Quite a few folks have the M2 Antenna System LEO pack antenna. I wanted to see how this antenna system would perform with Greencube (IO-117). Our LEO Pack is set up on a Glen Martin roof tower that we’ve modified to create a transportable ground station. Here are some of the specs for the setup we’ve tested:

• M2 LEO Pack Antennas (2MCP8A and 436CP16)
• Alpha-Spid Az/El Rotator
• M2 Polarity Switches installed in both antennas
• Advanced Receiver Research coax-powered preamps installed at both antennas+

The specifications for the 70cm antenna are as follows:

• Frequency Range: 432 To 438 MHz
• Gain: 13.3 dBic
• Front to back: 15 dB Typical
• Beamwidth: 42° Circular

The published gain number for this antenna meets the requirements for operation with Greencube, so we set up our transportable station in our backyard and proceeded to do some testing.

Transportable Ground Station

The ground station setup includes an IC-9700 Transceiver, a Green Heron RT-21 AZ/EL Rotator Controller, and two computers.

The Mac laptop runs MacDoppler, which handles steering the antennas and Doppler correction, and the Windows laptop runs the modem and client software to access Greencube’s Digipeater.

The antennas are located about 100 ft from the rest of the ground station and are connected using LMR-600uF coax cable. This results in about 40 watts of power being delivered to the feedpoint of the 70 cm antenna.

Testing The LEO Pack With Greencube’s Digipeater

I am happy to report that the LEO Pack 70cm antenna enabled us to make quite a few contacts using the Greencube Digipeater. The setup required the remote preamp to be on and the use of the polarity switching controls to optimize losses due to mismatched polarity, which occurred frequently during Greencube passes. The LEO Pack antenna/preamp combination provided consistent decodes of Greencube’s packets. The challenge was getting our packets to be Digipeated by Greencube. On some passes, this worked very well. During other passes, we were only able to get reliable Digipeats during the approaching portion of a pass at elevations above 25 degrees.

Optimizing Our Station

I spent a lot of time determining the best uplink frequency to use with Greencube’s Digipeater. The settings above are what I finally settled on for uplink and downlink frequencies.

I also spent some time experimenting with the Soundmodem settings. The lengthened Tx lead-in and tail settings above helped Greencube decode our signals more reliably.

These adjustments also improved the Digipeating performance of the larger antennas used in our main ground station, so they are not specific to the LEO Pack.

Conclusions About The LEO Pack and Greencube

I probably made about 50 contacts using Greencube and our LEO Pack antennas. If you already have a ground station built around the LEO Pack Antenna System, I would encourage you to add a preamplifier if you don’t already have one and try Greencube.

If you are building a fixed ground station for use with Greencube, it might be better to step up to a larger antenna such as the M2 Antenna Systems 436CP30.

I have also found that antennas with circular polarity are not necessarily the best for Greencube. This is likely due to a combination of the lengthened path through the ionosphere due to Greencube’s altitude, resulting in stronger polarity rotational effects and mismatches with the circularly polarized antennas we are using. I am anxious to do some more testing with the non-circularly polarized yagi that we are using with our portable station to see if I can confirm this.

More Fun With Greencube

This article is the fourth in a series that we are working on. You view the other articles via the links below. This is a work in progress, and we’ll be creating additional Greencube-related posts in the near future:

• Greencube (IO-117) – A New Satellite for DX!
• Greencube (IO-117) – Station Setup, Software, and Operation
• Greencube (IO-117) – Completing a Satellite Worked All States
• Greencube (IO-117) – A Portable Station for Activating Grid Squares
• Greencube (IO-117) – The Road to a Satellite DXCC?

You can also read more about our Satellite Ground stations here.

Fred, AB1OC