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Real time RF sample

1

1502gulfcoastMS

Member
Nov 2, 2015
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I have read a few times on this forum that you can take magnet wire and wrap around your coax and then use head phones. I need a "dumimes guide" on how to make this. Here are the questions I have.

1. How many wraps and where do you put it on at?

2. Do you just put a female jack on the wire ends and plug in?

3. Does the amt of rf watts change the installation?

4. What type of wire is best to use?

I talk the mostly on 11 meters 30 watts and 500 with dx.
 

You do not need to use magnet wire. Just a piece of solid strand copper wire, like the kind that is used in home wiring. Five or six turns of it around your coax and then connect each end to your freq counter or oscilloscope leads. No more difficult than that.

If you are running power; then that is a different can of worms. Run it on the coax between the radio and the amp. It does not affect anything.
 
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He's looking to build a demodulator. Which is just a scope pick up with more parts. I wouldn't just wrap it around the coax though. More wraps are needed for low power. If you make it for a 30 watt radio I wouldn't out it behind a 500 watt amp. If it doesn't fail you might blow out your headphones...or ears.

This is a crude design I posted on another forum. Just easier to post a link than upload pics. BTW, this only works on AM. It is useless on SSB or FM.

http://www.cbradiotalk.com/viewtopic.php?f=6&t=46378
 
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543_Dallas said:
He's looking to build a demodulator. Which is just a scope pick up with more parts. I wouldn't just wrap it around the coax though. More wraps are needed for low power. If you make it for a 30 watt radio I wouldn't out it behind a 500 watt amp. If it doesn't fail you might blow out your headphones...or ears.

This is a crude design I posted on another forum. Just easier to post a link than upload pics. BTW, this only works on AM. It is useless on SSB or FM.

http://www.cbradiotalk.com/viewtopic.php?f=6&t=46378
Click to expand...
Thanks alot guys, I'm looking to just hok up head phones for now. At some point I will get into using a scope before the antenna and understand that's a different can of worms
 
Robb said:
Never had a problem with 4-5 wraps. But if he wants to build a demodulator; then he should have said so in the first place.
Click to expand...

I'm not sure what it's called.these are the keys words you may have missed...
1502gulfcoastMS said:
I have read a few times on this forum that you can take magnet wire and wrap around your coax and then use head phones. I need a "dumimes guide" on how to make this.
Click to expand...

I'm guess an rf sample is not what's needed to use head phones.

Is it called demodulator?
Basically I want to hear my over the air audio without being pinched by the receive bandwidth of another radio. I don't feel that talk back is very accurate for what I want to do.
 
You're on the right track. Talkback is just audio out of the audio amp in the radio. You may sound great in the talkback and sound like garbage on the air.

For best results build it in a small enclosure. Look at the link I posted or Google demodulator or am demodulator circuit. It's just a coil of wire around or next to the center conductor, a diode (I used an nte583) and a .01 capacitor.
 
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543_Dallas said:
You're on the right track. Talkback is just audio out of the audio amp in the radio. You may sound great in the talkback and sound like garbage on the air.

For best results build it in a small enclosure. Look at the link I posted or Google demodulator or am demodulator circuit. It's just a coil of wire around or next to the center conductor, a diode (I used an nte583) and a .01 capacitor.
Click to expand...
Going to make this my weekend project. If I can over pay for parts at radio shack.

I have a stryker 655, the talk back circuit in that radio will make any mic sound great. Only one I have every seen that you can use a d104 with. Once I realized that, I leaned about talk back being what it is.
 
Just get a hand held CB radio like a Cobra Road Trip (or similar) and plug in a good pair of sealed headphones. These used walkie talkie CB radios are cheap-cheap on eBay and come with a rubber-ducky antenna perfect for near field monitoring of your broadcast audio. You will be limited to AM mode monitoring.

You absolutely need the "completely sealed around the ear" headphones so NO Sound At All comes from the headphones that the microphone will pick up when you transmit. Otherwise the audio will be tainted with feedback. This is true of any station monitoring headphones.
 
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I also noticed that I sounded different with different brands of headphones. I have 2 differnet pairs if the sealed ear muff phones. I sounded bad on one pair and decent on the others. I have some ear buds that I sound great on. The pot I installed to control causes some distortion when turned down. Maybe some headphones are a better impedance match than others.

This issue isn't very noticeable when testing a standard issue cb radio but wideband AM brings out the flaws. As of late I've been using a stryker 955 to monitor my transmit. I was hearing a hum in the audio through the receiver at first. The solution was to set my TR296 on top of the 955, run a single power cable to both radios and spilt it off right behind them. It works pretty good even though some experts insist stock radios can't hear wideband. :rolleyes:
 
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BBB said:
Just get a hand held CB radio like a Cobra Road Trip (or similar) and plug in a good pair of sealed headphones. These used walkie talkie CB radios are cheap-cheap on eBay and come with a rubber-ducky antenna perfect for near field monitoring of your broadcast audio. You will be limited to AM mode monitoring.

You absolutely need the "completely sealed around the ear" headphones so NO Sound At All comes from the headphones that the microphone will pick up when you transmit. Otherwise the audio will be tainted with
Click to expand...
BBB said:
Just get a hand held CB radio like a Cobra Road Trip (or similar) and plug in a good pair of sealed headphones. These used walkie talkie CB radios are cheap-cheap on eBay and come with a rubber-ducky antenna perfect for near field monitoring of your broadcast audio. You will be limited to AM mode monitoring.

You absolutely need the "completely sealed around the ear" headphones so NO Sound At All comes from the headphones that the microphone will pick up when you transmit. Otherwise the audio will be tainted with feedback. This is true of any station monitoring headphones.
Click to expand...
I would also be limited to the recive bandwidth of a small cheap handheld radio, correct? Im playing with wide banded tx.
 
1502gulfcoastMS said:
I would also be limited to the recive bandwidth of a small cheap handheld radio, correct? Im playing with wide banded tx.
Click to expand...

Yes,but not everybody has a radio modified or sdr to receive wideband audio

With the handheld radio you be able to hear how other people with regular radios can hear you and then you could tune your audio for the masses :whistle:
 

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