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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 |
User-agent: |
Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.15) Gecko/20101027 Fedora/3.0.10-1.fc12 Thunderbird/3.0.10 |
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
>>
>
>
>
> _______________________________________________
> Discuss-gnuradio mailing list
> address@hidden
> 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
http://www.sbrac.org