SDR: Let's Walk To The Space Station?

I had high aspirations on Wednesday to do a base-band SDR recording of a scheduled International Space Station (ISS) contact with a school in Ashford,  Connecticut. 

Burger Hill at Drayton Grant Park Rhinebeck, NY 12572

The weather was nice, so I decided to trudge up the measly 550 feet of Burger Hill for amazing views and to maybe cross paths with a passersby or two interested in what I was up to with my collection of equipment. 

What is a base-band recording?  Think of it like recording a television show with a DVR or VCR.  The only difference is a base-band recording lets you record a wide block of spectrum say from 162 to 163 MHz and be able to point and click on any activity received for later playback. This would be like recording multiple movies, news and sitcoms on different channels all at the same time.

Bummer: Well, no activity from the ISS on 145.800 MHz at 14:39 PM ET (1839 UTC). 

As it turns out, the ISS contact was cancelled at the last minute due to an experiment in the Columbus module that would have prevented the use of the functional radio in that part of the space station. 

The radio to be used was actually considered the spare radio as the main radio after years of service no longer is functional.  A replacement is supposed to be sent up before the end of 2018.

I only found out about this change of schedule on a Facebook Group that I joined once I got home which is more up to date than all my usual sources such as the official ARISS Project website, AMSAT mailing lists and various NASA pages.

Serena Auñón-Chancellor, KG5TMT preparing the
NanoRacks Cubesat Deployer-14

This just goes to show that social media is still the best spot for breaking news!

Looking on the bright side...

All was not lost though. Not many minutes later at 15:02 ET was a pass of the elderly SO-50 satellite and I quickly made a contact with Tom, K8TL in grid EM89, 500+ miles away from me in FN31 thanks to this "repeater in the sky".

All that was needed was 1 watt of transmit power & a directional antenna! 

However, the down-link for the SO-50 satellite is centered on 436.795 MHz and there was someone using digital voice on that frequency which made it hard to make more contacts as SO-50 reached its apex and started to move out of range.

I did not have a DMR capable radio with me, but I am pretty sure that is what mode it was and it was local versus coming from the satellite. 

Listen:  Do you hear a "digital sound" on 436.795 MHz?

Trespasser!!

No hot spot or repeater stations appeared listed on Brandmeister on that frequency in the satellite band, so it could be some joker or ill informed amateur about the suggested ARRL and ITU band plan just intentionally interfering. Rhinebeck is pretty much far away from any "majorly" strong out of band signals that could have interfered, so it had to be an amateur radio operator.

I knew the signal was also local because if it was somehow coming in from SO-50 by someone transmitting DMR on the VHF up-link of 145.850 MHz, it would have come from the direction of the satellite and not from another direction to my south west at a "terrestrial" elevation.

This sort of interference makes me sad because 436.795 MHz is well known for over 16 years that this is where SO-50 transmits back to earth on.

There are plenty of other frequencies that can be used for digital voice that would not interfere with those interested in satellite communications.

Lets change the subject back to base-band

While I was at the great location of Burger Hill, I decided to do a 30 second base band recording of the weather band from 162-163 though should anyone wish to test it out since every NWS channel is in use from that location.

A "Normal" Recording:

A center frequency of 162.475999 MHz with a bandwidth of 15 kHz can easily be recorded and played back using pretty much any audio player, but only just that one frequency can be heard. The file size is 1.9 MB. Play: Standard AF Recording (1.9 MB)

Play: Standard AF Recording (1.9 MB)

A "Base-band" Recording: 

Compared to the "Standard AF Recording", the base-band recording for the same 30 seconds is 60.9 MB or 3105% larger. However, you can listen to any signal of any bandwidth in any mode across the entire 162 to 163 MHz captured for 30 seconds.

SDR# will help you visualize the entire 1 MHz wide
recording without needing a radio

In order to play the base-band file, you can not use a regular audio application or otherwise the sound might sound like an Imperial Probe Droid from Star Wars.

Play/Download:  IQ Base Band File (60.9 MB)

If you are a Star Wars fan, you know the
audio I reference from Echo Base on the ice planet Hoth

Ham Solo: Return of the SDR#

Download and install the popular SDR# program and select the "IQ File" option as shown. 

Then navigate to where the "IQ Base-band File" was saved and press play in SDR#

From the Burger Hill location and its good line of site, multiple weather stations were received as well as a few other signals not related to the weather.

Hudson Valley National Weather Service (NWS) stations
broadcasting 24/7 on the 162 MHz spectrum

Hopefully this article gave you a taste of a few interesting things you can do with amateur radio or use equipment for a dual purpose unrelated just to ham radio.

Next time there is a planned live ISS contact receivable from the Hudson Valley, we will definitely try to get that recording, just as long as the astronauts do not get busy at the last minute! 

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Amateur Satellite Basics: Where, When & What to listen for

Interested in trying something new using your handheld VHF or UHF radio?  How about putting that old scanner to use or using one of those other bands not used in your "all mode/all band" HF radio?  What about using that $20 software defined radio dongle you may have gotten for Christmas?

Diana Eng photo with home made antenna in a 2009 Make magazine article.  Look here for more info

Consider satellite listening as your next adventure!

This article will only focus on when, where and what to listen for. Later articles will cover transmitting and other related best practices in using the amateur radio satellite constellation for your enjoyment.

What is out there to listen to?

The below chart from the radio amateur satellite corporation or AMSAT for short shows the name of current satellites and general usage patterns. As you can see, there is a lot floating and spinning around Earth that are amateur focused satellites.

Where to listen for these satellites?

There are sub-bands set aside for satellites and to ensure there is minimal interference from other users in different parts of the world or for those with other interests not related to satellite operations.

In the United States, the ARRL and FCC have negotiated a general band plan along with the ITU and other regulatory bodies such as OFCOM, JARL and many others. Here is a summary taken from the ARRL website for where these special allocations of frequencies exist for satellite only activity.

• 10m band  satellite down-link from 29.3 to 29.510 MHz
• 2m band new OSCAR sub band from 144.3 to 144.5 MHz
• 2m band linear translator inputs from 144.5 to 144.6 MHz
• 2m band linear translator outputs from 145.1 to 145.2 MHz
• 2m band OSCAR sub band from 145.8 to 146.0 MHz
• 70cm International satellite sub band from 435.0 to 438.0 MHz
• 23cm band satellite up-link sub band from 1260 to 1270 MHz
• 13cm band satellite sub band from 2400 to 2410 MHz

The above adds up to almost 24 MHz of total band width available for two way satellite communications.  Not included above are other frequencies available for "Earth-Moon-Earth" communications where you can bounce your signal off the moon as a passive repeater to communicate to other stations elsewhere on Earth. Also not included are frequencies at the 3.3 GHz, 5.6 GHz and 10 GHz frequency bands also used for satellite communication.

Have a look for more detail here on the ARRL website: http://www.arrl.org/band-plan 

Making it more simple

The below frequencies would be a good starting point for just listening, so save them into a radio that you have plenty of left over empty channels in or some other radio you do not use too often.

FM based satellites (down link frequencies)

• SO-50 on 436.795 MHz
• AO-85 on 145.980 MHz
• AO-91 on 145.960 MHz
• AO-92 on 145.880 MHz
• ISS on 145.800 MHz ( Over North America only)

There are a few others that can be looked up on the AMSAT website and the above are the most easy to listen for currently.  https://www.amsat.org/fm-satellite-frequency-summary/ 

SSB based satellites (down link frequencies)

• FO-29 on 435.8 to 435.9 MHz 
• AO-73 on 145.950 to 145.970 MHz

These will be in side band mode and may either be USB or LSB depending on what is sent up via up link and is then inverted on the way down. Other SSB or "transponder" satellites can be found here: https://www.amsat.org/two-way-satellites/

Data focused satellites (down link frequencies)

• APRS via the ISS on 145.825 MHz
• APRS via NO-44/PCsat on 145.825 MHz

There is a lot more not even touched on in this article such as FalconSat, LilacSat, XW-2 Series and others, but all the above should be easy to hear with even modest antennas such as a 3 element tape measure beam or a simple gain "rubber duck"

How to find when to listen?

There are many applications such as Orbitron, Gpredict and others for PC or MAC based computers, but are not very portable.  For an Android based smart phone, look for "ISS Detector" in the Google Play store. It does much more than just predict when the space station is overhead.

AMSAT has a prediction tool on its website here:  http://www.amsat.org/track/index.php

Also, NY2O has a great website as well for finding when to listen: http://www.n2yo.com/passes/amateur-radio.php 

Next steps?

K6KLS has a great website for getting started called http://www.work-sat.com and is worth having a look for more info.

There are also a number of dedicated discussions taking place on Echolink, D-Star and DMR where satellite enthusiasts gather to talk about best practices, so have a look at the HVDN activity calendar to learn more.