Am radio : oscilloscope......

Thread Starter

dmowziz

Joined Jan 18, 2019
76
Someone please assist

When I probe (10ms/div) at point x without my LC then I can see 60hz noise (not so thick like image)...When I add the LC, the amplitude of the 60hz noise just increases...Please what is wrong?

Also, where to connect the ground probe of scope?

Thank you

What kind of inductor? I am using a resistor like inductor.
 

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danadak

Joined Mar 10, 2018
3,577
Could be coupling to the coil, the 60 Hz, AC power wiring in your lab.
Turn off your AC in lab, and or flourescent lights. See if that helps.

Scope probe goes to ground, the common in your schematic.

Normally using a scope is a challenge because AM Radio signals often in the uV
region. Depends on antenna, proximity to transmitter, propagation.


Regards, Dana.
 

Thread Starter

dmowziz

Joined Jan 18, 2019
76
'Scope ground goes to the point marked as earth on the diagram.
What frequency is the LC tuned to?
Hi thanks...When I put the scope ground there then no signal on display...If I add an amplifier then use the battery ground, the signal is still 60hz but amplitude about 50v peak

I've used different inductors (like resistors)...the last attempt, about 80khz...It's low?
 

Thread Starter

dmowziz

Joined Jan 18, 2019
76
That's exactly what I would expect. The signal level will be too low to see on a 'scope.
hmmm, I dont understand...

Suppose just antenna and LC with nothing else...Then probe to top part(x of image) then scope ground to bottom of LC : something should show on display?
 

Thread Starter

dmowziz

Joined Jan 18, 2019
76
Could be coupling to the coil, the 60 Hz, AC power wiring in your lab.
Turn off your AC in lab, and or flourescent lights. See if that helps.

Scope probe goes to ground, the common in your schematic.

Normally using a scope is a challenge because AM Radio signals often in the uV
region. Depends on antenna, proximity to transmitter, propagation.


Regards, Dana.
Just seeing your post :( ....The scope ground : then no signal
 

Thread Starter

dmowziz

Joined Jan 18, 2019
76
fluorescent light reduces amplitude of signal : even after turning light off the signal does not increase again...

why is this
 

AlbertHall

Joined Jun 4, 2014
8,375
"The signal level will be too low to see on a 'scope." why is this
The received signal level will be low.
I live approximately 17 miles from the UK National Physical Laboratory time signal. The signal covers the whole of the UK, and can also be received throughout most of northern and western Europe. So you might expect that I would see a strong received signal across the aerial tuned circuit but it is not visible on a scope. The level is uV not mV and that is why radio receivers need sensitive, low noise amplifiers for good performance.
 

Thread Starter

dmowziz

Joined Jan 18, 2019
76
I do not understand your response.
You need an antenna that is more than 10 metres long and preferably outdoors away from any physical structures.
I used a sellotape to hold the wire on a wall (this isn't bad right?).... it works for an fm receiver i did (found schematic online)
 

MrChips

Joined Oct 2, 2009
19,280
How long is the antenna?

With a 10m antenna you ought to pick up a 50mV signal with a resonant LC circuit if there is a powerful AM radio station nearby.
 

Thread Starter

dmowziz

Joined Jan 18, 2019
76
How long is the antenna?

With a 10m antenna you ought to pick up a 50mV signal with a resonant LC circuit if there is a powerful AM radio station nearby.
I really dunno how long but not long enough : Will increase

Please how to delete my account? or kindly do it for me please (Moderator MrChips)

Thanks
 
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