MCS2000 TX emphasis

[WX5812]

There is a box in the cps that has tx emphasis. What exactly is that?

This radio has a slight tone with the signal when transmitting so was wondering if that is the cause of that?

 

[RFI-EMI-GUY]

FM Transmitters normally have preemphasis curve which enhances the high frequency energy of the voice when transmitting. The receiver has a mirror image de-emphasis curve to reverse that response. in that way the high frequency channel noise at the receiver is reduced while the voice comes across as a flat response.

What sort of tone are you hearing? If it is high pitched you might have a synthesizer problem. If low pitched, it may simply be a CTCSS tone. Also these radio have a modulation compensation adjustment that if fouled up can mess up the TX audio.

 

[WX5812]

Yes it is a high pitched tone. I can hear it somewhat in my icom and Kenwood radios but it really sounds worse on a baofeng. I will try and get a video clip or a link to it to see what you think

 

[mmckenna]

Yes it is a high pitched tone. I can hear it somewhat in my icom and Kenwood radios but it really sounds worse on a baofeng. I will try and get a video clip or a link to it to see what you think

Everything sounds worse on a Baofeng.

Is the offending radio a mobile? Could it be alternator/fuel pump whine?

 

[RFI-EMI-GUY]

I wonder if Baofeng even has proper deemphasis?

 

[mmckenna]

I wonder if Baofeng even has proper….

Even without finishing that question, the answer is NO.

 

[RFI-EMI-GUY]

They have a flashlight and are cheap!

 

[RFI-EMI-GUY]

Yes it is a high pitched tone. I can hear it somewhat in my icom and Kenwood radios but it really sounds worse on a baofeng. I will try and get a video clip or a link to it to see what you think

If it is a tone related to the channel spacing, such as 5.0 or 6.125 KHz or fraction thereof, it could be the VCO voltage is out of spec. Is the radio being operated out of band?

 

[WX5812]

The radio is being used as a repeater transmitter on 70cm the spec for the radio is 403-470 so it’s in range I. I took 2 videos of it on the baofeng and on the Kenwood. You can hear the tone on both of them but it’s more intensified on the baofeng. It won’t let me upload them on here because file is too big any ideas on how to upload it somewhere and get a link? Besides YouTube

 

[WX5812]

Baofeng:

Kenwood:

If those links don’t work let me know.
Thanks for the help

 

[RFI-EMI-GUY]

Getting back to your original question, the box for "emphasis" should be checked. Also, is this a wide band system ? +/- 5.0 kHz? If you have a NB WB mismatch, you will tend to turn the receiver audio up higher and hear more residual noise.

Is this a voted repeater with spectra tac or EIA tone control? Those can have some tone bleed through in the 2175 HZ range.

That tone sounds like PLL reference that is bleeding through the VCO filter. The extent of this being normal or bad is hard to determine without direct measurement per the EIA603 methodology. You would need a calibrated "companion receiver" and measure the residual noise level. A spectrum analyser might show it if it is out of spec.

Have you tried listening to other MCS2000 radio transmitters? Do you hear this when using a 50 OHM dummy load? A different power supply? With Mike audio removed?

You might also check to see if the shields in the synthesizer area are tightened down.