By David (VA7SZ)

Summary

Backup batteries that were already on site were wired in parallel and connected to a pair of programmable chargers. In the event of a power failure at EGO, these batteries will power the VHF and UHF repeaters for several days.

EGO’s repeaters can be turned on and off remotely via a microcomputer connected to the Internet. This is necessary in case a repeater malfunctions or needs a reboot. The repeaters automatically default to 12Vdc if 110Vac fails so we need the ability to switch off the new battery supply as well. Relays were installed and wired to the microcomputer to allow both mains and battery to disconnect.

It had been known for some time that the VHF repeater wasn’t performing well and this fact alone may be partly responsible for its lack of use. Simple diagnostics indicated the duplexer was badly out of tune and so we removed it for tuning. For now the VHF repeater is off but the UHF repeater is not affected. Hopefully we will be back on site with the retuned duplexer before it snows.

Site Visit

Paul fixes EGO's door

The team consisted of Mike (VE7KPZ), Terry (VE7TRZ), Paul (VE7KWA) and David (VA7SZ). We assembled at the gate at 10 am. David left his car at the gate and got a ride up the hill with Mike in his Unimog, while Terry and Paul came up in their 4X4 vehicles. The track isn’t in great condition and the final steep section isn’t for the faint hearted. If either the vehicle or the driver isn’t up to it there is parking at the ¾ point followed by a ten-minute hike up the steep section.

The shack door was hard to unlock and open but Paul fixed it using a pneumatic die grinder, with compressed air supplied by the Unimog. Inside was free from rodents but there were many “stink bugs” and lots of dust and dirt. Mike had brought his shop-vac and over the course of the day the shack was thoroughly cleaned.

A few years ago, Terry put together the hardware and programmed the Raspberry Pi microcomputer to perform some tasks and monitoring. Shack temperature is measured and the Pi switches a fan on to cool things down in the summer. It also monitors a door switch to alert us to unauthorized entry. The Pi’s main function is to turn off power to either or both of the Yaesu Fusion repeaters in case of malfunction. This has been needed from time to time when the operating software crashes. More important, no one wants spurious output from a broken repeater getting into the nearby vital infrastructure communications, so we need the ability to shut either repeater down immediately if there is a problem.

Paul installed two relays, controlled by the Pi, one for UHF and the other for VHF. Pairs of isolated contacts on each relay switch both the 110V and 12V lines.

While Terry figured out the Pi side of things, Paul and Mike worked on component layout for the 12V system, and then started wiring things together. Six lightly used, 12V, 102Ah AGM batteries had been donated to the club, along with two programmable chargers. All measured between 12.6 and 12.85V before installation.

Terry works on the Pi while Paul installs a battery charger

The batteries were wired in parallel and a Victron “Smart BatteryProtect” was installed in line to disconnect the load when the battery voltage drops below a set value – in our case we chose 12.3V. This will prevent damage to the batteries from over discharge, which would reduce their operational life. We also chose 12.7V as the reconnect value, allowing some battery recovery once charging recommences. The batteries will also be disconnected immediately the voltage exceeds 16V, in the unlikely event a charger malfunctions. “Smart” means these parameters can be set by a cellphone app, which also gives a readout of battery voltage.

The elegant new battery installation

A quick scan of the VHF repeater’s duplexer and antenna, using a power meter and antenna analyser, convinced us that the duplexer was the source of the repeater’s poor performance. It was removed for retuning

It was a successful day, and we enjoyed amazing fall weather. It had also been a long day, as we all finally made it down to the gate at 5 pm.

Future Projects

The interior of the shack is now clean and tidy. However, the coax exiting the shack to the tower is a mess with some of it on the ground where it can be trodden on and damaged. It would be nice to make a bridge from the tower to the shack to carry the coax.

A non-commercial antenna for the UHF repeater is mounted on a short pole near the tower and this should be replaced by the robust, commercial two-bay antenna, which is already on site. This will require some planning and tower climbing – perhaps a project for next year.

Terry is planning to use the Pi for remotely measuring battery voltage, which will give us a heads up to potential problems. 

The duplexer needs to be retuned and reinstalled. 

We need a folder on site that has all the relevant manuals, and schematic diagrams showing the systems we have developed. We also need proper labeling of wires and coax to avoid confusion and potentially expensive mistakes.

 Looking west from EGO - there are magnificent views in all directions