[GCARC] Tech Saturday February 8 - DMR Topics

[Jon Pearce]

Tomorrow is NOT Tech Saturday - it's NEXT Saturday following the General Membership meeting. The Tech Saturday topic will be an intro to Digital Mobile Radio (DMR) , which is becoming more relevant to the GCARC for two main reasons - first, that the KD2LNB repeater on 440.10625 is being repurposed for DMR use (thanks to K2ZA and N3PUU) and second because lower-priced DMR radios are becoming available. When combined with Raspberry Pi-based hotspots in your home DMR can be a useful communications medium especially for intra-club communications. The materials for the session were developed by Len Rust W2LJR but unfortunately he's away so I'll be presenting them.

We'll get into the details of DMR at these sessions but there are two steps you might want to take if you want to get ready to participate. The first is to obtain one of the lower priced DMR radios that support the OpenGD77 ham firmware. Several of the these are available as listed below. The one that I chose is the TYT MD UV380 radio, which costs about $85 on Amazon. Its primary advantage is its low cost; however it doesn't have an internal GPS which makes using the satellite and APRS functions somewhat impractical. These radios need to be flashed with the OpenGD77 firmware, which we'll discuss at the Tech Saturday session, and we may hold an additional session dedicated to firmware flashing if needed. We can also have a session on programming those radios since DMR radios require additional parameters beyond those used by analog radios.

These radios can be used on the repeater and with the hotspots located at the Clubhouse, but the best functionality exists when you have your own hotspot. These devices run on a Raspberry Pi computer (a Raspberry Pi 3 works fine) with an MMDVM RF “hat” mounted on the Pi. They connect via radio to your DMR HT and to the rest of the world over the internet. The Pi computers are widely available including from Amazon, and the MMDVM hat that I purchased was the GOOZEEZOO MMDVM Duplex Hotspot Module Dual Hat from Amazon for $56. This is a "duplex" MMDVM hat that has several advantages over the "simplex" hat that we'll be discussing at the session. The Pi needs to run either the PiStar or WPSD application. If there's interest we'll run a Saturday session on setting up these hotspots.

If you're interested in getting started you may wish to purchase these items in advance of the sessions. DMR offers an interesting mix of RF and internet-based communication that allows even Technician licensees to "talk" to DX stations, albeit using the internet to make part of that connection. We hope to see many of you at the Tech Saturday session

73 de Jon WB2MNF

NXP MK22 CPU Radios:

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Radioddity GD-77
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TYT MD-760
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Baofeng DM-1801
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Baofeng DM-1801A
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Baofeng RD-5R / DM-5R Mk2 (Tier 2 version)
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Radioddity GD-77S / TYT MD-750

STM32 CPU Radios:

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TYT MD-UV380 / TYT MD-UV390 / Retevis RT-3S
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TYT MD-9600 / Retevis RT-90
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Baofeng DM-1701 / Retevis RT-84
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TYT MD2017 / Retevis RT-82