International Space Station to be visible on Sept. 19-20

The International Space Station to be visible on Sept. 19-20. The key word being "visible" and is not the only time you can see the ISS though.

Radio amateurs can listen via wireless during most passes with the hope to either listen in during a scheduled astronaut contact with a school or to use the digital packet relay system known as a "digi-peater" to bounce short text messages through the ISS and back down to Earth.


Non-Visual Voice Communication

The astronauts do not have much time for casual amateur radio operation, but you might be lucky if you give the station a call on 144.490 MHz in North America or 145.200 MHz elsewhere in the world. You will need to listen to 145.800 MHz for transmissions from the Astronauts.

Using different receive and transmit frequencies is known as split operation.  Astronauts have the ISS radio programmed the opposite was as you would on Earth.   The reason for this is to minimize interference and increased reliability.

The below photo is of a post card confirming a contact with the ISS and a local amateur radio operator.  The "QSL" card was sent from a ground station on Earth and was not dropped 220 Miles above from the ISS, if you were wondering.

Non-Visual Data Communication

If you are interested in non-voice communication, tuning in to 145.825 MHz will allow you to receive APRS data through the ISS.  Your AX.25 capable radio will use the same frequency on transmit and receive.  A path of "ARISS" will help ensure your transmission is received by the ISS and passed back down to Earth automatically.


Viewing the ISS

Applications such as "ISS Detector" for Android smartphones, tablets and Chromebooks work great to "predict" when the next pass will come over your area.  Apple device users may use "ISS Spotter".  Many computer programs also exist such as "Orbitron" for Windows users,  "Gpredict" for multiple platforms and "Nova" as being the three most popular or easy to use options.

There are also additional augmented reality and web based tracking tools available that are easy to find.

It is best to adjust your eyesight to the dark for at least 10-15 minutes before looking at the night sky. This gives your eyes some time to adjust for maximum viewing benefit.

On September 19th, the pass coming over the Eastern United States will track from South to North

The following day at just about the same time will see the ISS pass over yet again, but just lower in the sky compared to the night before.

Beyond visual observation, it would also be good to keep an eye on the APRS activity via the APRS.fi website to see if radio amateurs are "bouncing" signals from the space station.

You can track the space station and APRS activity via the RS0ISS call sign which broadcasts from the Russian module of the ISS. It is not always active though.  The best way to confirm recent activity is by looking at the AMSAT satellite status page or by looking at the very active Facebook group focused on the International Space Station A.R.I.S.S experiments.

If anyone would like to take some pictures of the upcoming ISS pass, it would be great if they can be shared in the comments or emailed to info@hvdn.org for a future article.

SSTV: Images from the ISS

Zipping around planet Earth at 220 miles above on October 27th to 29th 2018 was the International Space Station and its special series of image transmissions using amateur radio slow scan television (SSTV)

What is SSTV?

Slow Scan Television or SSTV for short is a method of sending images over very narrow wireless bandwidth with fairly good color resolution in a short amount of time.

There are many different types of SSTV signals or modes and the one currently in use by the International Space Station is known as Robot36 or PD120

145.800 MHz is the "down-link" frequency for amateur radio operation from the ISS.  Sometimes it is used for voice communication and other times it is used for experiments such as SSTV.   On 145.825 MHz is data "packet" APRS operation for two way "text message" like contact with or through the ISS>

How To Receive SSTV Images?

There are two inexpensive ways to receive and decode an ISS SSTV transmission that can be done with less than $50 of equipment, not including the cost of your computer or smartphone.

Method #1:  USB SDR Dongle & Computer Setup 

Wide band software defined radio (SDR) receivers such as the RTL-SDR v3 can be used for many things, including the reception of signals orbiting above you and around you.  

Other things you can use this 24 MHz to 1.7 GHz  "SDR" receiver for include finding your lost car key remote, monitoring smart home devices, listening to weather, music and so much more.

With free software such as SDR#, its possible to record a "visualization" of the signal for later playback and decoding of SSTV signals. The same signal can also be sent from SDR# to MMSSTV software in real time for decoding of the SSTV transmission.

Method #2:  Inexpensive VHF/UHF Hand Held Radio & Smartphone Setup 

A basic dual band hand held radio can be purchased for about the same price or less as the receive only SDR but will also offer the ability to transmit on a narrow range of amateur frequencies also used by the ISS as well as by over 2,500,000 amateur radio operators globally. 

A very simple way of decoding a SSTV transmission is to simply hold the radio next to your smartphone while running the Robot36 application found on in your favorite mobile app store. By turning the radio volume up, the microphone on your smartphone will hear the SSTV signal and decode it. Sample signals to listen to are found later in this article.

The application will decode the received audio with no physical connection to the radio which makes this very easy to demonstrate for those not very computer savvy.  

Antenna Stuff:   Very important!

While any combination of radio receiver and computing device can be used beyond the examples provided, antennas are just as critical if not more so for receiving the best signal possible.

Having what is called a good "Signal To Noise Ratio" or SNR is needed to help differentiate white noise and static from the actual SSTV signal.  Any interference to the SSTV signal will just look like static like on a television screen, so a good antenna helps increase the SNR and produce a better picture

The good new is that the ISS SSTV signal is often very strong and easy to pick up with basic antennas, but a high power directive antenna is a good idea for optimal reception since it will focus the maximum signal strength from the ISS into your radio.

The reverse polarity SMA-J connector is common on Chinese origin radios such
as those for sale by Baofeng, Wouxon and a few others. 

While good reception results will often be had with the including telescoping dipole antenna with the RTL-SDR V3 or the longer "whip" antenna included with many of the inexpensive hand held analog radios such as the UV-8, a directional antenna is a good idea to consider.

Some options that can be purchased separately made by companies such as Nagoya, Comet and Diamond are easily sourced for VHF only of VHF/UHF operation.

It is best to pay close attention to what type of connector on an antenna like this can be used with your radio as they are not all the same.

The SMA antenna connector version of this same antenna is more common for radios
\made by Alinco, Kenwood, Icom, Yaesu, TYT and Retevis.

An alternate and higher gain antenna called the tape measure yagi beam can be constructed with simple hand tools and materials for less than $20.

There is also a ready made antenna available for purchase from the Arrow Antenna Company as well as the Elk Periodic from vendors such as Ham Radio Outlet.

The beam antenna is a great club project or one for a few like minded hobbyists. Many can be constructed quickly at one time if people work together in cutting and preparing different parts of the antenna for final construction..

What does a SSTV signal sound like and how do I find it? 

In order to know what to listen for, below are three very good signals and the resultant decoded image.

Feel free to try decoding these files with the MMSSTV or Robot36 applications to get familiar with the software since you do not want to miss the fast traveling ISS the next time they are transmitting SSTV images.

The "ISS Detector" app for Android is a great way to find out when the ISS will pass over your location next.
You an also track other satellites and even planets too with this program

To find out when the ISS will be over your location next, please visit AMSAT.org for more information about tracking the ISS, satellites and other interesting space related amateur radio topics.

Play MP3 Recording:  10:28AM 10/28/2018 ISS SSTV

Play MP3 Recording:  10:31 AM 10/28/2018 ISS SSTV

Play MP3 Recording: 12:00 PM 10/28/2018 ISS SSTV

How about SSTV with an SDR?

A nice feature with the SDR# software is you can play back a recording of spectrum at any point in time.

This is also called a base-band IQ file and was discussed in prior articles about receiving voice transmissions from the International Space Station.

• Happy Monday Again!; Ashford School and ISS Make Contact

• SDR: Let's Walk To The Space Station?

This file is a base-band IQ file for the "Atlantis and Mir" SSTV image to help with your own testing.

• Download 1200 PM ET SDR IQ SSTV 10/28/2018  (Caution: 225 MB File)

Select the  IQ file option  in SDR#
and play back the 225 MB recording 

Share your success stories, questions and comments below.  Thanks for reading!

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