CTCSS tones

Status
Not open for further replies.

w7cma

Member
Joined
Oct 4, 2011
Messages
23
Location
Missoula, Montana
I am a new feed provider, so please easy on me. Here is the problem. The city PD uses tone on their tx, I believe it is 203.5. I can hear this tone in my feed. The radio I am using does not have decode capability, if I add a decoder board and use tone squelch would I be able to attenuate the tone so it is not heard? I am sure it is the CTCSS I am hearing because none of the other stations do not have the tone in their tx.

Thanks for your time.
 

Ubbe

Member
Joined
Sep 8, 2006
Messages
8,944
Location
Stockholm, Sweden
It depends on the tone board if the audio goes through it so it can be filtered and then have a "clean" audio out connection to use.

/Ubbe
 

paulears

Member
Joined
Oct 14, 2015
Messages
769
Location
Lowestoft - UK
Radios with CTCSS usually have good tone suppression, as it would annoy the users, so if you use an external board, it is that making the difference. Of course, if you have an old high graphic EQ laying around, or even buy one one ebay, that would work - IF - your audio output from the radio is line level, and not speaker level, which it probably is. The hifi graphic works on discriminator feeds quite well, but not sure what your interface arrangements are. Otherwise, you'll have to build a high pass filter - only a few passive components.
 

cmdrwill

Member
Joined
Mar 30, 2005
Messages
3,984
Location
So Cali
No one in their right mind would use a CTCSS tone that high, except to discourage scanner listeners.

So yes, you would need a high pass filter in the audio to suck out the tone.
 

paulears

Member
Joined
Oct 14, 2015
Messages
769
Location
Lowestoft - UK
er, I use one near there on my repeater, a bit higher, actually - and it's not a bother to any of the users, as the Kenwood radios I have on it have pretty sharp high pass filters - you can just detect it. Scanner users don't come into it. I picked it because it was well away from the others I use.
 

w7cma

Member
Joined
Oct 4, 2011
Messages
23
Location
Missoula, Montana
Radios with CTCSS usually have good tone suppression, as it would annoy the users, so if you use an external board, it is that making the difference. Of course, if you have an old high graphic EQ laying around, or even buy one one ebay, that would work - IF - your audio output from the radio is line level, and not speaker level, which it probably is. The hifi graphic works on discriminator feeds quite well, but not sure what your interface arrangements are. Otherwise, you'll have to build a high pass filter - only a few passive components.

Thanks for answering , I am taking audio out of the headphone jack , the radio is a Yaesu FT 8100, there is a decode board available I can buy. I have installed a 300 Hz high pass filter on the phone jack output but does not work. I may order the decode board and try it. If I can find an EQ I will try that first, probably cheaper than the board. Thanks again.
 

paulears

Member
Joined
Oct 14, 2015
Messages
769
Location
Lowestoft - UK
If the 300Hz filter doesn't work - something else is wrong. If you have something like Audacity (a sound app) on your computer, you can record a little bit and actually analyse what the tone is to see if it really is a CTCSS tone, or something else. The filters in the tone boards are quite mild, so if the injection level of the tone is high, then I doubt they'd do much.
 

w7cma

Member
Joined
Oct 4, 2011
Messages
23
Location
Missoula, Montana
If the 300Hz filter doesn't work - something else is wrong. If you have something like Audacity (a sound app) on your computer, you can record a little bit and actually analyse what the tone is to see if it really is a CTCSS tone, or something else. The filters in the tone boards are quite mild, so if the injection level of the tone is high, then I doubt they'd do much.

Thank You For replying,
I have recorded and analyzed a portion with Audacity, the tone is right at 203 Hz right where the frequency listing says the station tone is 203.5 Hz. So I am confident thats what it is. What I don't understand is why the 300 Hz filter wont null it out. I have been monitoring this station locally for the last 7 years and the tone has been there, but now that I am broadcasting I would like to filter it out. My next step is to find an EQ . Thaks again.
 

ko6jw_2

Member
Premium Subscriber
Joined
May 18, 2008
Messages
1,448
Location
Santa Ynez, CA
No one in their right mind would use a CTCSS tone that high, except to discourage scanner listeners.

So yes, you would need a high pass filter in the audio to suck out the tone.

I guess the California Department of Forestry and Fire Protection is insane. They use 192.8.
 

nd5y

Member
Joined
Dec 19, 2002
Messages
11,226
Location
Wichita Falls, TX
No one in their right mind would use a CTCSS tone that high, except to discourage scanner listeners.
That's not an issue with high end radio radios or even most cheap chinese radios that use the WOC chipsets. The only radios I have seen that don't have a 300 Hz high pass filter for the speaker audio are scanners and Icom/Kenwood/Yaesu/Alinco ham rigs.
 

ecps92

Member
Joined
Jul 8, 2002
Messages
14,360
Location
Taxachusetts
Using the higher Tones has been done [and continues[ Very Well in many areas. :cool: Since the 80's

IT comes down to the proper adjustments, there are many 203.5 Hz
systems where you can not even detect the CTCSS, yet then there are
plenty of others where it is "over driven"
No one in their right mind would use a CTCSS tone that high, except to discourage scanner listeners.

So yes, you would need a high pass filter in the audio to suck out the tone.
 
Status
Not open for further replies.
Top