Sim900D , unusally low resistance between antenna & ...

tariq7868

New Member

• Mar 23, 2011

• #1

Hello,
I just bought Sim900D and i am getting very low resistance between the Antenna pin (33) and Ground pins, i.e it seems that antenna pin is shorted with ground, is it normal or my module damaged ???


Thanks

 

MikeMl

Well-Known Member

Most Helpful Member

• Mar 23, 2011

• #2

95% of the transmitters I have ever played with have what looks like a dead short (as measured with a DC Ohmmeter) from the center pin of the antenna connector to the coax shield (ground).

 

tariq7868

New Member

• Mar 24, 2011

• #3

Oh, ok thanks.

 

tariq7868

New Member

• Mar 24, 2011

• #4

I also got confirmation from the company that there is a inductor placed between antenna and ground which makes the antenna shorted with ground when DC volt applied.

 

D

DataPanik

New Member

• Jun 1, 2014

• #5

Hello there (just signed up for this particular thread)

So I was banging my head try to find the short circuit between the antenna pin and ground till I found your thread.

What I want to ask is if there is something similar going on with SIM_CLK pin and ground since my multimeter sees them shorted too.

 

ronsimpson

Well-Known Member

Most Helpful Member

• Jun 1, 2014

• #6

I don't think SIM_CLK should be shorted to ground. There should be a diode to ground and a diode to supply. No short.
Reference: hardware manual.

 

D

DataPanik

New Member

• Jun 1, 2014

• #7

Yes I know that I was talking if there is a circuit inside the chip like the antenna pin where there is an inductor shorting with ground in DC but cutting the connection in AC.

Ok now I have found where the short circuit was.... Stupid double layer....

Thanx for the response

 

Last edited: Jun 1, 2014