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Hack Chat Transcript, Part 2

A event log for AMSAT CubeSat Simulator Hack Chat

Making sure your bird will fly

LutetiumLutetium 12/04/2019 at 21:040 Comments

alan.b.johnston12:33 PM
FSK is a Fox-1 emulation mode, also known as Data Under Voice or DUV

alan.b.johnston12:34 PM
The BPSK mode is for Fox-1E (to be launched in 2020) and HuskySat-1 1200 bps

J12:34 PM
ah yeh can see the frequency jump now

J12:34 PM
(must be lagging a tad)

Casey Halverson12:35 PM
This LoRa FossaSat-1 will be interesting.

Casey Halverson12:35 PM
not to talk about another satellite ;)

alan.b.johnston12:35 PM
Here's the waterfall with the 3 different modes

steve.bossert12:35 PM
i am looking forward to FossaSat-1 more than you know :)

alan.b.johnston12:35 PM

Joe Latrell12:35 PM
@steve.bossert - me too!

alan.b.johnston12:35 PM
Yes, LoRA is cool!

Casey Halverson12:35 PM
I have my 1 watt LoRa radio waiting for it ... with a Yagi ;)

Joe Latrell12:36 PM
@alan.b.johnston - how did you go about building out the ground station you are using?

steve.bossert12:37 PM
An SDR I feed into spyserver is set to default to 911.25 Mhz and let others near my experiment with decoding Lora and other bursts down in 70cm.... back on subject now :) I would be interested to see the sim run Lora if possible (not today, some other time)

alan.b.johnston12:37 PM
My Web SDR ground station is an old Ubuntu laptop, running openwebrx with an RTL-SDR plugged into it

steve.bossert12:37 PM
antenna alan?

J12:37 PM
What is good about LoRa FossaSat-1? (first I've heard of it)

alan.b.johnston12:37 PM
I use remote.it to open a port to 7300 so that it is accessible outside my network, just while I do this demo

alan.b.johnston12:38 PM
My antenna for this demo is just a rubber duck!

alan.b.johnston12:38 PM
I also have a tape measure Yagi hanging out my office window

alan.b.johnston12:38 PM
I'm helping the CubeSat Club members here build a Lindenblad - it is almost finished!

steve.bossert12:39 PM
i bet your sim could also be helpful for those looking to test payloads for balloons.

alan.b.johnston12:39 PM
LoRA modulation is spread spectrum, so requires radically lower power levels or simpler ground stations. Could be a game changer for future satellite low bit rate communication

alan.b.johnston12:39 PM
Yes, it could be used with balloons.

J12:40 PM
Ah I see

alan.b.johnston12:40 PM
If you look at the Voltage tab on this graph https://docs.google.com/spreadsheets/d/1LB44eiODrIT9o9FA2rvRszA-hIo7iovx9XdL21Ge1vI/edit#gid=1311478884 you can see how the voltage dropped before

alan.b.johnston12:40 PM
When it went below 8V, the Pi automatically shut down

alan.b.johnston12:41 PM
Here's a screenshot of the voltage telemetry from before

alan.b.johnston12:41 PM

alan.b.johnston12:42 PM
Here's the current graphs

J12:42 PM
8V... is there a regulator there dropping below 5v?

alan.b.johnston12:42 PM

alan.b.johnston12:42 PM
Anyone receiving the satellite? ;-)

J12:42 PM
(probs a daft question I only wondered since I have my zero on a 5v usb

alan.b.johnston12:43 PM
Yes, I use a 9V NiMH battery

alan.b.johnston12:43 PM
So it isn't good to discharge it all the way down to 5V

Desu Ravi Kumar joined  the room.12:43 PM

J12:43 PM
ah gotcha

alan.b.johnston12:44 PM
I have a battery charging board made by MoPower that handles the charging

nitinvaishya000 joined  the room.12:44 PM

alan.b.johnston12:44 PM
So AMSAT has built 4 loaners that can be shipped to a classroom anywhere

Joe Latrell12:44 PM
Not seeing the sat via the proxy. Keep getting a timeout.

alan.b.johnston12:45 PM
Message me offline if you are a teacher or know a teacher who would like to show it off in the classroom

nitinvaishya00012:45 PM
Hello

alan.b.johnston12:45 PM
Here's the web sdr link http://proxy22.rt3.io:38006

alan.b.johnston12:45 PM
Make sure it isn't trying https - that won't work!

alan.b.johnston12:45 PM
Oh, and SatNOGS has a Dashboard for the Simulator, too! :-)

nitinvaishya00012:45 PM
I need help

alan.b.johnston12:46 PM
SatNOGS Dashboard: https://dashboard.satnogs.org/d/VesVjq6mk/amsat-cubesat-simulator?orgId=1&from=1563974788355&to=1563976686873

alan.b.johnston12:46 PM
The satellite is back, and now back on the right frequency again! 434.9 MHz

J12:46 PM
I'd definitely like to do something like that (build or demo one in the future) but defo need to learn more about it myself first. Need a bit more time with the Cube Sat Sim for starters. I've not tried the decoding yet.

alan.b.johnston12:47 PM
Nope, now it drifted again!

steve.bossert12:47 PM
Good to log Voltage against temperature/baro. There was some wacky telemetry with USMA West Point and the past two balloons sent up. At 98k feet, it got pretty cold (and wet) and affected the battery on one of the transmitters. lessons learned to send up two transmitters for redundancy. testing via balloon before going into orbit is good live test too. your doing some great work Alan. will message you offline.

alan.b.johnston12:47 PM
Sure, give it a try! I have a lot of fun with it

alan.b.johnston12:47 PM
Very good points, Steve. Thanks!

Chinna12:48 PM
what are the bare minimum electronic components required to build a very simple satellite apart from what I mention here 1) Arduino 2) Rechargable battery circuit 3) battery 4) solar panels?

alan.b.johnston12:48 PM
Here's the SatNOGS Dashboard for the Simulator

alan.b.johnston12:49 PM

Casey Halverson12:49 PM
J: We are using the 70cm band in the 430-440MHz range for high altitude balloon. Getting some very impressive results with it. A wire antenna @ 100mW can reach low earth orbit easily. Although who knows how much noise you will be competing with up in space. I can hit one of our 401MHz satellites with tens of milliwatts using BPSK and a whip antenna, so its certainly very possible.

Joe Latrell12:49 PM
@chinna, you need a radio system to relay data back or at least present a beacon.

alan.b.johnston12:49 PM
@Chinna That's about it. And a rocket :-)

Casey Halverson12:49 PM
steve bossert: what radios did you guys send up in the balloons that did that?

Casey Halverson12:50 PM
Chinna: one key thing is that you need to have two way telemetry and a way to change frequency, if need be.

Chinna12:50 PM
Hi @Joe and @Alan, what is the simplest telemetry thing I can have?

Chinna12:50 PM
any pointers?

Casey Halverson12:50 PM
@Chinna use a LoRa radio or HamShield

J12:51 PM
Chinna when I was looking into this there was a lot of info on the web page I think where I found the cubesatsim stuff

steve.bossert12:51 PM
@Casey Halverson some sort of generic module. will have to get back to you . (your the hamsheild team?, thats what may have been better)

Casey Halverson12:51 PM
@steve.bossert Yes, thats me. :)

Joe Latrell12:51 PM
@Chinna, I am using a DRU818U radio that is programmed via Python on a NanoPi processor board.

alan.b.johnston12:52 PM
Here's what the loaner units look like - self contained

alan.b.johnston12:52 PM

Casey Halverson12:52 PM
@steve.bossert the HamShield Mini is a small 200mW triband transceiver .. we also have a 1 watt LoRa version for 440MHz. Launching 144MHz and 915MHz LoRa shields next week. Although those will do 500mW.

Joe Latrell12:52 PM
@alan.b.johnston, NICE setup!

Casey Halverson12:52 PM
@alan.b.johnston thats impressive.

steve.bossert12:52 PM
@Casey Halverson i just took advantage of some black friday sales at inductive twig for hamshield and other stuff.

alan.b.johnston12:53 PM
Thanks! It has been in about a half dozen high schools and about a dozen universities so far.

steve.bossert12:53 PM
@alan.b.johnston do you have a schedule for any upcoming school demo you are doing?

Casey Halverson12:53 PM
@alan.b.johnston Yeah, thats very portable for that kind of thing.

alan.b.johnston12:54 PM
Frequency just changed again. I wish I knew why rpitx does that sometimes!

J12:54 PM
Out of interest, are you instructing it to change frequencies? or is that part of the protocol?

Chinna12:54 PM
@Joe, thanks for letting me know your radio

alan.b.johnston12:54 PM
@steve.bossert I don't have any scheduled right now

Casey Halverson12:55 PM
@steve.bossert I packed your NanoVNA in fact. I knew your name sounded familiar.

billybob12:55 PM
Some frequencies by their design are required to change when interference is detected. For instance, Wifi-N jumps off its current channel if Police are nearby using Speed radar :P

alan.b.johnston12:55 PM
@J I am not doing that intentionally! The rpitx library is jumping around for some reason

J12:55 PM
oh (question answered - had chat lag)

alan.b.johnston12:56 PM
I'm going to key up with my HT one last time ;-)

alan.b.johnston12:56 PM
I keyed up on 434.85 MHz this time

home12:57 PM
Fantastic Alan! Thanks for sharing! Great conversation!

J12:57 PM
Yes thanks for the chat and demo!

alan.b.johnston12:57 PM
Thanks! This has been fun. I hope some of you will build one!

alan.b.johnston12:57 PM
If you do, send me pix!

Casey Halverson12:57 PM
It is exciting that satellites are in such close reach.

Joe Latrell12:57 PM
Will be building one.

Casey Halverson12:57 PM
I think i am going to build one.

Chinna12:58 PM
One last question, does having GPS sensor on board is of any use?

alan.b.johnston12:58 PM
Well, it would work if you had it near a window

J12:58 PM
Well a build might be a way off yet but certainly seeing this today has reminded me to have another go at getting decoding going with the cubesatsim

alan.b.johnston12:58 PM
Since it doesn't fly around, it would always give the same location, but we have done it before

Casey Halverson12:58 PM
@Chinna I think even the UBlox in flight mode might have trouble in LEO. Could be wrong.

J12:59 PM
I gues a GPS might be fun if one was going to take it out and about

Joe Latrell12:59 PM
For GPS in LEO you need an unregulated version. They are not cheap and have a lot of export controls.

Casey Halverson12:59 PM
The FossaSat people literally made the exterior out of PCB and trisolx solar panels SMT'ed.. i thought that was interesting.

Chinna12:59 PM
@alan, would GPS will be of any use in the case of baloon experiment?

alan.b.johnston12:59 PM
The telemetry spreadsheet will be available after this chat is over https://docs.google.com/spreadsheets/d/1LB44eiODrIT9o9FA2rvRszA-hIo7iovx9XdL21Ge1vI/edit?usp=sharing

alan.b.johnston12:59 PM
But the web sdr won't!

Dan Maloney1:00 PM
So we're coming up on the top of the hour, which is when we normally let hosts go in case they have to get back to work. Of course the Hack Chat is always open, so please feel free to continue the discussion as long as @alan.b.johnston wants to stay on. I want to thank Alan for taking time out today to meet with us - this was really interesting to me, especially seeing how many people are so into CubeSats!

Joe Latrell1:00 PM
Thanks Alan!

alan.b.johnston1:00 PM
Thanks everyone for joining and for the questions!

Dan Maloney1:00 PM
And don't forget that we have a related Hack Chat next week - open-source thrusters for nano-satellites with Michael Bretti from @Applied Ion Systems:

alan.b.johnston1:00 PM
I do need to run, so 73!

Dan Maloney1:00 PM

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