Quote:
Originally Posted by Dubulumach
Get out one preamplifier stage and lower your gain as much as possible but still enough to detect the phenomenon, while cut sky/ground effect.
I will give you one idea. Add several different oscillator stages besides original 8MHz, for example 1MHz, 20Mhz, 100 MHz, and mix very small oscillator's output amplitude on the base of 1st transistor. On this way you will have very wide band detection.Amplitudes must be very low to avoid oversaturation of preamplifier, interferation and slope eadge modulation.Also good narrow band pass filter should be added after amplitude detector.
Interesting project but need a lot of mods.
All credits go to Franco Italy.
and remember:
NOISE IS YOUR FRIEND becuase can help you to find a lot of gold coins.  |
The idea seems good, but difficult to apply on the sensor stage, which in practice is an active high pass filter preceded by a sort of mixer (TR2). In practice the gain is optimized for a certain frequency, a separate sensor stage should be built for each frequency. In my opinion the frequency of the oscillator is not very important, let's not forget that the phenomenon comes from the antenna and is filtered by L1 / C10 and probably there is a carrier of about 100Mhz which is modulated by the phenomenon. On the basis of TR2 two signals arrive, the phenomenon and the oscillator signal. This is not frequency conversion, it is not a linear mixing, it simply increases the amplitude of the oscillator signal. The fundamental requirement for the operation of my lrl is that there is some transmitter in the 100Mhz band, for example private radio stations or satellite broadcasters.