DifCal vs 少年卫星跟踪台
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
DifCal
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Calculate diffraction angles for a particular crystal with a defined orientation matrix. New crystals can be added to the database. Energy/wavelength can be changed. Currently knows about 4-circle, Z-Axis and Theta-Theta diffractometers as well as 2-circle, powder and amorphous diffraction modes. Current crystals include silicon, diamond, GaAs, Muscovite (mica), graphite, many 3-5 and 2-6 crystals. There are separate screens for setting the crystal (or creating a new one), defining the orientation matrix, defining the diffractometer mode, and calculating either angles, given h,k,l, or hkl given a set of angles. With the larger screen of the iPad all the controls are visible on a single page.
少年卫星跟踪台
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Youth Satellite Ground Station helps HAM amateur-radio operators, satellite observers and educators plan passes, check radio data and coordinate compatible antennas and radios. Observation and preparation • SGP4 orbit calculations; map, sky, ground and camera-overlay views • Azimuth, elevation, rise, culmination and set times; search, favorites and pass filters • Satellite AI Assistant: names and NORAD IDs, upcoming passes, IARU notices and sources, introductory guides • One-click Satellite preparation page brings together the satellite, equipment and pass task; optional calendar subscriptions and reminders Public radio records do not guarantee that a satellite is currently transmitting. Pro rotator control (additional purchase) Basic tracking tested: RC2500 over BLE; legacy DTrac Rotor over TCP with external sensor. Compatibility options*: RC-3040S, GS-232B controllers, Yaesu G-5500 with GS-232B, and compatible dual-axis EasyComm II controllers. Hamlib rotctld*: use the actual server backend, such as GS-232, EasyComm, SPID Rot2Prog, EA4TX ARS or AMSAT LVB Tracker. Pro radio control (additional purchase) Connection and frequency control tested on iOS: Icom IC-705 and ID-52A/E, using CI-V over compatible BLE. CI-V options*: ID-52 PLUS, IC-9700, IC-9100, IC-7100, IC-910H, IC-7300 and IC-7610. Yaesu CAT options*: FT-817/817ND, FT-818/818ND, FT-857/857D, FT-897/897D, FT-891, FT-991/991A and FTX-1. Previous FT-817ND frequency-reading tests used Android SPP, not iOS. DTrac Radio options*: Lianchang HG-UV88, Quansheng UV-K6 V3 and UV-K1; matching DTrac firmware and BLE hardware required. Benshi AP-2*: new experimental BLE control with compatible firmware; not physically validated. Hamlib rigctld*: an external server connects its supported radio backend, for example Icom, Yaesu or Kenwood TS-2000/TS-790. * These iOS device/connection combinations remain untested. Shared interfaces or protocols do not guarantee command compatibility. iOS does not support classic Bluetooth SPP or direct USB serial here. CAT/CI-V requires a matching BLE adapter or network bridge; Hamlib requires your own server. HF/50 MHz models such as IC-7300, IC-7610 and FT-891 do not cover typical VHF/UHF satellite bands. Frequency readback, Doppler, uplink/downlink and tone synchronization depend on the model. Rotator tracking, calibration and end-of-pass actions depend on the controller. Purchasing does not add hardware compatibility. External radios handle voice transmission; the app never automatically activates PTT. Follow local radio regulations. Audio-source and pass-recording planning controls are included. Actual audio capture, recording, export and built-in SSTV decoding are not enabled in this version. Chinese/English, light/dark themes and Beijing/UTC time; designed for iPhone and iPad. Purchases The free ad-supported tier includes satellite search, observation, pass prediction, public radio data and the AI Assistant. Ad-free Base is a one-time US$0.99 purchase. Base owners can purchase Pro for an additional US$9.90 to unlock compatible rotator/radio control: US$10.89 normal total in the US. These are separate non-consumables, not subscriptions. Promotions and regional prices are shown by Apple at purchase. Eligible V1.04 and earlier users retain their original device-control and ad-free rights. Existing Pro purchases remain valid. Restore with the original Apple Account; rights apply to that account's iOS/iPadOS version.
Screenshots
Verdict
The clearest difference is in-app purchases: DifCal at none against 少年卫星跟踪台's 2. DifCal also leads on ads (none vs shown) and iOS requirement (12.0 vs 16.0). 少年卫星跟踪台's advantage is update cadence (every 4 days vs every 15 months). On price and device support there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
Both are free to download. 少年卫星跟踪台 sells 2 one-off in-app purchases. DifCal asks for nothing beyond the download.
DifCal ships an update every 15 months, 少年卫星跟踪台 every 4 days. The most recent releases landed on November 1, 2026 and October 31, 2026 respectively.
| Parameter | DifCal | 少年卫星跟踪台 |
|---|---|---|
| Price | Free | Free |
| Update frequency | Every 15 months | Every 4 days — better |
| Ads | No — better | Yes |
| In-app purchases | No — better | Yes |
| Devices | iPhone, iPad, iPod — better | iPhone, iPad |
| Requires iOS | 12.0 — better | 16.0 |
| Further details — not scored | ||
| Size | 9 MB | 10 MB |
| Age rating | 4+ | 4+ |
| Developer | Sean Brennan | 峰 于 |
In-app purchases
DifCal
No in-app purchases
少年卫星跟踪台
- Ad-free BaseFree
- Pro Device Control$9.90








