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August 6, 2022

The Magical Mythical Radioddity GD-77

—A review by Kevin Grantham N5KRG

  At a recent club meeting we were entertained by Clint Bradford, K6LCS, from AMSAT. During the presentation he mentioned the Yaesu FT-60R as being capable of working the “EasySats” or FM amateur radio satellites. Because they are not full duplex, they aren’t ideal.

  Dale Finley KB5NFT, sent me a text message describing the Radioddity GD-77 that features some amazing satellite capabilities. He suggested I get one; he ordered one and so did I.

Radioddity GD-77

  The base radio is around $100 new but is currently sold out. Nevertheless, I snagged an open box for about $85. These are DMR and FM dual band and sort-of-dual-receive. The magic sauce is an open-source software project from They have reversed engineered the radio and are offering free replacement firmware for the GD-77 as well as other models.

  The new firmware does a couple of things. It removes all the Part 90 commercial folderol found in most DMR radios and makes it much easier to program but it also adds “Satellite Mode.”

  With a click of a button on the programming software (aka “CPS”) you can fetch the latest orbital parameters for the ham satellites as well as the International Space Station and push them into the radio. When you start up the radio, you enter the date, time (in UTC or local time zone) and your decimal latitude and longitude.

  The radio calculates then displays a list of the next satellite passes. When you select one it shows where in the sky you will be able to acquire the satellite, the compass direction and shows a track, and it shows the time it will rise above the horizon and then set.

GD-77 screen 2.jpg
GD-77 screen 1.jpg

  It is very cool and Dale made about twenty contacts in short order with the unit he used at the Philmont Scout Ranch.

  This is identically the same HT as the Baofeng DM-1801 (version 1) and a TYT machine. There is also a firmware version for the Baofeng RM-5R and some clones but they lack a couple of features the GD-77/DM-1801 offer.

  The bad news is that the DM-1801 has had a hardware revision and will not work with the new firmware. If Radioddity gets any more GD-77 units in they may have the new processors and boards and may not work either. If you want to play, get an older DM-1801 or a GD-77 if you can find them.

  —73 Kevin

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