frequency flattness of oa90 and similar germanium giodes?

hello I have build this little transmitter http://www.qrp.gr/cwqrpp/index.htm and I would like to replace the 1n914 diodes with a pair of germanium diodes.
The most sensitive ones to my taste (used on crystal radios extensively) are the oa90.
I was wondering about how well they will respond to HF (1-30MHz), i.e how flat they are in rectifying the RF into voltage?

For example will a 0dbm signal at 1MHz give the same output voltage at 30MHz as well?