Radioddity GD-77
FAQ Frequently Asked Questions
New user to 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.
OK, I’ve checked all that, and I’m still not hearing any DMR transmissions. What
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,
you have your DMR configuration wrong.
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!
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 newer versions of
firmware, 2.6.7 and later, there is a bug that the reset sometimes doesn’t quite
refresh the memory properly; indeed a reset on later versions of firmware may even
induce new problems. To get around this problem, downgrade your firmware to
V2.6.3 first, then do a memory reset. As part of the reset process you may
see ’Factory init’ depending on how corrupt the memory had become. After
resetting under firmware version 2.6.3, you may like to load a simple codeplug to
test that the problem you were experiencing has been cleared. After that, upgrade
your firmware to your desired version, and finally re-send your codeplug back to the
GD-77 using the correct version of CPS that matches the firmware version.
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.
There are some bugs in the current V3.0.6, and if you find you can’t live with those
bugs, then version 2.6.6 is often preferred. 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.
Is there a list of bugs somewhere?
Not that I know of. I keep my own list, which currently has one critical, four medium
and four low priority bugs.
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:
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
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.
I have a Baofeng programming cable. Is it compatible with the GD-77?
No, it’s not.
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.
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
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.
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.
Is the GD-77 compatible with DMR Tier 3 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 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
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 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 voltage didn’t remain
perfectly constant on their charger base.
I have a Baofeng / Kenwood / other speaker microphone, will it work with the
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-8 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.
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. If those two solutions don’t work, then it’s a return to supplier,
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. I think that’s a hardware fault with the audio amplifier, but
no-one seems to have gotten to the core of that particular problem yet. Might be
best to return the radio to the supplier in this instance.
© Copyright Jason Reilly, 2018
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