Ground Station Hardware

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This is the project management page for the Ground Station Hardware project.

Introduction & Project Outline

The EARS Satellite Ground Station project has been around for a couple of years. Originally conceived to support an experiment aboard one of the University's satellites (unfortunately the experiment didn't fly in the end), it has since grown to the point where we will be installing ground station equipment for 3 different bands (VHF, UHF and S-band) on campus.

The aim of the project is to install fully functioning ground station equipment for the following three amateur radio bands:

  • VHF - 144 - 146MHz
  • UHF - 430 - 440MHz
  • S-Band - 2.3 - 2.45GHz

If things go well, we also have the option of adding a bonus, transmit-only band:

  • L-Band - 1.2-1.3GHz

For our purposes, "fully functioning ground station equipment" means a highly directional antenna/dish mounted on a two-axis rotator, with sufficient transmit power to easily contact any satellite and sufficient receive performance to pick up weak satellite signals. The radio, rotator and other equipment needs to be fully computer controlled for remote/automated operation.

Current Status

The dish installation party, 26th October 2013

The S-band dish assembly was installed on the roof of Tillingbourne accommodation block, using the Yaesu G5500 rotator. The rotator was then verified to be working. Several months later when we finally got around to continuing work on the rotator controller, the G5500 had seized up and refused to move. The cause of this has been determined to be the weight of the dish assembly. Current status as of 24/11/2014, the dish has been removed from the mount and the G5500 is in the Shack, waiting to be replaced with the Emotator.
All of the remaining hardware and electronics for S-Band receive are in hand, the only thing thing it needs is some time and people to work on it (and possibly a bit of code written) and we can be up and running.

It's become apparent that we won't be able to mount the VHF/UHF antennas on the same stack as the S-band dish. We need to decide on the best location to site this, and get the paperwork rolling on it for an approximate installation date of April 2015.
We have ~80% of the necessary hardware for VHF/UHF receive and transmit in our possession. Some of the important bits of equipment need some work. A lot of progress was made towards VHF/UHF during the Summer Ground Station project, but parts of this need beefing up for higher transmit powers. We particularly need to look into the area of cheap high power RF switching.

S-Band Receive

The current priority for the project (Nov 2014) is to get the S-Band dish up and receiving signals from satellites (S-band transmit will have to be added at a later date once we source/make an appropriate amplifier). The ideal timeframe for this is before things break up for Christmas, but mid-February at the latest. - Due to loss of equipment (Emotator, frequency converters, lots of coax) this portion of the project is on hold until either funding or replacement equipment can be sourced. 24/09/2015

Block Diagram

S-band block diagram nov 2014.png

Block Status

Updated 24/11/2014

  • S-Band Dish
    • On the roof, waiting to be mounted on new rotator.
  • 2-Axis Rotator
    • Emotator is sitting in the Shack waiting to be weatherproofed (new connectors added?) and then mounted on the roof.
  • Rotator Controller
    • The emotator official rotator controller works fine and is ready to go. We also have a couple of the SSTL rackmount rotator controllers which need testing, but should also work.
  • Rotator Controller Interface
    • The one used for Summer Ground Station is now properly calibrated and works well enough to be installed without further work. Would be nice to completely rewrite the code at some point. If we want to use an SSTL controller, we'll need to construct a new one of these.
  • Coax Switches
    • Not necessary for receive-only operation. Will be sorted as part of the VHF/UHF research.
  • LNA (Low Noise Amplifier)
    • This is the one bit of kit we don't have. this looks like it has potential. Probably not necessary to get started, but we'll need this sooner or later.
  • Dish Mount Assembly
    • Been installed on the roof for over a year now, and is holding up to the weather fairly well. A few bolts need replacing with better quality/more rustproof ones, but not urgently.
  • S-Band Downconverter/Upconverter
    • We have about 5 of these now(!!), all from SSTL. We assume that at least one of them is fully working, but in order to test properly we need to sort out a way of doing the CAN control.
  • HPA (High Power Amplifier)
    • We don't have one, and don't have a source for one. We haven't looked, but buying one is going to be expensive. Due to the output power (or lack thereof...) from the upconverter, we can't transmit anything without an HPA.
  • Radio (Kenwood TS-970)
    • We have one, it's in fully working condition aside from a slightly dim main screen. It'll work perfectly for this, but it's far too nice a radio to lock in an attic and only be controlled by computer. Down the line/when we have money, this needs to be replaced by an SDR.
  • Radio Control Interface
    • We have one, it's been tested and works fine. Ready to go.
  • Radio Data Interface
    • Not sure how to spec this, depends on the type of data (if any) we're expecting to receive. We have at least one PacCom Tiny TNC packet radio modem in working condition we could use here if needed.
  • Servers
    • We have these in abundance! Have a dozen 1U IBM servers, dual quad-core processors with a bunch of RAM. They all need a hard drive or other storage medium and initial setup.
  • Network
    • This is tricky. Our previous VPN has had to be taken down, and any useful network connectivity is unable to happen pending a meeting with University IT.
  • Webcam
    • This is also tricky, due to rules about placing cameras in residential areas. We have all the equipment, it's just a paperwork issue again.
  • Anemometer
    • We have the hardware for this, but it needs some thought about how we're going to integrate it into the system. Not essential for initial receive stuff, but needs to happen sooner or later.
  • Cabling
    • Rotator cabling is installed on the roof along with a single Coax run. The Rotator cabling currently consists of 2x 6way cable one with 8.3mm diameter and one with 10.3mm diameter.
  • AC & DC Switching
    • Not strictly necessary for receive-only, but a nice to have - we need to set up a way of doing computer controlled AC and DC power switching so we can remotely turn bits of kit on/off. We have some nice APC controllable power strips which may be useful here.

Job List

A priority-ordered list of jobs which need to be done, and people currently working on them.

  1. Weatherproof and install Emotator rotator - the Emotator needs weatherproofing (particularly around the area which is missing a connector) and putting out on the roof. The dish assembly then needs to be mounted on it, and the whole stack needs some decent testing.
  2. Downconverter control & testing - The S-Band frequency converters need to be tested properly, and one selected for use. In order to do this, a functioning USB-CAN adapter needs to be created. (PH/JP - CAN adapter)
  3. Server OS install and software configuration - The server has been fitted with a HDD and Debian has been installed. Software configuration is still required. - JamesW (talk) 12:27, 12 February 2015 (UTC)
  4. 12V Power Supply - A 12v radio power supply needs to be tested.
  5. Rotator Controller Interface code - The code behind the rotator controller interface needs rewriting from scratch to create a fully featured, standardised EARS rotator controller interface program. See EG-RC1
  6. Anemometer - We need to think carefully about how this integrates into the system (its purpose is to command the dish to the home position if the wind gets too high), then build/program the system.
  7. AC & DC switching - This system needs building from scratch. We have some nice APC computer controllable power switches which may be useful here (we could mod one for DC?), however they need their firmware flashed before they're usable.

Finally, once items 1, 2 & 3 are complete we'll be able to proceed to a final install day. This will take place on a weekend, and we'll probably end up spending the entire day up at Tillingbourne installing all the elements and performing some initial testing.

CAD render of the proposed VHF/UHF stack on Tillingbourne roof.


The VHF/UHF bands (2m/70cm wavelengths) are a slightly longer term project, due to problems with the original plan for mounting the antennas a huge priority now, with a planned install date of the week preceding June 25th. Paniiiiic! currently being held up whilst paperwork is shuffled regarding the installation on Tilly roof, things are slowly progresssing as of December 2015.

Block Diagram

Vhf-uhf block diagram nov 2014.png
Green: Okay and working well enough that we could install and use it tomorrow if need be.
Orange: Some progress.
Black: No progress yet.

Block Status

CAD render of the proposed VHF/UHF stack on Tillingbourne roof, lowered position.

Updated 25/06/2015

  • 2m Yagi
    • We have this, it's currently out on the AA roof storage area. Works beautifully, ready to be mounted.
  • 70cm Yagi
    • We have this, it's one of those crappy French Tonna F9FT antennas. And therefore it needs properly tuning to be centred around the satellite portion of the UHF band, this can be done using a VNA from labs and re-drilling the driven element's mounting holes. It also needs to be made ready to be permanently mounted on a roof - all bolts need threadlock, and the middle join needs some glue (JB weld?) to stop it vibrating apart in the wind.
  • Polarisation Switchers
    • These exist in that low-power versions were made for the Summer Ground Station project. These need re-building in a format which can handle 400W RF power - progress on this project is linked in with progress on the RF switching solution (see below).We also need to work out a test method to fully verify they're doing what we think they are.
  • RF Switches
  • 2m LNA (Low Noise Amplifier)
    • We have one, it needs proper testing and maybe some weatherproofing.
  • 70cm LNA
    • We have one, it needs proper testing and maybe some weatherproofing.
  • 2m HPA (High Power Amplifier)
    • We have several in various power ranges. Currently our biggest one (500W) is on loan to the Space Centre as they blew theirs up, we've been promised this or an equivilent back in time for April to be installed. got blown up by the Space Centre whilst on loan and is currently with some EE lab techs to see if they can cable-tie two broken amps together to make one working amp. We have a variety of smaller amps, I believe there's a ~100W solid state somewhere which works okay but needs testing.
  • 70cm HPA
    • We have a couple of these, both valve amps. They need careful testing and evaluating which is the best choice. Some sort of remote operation rig needs to be created for them.
  • 2-Axis Rotator
    • This will be the Yaesu G5500 which we originally used with the dish. It is now fixed and good to go, aside from a quick application of sealant to the elevation unit.
  • Rotator controller/rotator controller interface.
    • The hardware is currently finished and tested and prototype software exists. The except requirements of serial interface need ascertaining so the code can be completed and tested - ideally a version of the EARS rotator controller code written for the S-Band controller. See EG-RC1 Page.
  • Servers
    • Server currently has an OS installed on it but needs the full suite of software put on it.
  • Network
    • We now hopefully have a slightly higher priority with Uni IT and can hopfeully get moving on bridging the Shack/Tilly networks.
  • Radio
    • The Kenwood TS790e is ready to go whenever. Only known problem with it is the backlight on the displays is a bit dim.
  • Radio control interface.
    • Control interface for the Kenwood has been tested and used working before, though with some slight doppler tuning issues which need investigating.
      • This appears to be a known problem with TS790s (odd considering it's made as a satcomms radio...):

Mods. to audio drop problem in 790 computer control. In computer control from rear ACC1 terminal,frequency setting command makes 10m sec.of audio drop(mute),and data collapse occur in PACKET operation. This problem is fixed by killing the blanking pulse to IF amp circuit. remove Q4(2SC2712) on IF unit and short the collector circuit to GND (R15 470 ohm).This mods. is essential for auto freq. control with KCT/Tuner for low orbit Packet satellite. (, more detailed procedure here:

  • Radio Data Interface
    • We have a few packet TNCs which are presumed to be working, but need testing and ideally someone to figure out how the hell you use them.
  • Mast Assembly
    • We have ~15ft of steel truss for this, plus hardware to mount it to a wall and have it hinge down. Use of this truss is based on finding new truss for the [[Moonbounce project][Moonbounce]] to replace this, though not a priority at the moment. Badly need to do loading calculations on the Tilly wall, particularly as the truss winches over. Also need to find a winch! A base plate for this to spread the load of the truss to the floor instead of the wall needs to be designed and fabricated (ie sent to Bob1)
  • Power Switching
    • Remote AC and DC power switching needs to be put in, particularly for making sure the valve amplifier is okay. We have some APC server rack power switch units for AC whihc need configuring and installing, presumably something similar for DC?

Job List

A priority-ordered(ish) list of jobs which need to be done, and people currently working on them.

  1. Secure a site for the antennas - PH working all out towards getting this sited on Tillingbourne at the moment. Things will hopefully be cleared with E&FM as soon as we can.
  2. Creating a full system spec and list of parts needing to be ordered - This needs to happen ASAP so we can order anything with a lead time on it.
  3. RF switching - We really need to find a cheap way of doing RF switching which can handle high power (~500W). Coax relays are available, but generally cost about £120 each and we need a fair few of them as you can see from the diagram. A promising option seems to be using PIN Diodes. We need to research this further, then buy a couple and make a test rig.
  4. Rotator controller/controller interface - The AC Rotator control hardware is currently finished and tested apart from acquiring a box lid. Software currently allows control of rotator from front panel and in theory from Terminal with go to ('w') command. To complete software regarded functionality needs to be ascertained - See EG-RC1
  5. Rotator - We need to fix the rotator and then ideally test it with the full antenna stack. - Aside from a bit of sealant this is done.
  6. 70cm HPA - We need to evaluate the 70cm HPAs we currently have, test them, fix any problems, and decide which one to use.
  7. Antenna polarisation switching - For the Summer Ground Station we made some polarisation switching boxes which were suitable for receive-only. Once a high power RF switching method has been found, we need to remake these to cope with full transmit power. We also need to give some more thought to a method to test their effectiveness.
  8. Server software install - The server needs various radio-related packages (hamlib, gpredict, etc) installed and configured.
  9. 70cm/2m LNA testing - We need to test (and possibly weatherproof) the LNAs for both 2m and 70cm. (SS amps tested to 60 and 85W, significant degradation)
  10. Packet TNC testing - We need to see what packet modems etc we have knocking about and work out how to use them, then set up for use with the server/radio.
  11. 70cm Yagi Alterations - We need to fine-tune the 70cm yagi and then beef it up for being in an outdoor environment 24/7.
  12. 2m HPA - We need to find the best 2m amp we currently have at our disposal and run tests on it.
  13. Kenwood Computer Interface - The kenwood radio->computer interface needs playing with a bitmore to see if we can eliminate the problems with doppler tuning.
  14. AC Power Switching - The APC server power units need playing with, and a solution for AC power switching needs to come out of it.
  15. DC Power Switching - Do we need a similar setup for remotely switching 13.8V DC? If so, design and make.

Shopping List

  • Relays (~25)
  • IP-rated box for polarisation switchers (tbd)
  • Chassis-mount N-type connectors (~20)
  • Cable-mount N-type connectors (~30)
  • PL259 cable-mount connectors (2)
  • BNC cable-mount connectors (2)
  • PCB-mount screw terminals (5 core)
  • 5-pin lego connectors (panel + cable mount)
  • 2-pin lego connectors (panel * cable mount)
  • Threadlock
  • JB Weld
  • Rotator Cable Arrived 29/06/15
  • Wall anchors (technical data)
  • Rotator sealant
  • Winch?
  • U-bolts 38mm

Minimal Install Reqiuirements

These are the absolute minimum things we need ready before we go for an install to support a single satellite (which is on 70cm uplink, 2m downlink):

  • Mechanical:
    • Truss
    • Wall Mount + appropriate wall anchors + truss mounting holes on lower bracket
    • Winch + cable
    • Rotator
    • 2m Antenna
    • 70cm Antenna
  • Electrical/RF:
    • Radio with PC control
    • 70cm HPA
    • 2m LNA
    • Rotator controler with PC control
    • Door interlock
    • Server with network connection and appropriate software configured
    • Rotator cable and connectors
    • RF coax
    • Polarisation switchers
    • Radio data interface (soundcard or TNC)

Ready In progress


For bonus fun, once the VHF/UHF stack is up and working, we can add an L-band antenna!

Block Status

Updated 24/11/2014 (See VHF/UHF for block diagram)

  • L-Band Helical
    • We have it, it's somewhere in Tillingbourne. Needs testing.
  • HPA
    • We might have one, if so it needs testing. If not, one needs to be found/bought/made.
  • Upconverter
    • We need to find/buy/make one of these.

Job List

None at the moment, plenty of other things to be doing!