Is it practical to own a frequency counter?

[Beetle]

Don't forget: things like freq counters, o'scopes and the like require periodic maintenance and CALIBRATION. Even a Simpson 260 VOM used to keep track of line voltages and such need these every six months, or whatever the manufacturer requires.

 

[Radiomatrix]

Ok, so this took a little bit of a turn but thats ok. The Surecom device that you were looking at will display the frequency that it is reveiving by simply receiving it as a broadcast over its antenna (no need to directly connect anything to your setup). It's like having a receiver that shows you the frequency it is listening to. As Brandon stated it will work on AM with your radio hooked to your antenna or a dummy load and you just key the radio up (no modulation). It will display the frequency. If you wanted to see what the sideband frequency is you would need to play a 1Khz tone (from your phone as an example) and play that tone through your mic. The Surecom will display the channel frequency +/- 1Khz. For instance, on channel 19 am (no audio, just a carrier) it would display 27.185. If you were on LSB and played the 1Khz tone through the mic it would display 27.184 and USB 27.186. The surecom device eliminates the need to directly connect the frequency counter to your system which is ok as well. Make sense?

Keep asking questions. That's the only way any of us learn from others......

Why 1khz sound? How accurate or close to 1 khz would it have to be? What if the sound was 4khz or 10 khz?

 

[brandon7861]

Don't forget: things like freq counters, o'scopes and the like require periodic maintenance and CALIBRATION. Even a Simpson 260 VOM used to keep track of line voltages and such need these every six months, or whatever the manufacturer requires.

Calibrating a frequency counter that has a 2ppm tcxo but only displays to 100Hz would be like putting 1/8" tick marks on a crescent wrench. Pointless.

That device will always be accurate, but only because they limit the resolution far beyond what it could ever drift past.

 

[brandon7861]

Why 1khz sound? How accurate or close to 1 khz would it have to be? What if the sound was 4khz or 10 khz?

Because if you put 4kHz into your microphone, the audio would fall outside the IF passband and not much of anything would come out of the radio. You could use 2kHz, the carrier will shift by that much. So on 38LSB, 2kHz audio would cause the radio to transmit on 27.383MHz. Get much higher in audio frequency and you start losing signal ebcause it don't get through the crystal filter that keeps your signal a speciffic bandwidth..

Edit: Imagine if 10kHz got into your mic and actually got all the way through to the output. The carrier would be shifted by 10kHz. It would be on the next channel down. The channels are 10kHz apart, modulating more than 5kHz puts it firmly in the adjacent channel's space, so radios are designed to stop that by bandpass filtering the audio or modulated RF.

 

[Lkaskel]

Don't forget: things like freq counters, o'scopes and the like require periodic maintenance and CALIBRATION. Even a Simpson 260 VOM used to keep track of line voltages and such need these every six months, or whatever the manufacturer requires.

This is a good point but lets try to remember what is to be accomplished on the original question. Radiomatrix is looking for an easy/basic solution to undertand the frequency his radio is on. In these cases a perfectly calibrated device is a little bit of a reach unless the calibration was easy thing to do or have done. For anyone looking to repair or align radios as a service I would agree that they should consider calbrating thier equipment on a regular basis.

 

[Lkaskel]

Because if you put 4kHz into your microphone, the audio would fall outside the IF passband and not much of anything would come out of the radio. You could use 2kHz, the carrier will shift by that much. So on 38LSB, 2kHz audio would cause the radio to transmit on 27.383MHz. Get much higher in audio frequency and you start losing signal ebcause it don't get through the crystal filter that keeps your signal a speciffic bandwidth..

Edit: Imagine if 10kHz got into your mic and actually got all the way through to the output. The carrier would be shifted by 10kHz. It would be on the next channel down. The channels are 10kHz apart, modulating more than 5kHz puts it firmly in the adjacent channel's space, so radios are designed to stop that by bandpass filtering the audio or modulated RF.

Also, a 1Khz audio tone is a standard in radio use/service. It's just easy or better to stick with the standard and because of everything Brandon said.....