Saturday, August 24, 2019

Satellite Station 4.0 Part 9 – Upgraded Simple Portable Station AUGUST 20, 2019 BY FKEMMERER

We were up on Mt. Washington here in New Hampshire this past weekend and we decided to use the SOTA activation as a test for our updated Portable Satellite Station 4.0. It turned out that the station was also a great SOTA and Grid Square Activation station for terrestrial contacts.
An upgraded Portable Satellite Station has been part of our 4.0 Satellite Evolution plan from the start. The goals for the station included:
  • Support for FM and Linear Satellite Contacts
  • Computer Control to handle Doppler Shift
  • A simple, easy to deploy portable antenna system for 2m and 70cm
  • Full-Featured 100w/75w Transceiver with External Preamps for good weak-signal performance
  • Quite, Green Power using Solar Energy and Batteries

Station Components

Our upgraded portable station uses the following components:

Portable Antenna System

Elk Antenna on Tripod
We decided to keep our antenna system simple and quick to deploy. We choose a portable 2m/70cm antenna from Elk and mounted it on a camera tripod. A carpenter’s slope gauge is used as an elevation indicator and our iPhone serves as a compass to point the antenna in the azimuth direction. A weighted bag, Bungie cord, and a tent stake anchor the tripod in the windy conditions on the mountain. A 15 ft length of LMR-240uF coax with N-connectors make the connection between the antenna and the rest of the station.

Station Transceiver and Supporting Gear

Portable Station Transceiver and Preamps
We decided to mount the station Transceiver and supporting gear on a piece of plywood to make it easy to transport and setup. The components from lower-right moving counter-clockwise include:
The preamps are powered and sequenced by the IC-910H through its coax outputs. The 70cm side of the second diplexer is used as a filter to prevent transmissions on 2m uplinks from de-sensitizing 70cm downlink signals.
Portable Station Electronics
The use of the mounting board for all of the components allows the station to deployed quickly and helps to ensure reliable operation.
We used a MacBook Air Laptop running MacDoppler to control the transceiver’s VFOs (via a USB CI-V cable). MacDoppler also provided azimuth and elevation data used to point the antenna during satellite passes.

Portable Power

Portable Solar-Battery Power System
Powering a 100w radio in a way that allows continuous use for a day can be a challenge. It’s important to do this in a way that that does not generate noise so we do not disturb others trying to enjoy the outdoors. We met all of these needs using a combination of solar power and batteries.
Portable Solar Power
The primary source of power comes from a pair of 90w foldable solar panels from PowerFilm. The panels are wired in series and connected to an MPPT Charger which charges a pair of batteries. This approach allows the system to provide usable power when it is cloudy and the voltage output of the solar panels drops.
We use a pair of A123 10 Ah LiPo battery packs to supply high-current capacity when transmitting. The solar-battery combination is capable of maintaining full battery voltage while supporting the continuous operation of our station for a full day.
The MacBook Air Laptop batteries are adequate to operate the station during the available satellite passes. We have a 12V DC to 120 VAC inverter which can power the computer from our solar battery setup if needed.

Station Performance

View from Mt. Washington Summit
Our portable station did very well during its initial test! I had to move the antennas and operate the station by myself on this activation which limited my ability to make a large number of contacts during the limited number of satellite passes that were available. Still, I was able to make 6 solid contacts through AO-91 and AO-85 while on Mt. Washington. I did not have a suitable linear satellite pass to make contacts but I was able to hear the EO-88 beacon with no problems and confirm that the doppler correction system was working well.
The station also put in a great performance visa-vie 2m terrestrial contacts. We made a total of 70 contacts using 2m FM and USB! We received many good signal reports with our longest contacts being some 275 mi from our location. We also worked stations on four other SOTAs this way.

Learnings and Next Steps

Our station exceeded my expectations during our initial test on Mt. Washington – especially in terms of the number of Terrestial Contacts that I was able to make with it. I did notice that the transmit side of the system was quite a bit stronger than the receive side. This is an indication that a better antenna would help.
We changed the antenna polarization to vertical for 2m FM contacts and to horizontal for 2m USB contacts. This helped the receive side performance quite a bit.
I found that a headset was essential for satellite and terrestrial weak-signal operation in USB mode. I was able to use the hand microphone and the radio’s speaker for most of the 2m FM contacts that I made. This gave interested onlookers a chance to experience Amateur Radio.
Satellite operation would have been much easier and more productive with a helper to handle pointing the antenna while we operated. This improvement will need to be coupled with a headset/speaker combination that allows the person pointing the antenna to hear the quality of the downlink while moving the antenna and finding the best polarization.
I am looking forward to doing some grid-square activations using our upgraded portable station. It was a pleasant surprise to find as much interest in Terrestial contacts on the 2m band as we did. The Nashua Area Radio Society does several SOTA activations each year and I am looking forward to using that station for these as well.
Here are links to some additional posts about our Satellite Station 4.0 Projects:
Fred, AB1OC
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