Radioddity GD-77

FAQ Frequently Asked Questions


New user to the GD-77? Got a question you can’t find the answer to? Have a look here


My GD-77 won’t hear anything (analogue FM channel) even though the green LED is lit up?

The green LED doesn’t necessarily mean sound should be coming out of the speaker, it merely indicates that some sort of RF signal is on the frequency. It may or may not have matching CTCSS / PL tones. This is probably the reason why your GD-77 has remained silent - you’ve set an incorrect CTCSS / PL tone. Perhaps you don’t even need one at all?

My GD-77 won’t hear anything (DMR digital channel) even though the green LED is lit up?

The green LED doesn’t necessarily mean sound should be coming out of the speaker, it merely indicates that some sort of RF signal is on the frequency. Check that you definitely have the correct DMR colour code, correct timeslot and correct talkgroup programmed in to the channel. Unlike other DMR radios you may have been used to, the GD-77 absolutely requires a RX group list to be attached to each and every DMR channel. If you leave it set to ’none’ then nothing will be received.

The green LED is lighting up, shouldn’t I be hearing something?

The green LED doesn’t necessarily mean sound should be coming out of the speaker, it merely indicates that some sort of RF signal is on the frequency. On an analogue channel, there could be a signal with a CTCSS / PL tone that doesn’t match. On a DMR channel, it could mean another talkgroup or other timeslot is active, or even idle DMR data being transmitted will cause the green LED to light up.

Still not hearing any DMR signals. What do I check?

If you have, at any time, imported new digital contacts you must then go through and rebuild anything that makes use of the digital contacts. The software doesn't prompt you to do this, but you will have to rebuild your RX Group lists (which is why you don't hear anything after importing digital contacts) and re-enter your digital contact for each DMR channel.

OK, I’ve checked all that, and I’m still not hearing any DMR transmissions. What next?

Some people have reported success with the ’monitor’ function. You need to program one of the buttons for the monitor function, and then when on a DMR channel press that button. A solid black speaker symbol will appear to indicate that the monitor function is on. If this works however, it’s a sure sign that, somewhere, your DMR configuration isn’t quite right.

Nope, still not hearing any DMR transmissions. Anything else to try?

Yes, there’s two things you can try at this stage. First, see if there’s anyone else nearby who has a GD-77 working correctly and borrow their codeplug. Second, and as a last resort, perform a factory reset (below) and program a very simple codeplug to prove that it will receive a DMR channel. Then slowly build up your configuration from there.

My GD-77 is doing funny things eg: no transmit on any frequency / signal meter randomly goes full scale even though there is no signal genuinely present / other general strange issues. Help!

Cautiously try a reset (below) and then try a very simple codeplug. Many strange issues seem to stem from having a large codeplug, created bit by bit, added to ad-hoc etc. While in theory it shouldn’t be a problem, frequently it does lead to strange things happening. Often the solution is to start fresh and write a new codeplug from the ground up.

How do I do a reset on the GD-77?

Page 67 of the user manual says to hold down side key 1 (the black button underneath the PTT) and keypad button 1 while turning on. You’ll be greeted with ’Memory Reset?’ and to complete the process you have to confirm by pressing the green button. Don’t turn off the radio while it’s resetting. In some versions of firmware, between 2.6.7 and 3.1.1, there is a bug that the reset sometimes doesn’t quite refresh the memory properly; indeed it could even induce new problems. There is a way to correct it if you do face this problem, see my alignment page at:

Radioddity GD-77 Tuning & alignment project

How do I do a reset on the GD-77S (no keypad version)?

First turn the top selector to channel 16. Turn off the radio. Press and hold down the small black button below the PTT and the small top panel orange key, and turn on the radio. When the top panel LED turns to yellowish-green colour, you can let go of the buttons. Wait until LED stops flashing, then turn off radio, and turn back on again. Reset is now complete. No need to reprogram the radio.

How do I load new / upgrade / downgrade firmware versions?

Assuming you’ve downloaded the firmware package which includes the PC executable loader software and the firmware .sgl image, you need to connect your programming cable and hold down the two side keys underneath the PTT while turning the radio on. The screen of the GD-77 will be all blank and the top panel LED will glow green, indicating it’s ready to accept a new firmware image. It doesn’t matter if the firmware image is older or newer, it’ll accept it without problem so whether you are updating or downgrading, it doesn’t matter, the process is the same. Note that you don’t need to press & hold these two side buttons for normal CPS software programming, just plug in the programming cable, turn the radio on and program away.

What’s the best firmware version to use?

Generally, the later the firmware version, the more features you will have available. The most current official version is V3.2.1 which is stable and reasonably bug free. I have no doubt that Radioddity will iron out all the bugs eventually, and for that reason you should keep an eye out for later versions as they are released.

Where do I get newer (or older) versions of CPS software or firmware?

You can go to the Radioddity web page, click on the Support tab and then look for GD-77 software in there. Or, you can also find these at the Radioddity Facebook support web pages.

I heard it was best to use certain CPS versions with certain firmware versions. What are those versions?

It's not only good, in some cases it is absolutely vital to use matching versions. Here's a list of matching firmware to CPS software versions:
GD-77 and GD-77BB
Firmware earlier than 2.5.6 = CPS software 1.1.2
Firmware 2.5.6 = CPS software 1.1.4
Firmware 2.6.1 = CPS software 1.1.5
Firmware 2.6.3 = CPS software 1.1.6 and 1.1.7
Firmware 2.6.6 = CPS software 1.1.8 and 1.1.10
Firmware 2.6.7 = CPS software 1.1.12
Firmware 2.6.8 = CPS software 1.1.13
Firmware 2.6.9 = CPS software 1.1.13
Firmware 3.0.6 = CPS software 2.0.5
Firmware 3.1.0 = CPS software 3.1.0
Firmware 3.1.1 = CPS software 3.1.1
Firmware 3.1.2 = CPS software 3.1.1 (no change to the CPS for this firmware)
Firmware 3.1.3 = CPS software 3.1.1 (no change to the CPS for this firmware)
Firmware 3.1.5 = CPS software 3.1.1 (do not use unless you had problems with the GD-77 transmitting well off frequency)
Firmware 3.1.6 = CPS software 3.1.1 (no change to the CPS for this firmware)
Firmware 3.1.7 = CPS software 3.1.1 (no change to the CPS for this firmware)
Firmware 3.1.8 = CPS software 3.1.1 (no change to the CPS for this firmware)
Firmware 3.2.1 = CPS software 3.1.1 (no change to the CPS for this firmware)

There are also two versions of a 3rd party software called the GD-77 Community Edition CPS, one that is compatible with firmware 3.1.X and one that is compatible with firmware 3.0.6

GD-77S (no keypad model)
GD-77S firmware first version matches with CPS software versions 1.1.4 and 1.1.7
GD-77S firmware version 1.2.0 matches with CPS software version 1.1.10

When trying to read or write to the GD-77, I get an error message ’model does not match.’ How can that be fixed?

You might see this message if you use the wrong CPS version with the wrong firmware version. Make sure you’re using the correct version of CPS software to match the firmware version first. If you are sure the CPS version is correct, you may need to uninstall and manually delete any remnants of the CPS software and re-install it.

You will also see this message if you try loading a saved configuration file or codeplug that was made with an older version of CPS software. The best solution is to start your codeplug from scratch, this will make sure any problematic residual data from your old codeplug that may have crept in over time is eliminated. Alternatively, you can let the new version CPS software read what it can from the GD-77 and then fill in any missing information required (typically could be RX Group Lists, everything associated with Scan Lists, and perhaps your Digital Contacts)

Where can I get a codeplug for [insert your city / region here] ?

You can try your local radio club, or try the Radioddity Facebook support page, check the files area. You might get lucky. Otherwise, you’ll have to do the hard yards yourself by making your own codeplug.

So how do I program the GD-77 for DMR channels?

If you are looking for a quick guide on how to program the digital channels for your Radioddity GD-77 (or RD-5R), take a look here: (1.1 Mb)

I have a Baofeng programming cable. Is it compatible with the GD-77?

No, it’s not. In fact, use of a Baofeng USB cable with a GD-77 may even damage your PC USB port.

My computer won’t connect to the GD-77. Any hints?

The programming cable can be a tight fit into the speaker microphone sockets. Make sure the cable is firmly seated in the socket.
You can also try a different USB port on your computer. I have one USB port that refuses to work for any USB radio programming no matter what brand of radio is being used, but that same port works fine for a USB memory stick. On some computers you’ll need to use the same USB port that you used the very first time you successfully communicated with your GD-77.
You should also connect to the USB first with the radio turned off, then turn on the radio.
Others have reported success with using a powered USB hub to get Windows to detect the GD-77 when connected.

Is the CPS software compatible with Apple Mac or Linux?

No, though it reportedly works under PC emulation for those platforms.

Some menus and other items are greyed out in the CPS, and I can’t change them. What gives?

Early versions of software had a basic and advanced user mode, the default was basic. To switch to advanced, you hit Ctrl-Shift-Alt-F11 or Ctrl-Shift-Alt-5 and enter the password DMR961510

The software won’t install, my computer’s antivirus says it’s infected. What now?

That is a so-called false-positive. The software is fine, it has been proven harmless by thousands of users worldwide. You can safely instruct your antivirus software to make an exception for it, or disable the antivirus software if an exception can’t be made.

The software won’t install, I get a ’side by side’ error. How do I fix it?

You need to find and run vcredist_x86_208.exe which will fix that up.

Is the GD-77 waterproof / water resistant / shower proof?


Why can’t I scan? It says ’Scan fail’

If you have ’double wait’ set to ’double’ then you can’t scan. Another possibility is that scan hasn’t been set up properly. You need to nominate each channel to scan in a scan list, and also nominate which scan list a channel should belong to in the channel settings itself. This sounds like it’s a bit of doubling up, but is necessary to ensure scan works correctly. Finally, the last thing to confirm is that you have selected a channel that is a member of the scan group to commence your scan on.

My GD-77 is displaying strange characters on the display, it looks like Chinese. How can I switch it back to English?

There's three ways you can do this:
1) First try resending a saved codeplug to the GD-77
2) If that doesn't work, then using CPS software version 1.1.2 (the only version that enabled selection of language) enter advanced mode by the Shift-Ctrl-Alt-F11 or Shift-Ctrl-Alt-5 keyboard combination and enter password DMR961510. Then go to the Menu selection in the CPS and on the right will be a language selection, select English. Then write this to the GD-77 (no need to downgrade firmware version). After this, confirm your GD-77 is back to normal and reload your usual codeplug.
3) And if those don't work, try loading firmware version 2.6.3, reset the GD-77 and write a simple codeplug with CPS version 1.1.6 or 1.1.7 to the GD-77.

What do all the icons on the top line of the display mean?

The following guide from Radioddity should help you.

Oooh, that black screen in the picture above looks nice. How do I get that?

This is a special version of the GD-77 with a different LCD screen, called the GD-77BB. There's no setting in the software to change the screen like this, you have to buy the GD-77BB to get it.

Why can’t the GD-77 receive two frequencies at once? It shows two frequencies in double wait mode so it should, right?

Sorry, wrong. Just because two frequencies are displayed doesn't automatically mean the GD-77 has the ability to receive two frequencies at once. It can strictly only receive one at a time. In double wait mode, it quickly toggles receive between the two displayed frequencies or channels, just as if it were scanning them. But the GD-77 definitely is not able to receive two frequencies at once.

Is the GD-77 compatible with APCO P-25, NXDN, D-Star, Fusion, TETRA, etc?

No, it’ll only do plain analogue FM, narrow and wideband, and DMR Tier 1 and Tier 2.

I hear some radios are not fully DMR compatible or won't work on *both* timeslots or ’steps’ on the other timeslot when transmitting. Is the GD-77 one of those ’bad’ radios?

The GD-77 is genuinely fully compatible with DMR, can work on both timeslots just fine, and doesn’t step on the other timeslot. It's a ’good’ radio. NB: early versions of Radioddity GD-55 had some of these issues, but the GD-77 is definitely fine.

Is the GD-77 compatible with DMR Tier 3 / Connect Plus or Capacity Plus systems?

No. However, since the air interface for digital voice is common between Tier 2 and Tier 3, you can at least listen in on a Tier 3 / Connect Plus or Capacity Plus system. You’ll have to find the frequencies used by that system manually, and scan them as if they were individual DMR channels. It’s messy, but it sort of works.

When using a speaker microphone, my transmitted audio in FM is good, but sounds horrible in DMR mode. What’s going on?

DMR transmissions are pulsed RF, which are very prone to causing interference to other devices. In this case, the pulsed RF is getting in to your speaker microphone audio. A good quality speaker microphone, designed for DMR radios, is the solution. Alternatively, you can modify your existing speaker microphone with a RF decoupling capacitor directly across the microphone insert and adding an inductor in line with the microphone insert to keep the pulsed RF interference in check.

What’s this ’promiscuous mode’ and how do I use it?

Promiscuous mode, or ’monitor’ mode is a feature on DMR where the radio will hear all talkgroups on the current timeslot / colour code DMR transmission, whether you have those talkgroups programmed in your GD-77 or not. You MUST have the timeslot and colour code correctly programmed in for this to work, though. To activate monitor mode, you have to program one of your buttons for the monitor function. Then, select a DMR channel and press the monitor button, a solid black speaker will appear in the display to confirm monitor mode is active. At this point, any talkgroup on that channel will be heard. You can commence a scan of memories and the monitor mode will stay active, even though the speaker symbol will disappear at times while scanning across analogue channels.

Can I re-program the top orange button for something else other than an ’emergency’ feature?

You sure can. There’s no restriction at all with reprogramming that button.

Can the GD-77 be programmed with out of band frequencies?

Yes it can, but that will obviously negate it’s FCC Part 90 approval. It shouldn’t be used for out of band transmissions. The process to get the software to accept out of band frequency entry will require a little bit of technical know-how with a process called hex-editing.

How far out of band can the GD-77 go?

Not too far. Generally you should expect 130-180 MHz, 195-285 MHz and 390-520 MHz.

Does that mean the GD-77 can work on 220 MHz / 1.25 meters?

For receive only, yes, with reduced sensitivity, around 5uV for 12dB SINAD. Do not try to transmit here, the GD-77 will not put out much power in that band, and will be very rich in unfiltered harmonics. You may even damage the electronics in the GD-77.

Can the GD-77 receive the FM braodcast band eg 65-108 or 76-108 or 88-108 MHz?

No, the GD-77 lacks the necessary hardware to do this. In other similar radios that can receive the FM broadcast band, they use a custom FM band circuit to do this, and the GD-77 does not have this circuitry

Can I use another power supply, like my shack 13.8 volt supply, to power the GD-77 charging base?

Yes, you can, but check the voltage the charger base is going to deliver to an inserted battery first. The charging base should regulate the voltage to a steady 8.4 volts, and I found that an input voltage anywhere between 10 and 16 volts was acceptable on the many chargers I’ve seen, but some others report the 8.4 volts output voltage didn’t remain perfectly constant on their charger base.

I have a Baofeng / Kenwood / other speaker microphone, will it work with the GD-77?

If it fits in the speaker microphone socket of the GD-77, then it most likely will work. Just bear in mind the issues with DMR transmissions and pulsed RF getting back into the microphone; some microphones are better than others for this.

I connected my GD-77 to an external base station antenna. All the received signals disappeared! Why?

The GD-77 uses a SDR based receiver, and it’s a bit sensitive to overloading with too much RF. With traditional superheterodyne receivers, overload is observed with all sorts of interference being audible. On the other hand, SDR receivers simply shut down until the overload condition is removed.

Another receiver here picks up all transmissions, but the GD-77 is ’slow’ to hear them, is there a problem?

This is likely due to the battery save features of the GD-77. When the battery saver is working, the receiver goes to sleep, periodically waking up to check for any activity and then going back to sleep. That can delay the detection of a wanted transmission. Turn off battery saving options if this bothers you.

Where can I get a soft protective carry case for the GD-77?

No case has yet been made specifically for the GD-77, but the Retevis RT-3 / RT-8, TYT MD-380 / MD-390 and TYT MD2017 cases are supposed to fit very well.

Can I get spare batteries?

Depending on where you are, maybe. Sometimes you can get spare batteries on their own, other times you have to purchase them with your GD-77. It seems to depend on where you live, probably due to postal restrictions for sending just a lithium-ion battery on its own.

What’s normal behavior for the battery charger base?

With nothing in the charger base, there is a green LED lit, you can ignore that. When you put your radio, or just a battery, in the charger base, the LED turns red to indicate charging. Once the battery is charged, the LED will turn green. If your charger base doesn’t turn red when you drop in a battery, it means that either the charger base or the battery is faulty.

Can I use the GD-77 while sitting in the charger base?

For receive, yes. There have been some reports that RFI or noise from the switch mode power supply will mask weak signals, especially on VHF. You should not transmit on the radio while it is charging, even briefly. One user has reported that while pulling the radio out of the charger base, he accidentally hit the PTT. The transmitted RF was suspected to have gotten back into the charger circuitry and caused the charger base to become faulty. Also be aware that while the GD-77 is turned on while in the charging base, the charger LED will never turn green (fully charged)

When I turn on the radio, it beeps and makes all the right sounds, but there’s no display. It worked fine yesterday. What can I do?

There’s two things that people have done to help fix this problem. First is to do a factory reset and reprogram the GD-77 to clear the problem. The second is to open up the radio and clean and reseat the ribbon connector that connects the main radio to the front display. That requires a very gentle touch to do, but no other specialist electronic knowledge is needed. All you have to know is that there is a little ’collar’ that holds in the ribbon cable to its connector, and that you use a fine jeweler’s flat blade screw driver to flip up the retaining collar by its side ’ears’ to release the ribbon cable. Clean the ribbon cable by gently wiping it, and then firmly reinsert it to the connector and flip down the collar to retain it again. Repeat for the other end of the ribbon cable.
You can find more information at the bottom of this page: GD-77 Modifications
If those two solutions don’t work, then it’s a return to the supplier, unfortunately.

Can the start up picture be changed? The CPS help window mentions a 128 x 64 black and white bmp format picture, suggesting that you can load your own?

Sorry, it appears as if the ’picture’ - in reality it is just a scrolling 'welcome' plain text message - is fixed in the firmware and can’t be changed or customised. You can change this to a start up text message ’char string’ and customise that message, however.

There’s a soft audio whine coming through the speaker with any received transmissions, most noticeable with the volume turned all the way down. As the volume is increased, the whine fades into the background. It also isn’t heard when using a speaker microphone. Is that normal?

No, that’s not normal. This issue seems to have been resolved at the factory some time ago now. On the slight chance you are having this issue with a brand new radio, it might be best for you to return the radio to the supplier in this instance. Otherwise, if you are handy with a soldering iron, replacing one SMD resistor will fix the issue. You can find more information at the bottom of this page: GD-77 Modifications

Some other useful links

Absolute beginners guide to DMR

GD-77 Tuning & alignment information

GD-77 Modifications

© Copyright Jason Reilly (SK), 2018, 2019 does not claim ownership or intend to infringe any copyrights. This is mirrored here in effort to preserve the information due to the author's death.