Re: AW: LF: RE: Re: VLF

To:	[email protected]
Subject:	Re: AW: LF: RE: Re: VLF_8.79 kHz
From:	Andy Talbot <[email protected]>
Date:	Thu, 25 Feb 2010 12:34:17 +0000
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Yes, but what is the gain / antenna factor of your Miniwhip?

Measuing -115dBm means little in itself, you need to convert this to a calibrated V/m form.

IF the miniwhip were exactly 1m long and positioned over a good groundplane, fed an infinite input impedance, zero input capacitance voltage follower amp with unity voltage gain into 50 ohms, then -115dBm would equate to 0.4uV/m in 24Hz, or .08uV/m/ SQRT Hz.

If the value quoted recently of 150dB kTB is assumed, which is 25dB lower that my original calculation, it suggests a value in the region of 4uV / m / SQRT Hz may be more typical.

Andy
www.g4jnt.com

On 25 February 2010 12:02, Roelof Bakker <[email protected]> wrote:

Hello Andy,

I measured the noise on 8800 Hz received on my mini-whip.
Receiver: SPM-30, BW = 24 Hz, noise level = -115 dBm

The same measurement with a PERSEUS SDR and a bandwidth of 20 Hz revealed a noise level of -122 dBm.
PERSEUS has an input isolating transformer, which rolls off below 15 kHz, hence the lower measured noise level.

It does not look too bad to me, really.

73,
Roelof Bakker, pa0rdt

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LF: VLF_8.79 kHz, (continued) LF: VLF_8.79 kHz, Horst Stöcker Message not available LF: Re: VLF_8.79 kHz, John RABSON LF: Loran, GPS and jamming, Chris Trayner LF: Re: VLF_8.79 kHz, James Moritz LF: RE: Re: VLF_8.79 kHz, Ken Re: LF: RE: Re: VLF_8.79 kHz, M0FMT Re: LF: RE: Re: VLF_8.79 kHz, Chris Re: LF: RE: Re: VLF_8.79 kHz, Andy Talbot AW: LF: RE: Re: VLF_8.79 kHz, Stefan Schäfer Re: AW: LF: RE: Re: VLF_8.79 kHz, Roelof Bakker Re: AW: LF: RE: Re: VLF_8.79 kHz, Andy Talbot <= Re: AW: LF: RE: Re: VLF_8.79 kHz, Roelof Bakker LF: RE: Re: VLF_8.79 kHz, M0FMT Re: LF: VLF_8.79 kHz, Chris Trayner

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Re: AW: LF: RE: Re: VLF_8.79 kHz