Diary

To continue my enthusiasm in space engineering, I decided to did deeper in this field. After enrolling in MSST in VGU, I saw Dr Hien for more motivation and that was the idea of the ground station came from. That time, SDR is the only thing I had in my hand. That means I have to do a lot of things which are:

• Studying about the Keplerian elements
• Reviewing about satellites communication
• Designing the rotator system
• Designing antenna

However, the most difficult I have faced is about financial problem which was not easy to overcome!!!

These days, which was super tired on hunting things and part for the projects. I have to shuttle between Saigon and Binh Duong which was extremely exhausted.

People comes and becoming a part of the team: Dat, Khoa, Nghi, Dung and Hoang

There is a things call TLE: Two lines elements which drove me crazy. By beginning catching the idea about how planets move to estimating their orbits. In the help of many useful videos and websites, I finally can catch it

TLE -> Keplerian elements -> Turning them in to orbits coordinates at epoch -> Transform to Earth frames -> Manipulating the Julian days -> Combining with the latitude and longitude -> Figure out the elevation and azimuth of the alignment according to specific satellites.

Everything that play important roles in the structures I have hunted/bought so far:

• The combo step motor + harmonic for the azimuth (salvage from the A axis of CNC)
• The harmonic for elevation
• High load bearing for azimuth
• Aluminum frame and metal sheet for the basement

Have just finished the tilt system which can rotate in the elevation angle. This uses harmonic gear box combined with the worm gear attaching step motor which will give a huge torque at the output!!!

The proposal are approved by the RDM but the budget does not match my expectation. Can not afford what I has paid for this project. That actually not the big deal because rules are rules and the "herb" still play in safe. So, no more complains and I have to go on!!!

Below, there are general diagram of whole system.

Have just finishes the newest proposal and making the contract with the school. Waiting for money!!!

At the mean time, I am still looking for parts!

First day of Nghi on nearly "brand new" lathe machine. He will make leftTube, rightTube, topPoleAdapter and bottomPoleAdapter. He looks cool in work!

Building VHF antenna from scratch with the help of calculation tools in website. I bought aluminum and 3D printed the adapters for connecting the elements. The boom is attached in the tripod for pointing. Using one application in smartphone, we can determine the polar chart of the passing satellites.

Going to be tested very soon!

The first test of my 145Mhz antenna. Results about capturing any satellites passing with android app (ISS tracker). There were just AO7 and XW2B. The sky are not so clear I the position is good as well because of the blocking of buildings around. However, HackRF and my antenna did good jobs. Photos below are about those satellites using SDR#. Congrats me!!!

Nghi is continue with rightTube and topPoleAdapter. Just rushing before the holiday.

First field test with Dr Liu, Mr Nhu and the crew. We measured the response of the antenna using spectrum analyzer. The results comes well showing that the antenna does work "somehow". So far, there are no impedance matching, gain measuring... Just a raw test to prove the antenna. After that, we used the Hackrf again but unluckily, there was no satellite passing before the rain coming!

We almost get all parts ready except bottomPoleAdapter. We spent this day to tinkering, taping... preparing for assembling. Everything seems very positive.

Now just rushing for VIMF. Hopefully, the RDM will agree with Dr Hien's proposal and we will get extra for the budget!

Dat was setting up the CNC machine for correcting the leftWall

Rushing (for possible VIMF!!!) even the Sunday, because now we almost have enough parts (just missing bottom pole adapter and holes in another adapters). After tapping, widening... we started to attach bottom sheet to the lower base, top sheet to the upper base. The patches must be installed before adding 4 main poles.

Drilling, grinding, tapping... without electricity (using battery hand held) makes us stop earlier.

Another evening after whole day long class. I have finish attaching the bottomSheet to 4 big poles. It seems so difficult because every nuts needed to be aligned in the right way. I laid down in the base for fasten them. But by the lack of M6x15, the process had to be postponed (hopefully until tomorrow :)

I also put flange, motor, leftWall and the harmonic together. They look cool except one thing, need to grind it.

Yet another day of hard working. The CNC parts need to be modified and corrected a lot. At the very beginning, it was frustrated because some critical failures appeared. However, in the "holly way", some how, they are fit together, not bad like I thought.

Going to test the motor very soon. Before this, actually, we need the end stop for each axis.

Every parts are now completed, they are ready to be assembled. Nghi has already finish lathed all the tubes.

I bought one electronic case today, carrying it from Saigon to Binh Duong!!!

Today, we gathered almost entire members to prepare for next Friday when PB will have a visit on the Station. The crew worked that days.

We bought n-th hand antenna and repainted it with elegant VGU logo on that. I was a little pain but worth!

We already finished making the adapter for parabolic antenna and upperSheet. The Station looked so cool!

So proud of you guys!

//Khoa was making the cover

//Đạt and Dũng were working on antenna adapter

//Hoàng took care of administrative paper works

//Me - in my field!!!

Satellite ground station had a chance to participate the exhibition VIMF in Binh Duong. There were so many companies in industry and manufacturing coming to attend. Some of the exhibitors and visitors were interesting, some are not.

Whatever, this is practical opportunity for us to show off the outcomes and practicing for the defense coming!!!

The team has been invited to set up an interview with University Marketing team.

The crew was asked about their's roles in the project and what had been done so far.

Thanks Marketing department!

One other yagi was built. it is 144Mhz 6el and 50 Ohm. Follow DK7ZB and thanks to MMANA-GAL, the antenna was built successfully.

After built with aluminum rod, 20x20 boom and some 3DP spare parts, they are brought together.

This time, VNA was used to optimized S11 parameter for matching and SWR. The result is gorgeous

Be going to build the crossed yagi very soon!

Tracking with VHF antenna

Many "birds" were captured. Be potential was CAS4A, CAS4B

VHF antenna was mounted to the tripod. Tracking with ISS detector running in Android. Signal connect to RTL-SDR with LNA4ALL. Raw file was captured by SDR sharp, recorded and stored for further analysis.

Trying to design and fabricate the UHF (435Mhz) antenna. This guy is more complicated than the VHF. The reasons are because of dealing with higher bands and no given 50 Ohm designs of 10-element one. We have to calibrate the UHF so many time by changing the length of elements and their position

Next steps are about the feed horn of 2.4Ghz parabolic antenna. By looking the design on simulation, we have to make the appropriate horn with position of pin on the surface. Cutting down the pin a little and checking for the SPA.

Successfully done after many times of modification.

Mechanical verification part. The group was trying to verify the precision and accuracy of rotary system via many methods:

• Full round rotating
• A quad rorating
• Testing braking torques
• Laser spot