FYI - GPS

UB3AYH
Posts: 2
Joined: Sun Jan 29, 2023 6:09 pm

Re: FYI - GPS

Post by UB3AYH » Sun Jan 29, 2023 7:30 pm

Good afternoon!
This post will be useful for those who want to install GPS without having it in their radio (TYT md-uv 380/390, rt3s)
I installed MD-UV 380 GPS in my tyt.
I want to share the process.
To install we need:
  • GPS Module (Atgm336h GPS)
    Radio Frequency Amplifier (AT2659)
    SAW FILTER FOR GPS (safeb1g57kdof00)
    Ceramic chip antenna with a frequency of 1575.42Hz
I used the antenna described in the post above, but installed it in its original place. The nominal size of the antenna is 16x6mm. The antenna described above has a size of 20x6mm, but it fits perfectly instead of the standard antenna.
On the board from the 20x6 antenna there is a radio frequency amplifier marked AL5 (AT2659DFN6) with a gain of 23 dB, I used it soldered to the place where it should be (MAX2659ELT 20.5dB).
SAW FILTER FOR GPS (safeb1g57kdof00) I did not solder, due to its absence (long delivery time), I put a jumper instead.
Well, the GPS module itself (JS-N 210) I ordered for aliexpress. I installed an analog (ATGM336H-5N-3X).
Works better than GPS on my second Retives RT3S radio.
Catches better indoors.
Sorry for the text, I used google translator.
73!

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P.S. If someone is interested in a 1.5 kiloohm resistor, it is needed for standard firmware or openGD77 firmware (Backlight "None" option), so that the screen does not completely go out.

CU7AAZ
Posts: 76
Joined: Sat Mar 26, 2022 8:13 pm
Location: Azores

Re: FYI - GPS

Post by CU7AAZ » Mon Jan 30, 2023 6:34 pm

EA5JAQ wrote:
Sun Jan 29, 2023 11:35 am
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
Thank you very very much for taking the time to document the whole process. As soon as I receive the antennas I'll be trying it and I'll post the results ;)

Thanks! 73
It is with great pleasure that I used this time.
I'm sure you will get good results.
It's a less complete solution, but it helps a lot.
Other colleagues have also posted excellent options, but I no longer touch my RT3S, it has already been opened many times heheheeh

Best 73s

BG9EGA
Posts: 9
Joined: Tue Jul 28, 2020 3:29 am
Location: Shaanxi, China

Re: FYI - GPS

Post by BG9EGA » Thu Mar 02, 2023 7:03 am

CU7AAZ and UB3AYH proposes the scheme is very exciting.
Thanks for sharing !
I used the antenna they recommended
Transform active antenna into passive antenna, installed on top of the radio.
Replaced with AL5 radio frequency amplifier.
Positioning can be completed within one minute after booting(Outdoor). Good results.
My english is not very good ;)
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CU7AAZ
Posts: 76
Joined: Sat Mar 26, 2022 8:13 pm
Location: Azores

Re: FYI - GPS

Post by CU7AAZ » Thu Mar 02, 2023 7:25 pm

BG9EGA wrote:
Thu Mar 02, 2023 7:03 am
CU7AAZ and UB3AYH proposes the scheme is very exciting.
Thanks for sharing !
I used the antenna they recommended
Transform active antenna into passive antenna, installed on top of the radio.
Replaced with AL5 radio frequency amplifier.
Positioning can be completed within one minute after booting(Outdoor). Good results.
My english is not very good ;)
Image

Image

Image

Image

Image

Image

Image
Excellent job!
The house for the new antenna was excellent :!:
I just had a doubt, did you remove the rf amplifier from the new antenna and put it on the radio pcb?
I'm happy with your results.
Thanks for sharing the mod

Best 73s
CU7AAZ

BG9EGA
Posts: 9
Joined: Tue Jul 28, 2020 3:29 am
Location: Shaanxi, China

Re: FYI - GPS

Post by BG9EGA » Fri Mar 03, 2023 2:14 am

CU7AAZ wrote:
Thu Mar 02, 2023 7:25 pm

Excellent job!
The house for the new antenna was excellent :!:
I just had a doubt, did you remove the rf amplifier from the new antenna and put it on the radio pcb?
I'm happy with your results.
Thanks for sharing the mod

Best 73s
CU7AAZ
Yes, I try to combine two schemes.
CU7AAZ wrote:
Tue Jan 24, 2023 8:55 pm
It's amazing. I want to alert friends that the antenna is active. This dear RT3S uses a passive gps antenna. But no problem, to make the work easier, I advise you to remove the pcb components and then connect the small coax directly to the (positive) of the antenna and of course not forgetting the ground.
I removed all the components on the back of the antenna according to your scheme, and got an AL5 rf amplifier.
Image
UB3AYH wrote:
Sun Jan 29, 2023 7:30 pm
On the board from the 20x6 antenna there is a radio frequency amplifier marked AL5 (AT2659DFN6) with a gain of 23 dB, I used it soldered to the place where it should be (MAX2659ELT 20.5dB).
Refer to UB3AYH's scheme to solder the AL5 rf amplifier to the PCB of UV380, replaced the original LY rf amplifier.

Image Image

VK3KYY
Posts: 7475
Joined: Sat Nov 16, 2019 3:25 am
Location: Melbourne, Australia

Re: FYI - GPS

Post by VK3KYY » Fri Mar 03, 2023 2:21 am

Could you also supply backup power to the GPS module, this would improve the time to achieve GPS lock considerably

Perhaps a resistor and a zener diode from the main battery or a low power 3.3V regulator, or perhaps a connection to the MCU backup/RTC battery

BG9EGA
Posts: 9
Joined: Tue Jul 28, 2020 3:29 am
Location: Shaanxi, China

Re: FYI - GPS

Post by BG9EGA » Mon Mar 06, 2023 3:52 am

VK3KYY wrote:
Fri Mar 03, 2023 2:21 am
Could you also supply backup power to the GPS module, this would improve the time to achieve GPS lock considerably

Perhaps a resistor and a zener diode from the main battery or a low power 3.3V regulator, or perhaps a connection to the MCU backup/RTC battery
I've done a lot of testing of new GPS antennas outdoors these days.
From power-on to successful positioning, it takes 40 seconds each time.
currently tolerable
It will be faster if supply backup power to the GPS module.
I just had a doubt:
Will the GPS almanac be kept forever if the power supply continues?
Will an outdated almanac affect GPS positioning?

VK3KYY
Posts: 7475
Joined: Sat Nov 16, 2019 3:25 am
Location: Melbourne, Australia

Re: FYI - GPS

Post by VK3KYY » Mon Mar 06, 2023 4:01 am

BG9EGA wrote:
Mon Mar 06, 2023 3:52 am
VK3KYY wrote:
Fri Mar 03, 2023 2:21 am
Could you also supply backup power to the GPS module, this would improve the time to achieve GPS lock considerably

Perhaps a resistor and a zener diode from the main battery or a low power 3.3V regulator, or perhaps a connection to the MCU backup/RTC battery
I've done a lot of testing of new GPS antennas outdoors these days.
From power-on to successful positioning, it takes 40 seconds each time.
currently tolerable
It will be faster if supply backup power to the GPS module.
I just had a doubt:
Will the GPS almanac be kept forever if the power supply continues?
Will an outdated almanac affect GPS positioning?
Normally GPS modules specify 1 second operation from warm start and much longer time e.g 40+ second for cold start

If backup power is supplied permanently then the almanac will be retained permanently however, the almanac will become more and more incorrect the longer the time before the GPS is run again, because the satellite positions do not follow the almanac exactly and the position error will integrate over time.

However if you use the radio once a day or perhaps once a week, the almanac data is received in the GPS signal, so it will always become updated.

kq4ehe
Posts: 2
Joined: Tue Apr 25, 2023 7:55 pm

Re: FYI - GPS

Post by kq4ehe » Tue May 16, 2023 2:35 pm

Thanks @CU7AAZ - I finished the antenna replacement on my RT-3S and MD-380g with success. The 380 is a little slower than the Retevis, but not a huge deal. Cheap and easy mod, I figured why not!

CU7AAZ
Posts: 76
Joined: Sat Mar 26, 2022 8:13 pm
Location: Azores

Re: FYI - GPS

Post by CU7AAZ » Wed May 17, 2023 9:44 pm

kq4ehe wrote:
Tue May 16, 2023 2:35 pm
Thanks @CU7AAZ - I finished the antenna replacement on my RT-3S and MD-380g with success. The 380 is a little slower than the Retevis, but not a huge deal. Cheap and easy mod, I figured why not!
Hi Kq4ehe,
Believe me, I'm very happy about it!
I really like helping, and then I know that good results have appeared.
Thank you for your message.

My last project for the RT3s GPS will be to apply the AL5 radio frequency amplifier, like the BG9EGA and UB3AYH did. also an excellent idea.

done this, changes in the gps part, for me case closed hehehehe

Big 73s
CU7AAZ

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