Paul Butzi |||

Marathon Support

Yesterday I spent about half my day doing communications support for the Tunnel Marathon. Race support seems like a fine alignment between my running and amateur radio interests, so I suspect I’ll be doing this more in the future.

Other than some stations having difficulty hitting the W7PSR repeater that was being used, the 70cm radios everyone was using seemed the perfect way to communicate between the race start, race finish, and the various aid stations as well as mobile units used for sweep and mobile aid.

Naturally this has me thinking hard about how to improve the ability to hit the repeater. The basic problem is that although the course is monotonically descending at a gentle slope, it threads that easy descent in between some pretty major hills/mountains in the Issaquah Alps. That makes for serious line of sight problems.

The difficulty is that the usual tricks to raise signal levels at both ends - more power and better antennas - are of limited use.

It’s possible to put more power at the aid station. Raising the power from the typical 5W a HT will put out to the 50W a mobile rig would put out buys you 10dB more signal at the repeater. But that doesn’t improve things in terms of receiving the repeater on the HT at the aid station.

You can improve the antenna situation at the aid station as well. Moving from the usual 0dBi rubber duck antenna on a HT to something better would help both directions. Even just hauling a ladder line J pole up 15-20 feet into a tree would improve things considerably - the J pole doesn’t offer much more gain but the elevated antenna would help quite a bit. Picking any decent dual band mobile antenna or a Comet GP-1 would buy you 5-6dB, and be even better if you could get it up in the air a fair bit.

But I am thinking about whether clever siting of a cross band repeater might be just the ticket. Even just turning on a crossband repeater in the parking spot for the aid station might well help quite a bit.

Up next NVIS presentation I’ve been asked to do a presentation on NVIS and NVIS antennas for the Microhams club. Since I’ve had further thoughts on how to improve my NVIS antenna thinking After giving my newly revised presentation on NVIS propagation and NVIS antennas last night I was left unsatisfied with the last part of the
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