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alzomor
Joined: 09 Jun 2005
Posts: 626
Helped: 31
Location: Cairo
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 09 Sep 2009 10:18 gsm impedance antenna |
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Hi
I am using a GPRS/GPS module
I face a strange problem Suddenly the GPRS is not working and when I measure the impedance on the antenna connector I found it equals to 1.2 ohm, I m expecting to see 50 ohms
am I true?
dose that means that the LNA and PA has burnt out due to ESD?
Salam
Hossam Alzomor
www()i-g()org
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GSM Man
Joined: 15 Apr 2009
Posts: 357
Helped: 46
Location: New Jersey, USA
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09 Sep 2009 12:01 GSM antenna output impedance |
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| How are you measuring the impedance?
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09 Sep 2009 12:01 Ads |
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alzomor
Joined: 09 Jun 2005
Posts: 626
Helped: 31
Location: Cairo
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09 Sep 2009 12:13 Re: GSM antenna output impedance |
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| I am using ohmmeter
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GSM Man
Joined: 15 Apr 2009
Posts: 357
Helped: 46
Location: New Jersey, USA
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09 Sep 2009 14:06 Re: GSM antenna output impedance |
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| alzomor wrote: |
| I am using ohmmeter |
Then you're not measuring the impedance - you're simple measuring the DC resistance of the output. For that, 1.2 ohms is not unreasonable.
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alzomor
Joined: 09 Jun 2005
Posts: 626
Helped: 31
Location: Cairo
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09 Sep 2009 15:01 Re: GSM antenna output impedance |
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hi
do you know exactly what should be the value to be measured by ohm meter on antenna output?
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vfone
Joined: 10 Oct 2001
Posts: 2327
Helped: 326
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09 Sep 2009 18:11 Re: GSM antenna output impedance |
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Hmmm! You are using the ohm-meter to measure the impedance!?
I was so stupid to pay $50.000 for a Network Analyzer when actually a $10 multi-meter would be fine.
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alzomor
Joined: 09 Jun 2005
Posts: 626
Helped: 31
Location: Cairo
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10 Sep 2009 10:26 Re: GSM antenna output impedance |
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Hi
as you can see the ohmmeter was not suitable for doing the JOB.
but I think network analyzer is so expensive also .
what about using RLC meter?
Salam
Hossam Alzomor
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Chinaski
Joined: 17 May 2001
Posts: 217
Helped: 5
Location: Spain
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10 Sep 2009 15:11 Re: GSM antenna output impedance |
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RLC meters make measurements at low frequencies. As vfone said, you _do_ need a VNA for measuring the impedance of an antenna at GSM freqs. Of course, you can use a SWR meter (cheaper solution) but in that case you will not not measure the input impedance but something related with.
Good luck
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GSM Man
Joined: 15 Apr 2009
Posts: 357
Helped: 46
Location: New Jersey, USA
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10 Sep 2009 16:49 Re: GSM antenna output impedance |
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| alzomor wrote: |
| I face a strange problem Suddenly the GPRS is not working... and when I measure the impedance on the antenna connector I found it equals to 1.2 ohm, I m expecting to see 50 ohms |
I feel you may be wasting a lot of your time trying to measure the radio's impedance. The module is either good or bad, trying to measure the impedence isn't doing you much good. If you use a different module with your SIM card, does it work? Is it only GPRS that doesn't function, or can you not connect to the network? I've destroyed a few modules myself, and its always been fairly easy to determine if its working or not.
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