(meteorobs) [radiometeoren] Fireball meteors emit unique radiowave signals

[drobnock]

Hi
The 20 June 2014 article, 'Fireball meteors emit unique radio wave signals'  is interesting. I do wonder why the 1960 Hawkins article, 'Electromagnetic Emissions from Meteors, ' The Radio Noise Spectrum, Mentzel, Harvard  is not referenced by researchers. An observation at 475 MHZ (p87-88) , mag +3, "correlated with a  radio impulse of twice the noise level."  .... the noise level corresponds to a flux of 1x10(-22) jan at the antenna (p88) 218 MHZ no signals.   His conclusions (p91) "On the the basis of these measurements there seems to be no possible of a plasma oscillation occurring in the ionization column of a meteor trail." Yet he does offer hope (p92) Discussion. Hawkins: "Some enhancements of low-frequency magnetic noise were observed in 1959 at the time of the Geminid meteor stream."

More later.

George John Drobnock



l Jay Salsburg wrote:

> In my web site (download PDF), I have had posted a PDF Whitepaper for almost 20 years, it is for building a Lightning Detector that may be modified for Meteor Detection. Figure 1. shows a simple antenna amplifier utilizing 3 100 MHz wideband opamps. 2 opamps are used as an inline loop antennae amplifier. Do not use the third opamp; the output of the first 2 opamps may be applied to the I+/I- inputs of the TV Tuner Dongle modification referenced below, where the TR1 transformer is not used, the opamps are applied here, but to the capacitor inputs, not the RTL2832U chip inputs. It is important to apply the output of the opamps to the coupling capacitors of the RTL2832U or even better, substituting Silver Mica Capacitors, if you have them. Cut the I+/I- Tuner connections from the coupling capacitors. Utilizing the “direct sampling mode” of the TV Tuner Dongle, a 2.8 MHz-wide spectrum window may be displayed and recorded for scientific inquiry. Costing less than $50, this apparatus
> makes a very good tool for observing HF band phenomena like Meteor trails. While Lightning detection uses a shielded Antennae, the Antenna configuration for this application is not shielded and should receive design attention to the wavelength of interest. Also the Antennae is oriented to the sky, not the horizon.
> http://www.salsburg.com/Lightning-Detector.pdf
>
> http://mikikg.files.wordpress.com/2012/08/rtl2832u-dc-mods.pdf
>
> from: http://www.rtl-sdr.com/rtl-sdr-direct-sampling-mode/
> The rtl-sdr software defined radio can be told to run in a mode called “direct sampling mode”, which with a small hardware mod allows the dongle to tune to the HF frequencies where ham radio and many other interesting signals are found. This means that no upconverter circuit is required.
>
> -----Original Message-----
> From: radiometeoren-bounces at ls.vvs.be [mailto:radiometeoren-bounces at ls.vvs.be] On Behalf Of David Entwistle
> Sent: Friday, June 06, 2014 1:57 PM
> To: f6agr at orange.fr; Radio Meteors
> Subject: Re: [radiometeoren] Fireball meteors emit unique radio wave signals
>
> On Thu, 2014-06-05 at 07:18 +0000, Jean-L. RAULT wrote:
> > Hi folks
> >
> > I was wondering if such emissions could be observed with a "simple"
> > amateur set-up
> >
> > According to the paper below, the flux density of the detected meteor
> > emissions can reach 5000 Jansky. If we choose a frequency of 37.8 MHz
> > which was the frequency presenting most of the meteor radiations, a 3
> > el Yagi beam antenna ith 7.7 dBi of gain, and a band width of 75 kHz,
> > the voltage delivered to a 50 ohms load is 0.07 microvolt, which is a
> > value detectable with a modern amateur receiver.
> > However, I would be grateful to the one who could verify my
> > computations (performed lately yesterday night)
> >
> > I used the following data
> >
> > 1 Jy = 10^-26 W . m^-2 . Hz
>
> The paper says:
>
> A typical fireball observed by the LWA1 has a peak flux density of 1 kJy, 20 s after first light, and most are point sources with a measured beam size of 4.4◦ at 37.8 MHz.
>
> and with respect to Fig. 1
>
> One of the transients shown on bottom (green) was also recorded using 1s integrations (top), we show this light curve, offset by 2000 Jy, to illustrate that they this transient was smooth over 1 s timescales.
>
> So, I think you may have overestimated the peak flux density by 2000 Jy, it reaching ~3000 Jy, rather than 5000 Jy.
>
> Regards,
>
> --
> David Entwistle
>
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