What Is ISS HamTV?

The system is known as HamTV (onboard hardware: HamVideo), a Digital Amateur Television (DATV) transmitter installed in the ESA Columbus module of the ISS. It was originally installed in 2013, commissioned in April 2014, and used for ARISS school contacts from 2016–2018. The unit failed in 2019 and was returned to Earth for repair. It was re-launched on SpaceX SpX-30 in March 2024 and reinstalled on July 29, 2025. An updated version was tested successfully in October 2025.

Primary Purpose

The primary use of HamTV is for ARISS school contacts, when the astronaut uses a camera to show live video of themselves and the inside of the ISS to a school during a VHF radio contact. Outside of school contacts, the transmitter is frequently left on in “blank transmission” mode — the signal is fully formatted but the video content is black, providing a live carrier for ground stations to tune and test against 24/7.

Transmission Parameters

Why Is It Challenging?

This is a 2-watt transmitter roughly 400 km away, moving at approximately 7.7 km/s. The link budget is far less forgiving than VHF/UHF satellite work. The ISS is visible from any single location for a maximum of 11 minutes, often less, and at 2395 MHz the signal does not penetrate trees or structures. A minimum elevation of roughly 20 degrees is needed to begin receiving a stable picture.

The ISS is also not geostationary — unlike QO-100, it moves rapidly across the sky. A 1-meter dish at 2395 MHz has about 8 degrees of beamwidth, requiring accurate motorized tracking. This is the core mechanical challenge of the project.

HamTV vs. SSTV — What’s the Difference?

It’s important to distinguish the two ISS television modes. SSTV is easy; HamTV is a serious technical project:

Station Performance Tiers

The community has developed practical guidelines based on your local horizon and available equipment:

The GCARC 2.4-Meter EME Dish — An Ideal Starting Point

The W2MMD clubhouse already has a 2.4-meter mesh dish used for EME operations. This is an exceptional starting point for HamTV — here’s why:

Link Margin Advantage

A 1.2 m dish at 2395 MHz provides approximately 30 dBi of gain. The 2.4 m dish delivers roughly 36 dBi — 6 dB more signal. That is four times the collecting area of the community standard. This margin is so generous that even a moderately optimized front end will produce excellent results.

The One Real Challenge: Beamwidth and Tracking Speed

A 2.4 m dish at 2395 MHz has a half-power beamwidth of approximately 3.4 degrees. The ISS can move at up to 1°/second near zenith, giving roughly a 3-second tolerance on pointing error before signal degrades significantly. The rotator must be capable of slewing at 5°/sec or faster to handle high-elevation passes. If the current EME rotator is slower than this, low-to-mid elevation passes will still work well — the ISS moves more slowly at lower elevations.

The Dish Reflector Is Already Compatible

A mesh dish optimized for 1296 MHz EME has more than adequate surface accuracy for 2395 MHz. The rule of thumb is surface accuracy better than λ/16; for 2395 MHz that is approximately 8 mm — well within the tolerance of any proper EME mesh dish. The reflector itself requires no modification.

What Needs to Be Added: Component Breakdown

Since the dish, mount, and rotator already exist, the following components are needed to complete a HamTV receive station:

1. Feed — LHCP Helix or Patch, 2395 MHz

The ISS transmits RHCP. When RHCP reflects off a dish, the handedness flips — so the feed at the focal point must be Left-Hand Circular Polarization (LHCP) to receive the signal correctly.

The feed must also be matched to the dish’s F/D ratio (focal length divided by diameter). EME dishes typically have F/D in the range of 0.35–0.45. A feed designed for a shallow dish will under-illuminate a deeper dish, reducing effective gain. Know your dish’s F/D before purchasing a feed.

2. LNA (Low Noise Amplifier) — Mount at the Feed

An LNA must be mounted directly at the feed, not in the shack. At 2395 MHz, even a few feet of coax before the LNA will add noise and degrade the system significantly.

3. Bandpass Filter — Not Optional

The HamTV frequency of 2395 MHz is only 5 MHz below the 2.4 GHz WiFi band. A strong WiFi burst can cause the receiver to lose lock for several seconds. A bandpass filter is essential.

• Use a multi-pole interdigital BPF centered at 2395 MHz
• Ideally place the filter after the LNA to avoid degrading system noise figure — but place it before the LNA if the LNA is being driven into compression by local interference
• If using a downconverter, the filter can be placed at the IF frequency instead

4. Coaxial Cable — Microwave Grade Required

Standard RG-213 and RG-58 are not suitable for 2395 MHz. Use LMR-400 or equivalent, or professional-grade satellite coax. Keep the run from LNA to shack as short as practical, or use a downconverter at the masthead (see below).

5. Downconverter — Optional but Practical

A downconverter at the masthead translates 2395 MHz to a lower IF (for example, 731 MHz or 1255 MHz), allowing standard satellite-grade coax and reducing losses on long shack runs. It also enables use of receivers that don’t tune to 2395 MHz directly.

• Spectra Developments SPDC 2400 LNC — 1000 MHz frequency offset, confirms working with HamTV
• California Microwave S-band units — often available on eBay
• Nooelec “Ham It Down” — check output IF frequency for compatibility with your receiver

6. Satellite Line Amplifier

DVB-S receivers are designed for use with satellite LNBs that provide ~55 dB of gain. After the masthead LNA, add at least one inline satellite-grade line amplifier with >30 dB gain. The noise floor at the receiver input should read between -30 and -70 dBm with no signal present.

7. DVB-S Receiver

The HamTV signal is a 2.0 Msymbol/s MPEG-2 DVB-S transmission. The receiver must be pre-configured to the exact frequency and symbol rate before the pass — any receiver that needs to scan will not lock in the time available.

8. Tracking Software

Your existing EME tracking software almost certainly already supports ISS TLE-based tracking. Load the current ISS TLEs from Celestrak or Space-Track and confirm the rotator can achieve the required >5°/sec slew speed for high-elevation passes. PSTrotator is widely used in the HamTV community and supports nearly all common rotator interfaces.

Estimated Cost to Add HamTV to the Existing EME Setup

The dish, mount, rotator, and computer are already in place. The 6 dB of extra antenna advantage over a standard 1.2 m station means the front end does not need to be perfect to achieve excellent results.

Key Pitfalls to Avoid

• Pointing calibration: A 1-meter dish needs pointing accuracy within ±3 degrees. A 2.4 m dish requires ±1.7 degrees. Account for rotator calibration error, dish mounting, and mast flex/wind movement.
• WiFi interference: Only 5 MHz from HamTV. Intermittent WiFi bursts can cause the receiver to lose lock for several seconds. Filter before the receiver is mandatory.
• Cheap coax: RG-58 and RG-213 are not suitable at 2395 MHz. Even cheap SMA patch cables can vary by several dB depending on how they’re bent.
• Falsely advertised LNAs: Some budget units have worse noise figure and less gain than claimed. Stick to MiniCircuits or other reputable suppliers with measured data.
• Receiver overload: A receiver overloaded by WiFi may show a strong carrier signal but refuse to lock. If this happens, add or relocate the bandpass filter ahead of the LNA.
• High-elevation pass tracking: The ISS moves fastest near zenith. Rotators that can’t slew at >5°/sec will break lock on overhead passes — though lower elevation passes will still work fine.

Testing Your Station Before a Live Pass

Because ISS passes are short, it’s important to validate the system before relying on a live pass. Two proven methods:

Sun Noise Measurement

A well-configured S-band station should detect 2.0–2.5 dB of sun noise when pointed at the sun. This is an excellent system check for both gain and noise figure. Leave the rotator in solar tracking mode for a few hours and observe the noise level rising and falling as the dish moves through the solar disk. Systems known to receive HamTV detect this range of sun noise.

Local DVB-S Test Signal

Generate a local 2.0 Msymbol/s DVB-S test signal on 2395 MHz using a Raspberry Pi 4 running Portsdown 4 software with a PlutoSDR. Verify the receive chain decodes it correctly before the first real pass.

Watching Without a Ground Station

If you want to watch HamTV before building a ground station, the BATC/ARISS network streams live video whenever any ground station in the network has the ISS in view. Access the live feed at:

live.ariss.org/hamtv/

Joining the ARISS Ground Station Network

Once a reliable station is operating, W2MMD would be an excellent candidate to join the BATC/ARISS HamTV ground station merger network. Multiple geographically diverse stations chain together to provide continuous video coverage during ARISS school contacts.

To contribute, contact: hamtvops@ariss-i.org with examples of successful reception from your station.

With a 2.4 m dish and a well-configured front end, GCARC would be operating one of the higher-performance HamTV stations in North America — well positioned to provide reliable coverage for school contacts over the northeastern US.

Key References and Resources

• BATC Wiki — HamTV from the ISS (primary technical reference)
• BATC Wiki — How to Build a Ground Station
• ARISS — HamTV on the ISS
• AMSAT-ON — HamTV Station Profiles and Technical Details
• RF HAMDESIGN — ISS HamTV Dish Feed (LH-13XL)
• G3RUH — Helical Feed Design for Deep Dishes
• ARISS Discord — HamTV Discussion and Support
• BATC Forum — Current HamTV Thread