[Ground-station] Ballon launch - lightweight inexpensive 10GHz transmit

[Michelle Thompson]

Thanks Zach, good stuff and I think we're on the same "wavelength". The
ammo can prototypes got a lot of interest last year at Hamvention. Let's
keep some fire on all of this and the potential help it can lend to your
efforts.

If anyone's interested in seeing some more details about 'die Boxen' then
here are some diagrams:
https://github.com/phase4ground/documents/tree/master/Manufacturing/Virginia_Tech_prototypes

Zach if you have anything else about them then feel free to stow it there
in that folder. A brief discussion of the 10MHz signal (instead of the
traditional 22kHz I'm guessing) Would be a great addition.

I'll try and add some photos. I know we took some!

-Michelle W5NYV

"Potestatem obscuri lateris nescis."


On Mon, May 14, 2018 at 12:21 PM, Zach Leffke via Ground-Station <
ground-station at lists.openresearch.institute> wrote:

> Quick reply....haven't ingested everything yet.
>
> For Transmit, 10 GHz: (not practical for balloon due to weight/cooling,
> but maybe as a reference, or at least inspiration)
>
> For the 10 GHz payload 'simulator' we built into an Ammo Can at VT, we
> used the following Kuhne product:  https://shop.kuhne-electronic.
> de/funk/en/shop/industrial/prof-converter/prof-up-
> converter/KU+UP+107+B++Up+Converter/?card=513.  Nice part was the
> standard L-Band IF, so easy interface into a B200 USRP.  accepts 10 MHz
> ref, able to get up to +24dBm out (datasheet spec, not measured).  Part is
> likely to heavy for balloon launch though, and requires cooling (heatsink
> definitely too heavy for balloon launch).  Used One of Kent's Vivaldi PCBs
> for the TX antenna.
>
>
> For 10 GHz receivers:
> We used the Ku band LNB 'trick.'  PLL based LNB cost less than $10 bucks
> on Amazon and worked across the room (payload ammo can on one side, gs ammo
> can on the other side).  I forget the specific model at the moment
> (X-squared maybe?  But I might be mixing that up with M2 antennas...), but
> it was one of the 'universal' LNBs that extended the coverage to the lower
> end of the Ku-Band closer to the satellite service freqs.  Used pretty
> cheap minicircuits components for the Bias-T, but I'm betting could drop
> that cost significantly if you build your own (a little LC action) if your
> trying to power up multiple LNBs for a phased array.  In our single channel
> demo, I used a little step up voltage regulator, tied to the 13.9V input,
> plus a DPDT switch to select between 13.8V and ~18V for the DC on the coax,
> which switched between H/V pol.  All of that plugged into a B200 SDR, with
> the output IF a bit lower than the standard L-Band IF for these things
> (upper UHF, 700MHz or so is bouncing around in my head).  lots of super
> cheap 18 inch dish class parts on ebay for reflectors and such (at one
> point, someone was selling a pallet of like 50 Dish network dishes, with
> reflector, feed, and mount for about $200.00.....but the XYL said 'no').
>
>
>
> I'd be very interested in how the phasing of multiple LNBs plays out.
> first question concerns the LO/ref freq.  In our little Ammo Can demo, the
> Bias-T I used also injected 10 MHz onto the coax for 'future use' at the
> LNB to discipline the LO.  The intent was to eventually figure out how to
> tie it into the LNB to help stabilize the frequency, but never got around
> to finishing this.  I'm assuming something like this might be needed, with
> 10 MHz (or some other reference freq) distributed to all the LNBs.  Second
> question is how does the phase shifting and combining step work for this
> idea?  I'm guessing all the combining is done at the IF freq?  Is this all
> being done in hardware with maybe tuneable phase shifters to steer the
> beam?  As to the LNBs themselves, any thoughts on all the possible
> combinations of DC on coax for H/V pol, hi-band/low-band diseq control, use
> of 'dual' or 'quattro' LNBs with multiple outputs, how the designs of the
> dual/quattro matter relative to the ref freq/LO distribution and the
> phasing, etc. etc.  I don't know any of those answers myself on that, but
> am curious about how all that fits together and possibly could be leveraged
> for this idea.
>
> My interest in this is linked to something else I'm trying to get into,
> which is building a monopulse tracking feed at 10 GHz, for some large C/Ku
> band antennas we just came into 'possession' of at the Hume Center.  Sort
> of a '4 channel phased array' type problem.  Long term goal is to refurbish
> a 5m cassegrain design antenna to work at 10 GHz, with monopulse feed
> assembly, but doing the combining in software with a 4 channel SDR (X-310
> USRP w/ dual TwinRX, or maybe the N310 if the uhd random startup phase
> thing doesn't kill the idea...).  Idea is to precisely track GEO/HEO/Lunar
> spacecraft w/ 10 GHz downlinks.  The precise Az/El derived from the error
> signals from the monoulse tracker unit would then be used to 1) lock on and
> precisely track at 10 GHz for the 5m antenna (sum beams used for data
> link).  2) deliver precise enough information on the Az/El to due either
> orbit determination or 'trajectory determination' if a Lunar mission and 3)
> feed the computed Az/El to the 9m C-Band uplink antenna.
>
>
> So I'd definitely be interested to know how the LNB phasing goes.  Perhaps
> the lessons learned from that effort could be applied to a an 'easy'
> prototype of the above monopulse idea to demo the concept with a 4 channel
> SDR in a effort to get more $$ for the real deal (like I said, long term
> goals......).
>
>
> Good stuff!
>
> -Zach
>
> Research Associate
> Aerospace Systems Lab
> Ted & Karyn Hume Center for National Security & Technology
> Virginia Polytechnic Institute & State University
> Work Phone: 540-231-4174
> Cell Phone: 540-808-6305
>
> On 5/14/2018 11:27 AM, Michelle Thompson via Ground-Station wrote:
>
> For the balloon launch opportunity, and for groundsat in general, we have
> been asked to consider a lightweight inexpensive 10GHz transmitter for the
> balloon. And, obviously, receivers on the ground.
>
> Phil and the high school team doing the launches are interested in live
> video from the balloon. Launch schedule is flexible and it's an ongoing
> project.
>
> Kit bash something from DirectTV? I think Kerry and Drew got something
> working that way.
>
> Existing card or dongle?
>
> Design a board? We are capable.
>
> Effort invested improves groundsat side.
>
> We have a good handle on inexpensive 10GHz receive hardware. Deploying
> enough of it? That's going to be hard. How hard? We need to run the numbers
> for a variety of powers to find out how bad. We aren't going to get
> continuous coverage without seriously taking over the world. But, we can
> figure out what coverage looks like with a variety of configurations.
>
> (If we could just have a little telemetry app running on everyone's
> satellite TV dish/receiver, then we'd have a nice fat fence at least.
> DirecTV has not yet returned my call about this...)
>
> People of Twittertopia say DirecTV LNBs as phased arrays set up to wedge
> out likely high altitude paths. So I looked at phasing up DirecTV LNBs, to
> shape the beam a bit. You know it might actually work. Anyone done this
> already or know of a paper? Beamwidth of the LNB by itself is about 40
> degrees.
>
> Let's hear your video transmitter ideas and leads for this use case. It
> will be fun for everyone and a big learning opportunity and we might find
> (or forge) a really good path forward.
>
> Since the "infiltrate all DirecTV receiver installations across the US for
> amateur radio botnet" plan is probably not going to work out any time soon,
> we need to come up with buildable repeatable recipes and get them up and
> running.
>
> After Hamvention I'll publish everything we have about getting an
> LNB+PLL/bias-T/rtlsdr/odroid/VPN station deployed. Cost is not bad at all
> and it's very light weight and portable. Maybe we can make a kit.
>
> Another area for this receiver is to improve performance by alignment to a
> fixed synthesized tone. Hardware is figured out for that but the correction
> isn't tested yet.
>
> There's got to be other solutions or ideas out there in various
> communities. If you are part of one of them then please share this so we
> can learn.
>
> More soon!
>
>
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