OpenGD77

Guauuuuuu, beautiful, nice, amazing...... and the wire where is soldering? Is it a normal wire?

eb4adc wrote: ↑

Sun Jul 21, 2024 10:41 pm

Guauuuuuu, beautiful, nice, amazing...... and the wire where is soldering? Is it a normal wire?

It is soldered to the antenna pad (input).

Thanks¡¡¡¡ I'm going to make the mod as soon I could.

eb4adc wrote: ↑

Mon Jul 22, 2024 10:37 pm

Thanks¡¡¡¡ I'm going to make the mod as soon I could.

I'm not an expert in SHF antenna design, but it looks like, unless you use a small piece of coax, you are using a semi-random length of wire as the antenna, and the braid at the end may not be doing anything special, except perhaps operating parially has a capacity hat.

VK3KYY wrote: ↑

Mon Jul 22, 2024 11:59 pm

eb4adc wrote: ↑

Mon Jul 22, 2024 10:37 pm

Thanks¡¡¡¡ I'm going to make the mod as soon I could.

I'm not an expert in SHF antenna design, but it looks like, unless you use a small piece of coax, you are using a semi-random length of wire as the antenna, and the braid at the end may not be doing anything special, except perhaps operating parially has a capacity hat.

I used two active antennas with the gp-02 module and neither had good results, one of the antennas did not receive any satellite signal. I had to solve the problem in an artisanal and empirical way, starting from the idea that our hobby (amateur radio) is an experiment... The antenna that comes with the gp-02 is passive and not active, which is why I used a small short wire and a mesh to serve as an antenna. The small wire that also serves as an antenna added to the coaxial mesh, which in addition to helping with reception, has capacitive interaction with the equipment structure (HT) favors better reception. It was the best way found to obtain the best satellite signals in non-ideal conditions.

BH7PUE wrote: ↑

Tue Jul 02, 2024 2:11 am

Follow the instruction to test my GD77 for add GPS module?finally succeed~~

I used a GPS module call GT-U7 for test. It's too big.But it can tell me if I succeed or not.

And I use a N-MOS to switch GPS module ON/OFF.

Hi BH7PUE, do you have the number for your N-MOS? My knowledge about Mosfet is equal to zero. If you have any recommendation that should be great. I'm looking at SI2300 on e-bay, but it seems to be for 12V applications. Is this a good candidate?

Thanks, for the diagram.
Charlie,

With GP-02 kit you can use 3.3 regulator onboard to ENABLE/DISABLE power to GPS module.
I made this in my gd77 and works perfectly. Even without cutting pullup resistor on 3.3 regulator on gp02 kit board. CPU in gd77 have enough power to pull down "enable" leg in this regulator.

SQ1TAO wrote: ↑

Sun Mar 30, 2025 8:56 pm

With GP-02 kit you can use 3.3 regulator onboard to ENABLE/DISABLE power to GPS module.
I made this in my gd77 and works perfectly. Even without cutting pullup resistor on 3.3 regulator on gp02 kit board. CPU in gd77 have enough power to pull down "enable" leg in this regulator.

Thank you for coming back. Do you mean I can connect pin 97 (Power control) from the MCU directly to Vcc on the GP-02 Kit?

KA1CM wrote: ↑

Sun Mar 30, 2025 9:23 pm

SQ1TAO wrote: ↑

Sun Mar 30, 2025 8:56 pm

With GP-02 kit you can use 3.3 regulator onboard to ENABLE/DISABLE power to GPS module.
I made this in my gd77 and works perfectly. Even without cutting pullup resistor on 3.3 regulator on gp02 kit board. CPU in gd77 have enough power to pull down "enable" leg in this regulator.

Thank you for coming back. Do you mean I can connect pin 97 (Power control) from the MCU directly to Vcc on the GP-02 Kit?

IMG_2055.jpeg

You should measure the actual current taken by the GPS module, because the Maximum current from a single pin on an official STM32 is 25mA.
You should also measure any transient current spikes.
There is also a maximum total current from all pins, which I don't know off the top of my head.
i.e you can't take 25mA from all pins as that would overload the whole CPU.
Albeit I don't think any of the other pins is likely to be loaded with more than a few mA, but we don't know this for sure.

I had a quick look at the online references / data sheets for the GO-02, but the current consumption seemed to be different in the various data sheets that you can find.

I'm also slighly sceptical about the claimed current consumption of 25 or 30mA

You should measure this youself and make sure you are confident that you won't be overloading, the pin, as if you blow that pin, it can take out other pins at the same time and potentially make your radio useless, as it won't work if any of the CPU pins stop working.

Can this RD5R be retrofitted?73