Before the flames get too high, Dstar is NOT for everyone. I don't use Dstar to work DX and would rather have a technical discussion with someone 10 miles away than exchange a 59 half way around the World during a contest.
However if you like radios, computers, the Internet and like to build, constructing your own Dstar repeater / hot spot can be very addictive! After finding out how easy it is, I built two more Dstar repeaters even though I don't have a location to install them at (yet).
Years ago I noticed Dstar but there was not any ICOM Dstar repeaters near me. Since the repeaters were thousands of dollars, there wasn't much chance any would be installed within range and certainly not by me! Then I discovered a small group of hams building their own non-ICOM repeaters for a fraction of the cost and performance was reported to be better. Now I was interested!
I should mention that I still had to invest in ICOM radios to communicate with the non-ICOM repeater I was building. Currently I own a IC-92AD (which is an outstanding HT) and a IC-2820H mobile radio. However presently there are a couple of projects being developed that will take the place of a ICOM radio.
Here is a picture of a Dstar UHF repeater I built using two Motorola GM300 analog mobile radios. The power supply is an Astron RS-20. A small duplexer is mounted above the radios. The small aluminum die-cast enclosure on top houses the StarBoard GMSK modem from MoenComm.
Here's a look inside the enclosure. I supplied the enclosure from some early projects and the modem fits nicely inside with room to spare.
The modem is the interface between the GM300 mobiles and the computer. It is connected to the computer with a USB cable and is also power from the same cable. A DB9 connector has the connections for the radio. Transmit data, discriminator data, PTT and ground. The modem board also has a few status LEDs to indicate power, receive and transmit conditions.
Since the GM300 is a commercial radio, it's transmit duty cycle rating is not very high and certainly not intended for the long transmissions heard on the ham bands! I do prefer the GM300 because Motorola designed a thermistor in the power amplifier that will decrease output power if the PA gets too hot. However I would prefer to keep the heatsink cool with forced air cooling and use the thermistor as a failsafe if the fan fails.
Here is my design for keeping the transmitter cool. I've used this design on several Echolink nodes over the years. And to date, they're all still in use. A snap disc thermostat is fastened to the heatsink with a small amount of heatsink paste for heat transfer. The thermostat closes around 110F turning on a cooling fan for the transmitter and the power supply.
Here is the other side of the radio stack showing the antenna connectors and 16 pin connectors bring signals from the GMSK modem.
If your the only ham in your area with a Dstar HT or mobile, building a repeater might not be the best solution. There won't be anyone to hear your repeated signal. Instead, remove one of the GM300 mobiles and the duplexer. Now you have a simplex Hot Spot and can use your Dstar mobile or HT within range of your shack. A DVAPis a similar product with only 10mw of output power. If this will cover your area of interest, go for it. Otherwise a Hot Spot can extend your coverage for a much larger area.
Here is a link for a great web page on building your own Hot Spot. There is also a link on that page telling how to convert to a repeater when more Dstar radios show up in the neighborhood.
Hopefully I have inspired some of you to find out what the DV (digital voice) mode is on your Dstar mobile or HT is for. You know the rig you only use on analog. Or maybe you do work a Dstar repeater in a neighboring city only to drive out of it's range when returning home.
Now you don't have an excuse when you drive out of range!
73's
Randy
randy at wb0vhb.com
However if you like radios, computers, the Internet and like to build, constructing your own Dstar repeater / hot spot can be very addictive! After finding out how easy it is, I built two more Dstar repeaters even though I don't have a location to install them at (yet).
Years ago I noticed Dstar but there was not any ICOM Dstar repeaters near me. Since the repeaters were thousands of dollars, there wasn't much chance any would be installed within range and certainly not by me! Then I discovered a small group of hams building their own non-ICOM repeaters for a fraction of the cost and performance was reported to be better. Now I was interested!
I should mention that I still had to invest in ICOM radios to communicate with the non-ICOM repeater I was building. Currently I own a IC-92AD (which is an outstanding HT) and a IC-2820H mobile radio. However presently there are a couple of projects being developed that will take the place of a ICOM radio.
Here is a picture of a Dstar UHF repeater I built using two Motorola GM300 analog mobile radios. The power supply is an Astron RS-20. A small duplexer is mounted above the radios. The small aluminum die-cast enclosure on top houses the StarBoard GMSK modem from MoenComm.
Here's a look inside the enclosure. I supplied the enclosure from some early projects and the modem fits nicely inside with room to spare.
The modem is the interface between the GM300 mobiles and the computer. It is connected to the computer with a USB cable and is also power from the same cable. A DB9 connector has the connections for the radio. Transmit data, discriminator data, PTT and ground. The modem board also has a few status LEDs to indicate power, receive and transmit conditions.
Since the GM300 is a commercial radio, it's transmit duty cycle rating is not very high and certainly not intended for the long transmissions heard on the ham bands! I do prefer the GM300 because Motorola designed a thermistor in the power amplifier that will decrease output power if the PA gets too hot. However I would prefer to keep the heatsink cool with forced air cooling and use the thermistor as a failsafe if the fan fails.
Here is my design for keeping the transmitter cool. I've used this design on several Echolink nodes over the years. And to date, they're all still in use. A snap disc thermostat is fastened to the heatsink with a small amount of heatsink paste for heat transfer. The thermostat closes around 110F turning on a cooling fan for the transmitter and the power supply.
Here is the other side of the radio stack showing the antenna connectors and 16 pin connectors bring signals from the GMSK modem.
If your the only ham in your area with a Dstar HT or mobile, building a repeater might not be the best solution. There won't be anyone to hear your repeated signal. Instead, remove one of the GM300 mobiles and the duplexer. Now you have a simplex Hot Spot and can use your Dstar mobile or HT within range of your shack. A DVAPis a similar product with only 10mw of output power. If this will cover your area of interest, go for it. Otherwise a Hot Spot can extend your coverage for a much larger area.
Here is a link for a great web page on building your own Hot Spot. There is also a link on that page telling how to convert to a repeater when more Dstar radios show up in the neighborhood.
Hopefully I have inspired some of you to find out what the DV (digital voice) mode is on your Dstar mobile or HT is for. You know the rig you only use on analog. Or maybe you do work a Dstar repeater in a neighboring city only to drive out of it's range when returning home.
Now you don't have an excuse when you drive out of range!
73's
Randy
randy at wb0vhb.com
