Small signal diode to make broadband RF detector/FS meter?

[cdev]

I am wondering what my best choice would be in diodes to make an simple RF detector that can detect RF of all kinds around the house, from wifi access points to the sources of RFI that may be fairly low frequency.. kHz range (with different antennas) ?

1N34 or something else?

[KJDS]

I always like the BAT63 dual diode with two TLC2652, one using teh second diode to provide temperature stability and the second to give lots of gain.

Make sure you put the diodes with the anodes facing the op-amp input pins.

[HB9EVI]

What upper frequency range and what sensitivity do you want to cover?

As you maybe know, there are various log-detectors; like the AD8307 which starts at ~ -75dBm but only covers upto 500MHz.

Maybe you take a lot at this option

[Wolfgang]

I am wondering what my best choice would be in diodes to make an simple RF detector that can detect RF of all kinds around the house, from wifi access points to the sources of RFI that may be fairly low frequency.. kHz range (with different antennas) ?

1N34 or something else?

yeah, either good old Germanium or some more recent Schottky diode, like an 1N5711 or something in SMD. Careful SMD construction on an RF PCB and good Schottky diodes could give to a useful detector to 3GHz without too much effort.

http://www.dl5neg.de/diodesensor/diodesensor.html

has some info about this

[David Hess]

Low barrier (zero bias) schottky diodes are ideal but any small signal schottky diode will do.  I have used 1N270s to good effect up to 1.2 GHz and they might be considered improved 1N34s.  If you are going to directly drive a 50 or 100 microamp meter, then the diode type becomes less important as long as it is fast enough.

The detector configuration matters also.  More complex designs forward bias the diode reducing the effect of forward voltage drop and may chop the input or use a second diode for temperature compensation.

If I were experimenting with a new biased detector design, I might use transistor base-emitter junctions as RF diodes.

[cdev]

David,

thank you for this info!
I have some old meter movements that would be perfect for this. It will be interesting to see if they can rectify 2.4 GHz!

Low barrier (zero bias) schottky diodes are ideal but any small signal schottky diode will do.  I have used 1N270s to good effect up to 1.2 GHz and they might be considered improved 1N34s.  If you are going to directly drive a 50 or 100 microamp meter, then the diode type becomes less important as long as it is fast enough.

The detector configuration matters also.  More complex designs forward bias the diode reducing the effect of forward voltage drop and may chop the input or use a second diode for temperature compensation.

If I were experimenting with a new biased detector design, I might use transistor base-emitter junctions as RF diodes.