A
anc
- Jan 1, 1970
- 0
I think there may be an error with the value of C1 in this circuit:-
http://www.uslink.net/~cybercir/cir2.htm
The value is shown as .22uF, I did some calculations and believe it should
be .22pF
I estimated lead inductance around 7nH of 0.5 inch of lead for a capacitor
and worked out resonant frequency using 1/(2pi LC^0.5) estimated a
resonance at just over 4GHz.
I am not sure about the small signal equivalent circuit at these microwave
frequencies, whether each component lead will introduce inductance or the
effect on the input of the opamp.
Having said all this, I made the above circuit using a .22u (220n) capacitor
and nothing was received from any road camera in the UK, only an annoying
squawk from a mobile phone (960-980MHz).
If the microwave energy from a road radar camera is high enough, I would
imagine that even a "badly tuned" resonant circuit may recieve something.
Radar cameras in the UK use 10G and about 24GHz, has anyone else built or
tried the economy radar detector?
My estimation of 7 nH arises from this equation using r =0.05 and l=1.2
Lac = 2L[ln(2L/r) - 1.00]
from the following page:
http://www.ee.scu.edu/eefac/healy/indwire.html
http://www.uslink.net/~cybercir/cir2.htm
The value is shown as .22uF, I did some calculations and believe it should
be .22pF
I estimated lead inductance around 7nH of 0.5 inch of lead for a capacitor
and worked out resonant frequency using 1/(2pi LC^0.5) estimated a
resonance at just over 4GHz.
I am not sure about the small signal equivalent circuit at these microwave
frequencies, whether each component lead will introduce inductance or the
effect on the input of the opamp.
Having said all this, I made the above circuit using a .22u (220n) capacitor
and nothing was received from any road camera in the UK, only an annoying
squawk from a mobile phone (960-980MHz).
If the microwave energy from a road radar camera is high enough, I would
imagine that even a "badly tuned" resonant circuit may recieve something.
Radar cameras in the UK use 10G and about 24GHz, has anyone else built or
tried the economy radar detector?
My estimation of 7 nH arises from this equation using r =0.05 and l=1.2
Lac = 2L[ln(2L/r) - 1.00]
from the following page:
http://www.ee.scu.edu/eefac/healy/indwire.html