5kHz receiver

5kHz is audio band so a largish pancake coil of wire and a hifi amp should see it. (or maybe even cheaper a crystal earpiece on the loop )

Low noise preamp followed by a PLL detector probably needed to pick signal from noise. Are you sure it is on a 5kHz carrier? Seems an awfully low frequency.

--
Regards,
Martin Brown

Sparkfun sell a reciever

but it should be possible to build one very cheaply

Thanks for the link, I didn't know it existed. It costs almost twice the price of my watch though, and it's from another brand so I'm not certain it would be compatible.

Would any tuning be necessary, or a simple coil would suffice ?

Do you think an LM567 could be a good choice for a PLL detector down the chain?

I was surprised as well, but I checked several sources and they are consistent. I guess this might have something to do with power consumption since the belt is supposed to be able to operate on a CR2032 battery for 1 year.

I'd try it without and at close range first. Tuning would involve fairly large capacitors or a huge coil.

567 is a bit long in the tooth now. CMOS 4046 would need less power.

How odd.

--
Regards,
Martin Brown

5khz is in the VLF band (also in the human hearable audio band)

This looks like a suitable VLF receiver circuit:

(Magnetic Pickup) at

you probably dont need the second op amp and should feed the output into a tone decoder pll like the lm567

an even simpler circuit on the same page might work too (Super-Tiny VLF Receiver)

see

for an example lm567 circuit

Why is the brand a secret ??

This discussion would go a lot faster with that secret information.

hamilton

whistle.htm#Magn...

s/VLFwhistle.htm#Supe...

Thank you for these URLs! I didn't see any mention of Chernov Radiation being a source of VLF.

It is my understanding that as a cosmic particles enter our atmosphere they slows down, thus giving off energy, called Chernov Radiation. I understand that the effect is greatly enhanced by using a tank of water to slow the particles down and using photon multiplier tubes to 'view' the light trail these particles give off. Japan has a cave lined with some 1,000+ multiplier tubes [at $20,000 each that's impressive!]

Further by calculating the information from the light trails it is possible to determine energy/origin essentially making a form of telescope that can look deep into space. Note: the cave setup in Japan went through an unexplained failure mechanism where by they lost almost ALL tubes, going off like a popcorn string. They had to drain, replace, only to lose them again.

There was a Professor in New Mexico who contended that by measuring VLF, you could surmise the Chernov Radiation of these particles as they went through the atmosphere, thereby making a much cheaper form of telescope. I designed the magnetic VLF receiver with noise floors

50X less than earth's field's noise floor and I got to add the concept of placing many such VLF receivers spaced every so far along the US, for 1000's of miles, essentially a phased array antenna. The end result would be creating an extremely wide lense telescope capable of looking deeper into space than man has ever looked in his history.

Can you tap the demodulated signal out of the watch?

I have one of those Polars. They are coded, so I think you would save yourself a lot of work just getting the sparkfun board.

I guess if you are using a treadmill, you could use such a monitor. I only use mine outdoors. The real advantage to a Polar monitor is zone conditioning. You set up the watch such that it tracks your heart rate, and then you try to stay in a zone. The watch can also estimate the calories burned. It also yells at you if you haven't exercised in a while.

Sorry. The brand is Géonaute, and the model Kalenji 100.

theres the Kalenji cardio connect

LFwhistle.htm#Magn...

The Stanford University VLF Group (

) may be involved in that area of research

theres an interesting vlf page here (

) and a yahoo discussion group ( / )

/VLFwhistle.htm#Magn...

p/

Thanks for the URLs!