DCS and CTCSS Troubleshooting

[jdoolin]

Has anyone encountered periodic low or lower volume of incoming voice while using DCS instead of CTCSS.  My girlfriend and I have the same radio a Midland MXT575 and I programmed a simplex channel using a DCS squelch and she said about every other transmission my audio was really low but readable.  We were about 7 miles away when we started talking and the dropouts occurred as close as a mile away so signal shouldn't have been an issue.    I remember having a similar issue using DCS between 2 cheap handhelds whereas sometimes it would open the squelch and sometime it wouldn't.  I changed the channel on the midlands to a CTCSS and the problem disappeared.  No dropouts whatsoever and voice loud and clear on every transmission.  I kind of preferred using DCS on some of my channels just to reduce the possibility having the same code as someone else.  If anyone has any suggestions I would appreciated it.   

[Sshannon]

2 hours ago, jdoolin said:

Has anyone encountered periodic low or lower volume of incoming voice while using DCS instead of CTCSS.  My girlfriend and I have the same radio a Midland MXT575 and I programmed a simplex channel using a DCS squelch and she said about every other transmission my audio was really low but readable.  We were about 7 miles away when we started talking and the dropouts occurred as close as a mile away so signal shouldn't have been an issue.    I remember having a similar issue using DCS between 2 cheap handhelds whereas sometimes it would open the squelch and sometime it wouldn't.  I changed the channel on the midlands to a CTCSS and the problem disappeared.  No dropouts whatsoever and voice loud and clear on every transmission.  I kind of preferred using DCS on some of my channels just to reduce the possibility having the same code as someone else.  If anyone has any suggestions I would appreciated it.   

I’m not sure how DCS could cause a weaker signal; both it and CTCSS cause squelch to either open or close, not throttle somewhere in between, unless there’s a software issue with the radio.

[OffRoaderX]

I've tested quite a few different radios and I've never run into this. DCS (and CTCSS) squelch tones work in an ON or OFF way - its either on, or its off, no in-between - thats not to say something couldn't be wrong with one of your radios - I've just never seen/heard of this happening. 

If its working now with CTCSS, I would leave well-enough alone.. the odds of running into someone else using the same tone is very low, as long as you're not using one of the common tones - just use one of the higher ones and enjoy your radios.

[marcspaz]

I agree with Steve and Randy.

 

If you want a light weight explanation on how this stuff works, you can read about it here...

 

 

Good luck and have fun.

[jdoolin]

4 hours ago, Sshannon said:

I’m not sure how DCS could cause a weaker signal; both it and CTCSS cause squelch to either open or close, not throttle somewhere in between, unless there’s a software issue with the radio.

She was explaining to me as I was talking to her the conversation would start with a strong voice then quickly quiet down to maybe less that half volume and at the time we are just a few miles apart.  I have no clue as to how DCS would affect that but I remembered the issues I had with a couple handhelds.  All I know is after switching to CTCSS its been perfect.  I'm familiar with the different types of tones and I used to program our radios for the police department but our channels didn't use any with DCS.   I've been programming my radios for a long time and I did have a couple of Wouxun handheld radios I couldn't trust to open up every time if I used DCS.   I live in a rural area anyway and don't see having any problem using CTCSS anyway so I'll stick with that.  When we were on vacation in Galveston, several times we had to change channels and CTCSS at times to find a quiet channel. 

[OffRoaderX]

are you 100% certain you werent just getting lazy-arm and the mic was getting further from your noise-output hole as you were talking?

[jdoolin]

29 minutes ago, OffRoaderX said:

are you 100% certain you werent just getting lazy-arm and the mic was getting further from your noise-output hole as you were talking?

I did think of that too so I made sure I maintained the same distance.  I have caught myself doing that before.  This one just has me perplexed.  I know it will work fine using analog but now its just a challenge to figure it out.

[marcspaz]

Try swapping radios. You will get to experience what she hears, to help better understand, or establish if it's environmental interference. 

 

Let us know what the firsthand experience is. If you can use your phone to share a video, we may pick up an indicator, too.

 

You may just have a defect in that radio.

[jdoolin]

4 hours ago, marcspaz said:

Try swapping radios. You will get to experience what she hears, to help better understand, or establish if it's environmental interference. 

 

Let us know what the firsthand experience is. If you can use your phone to share a video, we may pick up an indicator, too.

 

You may just have a defect in that radio.

Well I spoke with a radio guy that programs radios for emergency services and he suggested to try a different DCS code. He is not real versed in gmrs but he did say he thought there were a few codes on the upper part of the chart that could cause some problems. He went into technical details about how Motorola started the whole DCS thing and other manufacturers have added codes to expand on what Motorola implemented but the Motorola ones were tested and verified and the additional codes were not or at least by Motorola. In a nutshell I changed DCS  codes to a lower one on the chart and no more issues whatsoever. 

[KAF6045]

1 hour ago, jdoolin said:

Well I spoke with a radio guy that programs radios for emergency services and he suggested to try a different DCS code. He is not real versed in gmrs but he did say he thought there were a few codes on the upper part of the chart that could cause some problems. He went into technical details about how Motorola started the whole DCS thing and other manufacturers have added codes to expand on what Motorola implemented but the Motorola ones were tested and verified and the additional codes were not or at least by Motorola. In a nutshell I changed DCS  codes to a lower one on the chart and no more issues whatsoever. 

Filtering I suspect... Typically higher codes (especially CTCSS, but I suspect DCS may also be using multiple actual tones, not just a pair of tones in FSK equivalent). These tones are supposed to be "subaudible" -- even though human hearing can go down to around 30Hz, the typical radio only passes 300-3000 for audio so the tones are not audible. The tones are likely on a (different) low-pass filter, and that filter is not sharp enough to pass the upper-most tones (those around 200Hz and above)

[MichaelLAX]

Per Wikipedia: 

Quote

In radio or wireless telephony, Private Line is a term trademarked by Motorola to describe an implementation of a Continuous Tone-Coded Squelch System (CTCSS), a method of using low-frequency subaudible tones to share a single radio channel among multiple users. Each user group would use a different low frequency tone. Motorola's trade name, especially the abbreviation PL, has become a genericized trademark for the method.

 

[BoxCar]

Another point to consider, antenna orientation. If your GF points her antenna to you, the signal will also drop because antennas radiate from the middle, not the end.

[marcspaz]

On 10/24/2022 at 10:25 PM, jdoolin said:

Well I spoke with a radio guy that programs radios for emergency services and he suggested to try a different DCS code. He is not real versed in gmrs but he did say he thought there were a few codes on the upper part of the chart that could cause some problems. He went into technical details about how Motorola started the whole DCS thing and other manufacturers have added codes to expand on what Motorola implemented but the Motorola ones were tested and verified and the additional codes were not or at least by Motorola. In a nutshell I changed DCS  codes to a lower one on the chart and no more issues whatsoever. 

 

This makes zero sense to me.  I mean, I am glad that picking another code helped you, but there is zero correlation between a digital binary code being injected into your carrier and your audio quality and audio level.  Something else is wrong.

 

Just a quick explanation, if you are interested...

Digital Code Squelch is a non-audible digital square wave that is injected in between the the audio deviation in the radio waves.  It is literally zeros and ones.  Injecting different combinations of zeros and ones doesn't change how any of it works, at all.  It doesn't matter who originally thought of the binary combination.  The radio creates and deciphers the digital code using the exact same process, every time, regardless of the code.  There isn't different software or circuitry or methods used if a combination of zeros and one were originally packaged in Motorola radios or not.

 

These are what the square waves look like...

 

This is an actual image from a signal analyzer showing the square wave mixed in between the voice deviation...

 

[jdoolin]

37 minutes ago, marcspaz said:

 

This makes zero sense to me.  I mean, I am glad that picking another code helped you, but there is zero correlation between a digital binary code being injected into your carrier and your audio quality and audio level.  Something else is wrong.

 

Just a quick explanation, if you are interested...

Digital Code Squelch is a non-audible digital square wave that is injected in between the the audio deviation in the radio waves.  It is literally zeros and ones.  Injecting different combinations of zeros and ones doesn't change how any of it works, at all.  It doesn't matter who originally thought of the binary combination.  The radio creates and deciphers the digital code using the exact same process, every time, regardless of the code.  There isn't different software or circuitry or methods used if a combination of zeros and one were originally packaged in Motorola radios or not.

 

These are what the square waves look like...

 

This is an actual image from a signal analyzer showing the square wave mixed in between the voice deviation...

 

I agree with you but his suggestion corrected the problem. He wasn’t 100% sure himself. I did go back to the previous code and the problem returned. I called him back and told him what happened. His suggestion avoid that code pick another you have plenty. Lol  He said it didn’t make sense to him either. He just said he’s had a few friends that have have issues with dcs and just conveyed what experience they have had but can’t explain why and they too changed codes and problem resolved. 

[BoxCar]

It may also be a flaw in the radio's design where that particular code causes a harmonic in a different part of the radio.

[marcspaz]

56 minutes ago, jdoolin said:

I agree with you but his suggestion corrected the problem. He wasn’t 100% sure himself. I did go back to the previous code and the problem returned. I called him back and told him what happened. His suggestion avoid that code pick another you have plenty. Lol  He said it didn’t make sense to him either. He just said he’s had a few friends that have have issues with dcs and just conveyed what experience they have had but can’t explain why and they too changed codes and problem resolved. 

 

Understand.  Like I said, I'm glad it helped.  I would love to know the root cause, but it's good to know that there is some goofy thing out there with an easy work-around. 

[jdoolin]

11 minutes ago, BoxCar said:

It may also be a flaw in the radio's design where that particular code causes a harmonic in a different part of the radio.

My radio guy did mention about code causing harmonic issues.  He was getting over my head with the deep technical aspects of it.  I think in a nutshell he was just saying maybe that code just doesn't play well with that particular radio.  They are both midland MTX575 radios.  Not the biggest fan of midland but it they work well for my application. (lack of mounting locations)  I do like how easy it is to change codes on the fly but I'm limited to fixed channel list.  My previous radio was an Icom 1721 I used and worked great for years until the display went out. Loved that radio.

[MichaelLAX]

3 hours ago, jdoolin said:

...maybe that code just doesn't play well with that particular radio.  They are both midland MTX575 radios. 

Another out of the box, easy to use Midland feature! 

[marcspaz]

1 hour ago, MichaelLAX said:

Another out of the box, easy to use Midland feature! 

 

Better than hearing "the scream talker".  LOL

[MichaelLAX]

14 minutes ago, marcspaz said:

 

Better than hearing "the scream talker".  LOL

I googled that phrase and all that came up was a Reddit thread of "Neighbor from Hell!" 

[marcspaz]

56 minutes ago, MichaelLAX said:

I googled that phrase and all that came up was a Reddit thread of "Neighbor from Hell!" 

 

It's It's common phrase around my circles. Figured it was a radio thing. Basically it's the guy/gal you is talking extremely loud into their phone/radio because they think you can hear them better. Some of them sound like their mic is in their mouth, too.

[OffRoaderX]

2 hours ago, marcspaz said:

 

It's It's common phrase around my circles. Figured it was a radio thing. Basically it's the guy/gal you is talking extremely loud into their phone/radio because they think you can hear them better. Some of them sound like their mic is in their mouth, too.

We call those "loud talkers".. closely related to low-talkers and long-talkers.. The WORST is a long-talker, long-talking while eating the mic..

[WRUU653]

This maybe a stupid question, I really don’t know but could this be a thing that happens if one radio is in wide band and the other in narrow?

[marcspaz]

1 hour ago, WRUU653 said:

This maybe a stupid question, I really don’t know but could this be a thing that happens if one radio is in wide band and the other in narrow?

 

The expected behavior is, if the transmitting radio is on narrow and the receiving radio is on wide, than the voice will sound quiet and possibly static-filled.  It will also sound tinny due to how the audio filters are tuned.  Where the processor normally pulls audio for bass, there is no voice to sample.  This is because, best case, only half of the receivers channel space is occupied with data.  The rest is noise.

 

In the opposite case, if the transmitting radio is on wide and the receiving radio is on narrow, than the voice will sound overly loud, possibly distorted and possibly have a lot of bass.  This is because only half of the transmitter's signal is being heard on the receive side, making is sound over-modulated and the audio segment where he treble is sampled is missing.

 

Based on that understanding, mismatching bandwidth should not cause a variation, starting out loud and shifting quiet.  Its either loud and bassy or quiet and tinny, depending on which side of the mismatched bandwidth setting you're on.

[WRUU653]

11 minutes ago, marcspaz said:

 

The expected behavior is, if the transmitting radio is on narrow and the receiving radio is on wide, than the voice will sound quiet and possibly static-filled.  It will also sound tinny due to how the audio filters are tuned.  Where the processor normally pulls audio for base, there is no voice to sample.  This is because, best case, only half of the receivers channel space is occupied with data.  The rest is noise.

 

In the opposite case, if the transmitting radio is on wide and the receiving radio is on narrow, than the voice will sound overly loud, possibly distorted and possibly have a lot of bass.  This is because only half of the transmitter's signal is being heard on the receive side, making is sound over-modulated and the audio segment where he treble is sampled is missing.

 

Based on that understanding, mismatching bandwidth should not cause a variation, starting out loud and shifting quiet.  Its either loud and bassy or quiet and tinny, depending on which side of the mismatched bandwidth setting you're on.

Thanks for explaining this marcspaz, helps my understanding of things even if not the issue here. 
Gil