Quectel UC20-E 3G Mini PCIe module interfering a lot on VHF marine radio!

I’ve been working on a project for some time now, and just noticed that the Quectel UC20-E 3G Mini PCIe module what I’m using in a GL-MiFi board is interfering a lot (and I mean a lot) on the VHF marine radio here on the boat.

It’s so bad that only very strong VHF radio stations are being received!
(VHF radio is NOT usable this way!)

I 1st thought that it was the VHF radio (an Icom), and got it tested. No problems with it.
Replaced the antenna did also not fix it the problem.

I than decided to shutdown everything, except the VHF radio, and the VHF radio worked again as it should!
After this I turned on one device at a time, and discovered that the GL-MiFi was the cause!
After some more testing I removed the Quectel UC20-E 3G Mini PCIe module, and found that this was the main cause.

The GL-MiFI is mounted in a polyester dome on the same mast as the VHF marine radio antenna (about 6ft apart).
Moving it any further is not possible.

Any suggestions on how to fix this problem?

from wiki, VHF radio is working in 156.0 and 162.025 MHz. Seems this is very different from UC20’s frequency. Maybe the module emit unexpected radios. Need to check the modules’s CE/FCC test report if there is any information about this.

One method could be use metal shield to cover the UC20 module inside the case and use external antenna for 3G. But this must be careful.

Maybe you can try a different module.

Thank you for the info.

When I am home again I will make an aluminium case/shield for the GL-MiFi and will see if this will make any difference.
Obviously I will leave both WiFi and 3G antenna outside the case.

Will report back when I know more.

I’ve done some “RF” shielding experimenting, and it does seem to work!
As mentioned before… I’m at the moment on a boat, and material being available is limited.
All I had at hand here was a “painters” can, and after drilling some holes in it (one for the UTP cable and one for the GSM antenna) I mounted everything on the mast again (as test)

Well… The VHF radio signals are now received way better, but I can still hear signal differences when the Quectel UC20 is powered on or off.
When I’m back home I will do some propper RF shielding and do some more testing.

Will keep you guys updated.


Did some more testing, and discovered when putting the GL-MiFi on separate power supply (ie: another 12 volt car battery > 5 volt) will kill all the interference!

Basically I have one big 12 volt car battery supplying all the needed 12 on the boat.

All equipment (VHF / TV / Navigation, power inverters to 220 volts / 5 volts and in this case networking) are connected to it.
Doing this is asking for interference trouble :-/

I’m now looking into getting RFI / EMI filters to see if I can still use it this way. If not I will need to get a separate 12 volt battery or start using 220 volts with the usual 5 volt USB transformer to power the GL-MiFi.

Will keep you updated.


maybe you can use a better AC/DC power adapter. Seems the power is not stable, making the UC20 working not good.

The needed 5 volt DC comes from the 12 volt DC by making use of a voltage regulator, so I do not think changing the AC/DC converter will make any difference.

At the moment I’m doing some testing with EMI filters between the 12 volt input’s, and they do seem to filter some of the noise.