[SOLVED] does this mean the voltage controlled oscillator is transmitting a radio signal?

[dl09]

I connected a voltage controlled oscillator to a 12.28 volt battery. if I don't connect the battery to a voltage controlled oscillator, the amplitude of the radio waves is -25 decibels, and if I connect the battery to a voltage controlled oscillator, the amplitude of the radio waves is reduced to roughly -60. does this mean the voltage controlled oscillator is transmitting a radio signal?

 

[BigBoss]

How do you measure ??

 

[dl09]

i used a spectrum analyser to measure this. does this mean the voltage controlled oscillator is transmitting a signal?

 

[volker@muehlhaus]

if I don't connect the battery to a voltage controlled oscillator

The VCO has two inputs: one supply and one for tuning frequency. Which of them do you mean here?

 

[dl09]

I connect the battery to the supply input. the seller says if the input for tuning frequency is 0 volts, the output is 70 megahertz I think. does this mean the voltage controlled oscillator is transmitting a radio signal?

 

[KlausST]

Hi,

if the input for tuning frequency is 0 volts, the output is 70 megahertz

General rule: Never leave any input pin floating.
"Unconnected" does not mean "0V" it rather means "undefined". It can be any voltage.

Klaus

 

[FvM]

if I don't connect the battery to a voltage controlled oscillator, the amplitude of the radio waves is -25 decibels, and if I connect the battery to a voltage controlled oscillator, the amplitude of the radio waves is reduced to roughly -60.

dB is no magnitude quantity. Do you mean dBm? What do you see, noise background? Discrete lines?

i used a spectrum analyser to measure this.

How you connect the SA? Antenna, cable?

 

[dl09]

I connect a coaxial cable that acts as an antenna.

--- Updated Jul 22, 2020 ---

when I use the spectrum analyser. I see background noise at -25 dB, no I don't mean dBm. then when I connect the battery, to the supply pin, the noise is reduced to -60 dB.

--- Updated Jul 22, 2020 ---

1 axis on the spectrum analyser reads dB.

--- Updated Jul 22, 2020 ---

1 axis on the spectrum analyser reads dB.

 

[FvM]

on the spectrum analyser reads dB.

dB is a relative quantity, it's meaningless without an absolute reference. Please tell the SA brand and type.

As previuosly discussed, a coaxial cable is no antenna. Please describe the complete test setup. (oscillator, analyzer, cables, antennas)

--- Updated Jul 22, 2020 ---

It might be that a strong out of band RF signal is blocking the analyzer input. If so, the reduced floor would indicate RF, but that's just a guess. More information needed.

 

[dl09]

dB is a relative quantity, it's meaningless without an absolute reference. Please tell the SA brand and type.

As previuosly discussed, a coaxial cable is no antenna. Please describe the complete test setup. (oscillator, analyzer, cables, antennas)

--- Updated Jul 22, 2020 ---

It might be that a strong out of band RF signal is blocking the analyzer input. If so, the reduced floor would indicate RF, but that's just a guess. More information needed.

The voltage controlled oscillator is connected to a coaxial, which serves as an antenna. I shaved off some insulation and I shaved off the outer copper layer. I removed the outer copper layer. The upper pin is connected to the positive terminal and the pin below that is connected to the negative terminal. Two pins are not connected to anything. I use a spectrum analyser to confirm there is a signal. I check at 80 megahertz and nearby frequencies. The battery is a 12.28 volt battery. The amplitude of the radio waves is only reduced when I connect the battery, I think.
I see a red light when this happens. The seller says this means the voltage controlled oscillator is connected to the supply voltage. There I think I described the setup.

 

[KlausST]

Hi,

I shaved off the outer copper layer

-> Then it's no "coax" anymore

"Two pins are not connected to anything" ...

All in all I don't see any progress. It's time for me to leave this thread.

Klaus

 

[volker@muehlhaus]

The amplitude of the radio waves is only reduced when I connect the battery, I think.

LESS power with device conncted to the battery? Then you have created a transmitter with negative output power, which absorbs the background signals. A black hole maybe?

 

[dl09]

Can you explain this or not?

 

[betwixt]

dl09 - the problem is you keep giving us conflicting information or incomplete information. We are trying to answer your questions but some of the things you are doing are illogical. Can you post us a picture of what you are doing, it might help us understand what you see.

Brian.

 

[dl09]

I will have to wait until I get home. Give me a few hours.

 

[dl09]

When the battery is not connected to the voltage controlled oscillator I see this on the spectrum analyser

When the battery is connected to the voltage controlled oscillator I see this on the spectrum analyser

So is the voltage controlled oscillator transmitting a signal?

 

[betwixt]

Aside from a 5dB difference in background noise, which could be due to other things, I see no significant additional signals. We still have no idea what this VCO is or how you have it connected though. A picture of the VCO and how you have it coupled to the spectrum analyzer would be useful.

Brian.

 

[FvM]

How has the setup changed compared to post #1 which claims -60 dB.

 

[dl09]

Well sometimes the difference is 5 do. Sometimes the difference is greater.

--- Updated Jul 24, 2020 ---

Well sometimes the difference is 5 dB. Sometimes the difference is greater.

--- Updated Jul 24, 2020 ---

The setup has not actually changed.

--- Updated Jul 24, 2020 ---

In post #8 I mentioned I connected a coaxial cable to the voltage controlled oscillator and the coaxial cable acts as an antenna. The coaxial cable is not connected to a spectrum analyser. The coaxial cable, which acts as an antenna, is supposed to radiate radio waves. The spectrum analyser is suppose to pick up radio waves.

 

[FvM]

O.k. you want to say that the analyzer is picking up the radio waved by its own antenna. Post #9 question (brand and type) is still pending.