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

[Zach Leffke]

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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