Bob Bob, you are outstanding! The Winradio is actually a capable and
affordable solution. From the specs, it looks like it will fit the
bill, and the fact that they have a Linux version is great. Take care.
-Lars

Bob Bob wrote:
This looks like an interesting project! Not quite what I was thinking in
my original answer. I think your requirement is a lot simpler and cheaper.

A yes no indicator for RF between 570Hz and 4Mhz should be relatively
easy, especially if it is a large signal in comparison to the ambient
level. You could probably do it with a band pass filter network, a few
transistors and some kind of display device (eg a LED). Some sensitivity
calibratation over the freq range will need doing and maybe a subsequent
adjustment to the BPF.

Determining if it is encoded depends on how it is encoded. If it creates
pulses of a known PRF then a simple AM receiver to detect the envelope,
followed by whatever ever band pass at the PRF and a subsequent display
device. I cant comment on this further without knowing how you modulate.

Both circuits could be mounted in a box with an "RF detected" and
"Modulated signal detected" LED along with a resetable timer. You are
talking maybe $30 worth of parts!

Note that you will need to test its susceptability to other RF in the
area so it doesnt give false readings.

One assumes you want to log the above events? For that a PC can be used
for with a simple low rate data acquisition module or even via the
parallel port pins. As horrible as it sounds using an old clunker and a
DOS version with debug will allow you to poll the printer port and print
a report on completion. You can also do it with the normal tools in a
current Linux versions. I think software would need to be written for a
Windows environment. Probably already exists as GPL. Shd be pretty
simple to write though if not.

The above assumes you dont need to measure the actual exposure level..

You might be interested to know that back in the early 1980's I was
involved in medical ultrasound. Most of our products were for imaging
and doppler. We were however developing a higher energy device for
focussed heating on cancerous etc areas. The initial tests were done
with a beefed up transducer (about 50mm dia a 5mm thick) in a water bath
and excited with an old Yaesu FT101B transceiver on about 3.6MHz! It was
impressive to watch it boiling the surface of the water. It looked like
a 360 degree waterfall..

If you want to go down the separate radio and PC device have a look at
the Winradio (or similar) boxes. They use a PC as control and display
for an external box with an RS232 and antenna port on it. Dont know
about the software side of this though.

Cheers Bob VK2YQA

wrote:

Specifically, the application is one which uses a HAM radio transciever
utilizing approx 20W-100W power and a Class E transmitter to drive
data signals and power from an external coil to a series of smaller
receiver coils which are implanted in biological tissue for biomedical
application. I have to police/enforce the research personnel to ensure
limits regarding std practices are not exceeded in regards to duration
and length of RF exposure fothe patient. Of course I need to do this
independently, because in this situation relying on their "good word"
or verbal agreement isn't sufficient. I have to be able to be able to
1.) determine if there is a 570Hz to 4MHz signal present, and 2.)
determine if it is encoded or modulated to carry the power and data
signals. Not up my alley exactly, but I need to get it done. If there
is an expansion card or USB interface device for PC, that would be
preferable to aquiring an entire HAM rig. Any help appreciated. - Lars