At 1:11 PM -0700 1/25/09, Thomas Ashcraft wrote:
>Thanks folks ( Rob , Oryoki and all) for the rapid replies.
>
>My application is to audio record for possible direct electrophonic
>and/or electromagnetic emissions from meteors at VLF (very low
>frequency). There is a debate in science as to whether or not people can
>hear or have actually heard ( or can sense somehow) meteors directly.
>Actual scientific proof and documentation are sparse. So I think I will
>give it a go.
>.
>Microphones will not be in play. Rather, I will be using a McGreevy
>WR3-e sferic/natural radio type receiver. The challenge with recording
>VLF is that the 60 Hz power grid causes buzzing interference so it is
>best to be far away from power lines of any sort. I need stereo
>recording ability so as to be able to record a second short wave radio
>that will be tuned to WWV time signals so that time stamping will be
>absolutely precise. Once I have the audio recording then I can analyze
>it via spectrograph and compare it to my nightly all-sky video fireball
>captures.
>:
>It seems like all is solvable except for the 8 hour field recording
>device. Also, continuous filing without gaps may be an issue...or
>perhaps a compromise?
>:
>Also, battery recharging is no problem as I can plug batteries in at my
>house during the daytime. No need for solar panels.
Thomas--
Oryoki compiled a list of recorders that will automatically start a
new file when the 2GB file size is reached which includes the Edirol
R-09 HR, the M-Audio Microtrack II, the Sony PCM-D50 and the Marantz
PMD620. There may be more models he knows of.
If synchronization is key, some of the digital recorders, like the
LS-10, exhibit rather significant, "drift." Not sure if this is
common to the card recorders or not.
I agree with Oryoki about making an external "sled" of larger
capacity batteries to supply the correct voltage. The PCM D50 has a
6 volt DC coax input jack. 5- "D" size NiMH batteries (5 X 1.2
volts) should get through the night with the monitoring turned off,
LCD display off, etc. "D's" go up to a 10000 mAh if need be:
http://tinyurl.com/c8ftox
Imagination aside, the whine of my nervous system is probably loud
enough to mask sounds considerably louder than those you seek. Rob D.
>:
>Hearing meteors directly ( and auroral phenomena for that matter ) may
>be so subtle that it merges with the observer's imagination of the
>sound. It would be cool to have some solid data.
>
>Thanks!
>
>Thomas
>
>oryoki2000 wrote:
>> Tell us more about the recorder and microphones you plan to use, and
>> how you will use the recordings. There are portable recorders that
>> can record for 12 hours or more using their internal battery alone.
>> (Sony PCM-D50 is one example.)
>>
>> Assuming you will need an external battery, check your recorder's
>> external AC adapter to determine what DC voltage and amperage it
>> provides to the recorder. Use this to guide your selection of an
>> external battery pack.
>>
>> A few external battery solutions mentioned here in the past week include
>>
>>
>><http://www.laptopsforless.com/portable-dvd-battery/pr2e.htm>http://www.laptopsforless.com/portable-dvd-battery/pr2e.htm
>> <http://www.bixnet.com/5v7libapa.html>http://www.bixnet.com/5v7libapa.html
>>
>><http://www.bixnet.com/mumiexbapaki1.html>http://www.bixnet.com/mumiexbapaki1.html
>>
>><http://www.bixnet.com/misihicabapa.html>http://www.bixnet.com/misihicabapa.html
>> <http://tinyurl.com/8zjel8>http://tinyurl.com/8zjel8 (Amazon.com)
>> <http://tinyurl.com/96fpmb>http://tinyurl.com/96fpmb (Amazon.com)
>>
>> Here's a forum that talks about battery power solutions for
>> long-duration recording
>>
>><http://taperssection.com/index.php/board,25.0.html>http://taperssection.com/index.php/board,25.0.html
>>
>> And here's a fellow that makes custom C and D cell battery sleds with
>> the proper electronics and connector to power different recorders.
>> These are expensive, but work well.
>>
>><http://www.sonicstudios.com/batsys98.htm>http://www.sonicstudios.com/batsys98.htm
> >
> > --oryoki
>>
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