Signal meter

[Driverj30t9]

Hi there, I'm just wondering about the signal bars on scanners and any radio, but I only scan and use cb.

My question is why does a radio pick up a signal bar on a frequency, be it 1, 2, 3, 4 or 5 bars, when no one is transmitting?

Do transmitters/transceivers always emit some radio waves from there antennas even when the radio isn't being keyed and then my reciever antenna picks those up and shows how strong the signal is?

 

[jonwienke]

Do some Google searching on how trunked radio systems work. Many types use a control channel that broadcasts continuously.

 

[jwt873]

And, if you're listening where no one is transmitting, you're probably hearing natural noise https://en.wikipedia.org/wiki/Atmospheric_noise or signals generated by equipment in your home (computers, battery chargers TV sets etc). These things will cause your meter to show a reading.

 

[Whiskey3JMC]

Could be numerous reasons. As jonwienke pointed out it might be a control channel on a trunked radio system but it might also be QRM (interference) from a nearby appliance in your home. Are you hearing any audio or data noise in addition to seeing the bars? Is your scanner set manually on one channel or scanning when this happens? What make/model scanner are you using? Perhaps posting this question to your scanner make's forum on this site will get you more relevent answers. Welcome to RR!

 

[Driverj30t9]

Okay, it's making sense now. Atmospheric noise, maybe galactic noise and universal, and human made noise.

I pretty much get the blinking or a fixed bar or two on every frequency 20 mhz to about 2 ghz. I get like four or five bars though on 1 to 2 ghz must be my data card and or computer. When in my truck the s meter was jumping up around 28 mhz to like 40mhz.

Just been using my TRX1 and WS1040 in scan mode or tune mode, or listening to one frequency at a time, not just control channels. No data, some frequencies have transmissions on them, most are empty

I can't hear any of that noise on my radio now even with the squelch wide open. I must have changed a setting. Might be good to hear if I wanna pick up a far away frequency. I believe there was some button on my cb I pushed to turn off the noise. Noise blanker maybe?

Thanks, good to be here.

 

[JamesO]

Many radio receivers have "Birdies" which are internally generated signals that are usually mixer artifacts.

I also have found that the stupid cigarette lighter USB adapters can generate a LARGE amount of broadband lower frequency noise as man of these USB adapters may be some form of Voltage converter or switch mode power supply rather than an old school analog Voltage regulator.

You may also have other in vehicle interference with computerized modules, Infotainment systems and even the LCD display that some modern vehicles have.

The LCD screen can actually trigger the Laser portion of radar detectors if you have them mounted in the headrest area of the seat and not up on the visor.

Lots of things to consider.

 

[Driverj30t9]

Many radio receivers have "Birdies" which are internally generated signals that are usually mixer artifacts.

That's true, was just reading up on something about that.

I also have found that the stupid cigarette lighter USB adapters can generate a LARGE amount of broadband lower frequency noise as man of these USB adapters may be some form of Voltage converter or switch mode power supply rather than an old school analog Voltage regulator.

I don't really use those, but when I plug in my inverters into a cigarette lighter and then plug in the ac adapter into the inverter and into my scanner it generates lots of noise, my WS1040 will start sticking on a bunch of frequencies mostly lower band and I"ll have to lock them out, it's really annoying. If I plug in a usb cord into the inverter and my scanner or run batteries everythings fine, no sticking on frequencies.

I'm going to try putting some ferrite beads on the ac adapter and see if that resolves the issue.

You may also have other in vehicle interference with computerized modules, Infotainment systems and even the LCD display that some modern vehicles have.

I do have have a display screen, it's probably led, don't know for sure.

Interesting about the radar detector. Where not allowed to use those in semis so I don't have any.

Yes, there is lots to consider.