6 replies to this topic

[GPPI_JMe]

I'm interested in finding, or making, an EMF meter that measures only in the frequency range of 30-40Hz. In fact, it could measure from .5Hz to 40Hz, but I'd rather it not exceed 40. I'm sure there's at least one person out there who can tell me whether they've found anything like this? Or if there are plans out there I just haven't located, to make one of these? (Not that I could hack it, but they'd at least be interesting to see..)

[Joven76]

I'm interested in this as well, but also interested in why you want to measure in that frequency range... What would be the purpose of that???

[CaveRat2]

It would not be hard to build one. I have schematics on my website for an EMF wand for use as a dynamic EMF monitor. This device covers a wide range of frequencies. While I have not built anything like you mention, the wand could easily be used with a narrow band parametric filter to set any band that you want. I have built those as well, just never put the two together. But it could easily be done.

If you want to send some more precise requirements (bandwidth, gain, type readout / output desired, etc.) I could give you a quote on a device through BEC Labs..

[GPPI_JMe]

Well, I'm interested in measuring that frequency range due to some of the information I read on EEG scans, and the electromagnetic field from our brain seems to stick in the .5Hz-30Hz range. I also read that they've noticed that many people, just before passing, enter the same range as that of drowsiness (or the first stage of sleep), which is the 4Hz-8Hz range. I just figured if I was able to eliminate measuring the 50/60Hz range, it might cancel out a lot of the background EMF, and stick closer to what I'm actually looking for?

I'll look into more detail on specifications, and get back with you when I get something more solid. Any idea of a decent spectrum analyzer software that's both a good quality, and a good price? Thanks for the quick response time, guys.

[CaveRat2]

Spectrum analyzer software is by nature very limited. The problem is that by using your computer you are limited by the hardware installed in the computer. Since the primary reason for a spectrum analyzer in the first place is to get an accurate representation of a given range of frequencies it is a requirement that any device pass those frequencies in a uniform manner to give that representation.

However most computers use the audio board as the input for the analog signal and as such are limited to its frequency response. Those which use the audio board will not pass harmonics which could be a factor in even relatively low frequency signals. There are mid priced spectrum analyzer front end boards available as an aftermarket item you can plug in to your computer motherbord, these generally come with their own software based on their capabilities. Performance would be depenent on the system you obtain, costs start at around $500 and can go up to a few thousand.

Personally I prefer a stand alone system when it comes to test equipment. Hardware is designed specificly to do the task you require of it. Hwever most investigators, unless they have another reason for doing so (such as an electronics business like I do) could not justify the purchase of a piece of equipment like a spectrum analyzer. ( Mine was a refurbished model for $8,900.) Unfortunately there just is no inexpensive way to do that level of work with accuracy.

[GPPI_JMe]

So what you're saying is.. I should send you my captures, and have you analyze them for me? Joking..

Well, thanks again for the speedy replies and excellent information. As always, it's great to hear from the couple of you that seem to always have answers for me!

[CaveRat2]

Actually Independent Research Associates does provide analysis services to other groups in various areas of sciences provided the evidence is obtained and handled in a manner to insure its integrity and the ability to process. For instance, in audio, if the recording meets our standards as to how it was obtained I can run a full spectrum analysis. However I caution anyone that can't be done with audio from cheap recorders since it lacks the required frequency response. Thus it would be a waste of everyone's time. But in the case of quality evidence I can do this for outside groups and investigators. You would need to supply background info on any prospective submission before sending it.

BTW, all analysis of evidence for private, non-commercial cases is done at no charge.