The rocket didn't go too high or far so I didn't have any range problems
with the primary TM (900 MHz) stream. I made a PVC support that pointed
the TM antennas straight up and that kept lock until the very end of the
flight. The last packet received just a few seconds before landing and
it lost the signal since it was essentially perpendicular to the Yagi
antenna. I added an az/el/range display to the ground station and I had
intended to have somebody point the antenna at the rocket but with the
expected short flight, I just left it pointing vertical. With the GPS
issues, the az/el values might have not been that useful anyway. Once I
re-aimed the antenna downrange, I reacquired the signal. Paul Breed
sent his drone to go look for the rocket and the first set of
coordinates I gave him were when the last packet was received but the
GPS hadn't completely reacquired lock so the data was garbage. Once I
realized that and sent him the new coordinates, he was able to go right
to it on his ATV. I need to look at the TeleMini data again but the
TeleDongle didn't seem to want to reacquire the signal after landing,
even when I re-aimed the antenna downrange. I didn't spend any time
troubleshooting that since we had solid coordinates for the landing
location and he had already found it.
Using 1W for the primary TM was probably overkill. Since I had
bi-directional TM between the ground and rocket, I contemplated starting
with 10 or 100 mW, and automatically bumping up the power if the
heartbeat from the other end wasn't received. It seemed simple enough
but I didn't want to make a change like that at the last minute. The
reported RSSI at the ground station started at -55 dBm, peaked at -40
dBm after liftoff (because the rocket was directly in line with the
ground antenna), then was around -70 to -80 dBm for most of the flight,
gradually decreasing with the last packet at -100 dBm when the rocket
descended below the horizon downrange. It landed just a few seconds
later. I'll add the plot to the data on the website tonight. The RSSI
as received by the rocket generally matched the RSSI reported by the
ground station as it was also 1W.
-Bob
On 1/25/22 11:26 PM, Craig Strudwicke wrote:
Fantastic achievement Bob, truly a massive effort over a sustained period to end up with a result you deserve!
Any comments on your telemetry and tracking? I note that you had some concerns about this aspect (which in the end were not needed due to the very civilized recovery).
On Wed, Jan 26, 2022 at 3:12 PM Robert Watzlavick <rocket@xxxxxxxxxxxxxx <mailto:rocket@xxxxxxxxxxxxxx>> wrote:
I added a complete write up on the launch at:
http://www.watzlavick.com/robert/rocket/index.html
<http://www.watzlavick.com/robert/rocket/index.html>
Here are some more photos, videos, and plots:
http://www.watzlavick.com/robert/rocket/rocket1/tests/index.html
<http://www.watzlavick.com/robert/rocket/rocket1/tests/index.html>
-Bob
On 1/16/22 8:57 AM, Robert Watzlavick wrote:
> I finally launched my 250 lbf LOX/kerosene rocket yesterday at
FAR. It got to 10800 ft with a 10 second burn and winds were calm
so there were no weathercocking issues off the rail. The drogue
and main deployed as intended and we recovered it about 6000 ft
down range. I’ll post more details in a few days but I want to
thank everyone on this list that has helped me over the years. I
had a lot of really smart folks help me along the way and I
appreciate it!
>
> -Bob
>
