We’ve been using our Portable Satellite Station 2.0 for some time now and it works great. One area that can be improved is the interface between the MacDoppler Satellite Tracking program we use and the GHTracker application which controls the Green Heron Engineering RT-21 Az/El Rotator Controller in our setup…
The Raspberry Pi is an inexpensive computer and control platform for many Ham Radio projects. We recently used a Raspberry Pi 3 to build an interface between the MacDoppler Satellite Tracking Software in our Portable Satellite Station and the Rotator Control System points the ground station antennas during satellite tracking. We put together an article about how we went about this project and some details of the hardware and software we used to put a Raspberry Pi 3 computer together for our project.
I wanted to make an article that would explain to anyone who visits my home or QTH that would answer the question on “How did you get that rope so high in the trees and how did you get that rope over the perfect branch?
I started out with a fishing pole and a 4-inch long stick from the woods. After a few attempts of getting the stick up and over the tree with the fishing line it finally made it over the tree and back to the ground. I then reeled in all the fishing line while pulling a string over the tree. After the string, I used it to pull over 3/8” poly rope.
I came up with the following idea to get a rope over the perfect branch.
The 3/8″ line holds an old branch from the woods in the center. The yellow rope to the left is the “control line” and the right side has a half rotten log as a weight secured with a slip knot as shown below.
In the diagram below the light blue line represents the yellow control line from the photo. As you lift the whole unit you should consider that the weight of the control line may offset your balance as you go higher. The magenta line shows the string with a slip knot. When the half rotten log made it over the desired perfect branch by combinations of pulling the 3/8″ rope at either end (shown black) and/or the control line (shown light blue) I pulled out the slip knot and the half rotten log fell over the perfect branch along with the string (shown magenta).
I replaced the string with rope and then a wire rope loop (shown red). The wire rope will not fade and fall apart from the sun’s UV rays. The yellow circle represents a pulley for the poly rope that holds up the dipole. When the poly rope breaks down from UV, wear and tear it can easily be replaced by lowering the pulley. I added weight to maintain proper tension on the dipole antenna as shown below.
In theory, the tension will remain the same even in wind storms when the trees swing back and forth. It turns out that an old cast iron rotor from my Toyota was the perfect weight for the application!
The heart of any Go Kit is the Transceiver. We’ve been using Kenwood equipment for our APRS iGate for some time now and we have had good results with it. Kenwood’s latest 50W transceiver with APRS is the TM-D710GA. This unit provides full support for APRS tactical applications and now includes a built-in GPS receiver making it ideal for our Go Kit application.
We had a chance to look at the iPortable enclosure at Dayton and decided that their Pro 2 4U deep unit would be a good choice for our Go Kit application. The iPortable enclosures are based on a portable rack mount case and include a DC power system, speaker and headphone hookups, a light, and provisions for a cooling fan.
EMCOM Go Kit Construction
With all the components in hand, we began the construction of our Go Kit. Reliability is important in any portable system like this so we put some time into securely mounting all of the equipment and neatly arranging the cabling. First came the shelf which holds the Kenwood transceiver and a SignaLink USB sound card. A combination of drilling the shelf to secure gear with large cable ties and #8 stainless hardware was used here.
Our iPortable case was equipped with both SO-239 and N-connectors on the front panel to allow for antennas and feed lines equipped for either connector type. To make the change over between the connector types easy, we installed separate PL-259 jumper cables for each connector. One simply connects the appropriate jumper to the radio.
The power and AvMap display shelf were next. The AvMap display mount was dissembled and modified to accept a custom mounting bracket.
The iPortable enclosure was drilled to mount a West Mountain Radio PWRgate to handle backup battery charging and management. The PWRgate supports instantaneous switching between an AC power supply and a backup battery and can accommodate a wide range of battery types and sizes.
The last piece of the setup was the antenna. We wanted something that was portable, easy to set up and would provide good performance. We choose a Diamond X-30A 2m/70cm ground plane antenna and mounted it on a 12′ fiberglass push up mast. The feed line is made from 25′ of LMR-400UF coax. Several bungee cords are used to attach the mast to a fence post or other vertical structure.
The picture above shows the completed Go Kit in operation. We typically set one side of the Kenwood TM-D710GA to operate as an APRS transceiver and Digipeater and the other side to operate on a local repeater or simplex FM. The SignaLink sound card is used with a laptop computer running Fldigi and NBEMS for messaging applications. The iPortable case has a 13.8V lighter socket which connects to a power brick to power our laptop PC.
The Go Kit is quite portable when closed. All of the equipment and cable connections are enclosed and protected by the case’s removable end caps. We’ve tested our Go Kit during our club’s weekly repeater net and it worked great. The first real use of our new Go Kit will be at Field Day this year. It will be located in our public information tent and will be used as a “talk-in” system.
We decided to put up a third tower as part of our 2017 Field Day operation. The new tower will support a tri-band yagi and wire antenna for use by our Digital and GOTA stations this year. Our Field Day plans call for this tower to be located on the middle-level soccer field at the Hollis-Brookline High School. To overcome terrain limitations, we decided that our new tower should be a 60 ft setup.
The project began with some mechanical design and planning for a new, heavy-duty Falling Derrick System. Mike K1WVO, Dave N1RF and I secured the necessary materials and hardware to make the new Falling Derrick System.
The team in the two pictures above met at our QTH this past weekend to transport all of the equipment for the new tower to the high school for a test setup.
The first step in the test was to locate the tower base in the center of our test area and ensure that it was level. Steel stakes were driven and retainers added to secure the base to the ground.
Next, we assembled the falling derrick and the first section of the tower to the base.
With the Derrick in place, we assembled the remaining sections of our 60 ft tower on the ground.
WIth the tower, Derrick and base together; we carefully located and drove the steel stakes for guying the tower, the derrick and for anchoring the pulleys associated with the falling derrick system. With this done, we made up and attached two levels of guys between the tower and the anchor stakes.
The tower is lifted by two wire cables which run between the derrick and the tower. We made these cables up to length during our test session. Multiple cables are used to ensure that the tower is fully supported during the lift.
Here’s another view of the tower and Derrick prior to the lift. We supported the tower on a ladder to make the initial lifting easier. The ladder will also be needed on Field Day to allow our tri-band yagi to be installed on the tower prior to standing it up.
There is a considerable amount of rope that needs to be pulled through several pulleys to lift the Tower/Derrick system. The pulleys provide mechanical advantage and slow the lift rate to a safe level. We used a heavy-duty gasoline powered capstan winch to pull the considerable length of rope required to lift our tower into the full upright position
With our crew fully briefed on the process and safety procedures, it was time to lift our tower. The picture above shows the lift in progress. Our setup ensures that no one needs to be in the tower’s fall zone during the lift.
Here’s a picture of the tower after it was up and fully guyed. Our new heavy-duty Derrick system worked very well and lifting the tower was completed smoothly and safely with very modest effort.
After a few pictures, we took the tower down and disassembled it. We had quite a few members turn out to help us with our new tower test. Thank you to everyone who pitched in to make our third tower project a success! We are looking forward to using it during Field Day 2017!
Notice: falling derrick tower systems can be dangerous if they are not engineered, built and used properly by a well-trained team. The tower system described here is unique and is not a standard falling derrick system. Significant steps and material choices were taken to ensure the safe use of the system described here to put up our tower Time was spent to train the team who used the Derrick system to use it correctly and safely. We do not recommend the system here to others as the engineering, materials, and training required for its safe construction and use may not be readily available.