John's Meanderings

I have been interested in D-STAR for a number of years and finally took the plunge in 2007 and bought my first D-STAR radio. It is an Icom IC-91AD and I still use it today as my handheld connection to the D-STAR network.  Since that time, I received a very nice Icom IC-2820H mobile radio and recently purchased an ID-880H for use at the desk here in the ham shack.

During my whole D-STAR journey I have been intrigued with the software/networking side of things and have studied the various applications that others have written and have goals to write some myself.  To that end I am the gateway administrator for a D-STAR repeater system in Bellevue, WA, owned and operated by the Lake Washington Ham Club.  This repeater system is a very high end system and sits atop a 42 story building.  Consequently, it is a resource for both casual amateur radio use and for two ARES (emergency communications support teams).  This is probably not the best place to experiment with new software designs that may take the repeater(s) down.

There is a growing community that has started building D-STAR compatible devices using GMSK modems, called “node adapters.”  These devices typically connect to a computer using an USB cable and provide GMSK modulation and demodulation when connected to the discriminator and modulator of a true FM radio, as well as detecting signal presence and providing transmitter keying when there is data to go out.  I purchased one of these “node adapters” several months ago and have been playing with it, using various radios available around the shack.

I have never had an interest in owning my own repeater, but I got a hankering to build up a repeater to support my experimentation.  With the help of a friend who is in the commercial 2-way radio business, I was able to purchase a used Kenwood TKR-820 UHF repeater with a duplexer.  I wired the node adapter to its accessory plug and after a few adjustments and tweaks have a fully operational, albeit low power and short antenna, repeater that talks the D-STAR protocol using GMSK on an FM carrier.  It is fully compatible with commercially produced D-STAR radios.

It is on the air, from my garage, on 440.0125 mHz. with a plus 5 mHz. receiver.  Even at its low power and without the antenna mounted high above the ground it is still usable for a couple of miles around as I drive and have friends with higher home antennas who have been able to talk through it from a couple of towns away in Brier and Whidbey Island, WA.

In future posts, I will describe, in greater detail, the steps to create a similar repeater.

This entry was posted on Thursday, June 17th, 2010 at 22:10 and is filed under Amateur Radio, D-STAR. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.