CC2650STK: Problem with using an external antenna

Pascal Jeworek59

Part Number: CC2650STK

Hello,

I´m using the SensorTag board right now and wanted to test a external antenna of mine.

Below is a part of the sensortag schematic. I just removed the 0 Ohm resistor ANT5 and changed the coaxial switch J1 with an JSC connector.

I thought i would be done with it and the PCB antenna wouldnt be in use anymore. As it turns out the with no antenna connected (external) and the resistor removed i still get a signal on my phone (via the starter app for the sensortag). So somehow the antenna is still working. For further testing it is obviously quite hard to determine which antenna im measurring.

Does anyone have a clue what i did wrong? Do i even have to remove the ANT6 capacitor? Or something else completly?

Btw. the JSC connector is solder on correctly i did a few conductivity tests.

Many Regards,

looking forward for your good answers

over 8 years ago

0 Fredrik K over 8 years ago

TI__Guru** 106705 points

Hi Pascal,

Even without an antenna connected, there will still be some radiated power coming from the rest of the RF network. This is sufficient to establish communication over (very) short range.

Cheers,
Fredrik

0 Pascal Jeworek59 over 8 years ago in reply to Fredrik K

Prodigy 30 points

Hi Frederik,

thansk for your reply.

I had a signal about 1-2 meters away from the sensortag. So i guess thats the rest of the radiated power.

But is there any way to test an external antenna with the sensortag? or do i just have to believe that the new RSSI the app shows me is purely the new antenna connected?

0 Fredrik K over 8 years ago in reply to Pascal Jeworek59

TI__Guru** 106705 points

Hi Pascal,

Yes, a few meters makes sense.

Unfortunately, the only good way to measure an antenna is to use an anechoic chamber. Without access to that, you can do range testing outdoors in an open area (field, parking lot, etc). When getting more than a few meters away it is safe to assume that all power is radiated through your antenna.

Cheers,
Fredrik

0 Pascal Jeworek59 over 8 years ago in reply to Fredrik K

Prodigy 30 points

Hi Frederik,

allright. But in general i made the right move with removing the 0 Ohm resistor and changing the switch with a connector obviously? or is there something else i would have to do? i read in othere topics for other boards that you would have to change some capacitors aswell but i did not saw anything in the schematic that would hint to that.

0 Fredrik K over 8 years ago in reply to Pascal Jeworek59

TI__Guru** 106705 points

It seems like you have done everything right!

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CC2650STK: Problem with using an external antenna