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Re: [Discuss-gnuradio] Maximum antenna input voltage on LFRX

From: Marcus D. Leech
Subject: Re: [Discuss-gnuradio] Maximum antenna input voltage on LFRX
Date: Fri, 24 Dec 2010 20:26:53 -0500
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On 12/24/2010 08:02 PM, Nick Smith wrote:
> I tried with a 330 ohm and 33 ohm resistor, and the voltage stayed the same 
> as without. I have no doubt that it is mostly power line and the 1kW AM 
> station that is within walking distance. :)
> Also, the ground here isn't a very good ground, so that probably throws 
> measurements off.
> As for where it's situated, it's an indoor antenna. In a very noisy house.
> I long for a better location. :)
> --- Nick
>> From: Mark J. Blair <address@hidden>
>> Subject: Re: [Discuss-gnuradio] Maximum antenna input voltage on LFRX
>> To: "discuss-gnuradio" <address@hidden>
>> Date: Friday, December 24, 2010, 7:20 PM
>> A multimeter has very high input impedance. If you attach a
>> 50 ohm resistor(*) between the antenna and ground to
>> simulate the input impedance of a radio receiver, then you
>> should no longer see a measurable voltage with a
>> multimeter.
>> Also, a multimeter won't properly measure RF voltage.
>> You're probably just seeing 60 Hz power line noise, unless
>> you're very close to a high-powered transmitter. If there's
>> a 100kW broadcast transmitter next door, then all bets are
>> off. :)
>> (*) or any other value you can get your hands on between
>> around 25 and 500 ohms
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> Discuss-gnuradio mailing list
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> http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
So, you measured above 1V with a 33ohm resistor across the multimeter?

I'm glad I don't live in that house!  Yikes!

Principal Investigator
Shirleys Bay Radio Astronomy Consortium

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