Decode success!

[Justin Dolske]

Hurrah, after a few failed attempts I got good data! \o/

Raw data @ http://dolske.net/hacks/kicksat/pass_0424/

1:36:47 PT
"P4C,770,0,468,0,U..."

I still haven't tried the other afsk1200 decoders suggested here. But
looks like I'll need to because mine only dumps printable ASCII, which
probably isn't useful to Zac's decoder.

I think this pass was successful as a result of better antenna pointing,
a great overhead pass (although the actual packet looks to have come
around 50-60 degrees alt.), and a tweak to the RTL2832 RF gain for a
better signal/noise balance.

Justin

[Matthew F Reyes]

Hi Justin!

Can you elaborate on the tweak you're referring to? We heard the packets nicely here on our Kenwood rig but had no luck with the RTL dongles.

Let's chat!

 Matthew F. Reyes

 about.me/motorbikematt

Justin

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[Bill Arnold]

Justin,

1) Did you use an LNA?  

2)Please send your tweak info re RTL dongles to kicksat-gs.

I'm still trying.
- Bill K4IB

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[Matthew F Reyes]

Justin...

I see on your recent twitter post that you have a rather large LNA or pre-amp.

https://twitter.com/dolske/status/459412331701624832/photo/1

What is that big brick there?

Also, can you expand on not just the dongle tweaks but also your SDR# configuration? How much gain are you turning on in the system?

Thanks!

 Matthew F. Reyes

 about.me/motorbikematt

[Justin Dolske]

On 4/24/14 3:32 PM, Matthew F Reyes wrote:

> Can you elaborate on the tweak you're referring to? We heard the packets
> nicely here on our Kenwood rig but had no luck with the RTL dongles.

Sure!

Here's an annotated screenshot of what I'm twiddling:

http://dolske.net/hacks/kicksat/pass_0424/rtl2832_tweak.png

I ran across it in one of the SDRSharp guides. I forget what the default
is (far left? middle?), but the guide noted that increasing it can
improve signal strength -- but that the noise floor goes up too, so one
needs to find a good balance for it. At first I wasn't seeing any
obvious balance point, so I just put it at the maximum setting. But I
later noticed that there is an abrupt jump in noise at the maximum
(42dB), and that one notch down (34dB) is much much better. So that
seems to be working for me so far.

TBH, the gain settings are all a little confusing. There's this manual
control, two other automatic settings (RTL AGC / Tuner AGC), and yet
another in SDRSharp's AGC sidebar. I'm not sure how they're related.
Also, enabling either of the two automatic checkboxes in this panel just
seems to result in noise swamping out everything. Could be these are
really only useful with strong signals?

To answer Bill's question, I am using an LNA.
http://www.dg0ve.de/en/lna70_en.htm from the KickSat wiki. I've been
using an E4000 dongle with it, I've also got a R820 dongle that I may
try next (but they're supposedly less sensitive, so I'm just curious).

I think my first couple of attempts right after launch were complete
failures (no signal at all) due to a bogus TLE, but since then I've been
using the "Object F" tracking, I've seen something on each try. This is
the first one strong/clear enough to actually decode, though. Note that
between doppler and RTL2832 dongle-imprecision, you probably won't see
signal at exactly 437.505 Mhz; it's been ~15 kHz low for my particulars.
I also switched for SDRSharp so that I could easily record and replay
the raw data, without stressing about getting all the fine tuning and
decoding just right in real-time.

> On Thu, Apr 24, 2014 at 3:02 PM, Justin Dolske <dol...@gmail.com

> Raw data @ http://dolske.net/hacks/__kicksat/pass_0424/

> <http://dolske.net/hacks/kicksat/pass_0424/>
>
> 1:36:47 PT
> "P4C,770,0,468,0,U..."
>
> I still haven't tried the other afsk1200 decoders suggested here.
> But looks like I'll need to because mine only dumps printable ASCII,
> which probably isn't useful to Zac's decoder.

Also, small update: I was able to use UZ7HO's soundmodem to get a decode
with binary data, which I then ran through a hex dump. (Zac, is there a
preferred format you'd like this stuff in? Or, better still, is the
KickSat telemetry documented somewhere, so that I can write my own decoder?)

1:Fm KD2BHC To CQ Via TELEM <UI F/R Pid=F0 Len=121> [15:56:18R]
P4C,770,0,468,0,U‰ñ NŠ[Š2Š°Ša @ Q _ g‰¥ 1 + ñ þŒÕ…÷ˆ,ëm·L í ë‘à ðƒÐ Ÿ‚^€•}à~ñ ¦ ¸ æ ÇŽH Ú
(hdÉ4@"|ýÕDÐ ˜±

$ xxd soundmodem_output.txt
0000000: 5034 432c 3737 302c 302c 3436 382c 302c P4C,770,0,468,0,
0000010: 5589 f190 4e8a 5b8a 328a b08a 6190 4090 U...N.[.2...a.@.
0000020: 5190 5f90 6789 a590 318f 2b90 f18f fe8c Q._.g...1.+.....
0000030: d585 f788 2ceb 6db7 4c90 ed90 eb91 c390 ....,.m.L.......
0000040: f083 d08f 9f82 5e80 957d e07e f18f a68f ......^..}.~....
0000050: b88f e68f c78e 488f da20 2020 2028 6864 ......H.. (hd
0000060: c934 4022 7cfd d544 d020 2020 2020 2098 .4@"|..D. .
0000070: b120 2020 2020 2020 20 .

Justin

[Zac Manchester]

Hey Justin,

This is really good stuff - glad you got it working. It does sound like staying away from the hardware AGC on the RTL dongles is the way to go - they're optimized for terrestrial TV signals which would be quite a bit stronger than these satellite signals. The next thing to add to my GNURadio blocks for KickSat might be a software AGC that tries to optimize SNR.

Since you got a packet, you get a mission patch/pin: https://www.kickstarter.com/projects/zacinaction/kicksat-your-personal-spacecraft-in-space/posts/804595

Take your pick and let me know where you want it mailed.

I have no problem releasing the packet decoder, but it was developed by the PhoneSat team at NASA Ames and I'll have to check with them first. Here's the decoded data from your packet:

battery_volt	770
mag_bef_x	-889.85166
gyro_bef_x	14.72008
magP_actHI_x	291.94493
magP_actMed_x	300.82493
magN_actHI_x	1.85166
magN_actMed_x	477.86744
gyroP_actHI_x	-9.33254
gyroP_actMed_x	2.87195
gyroN_actHI_x	9.56692
gyroN_actMed_x	9.04395
mag_aft_x	477.86744
gyro_aft_x	-8.26348
mag_bef_y	1.29417
gyro_bef_y	9.01844
magP_actHI_y	-555.47785
magP_actMed_y	2.52861
magN_actHI_y	450.47085
magN_actMed_y	-357.96753
gyroP_actHI_y	-2.742
gyroP_actMed_y	9.03518
gyroN_actHI_y	9.01844
gyroN_actMed_y	-16.83508
mag_aft_y	-8.46188
gyro_aft_y	9.01844
mag_bef_z	460.70475
gyro_bef_z	9.01764
magP_actHI_z	461.22242
magP_actMed_z	477.30996
magN_actHI_z	459.58978
magN_actMed_z	735.26798
gyroP_actHI_z	4.05899
gyroP_actMed_z	7.10115
gyroN_actHI_z	-1.77578
gyroN_actMed_z	9.21854
mag_aft_z	-305.72287
gyro_aft_z	6.9999
i_MHX	742.14649
i_ADCS	747.30481
i_solarXp	742.14649
i_solarXn	747.26404
i_solarYp	887.96604
i_solarYn	551.36999
i_solarZp	455.44143
i_solarZn	514.83354