April 03, 2023

RCARC heads off to the races...AGAIN!

For the fifth year in a row, local radio operators supported the Resurrection Race this year in city of Henderson. The run, organized by a local church, offers runners a 5K, a 10K and a 1K fun run. The race route winds through a number of Henderson neighborhoods and parks. Rusk County ARC club members real-time updates along the race route along with general communication support and weather updates when severe weather threatens (as it did a couple of years ago). 

This year we had nine operators including our a GMRS user which marked the first time we have ever  deployed a GMRS unit in a public service event. The club recently put a GMRS repeater on the air locally and added a handful of club members who only operate GMRS. While our Net Control Operator (KG5IPO) primarily used the club's main ham repeater frequency, the back-up NCO (N5NDC / WREM784) monitored the GMRS repeater to relay reports to main net.

The race had nearly 100  runners on the 5k route and around 20 on the 10K path. Stations were deployed to major race turns where issues could (and have in the past) occurred. After the last runner past the station, the operator would generally redeploy to another point along the route or return to the HQ at the finish line. 

The operation was a success and race organizers were very appreciative of the group's service. "We couldn't do this race without you all," said Kayla Tillison, the race coordinator. "When all these runners are out on the route, your group's minute-by-minute updates gives us real peace of mind."


April 02, 2023

Choking out RFI on an EFHW antenna

(By Keith / KN5G) While the new End Fed, Half-Wave antenna has worked well on the HF bands I did notice that it had some RFI coming back into the shack and causing some issues with the USB cable’s signal between the computer and the radio. The EFHW antenna is an unbalanced antenna so it is normal to see some RF coming back down the outside shield of the coax towards the shack. 

The fix is a Common Mode Current Choke in the coax before it gets to the radio.

You can buy a CMC Choke but they are kind of expensive considering what they are made of and how simple they are to make. 

Here is one I built with a 240-43 Toroid core wrapped with 12 turns of RG58 coax. I need to put it in a box and solder the coax to the PL-259 connectors.

You can see from the VNA sweep that it has -36.4 dB of attenuation at the bottom of the 40 meter band which is pretty good. If I am not mistaken a 240-31 mix core would provide more attenuation on the higher bands, 20 meters - 10 meters.

Hopefully this will take care of the RFI issue I was seeing with the EFHW antenna.