Dirty 30 Bicycle Race

Ionia County ARES / RACES group joined by many members of the RRA group and other area amateur radio operators, volunteered under the guide of the Ionia County Emergency Manager Sgt. Hoskins, Ionia County Emergency Coordinator Michael Carigon and Race Coordinator Raymond Passchier as communication assistance for the Dirty 30 Bicycle race on Saturday March 31, 2018 in Saranac Mi.
We had volunteers with their own communication equipment positioned throughout the course assisting in bicycle traffic and needs the bicyclist may have presented throughout their 14 or 30 mile race.
Thank you to all that helped out and volunteered! The whole event was a great success, everyone had a great time and we look forward to the next one!

Duplexer Tuning

After the club meeting on Tuesday March 13, 2018 we moved to Jay K8DC’s lab in order to analyze and tune Mike N8MRC’s mobile duplexer. We used a MiniVNA Tiny vector network analyzer to measure the duplexer’s frequency response.

The DUT (transmit) port of the analyzer was connected to the low-pass side of the duplexer on which the repeater will transmit, while the DET (receive) port was connected to the high-pass side on which the repeater receives. A 50-ohm dummy load was connected to the antenna terminal in the center.

The duplexer was purchased some time ago “pre-tuned” for the frequencies of Mike’s portable repeater but the frequency response showed relatively poor tuning of the cavity filters and an isolation of only about 55 dB.

Attendees were fascinated to watch Jay turning duplexer screws for what seemed like an eternity in order to optimize the resonant frequencies of the cavities. Shown here are Gene AB8KP, Robert KD8TOV, and Raymond KE8IUH. If you look very closely you can also see Mike N8MRC.

After a lot of trial and error, the final frequency response showed sharply-defined notches centered on the transmit and receive frequencies of the repeater. The attenuation was about 65 dB, which is a 10 dB improvement from where we started. This should reduce unwanted signal coupling from the transmitter to the receiver by about a factor of 10.


Fun and fellowship while advancing the radio art and providing service to the public.