# I created a hobby-level satellite enhancement version for Look4Sat.
After a long time of amateur satellite experimentation, most people probably have this feeling:
I can easily check information on my phone, but when I actually need to connect, I still have to switch back and forth between several tools repeatedly.
One app viewed the environment, one web page checked if both parties could see satellites simultaneously, one software calculated Doppler frequency, and one table recorded linear forwarder frequencies.
If it's just FM satellite, that's fine. But when you start using linear satellites, cross-band communication, or CW beacons, things become more complicated.
Therefore, I recently created my own enhanced version of the open-source satellite prediction software, **Look4Sat**, based on it. The main changes were made to address the specific needs that I encountered while using the software in practice.
Project address:
> https://github.com/atsunatsu/Look4Sat
## Why Choose Look4Sat
The original version of Look4Sat was already very good to use:
- Offline prediction satellite transit
- The radar chart displays azimuth and elevation.
- Supports updates to TLE/OMM data
- Support displaying repeater frequency
- Use directly on an Android phone
Furthermore, it is open-source.
This is important for amateur radio enthusiasts: they can modify it to their liking.
This fork isn't intended to turn it into a completely different software; rather, it aims to add some "special features that " 通联" specifically wanted.
## 1. Matching Page: Can two people actually hit this star at the same time?
This feature draws inspiration from the approaches used in **SatMatch** and **satlover.de**.
Enter the positions of both parties, such as latitude and longitude or Maidenhead Grid. It will then identify the satellites that are visible to both parties simultaneously and draw their respective elevation angle curves.
This eliminates the need to manually ask for the other person's grid and AOS/LOS while making QSOs from different locations.
Suitable for quick assessment:
- Which stars are visible from both sides?
- How long has the overlapping window lasted?
- Is the maximum angle of elevation too low for both sides?
- Is this particular "pass" worth pursuing?
Just by looking at the curve, you can usually tell if it's possible to hit.
## 2. Dual-station radar plot: Don't just look at your own side
The original radar plot only displayed the satellite trajectories observed by local stations.
I overlaid the trajectories of both parties.
After entering the radar from the matching page, you can see:
- Local station satellite trajectory
- The satellite trajectory of the opposing station
- Current positions of both satellites
- Automatically exit dual-site mode after transitioning.
This is very useful for practical communication.
For example, you might see that your satellite has already been launched, but the other side's may not have even cleared the horizon yet.
Or, you're about to lose out here, while the other side has just arrived at Gao Yangjiao.
This provides a much clearer picture than simply looking at a sequence of AOS/LOS times.
## 3. Calculation of Linear Forwarder Frequencies
With FM satellites, it's relatively simple to tune in – just adjust the frequency.
Linear satellite presents some difficulties:
- The uplink and downlink frequencies are a range.
- Positive/Negative Signal Forwarder
- Both the uplink and downlink are experiencing Doppler shift.
- Some stars require a frequency offset.
Therefore, I added a linear forwarder calculator.
On the radar page, if the current satellite has a linear/SSB transmitter, a "Calculator" tab will appear.
You can input the downlink frequency, and it will automatically calculate the uplink; or you can input the uplink, and it will reverse-calculate the downlink.
Supported:
- Bidirectional calculation for TX/RX
- Doppler real-time correction
- inverted transponder
- Downstream offset input, for example, some linear satellite actual frequencies are slightly off.
This feature primarily aims to reduce confusion and streamline operations.
Especially when using a phone to look at stars and tuning a radio while sitting nearby, I don't want to open multiple web-based calculators.
## 4. CW Decoder – Primarily a toy, but quite interesting.
I also integrated a CW decoder, which uses a decoding engine related to Morse Expert, reverse-engineered and implemented by BG7NTA.
It is now located in the calculator within the radar page, and can display:
- Waterfall chart
- Real-time text decoding
- Start/Stop/Reset control
To be honest, using a smartphone's microphone to directly decode satellite CW signals isn't always reliable.
Background noise, volume levels, frequency deviations, and microphone quality of mobile phones can all affect the results.
## 5. The Chinese interface has also been modified to be more user-friendly.
The original version already has Chinese, but some parts don't quite align with local customs and preferences.
I made a few minor changes for convenience.
- Date and time displayed according to Chinese conventions
- "Station position" changed to "Site location"
- Adjusting some satellite, transit, and radar-related content.
These changes aren't significant, but they will make it more comfortable to use every day.
The APK can be downloaded from the GitHub Releases page:
> https://github.com/atsunatsu/Look4Sat/releases
Currently, it's a self-built version with a similar version number:
```text
v4.4.3-ba7opf.3
```
## Conclusion
This project isn't fundamentally about "creating a completely new satellite software."
I've just put together a few small tools that I often use when playing with satellites, and tried to fit them all into one Android app.
If you can close one web page, close it.
If you can reduce the frequency calculation by one, do so.
This allows you to view both windows directly on your phone, eliminating the need to switch between chat and spreadsheets.
If you also enjoy satellite communication, especially linear satellites and cross-country point-to-point links, please give it a try.
If you find a bug, or if there are new requirements, please submit an issue and comment on the post!
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