Help with russian pirate pi

[Tariq]

Hello everyone I?m sorry about my poor English

I?m beginner in electronics I just start learning since a month

I made the russian pirate pi on a bread board and its work fine with 9v battery but the depth of detection is not good about 8cm with coins . I?m trying now to change the frequency in Ne555 to achieve better depth but I have many questions

does the duty cycle here important in pi metal detector
what it should be % ? Time on and time of

Is there?s relationship between coil and frequency, im using now 17cm diameter coil with 340uh

I?m using online calculator with NE555 timer
R1 = 63k
R2 = 440 ohm
C1 = 100nf

frequency that I get = 220Hertz
Duty cycle = 99.3%
Time high = 4.5 millisecond
Time low = 31.3 microsecond

any advice about duty cycle and frequency to achieve good depth???

[surfdetector]

Here is some good information on the Pirat PI:
https://vk.com/topic-33752123_31206872?offset=0

[Tariq]

Thank you so much Guru
I will try to use google translate to understand the language