useful for any low level RF work
http://sound.westhost.com/project74.htm
small RF probe that connects to a multimeter
http://www.io.com/~n5fc/rfprobe2.htm
used with a digital multi meter to indicate the voltage level as dc voltage which is equivalent to the RMS value of the RF voltage being measured
http://www.flashwebhost.com/circuit/rfprobe.php
http://www4.tpg.com.au/users/talking/Logic%20Probe%20with%20Pulser-Intro.html
...across devices which are not ground referenced. These probes can be used in the same ways as the normal (resistor) probes, with some exceptions.
http://www.libinst.com/Difprobe.htm
http://www.qrpp-i.com/KA8MAV_RF_Probe.htm
Probe switches automatically between AF and RF
http://www.lh-electric.4t.com/bin/af_rfprobe.gif
for testing TTL circuits
http://home.maine.rr.com/randylinscott/feb99.html