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# Frank Liuzzi 2012-12-08 02:00
Hello,
I have the RF Explorer 3G Combo and would like to know the maximum DC voltage that each of the instrument's two SMA inputs can safely handle if I directly connect the RF Explorer to a circuit under test that might exhibit a DC offset.

I'm not sure if the RF Explorer 3G Combo is AC coupled or DC coupled.

Thanks
Frank
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# Webmaster 2012-12-08 19:12
Quoting Frank Liuzzi:
Hello,
I have the RF Explorer 3G Combo and would like to know the maximum DC voltage that each of the instrument's two SMA inputs can safely handle if I directly connect the RF Explorer to a circuit under test that might exhibit a DC offset.

I'm not sure if the RF Explorer 3G Combo is AC coupled or DC coupled.

Thanks
Frank


Frank, that is a good question. I've added that detail on the www.rf-explorer.com/models comparison table. The WSUB3G is DC decoupled in both RF connectors up to 16V.

Regards.
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# Renato Galani 2013-03-06 12:33
Hi there!

I was looking the specification of 3G combo and I noticed that left port has a max input of +5dBm and the right has +30dBm. Does it mean that only the right port (WSUB3G) is well protected against strong signals?

Regards,
Renato
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# Webmaster 2013-03-06 14:34
Quoting Renato Galani:
Hi there!

I was looking the specification of 3G combo and I noticed that left port has a max input of +5dBm and the right has +30dBm. Does it mean that only the right port (WSUB3G) is well protected against strong signals?

Regards,
Renato


Renato, that is correct, the connector at the right is +30dBm protected. If you are working in a strong signal EMI environment, use the right connector antenna and keep the left connector with no antenna. Use the left connector when you want extra sensitivity only in low noise environments.
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# EngineerZ 2013-03-09 21:51
Wouldn't an SMA shorting cap offer more protection than a 50-ohm load when the device is not in use? Couln't a strong RF field still induce a voltage across a 50-ohm load, especially if the load wasn't particularly well-shielded?
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# Webmaster 2013-03-11 17:15
A 50ohm termination is the best protection you can get. It not only protects you from external EM fields getting into the internal RF circuit, but also makes a reliable load in case you switch on the internal RF Generator in RF Explorer models that include it.

All recommended SMA termination loads are always shielded, industry standard, if you cannot get one nearby you can order it from SeeedStudio http://www.seeedstudio.com/depot/sma-termination-50ohm-p-1256.html

With a SMA termination in place, you will need kilowatts of external power nearby to get any noticeable power into the RF circuit.

On the other hand, a shunt capacitor will not offer a predictable protection because the impedance will vary with frequency. For instance a capacitor will not protect you at low frequencies, usual in some RFID congested areas. In contrast, a SMA termination has a predictable, stable response from DC to 3GHz, usually much more.
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# hubert 2014-06-21 12:23
Hello,

I have a RF explorer 3G combo. I put a RF Explorer Power Limiter on the left SMA. If I want to measure next to a talkie walkie that emits 4W (UHF GP340 for example), how I should proceed to not to bend my RF explore and have a proper measure ?

cordially
hubert
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# Webmaster 2014-06-22 21:27
Quoting hubert:
Hello,

I have a RF explorer 3G combo. I put a RF Explorer Power Limiter on the left SMA. If I want to measure next to a talkie walkie that emits 4W (UHF GP340 for example), how I should proceed to not to bend my RF explore and have a proper measure ?

cordially
hubert


The power limiter will certainly protect your RF Explorer even if it is very close to the 4W RF source. However for the measurement to not overload the analyzer, start by a 10mts distance and get closer till you are measuring no more than -30dBm.
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# Tony 2014-09-26 05:38
Quoting Webmaster:
Quoting hubert:
Hello,

I have a RF explorer 3G combo. I put a RF Explorer Power Limiter on the left SMA. If I want to measure next to a talkie walkie that emits 4W (UHF GP340 for example), how I should proceed to not to bend my RF explore and have a proper measure ?

cordially
hubert


The power limiter will certainly protect your RF Explorer even if it is very close to the 4W RF source. However for the measurement to not overload the analyzer, start by a 10mts distance and get closer till you are measuring no more than -30dBm.


But how do I understand the RF-Level present in the measuring zone. For instance let say I am transmitting at 100watt in ham band and there is a rf leakage which i am not aware of it - WHAT HAPPENS IN this scenario to RF EXPLORER
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# Webmaster 2014-09-26 09:07
Quoting Tony:
But how do I understand the RF-Level present in the measuring zone. For instance let say I am transmitting at 100watt in ham band and there is a rf leakage which i am not aware of it - WHAT HAPPENS IN this scenario to RF EXPLORER


There is no perfect answer to this, all sensitive RF devices including your cell phone are in danger if a strong RF source is very close. If you need 100% safety, use a narrowband pass filter so all frequencies are attenuated except the one you are trying to measure. This is standard industry practice with spectrum analyzers of all sizes and prices if they have to work in a risky environment.
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# JW 2015-01-01 10:14
Is it safe to connect my 3G Combo directly to my TV antenna? We aren't particularly close to the transmitter, but the signal is strong (according to my receiver).

Also, how about connecting it to the 'RF out' of my VCR?
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# Webmaster 2015-01-07 11:16
It is safe if your TV antenna is not DC feed with more than 16VDC. In addition to that, you need 30 or 40dB attenuation for the signal to fit in the linear range of the device.
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