# radio waves on an oscilloscope

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#### Chapi

##### New Member
Hi guys.

I can view the waves from my transmitter on the scope, inc frequency, when the scope's probe is really close to the transmitter (up to 20'). But how can I do it from 20 miles? Is there any way to get a reading of the rf from a receiver? maybe using a bandpass filter?

I need to have it exactly like the probe, ie that when I start the transmission I will see the waves on the scope, and when I end it, the waves will disappear.

Any ideas how to do it?

Thanks.

#### MikeMl

##### Well-Known Member
Depends a bit on what frequency your transmitting on?

Hook the scope probe to an IF stage in a superheterodyne receiver tuned to your transmitter.

#### Nigel Goodwin

##### Super Moderator
I suggest you tell us EXACTLY what you're trying to do? (and why), as basically it makes no sense.

#### Chapi

##### New Member

For an experiment in physics, I am trying to measure the arrival time of a particular signal to 2 channels on a scope from as far as possible with a nanoseconds accuracy. I've done it with a modulated signal for a short distance (up to 1 km). see:

But I need much larger distance. The ideal situation will be measuring an rf from a satellite's beacon, or maybe wwv.

#### MikeMl

##### Well-Known Member
Are you reinventing the aeronautical RADAR system, the GPS system, or maybe the LORAN system? Read up on both an learn how it was done with those systems. They all use either phase of a continuous wave, or time-of-flight of radio waves.

#### crutschow

##### Well-Known Member
The ideal situation will be measuring an rf from a satellite's beacon, or maybe wwv.
But would you use for time zero reference to measure the delay against?

#### Chapi

##### New Member
The experiment is in speed of light variations. channel 1 is the zero reference. the probe on channel 2 is handled with additional equipment.

#### Chapi

##### New Member
I was able to see the carrier wave of a distanced am station with a crystal radio.

Crystal radio is the ideal choice for the experiment since it has very little components.

Any one has an idea how to get or built a crystal radio with a defined frequency, 423mhz for example, with a single solid capacitor?

Thanks.

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