OpenGD77

DL1GG wrote: ↑

Wed Jul 17, 2024 8:57 am

Hey guys,

I have two units of Retevis RT3S, both were sold to be w/ GPS, same firmware setup.
While one unit gets a fix within a reasonable amount of time, the other gets absolutely nothing (same device positioning).
Is there a way to check, if there is a GPS module really build-in and operating?
Or should an error be reported by the firmware anyways, when trying to activate it in the menu?

I like the idea of that antenna mod. I should try that as well indeed.

Manuel



PS:

The forum search does not work well. I entered "problem with gps" and it says "The following words in your search query were ignored because they are too common words: gps problem with.". Kinda senseless.

SA0BUX wrote: ↑

Wed Jul 17, 2024 9:08 am

You can set the GPS to output NMEA on the programming cable.
As you can set GPS to "on" , the GPS module isn't totally dead but it can a bad connection to the GPS antenna.

SA0BUX wrote: ↑

Wed Jul 17, 2024 9:08 am

It's only possible to set GPS to "on" if NMEA data is detected by the OpenGD77 firmware when you power on the radio.

VK3KYY wrote: ↑

Mon Sep 18, 2023 5:04 am

AliExpress has the same antennas

https://www.aliexpress.com/item/1005004218247122.html

I have used them and they work OK.

For anyone who wants to fit a GPS inside their radio

These modules are very small and should fit in the RT3S and GD77 etc

https://www.aliexpress.com/item/32764345698.html
(The option called "GP-02" NOT "GP-02 Kit")

I have some of these and they are compatable with the firmware

These also work with the firmware

https://www.aliexpress.com/item/1005001704030454.html

But they are too large to fit inside any radio except the MD9600, because the have a battery and this makes the module too thick

OK1TK wrote: ↑

Thu Jul 18, 2024 5:51 am

VK3KYY wrote: ↑

Mon Sep 18, 2023 5:04 am

AliExpress has the same antennas

https://www.aliexpress.com/item/1005004218247122.html

I have used them and they work OK.

For anyone who wants to fit a GPS inside their radio

These modules are very small and should fit in the RT3S and GD77 etc

https://www.aliexpress.com/item/32764345698.html
(The option called "GP-02" NOT "GP-02 Kit")

I have some of these and they are compatable with the firmware

These also work with the firmware

https://www.aliexpress.com/item/1005001704030454.html

But they are too large to fit inside any radio except the MD9600, because the have a battery and this makes the module too thick

Hi guys, I am trying to find the 28dBi antenna but without success. I found this one and assume it might also work and looks bit smaller: https://fr.aliexpress.com/item/3303194 ... Redirect=n

I received my RT3S yesterday and switched to opengd77. From my balcony I got 4 bars (metal concrete building) so I will test it outside today but because the main purpose I bought this radio is for salellites I assume the GPS Md would be needed.

I have also TYT MD-390 Plus 10W on the way and would like to ask what is the experience with its GPS ?

CU7AAZ wrote: ↑

Fri Jan 27, 2023 10:47 pm

Hello everybody,

In the link there are some tips for those who want to try to mount a new GPS antenna on the RT3s.

https://drive.google.com/file/d/1qomyZf ... sp=sharing

Some pictures with higher resolution
https://drive.google.com/file/d/1-G001m ... sp=sharing

I hope I have contributed something useful

Good tests and good Qsos
73s

py2pcr wrote: ↑

Tue Jul 02, 2024 9:35 pm

UA0LMC wrote: ↑

Sun Jan 01, 2023 11:30 pm

UA0LMC wrote: ↑

Mon Dec 19, 2022 7:12 pm

Now I'm working on the mod to at least keep the almanac until the radio is on. Will write a post about it if/when I finish.
There are some PCB design flaws which make it a little harder to do than I thought.

DISCLAIMER: this mod requires some fine soldering.
I performed this mod and tested it on my radio - but your radio is only yours. Do it at your own risk.

What it does:
It keeps GPSr Vbackup powered all the time the radio is on - thus retaining the almanac regardless of GPS on or off state. This mod significantly speeds-up the re-acquisition when re-enabling GPS.
Also it allows some kind of GPSr Eco-mode as hot-start is now supported - but it's up to developers whether it will be implemented in software or not.

What it does not:
It does not speed-up the first acquisition. Also it does not improve overall GPS reception.
It won't retain the almanac when the radio is powered off. Using the onboard RTC battery for GPSr backup is impractical as GPSr will drain it in 3-4 days. Adding a separate stand-by power supply was considered too difficult for most of the users to implement it.

OK, so what do I need to do?
0. Open the radio, locate the GPSr module on the front panel PCB.
1. Remove the resistor and cut two traces along the red lines.
2. Connect two yellow dots with a thin wire jumper (preferably PTFE-insulated).
3. Connect two blue dots the same way.
IMG_20221221_141223_1.jpg

First, sorry for my poor English...
And thank you very much for the idea!!!! If you have any opinions, I would like to hear them!!!

I am testing this configuration. When I open my RT3S again, I will take some pictures. Now I am trying a micro battery, the same as the RTC, but I am waiting for the new battery (LIR2025 rechargeable from Aliexpress) to arrive.

I think this little bat will be OK if I turn on the radio once a month.

The diode is CUS08F30, which I think retains only about 0.4V or less...

This diode is to be able to recharge the battery when the radio is on. When the radio is off, this GPS will "eat" only 11uA from the battery. In 30 days, it can "eat" 7mAh, and the LIR2025 has about 30mAh. I think these are good numbers.

OK1TK wrote: ↑

Thu Jul 18, 2024 6:46 pm

CU7AAZ wrote: ↑

Fri Jan 27, 2023 10:47 pm

Hello everybody,

In the link there are some tips for those who want to try to mount a new GPS antenna on the RT3s.

https://drive.google.com/file/d/1qomyZf ... sp=sharing

Some pictures with higher resolution
https://drive.google.com/file/d/1-G001m ... sp=sharing

I hope I have contributed something useful

Good tests and good Qsos
73s

Hi, looks like the first link doesn't work anymore. May I ask you if you can share the guide again, please ?
Thank you Tomas