaper than a pair of FT-817s. Its also a tribander on TX, NBFM (2m/222/70cm) and a multimode/multibander on RX (~1-1300 MHz)......but that doesn't matter if there aren't birds that could support that ....... 3. Lets not forget the transponders themselves......something that came up on a thread a few years ago. Given that commercial solutions exist for FM up and SSB down, hybrid designs for the transponders themselves should be considered. I think this is a VERY important part of what the GOLF series should seek to (and I believe will be able to ) demonstrate with the SDR onboard....re-configurability. On launch day, maybe an FM single channel transponder and some standard linear transponder waveforms (maybe stacked side by side in the spectrum). Then maybe we can think about waveforms that demodulate the FM uplink, and remodulate a sideband downlink stuck in the passband of the existing linear transponder. I could list out all the possibilities here, but the point is...hybrid architectures that can be re-configured based on user demand and interest of the day. FMtoFM(single and multi-user) / FM up to SSB down (multi) / SSBtoSSB (normal linear) / digital modes /some of those things simultaneously / etc. etc. . I mean it's just software right (hihi). 4. Standard caveat/disclaimer: doing any of those things might be possible with GOLF, but that doesn't mean doing even the simplest transponder update is trivial.....lots of design features to factor in, resiliency (don't want to brick the bird with an update), procedural implications for ops and controllers, power consumption concerns (especially if multiple TX systems are active), even regulatory concerns/implications.......but maybe there is a simple demo that might be possible to show in this area with one of the GOLFs. I'm mainly using GOLF as an example given that it flying an SDR based trasndponder....other missions (AMSAT or maybe University) could do/demonstrate the same things. 5. Also, hardware designs should still be on the table. I know some older birds had this 'cross mode' capability......maybe we should factor that into future designs. Maybe older larger systems could be 'recreated' (and newer capabilities added) in a more compact form factor given modern devices on the market. 6. To circle back to the handheld discussion......maybe theres an avenue for an open source/open hardware handheld transceiver design that support SSB TX (and RX)......pretty big design effort, and maybe already done........end goal of this thought is if there were something out there, maybe it could be easily and cheaply mass produced and then sold through the AMSAT store to make it easy for the end user to get their hands on. Given the desirement (desired feature + requirement) for open source/open hardware....it could also be something that the kit builders out there might be interested in (right nothing new here.....buy the built version for X dollars, buy the kit version for less and assemble yourself). I'm thinking things as simple as Arduino microcontrollers to drive LCD displays and all that......theses sort of components needed for this are all over the place now, including the open source software to interact with many of them. Organizations exit that might support something along these lines, Kickstarter for one for funding. Of course...two cruxs of the issue to overcome (at least).....where is that base design and where are the volunteers to step up and get it all done (from the design through deployment, including good documentation!). Definitely agree with Paul that its probably not cost effective to the major manufacturers....so maybe we (as in the collective AMSAT population) can literally DIY it. 7. Last thought....even simple SDR systems can be challenging to the masses that don't play around with SDRs every day. So for # 6 above, I was thinking a HW design that is more akin to what folks are comfortable with in the kit building world, even if the first version is a huge clunky handheld (that maybe only requires a multimeter to checkout)....that said I love SDR, so let's do it all and go for HW and SDR designs!
Just my two cents....I hear these challenges to the operating community as opportunities to come up with fun and novel technical solutions....and a need for more birds...always more birds :-) (and more volunteers with the time to get stuff done! I know I throw my two cents out a lot, but never have time to follow up and make things happen....something I wish I could change......)
-Zach, KJ4QLP
participants (4)
-
Leffke, Zachary -
Paul Stoetzer -
Stephen DeVience -
Zach Metzinger