Tuesday, September 18, 2018

Getting Ready for Action on Digital Radio

After rigorous testing, the Galway DMR Repeater, on 70cms, and the 2 Metre Multi mode Digital Gateway are ready for re-siting to their high spot on the west side of the City in the first week of November 2018. 

The Gateway was placed under test last November, 2017, and has withstood 24 hour operation since without any software crashes. The Gateway has operated on Yaesu Fusion and DMR although there is a possibility of D-Star and P25 further down the road.

The 70cm DMR Repeater was procured in May and has undergone tests throughout June but was off air due to the EI5DD annual holiday to the UK. The repeater is now back on air as of mid September with a review of Parameters and is undergoing a soak test until it is ready to go on site. The antenna system will be a vertical co-linear for the 70cm repeater and a folded dipole for the 2 metre Gateway.

Aengus, EI4ABB, kindly tuned up the cavity filter shown below in situ. Due to the 50% duty cycle of a DMR transmission the Procom filter is not subjected to too much heating from the transmission. This in turn does not cause drift making life much easier than on an analog system with full duty cycle which generally renders this type of cavity filter unsuitable.

In amongst the items collected over the years, a fine ABS case, just the perfect size to house the equipment was found.  EI3IS, made a shelving unit suitable to accommodate the gateway with a fan underneath to cool the Motorola GM 350 transceiver for the Gateway. 

A seen above,  this is is nice and compact and saves a lot of carrying around. There is adequate cooling on the heatsink of the repeater and operation at 40 watts will not stress the P.A. The Gateway will run at 20 watts on 2 metres on both DMR and Fusion. 

The Gateway operates on Slot 2, colour Code 1 and the EI Talk Groups 2722 and 2723 are static which means any activity on either channel will be retransmitted.

The Repeater will work on both Slot 1 and Slot 2, Colour Code 1. Both time slots can operate independently and simultaneously. Effectively this is two repeaters operating from the same box so becomes great value for money.

Both systems will be connected via Ethernet cable to a Three Mobile 4G Router which is more than adequate for the amount of data usage. 

Full control of the Gateway is possible through a remote connection and it is even possible to update the pi-star software by this means. 

The repeater power is controlled by a GSM switch, see below, to power it on or off in the event of any hang up or failure. On switch on. the Repeater will automatically re-boot. So far it has not been necessary to do a reset. 

Whilst DMR and digital radio is in its infancy in Ireland, it is necessary to get the infrastructure up and running to facilitate newcomers to the hobby. Galway currently has ten operators with DMR equipment and eleven Yaesu Fusion operators. Hopefully there will be more interest with the new facilities available. 

A second DMR Repeater has been procured to be located in the middle of County Galway which will considerably enhance the total DMR coverage in both the County and neighbouring counties. The facility to roam between the footprints of both repeaters will be possible allowing seemless operation between both. 

There are currently two DMR repeaters in the Waterford area with the possibility of a third in the near future. Galway will eventually have two. There are applications for a DMR repeater in hte Mullingar area, Dublin and possibly Dundalk.
The Mayo area will be setting up several low lying installations on air to cover a wide area of their county so the West of Ireland will see plenty of activity  over the next year.

Note that TG 2724 is linked from DMR to Yaesu Fusion so those wh o do not have Fusion equipment can access the DMR system and those on DMR will be able to communicate with Fusion users.