Since 1993, CCARS have been providing 2-way radio communication support for Mon Sheung Foundation during their annual fun walk(fund raising) event. We faced a serious challenge this year since the route was changed from that of previous years. As seen in the map below, the route(orange line) starts from Baycrest hospital, goes north on Bathurst until reaching entry of Earl Bales Park (200m south of Sheppard). It then goes downhill which is a steep drop of over 100m and extends into the valley underneath Sheppard. These areas are mostly hidden trial surrounded by dense forest until the route reaches end point at Bathurst Jewish Center.

As compared to walk route in recent years that mostly circled inside side streets east of Baycrest, this is the longest route we ever encountered. What makes it worse is the terrain blockage at Sheppard. High buildings there plus a hill top position seriously attenuate signal between end point and start point area. As we tested, UHF transmission from a 2 watts hand held at end point can't even be heard at Wilson.

As we learned from past experiences, and at the request of Mon Sheong Fun Walk organizers, our team's primary function is to monitor and report on walk progress and safety of the participants. In fact, just a few minutes after the start of the walk, we were requested to issue an All Point Bulletin for keeping an eye out for an 86 year old elder who apparently got separated from her escort. Our team's secondary function is to provide reliable 2-way radio communication support to Mon Sheong's organizers located at the starting point and the end point. In order to provide a stable and clean communicating media, we immediately agreed that deployment of a temporary repeater system for this event would be necessary. We knew we are able to set up temporary short range UHF repeater system as we have done in the past by using two mobile stations operating in cross band repeat mode. This set up forms a "split site repeater system" which doesn't need to employ expensive and bulky cavity filters. As long as the two mobile stations are placed 400m apart, desensitization is not a concern even if standard 5MHz frequency offset between transmitter and receiver is applied. Unfortunately, even such support is insufficient for what we are facing this year.

Repeaters only repeat what they hear. They cannot improve quality of poorly received signal. We must have good quality reception from users at both north and south area. To make it simple - to support weak (100mw grade) transmission or in-house portable transceivers, receive unit serving them must be placed within 1km range from the worst scenery area. One single common receive unit simply can't satisfy reliable pick up of both area! But it is equally difficulty to place multiple repeater units due to limitation in frequency resources and equipment.

After spending some time in searching for locations that meet the above criteria, we suddenly realized that users don't really need to be operating as repeater access. We can place both mobile repeaters at optimal spots of both ends with a change in frequency plan. Both units can be programmed to operate on different simplex UHF(traffic) channels but carries the same VHF(link) channel. Their prime duty is limited to pick up users close to them while the received signals are relayed to the opposing mobile unit (via VHF). The signal will then be re-transmitted on UHF channel of the other zone. We assigned a control operator at both mobile stations to assume manual control if required. Users in the same zone are close to each other and don't need radio enhancement anyway. Traffic from both zones is thus transparent to each other. They can talk on their assigned area frequency and can hear users from the other area. They might not even notice that some of the transmissions are from a repeated environment.

Followed two separate site tests and with a short meeting before D-day, all involved members received their assignment. We showed up on site at 7:30 a.m. for a coffee break, job finalizing and activation of the temporary repeater. By 8:00, all assigned stations were in position and functioning. The team served the activity until noon.

Minor losing of contact did occur between some low powered portables located inside the building with the southern mobile unit. This problem could be solved if we place the south zone repeater closer to start point. But that might degrade quality of the VHF link channel between both repeaters (which will have more severe impact to the overall performance). This compromised set up worked out very well in general. No serious drop out or loss of message was experienced throughout the whole operation.

Thanks to all participating members who made this day yet another success for "CCARS serving the Community".