Thanks Jim.  With 1N5822 diodes response is within +/- 1 dB from 10 to 300 kHz. 
When I have the 1N4148s I will try them.

73
John F5VLF

On 11 Jan 2011, at 14:47CET, James Moritz wrote:

> Dear John, LF Group,
> 
> The 1N4007 and similar HV rectifiers have a notoriously slow recovery - it is 
> sometimes seen in amateur literature used as a PIN diode for this reason. So 
> one could expect problems using it as an RF rectifier. I have made a number 
> of versions of this ammeter circuit, using various small switching diodes 
> without problems at 136k and 500k. The Schottky rectifier diodes you 
> mentioned should have no problem with switching speed. They have quite high 
> capacitance, but I guess this probably won't be a problem in this relatively 
> low impedance circuit.
> 
> Cheers, Jim Moritz
> 73 de M0BMU