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

[Marcus D. Leech]

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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>
>
>   
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