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Author Topic: Questions on CTCSS and P/L  (Read 22178 times)
W9KDX
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Posts: 771




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« on: October 19, 2011, 05:23:38 PM »

I am programming my Wouxun HT and I need to clarify something.  O assume that when a repeater lists a PL tone it is the CTCSS tone that I need to use when I transmit to the repeater.  My software lists these as both encode and decode.  Am I correct in assuming that the encode is what I use?  I am guessing that the decode would only be used to block reception to only signals that use that tone, and I don't want to do that.

If I have things wrong, straighten me out.  The software also has a section that would allow me to enter a single tone for the entire band and I am pretty sure that would not apply here as the repeaters I am looking at use different tones.
Thanks
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Sam
W9KDX
KJ4OBR
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« Reply #1 on: October 20, 2011, 07:16:48 AM »

You've got it. Decode mode would not let you hear any signal that did not contain the set PL tone. You can usually set the encode/decode mode to encode only. My quansheng and my ft-8900 software both have a dropdown selector: enc, enc/dec, off.

Set the encode tone to the correct  value for your repeater at the single memory level. It might not be the same with the Wouxon, but on my Quansheng I also have to set the correct offset frequencies for the repeater shift (tx in one column rx in another)  

You are also correct that you do not want to set the PL tone globally.

73

Dave


I am programming my Wouxun HT and I need to clarify something.  O assume that when a repeater lists a PL tone it is the CTCSS tone that I need to use when I transmit to the repeater.  My software lists these as both encode and decode.  Am I correct in assuming that the encode is what I use?  I am guessing that the decode would only be used to block reception to only signals that use that tone, and I don't want to do that.

If I have things wrong, straighten me out.  The software also has a section that would allow me to enter a single tone for the entire band and I am pretty sure that would not apply here as the repeaters I am looking at use different tones.
Thanks
« Last Edit: October 20, 2011, 07:18:25 AM by KJ4OBR » Logged
W9KDX
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Posts: 771




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« Reply #2 on: October 20, 2011, 07:22:45 AM »

Great.  Glad I got one right.  Maybe I'm getting better at this. Smiley
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Sam
W9KDX
AI8O
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« Reply #3 on: October 23, 2011, 03:12:17 PM »

I am programming my Wouxun HT and I need to clarify something.  O assume that when a repeater lists a PL tone it is the CTCSS tone that I need to use when I transmit to the repeater. 

 My software lists these as both encode and decode.  Am I correct in assuming that the encode is what I use?  I am guessing that the decode would only be used to block reception to only signals that use that tone, and I don't want to do that.

.

Most amateur repeaters only use input encode, that is on the input frequency to the repeater.
Most do NOT ouput a CTCSS tone.
If you use DECODE CTCSS in your HT, on most repeaters you will not hear anything, because your HT must hear the correct hearing a tone to open the squelch.
The squelch will not open because  it is not hearing any tone at all.
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Semper Ubi, Sub Ubi!
PE1HZG
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Posts: 60




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« Reply #4 on: October 25, 2011, 01:56:33 AM »

Most amateur repeaters only use input encode, that is on the input frequency to the repeater.
Most do NOT output a CTCSS tone.

The repeaters I maintain DO output a CTCSS tone. This has several advantages:
  • * The radio does not open on other signals, e.g. when conditions improve
  • * The squelch doesn't break when you walk past a noisy, radiating cash register e.g. in a shopping centre
  • * My repeaters ID every 5 minutes (Netherlands, different rules). The radio does not open on ID alone, only when there is activity. After 35 years people tend to know the callsign of the repeater..

The bottom line: check, or ask the repeater owner. I publish the details on qsl.net/{pi3ehv,pi2ehv,pi6ehn}

73, Geert Jan
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W3DL
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« Reply #5 on: October 29, 2011, 04:20:16 PM »

Around here most repeaters DO encode CTCSS tone on their output. It makes good sense for the reason mentioned earlier. On the few channels around here which do not encode, and my receiver must be on carrier squelch, I always get noise bursts as I drive around, passing sources of signals like traffic lights, gas stations, etc.

With so many sources of spurious signals in our environment these days, I believe it is a courtesy by repeater owners to send a CTCSS tone on the repeater output signal which users can make use of by setting their mobiles and portables to decode.

Sure, when the band opens up and you want to hear distant signals, you may have to temporarily disable the decode function, but on most days you will be glad you are set for decode.
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KM3W
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« Reply #6 on: November 23, 2011, 12:51:44 PM »

True,

Both of my repeaters (440 and 220) generate tone on the output, set to follow the receiver COR...this is done so that remote base users can set decode on their receivers, and link in without having to wait for the repeater to drop before transmitting. This allows for a much smoother conversation.

KM3W
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AE6ZW
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« Reply #7 on: November 25, 2011, 09:27:36 PM »

my radio Yaesu FT-2800M can not use different frequency tone for decode and encode, some repeaters uses different tone for encode and decode, so I can only use it for encode.  I think many of the HAM radio are same, I understand commercial radio are often capable of separate tone freq doe decode and encode.
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W3DL
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Posts: 13




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« Reply #8 on: November 26, 2011, 05:07:30 AM »

I don't see a good reason for a repeater to use a different tone for encode than for decode. If the tone is good for one it is good for the other. Let's accommodate all the ham radios features.
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WB6DGN
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« Reply #9 on: November 26, 2011, 10:11:23 AM »

Quote
I don't see a good reason for a repeater to use a different tone for encode than for decode. If the tone is good for one it is good for the other. Let's accommodate all the ham radios features.

There are a number of reasons why a repeater may use a different tone on its output than it uses on its input.  One of the most common reasons is where multiple receivers are used on the input to a repeater.  By using different tones on each receiver, the user can select the receiver he thinks will provide the best input to the repeater (sort of a user-selected voting).  This also prevents the weaker receiver(s) from introducing noise into the system.  There are many other reasons why a repeater operator may choose a different tone for the input while keeping the same output tone but this is one of the most common.
Tom DGN
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W3DL
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« Reply #10 on: November 26, 2011, 11:02:19 AM »

Ah yes, I forgot about that. We had a system in this area with multiple inputs, we called it a poor man's voting system.
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AK2O
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Posts: 8




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« Reply #11 on: May 17, 2014, 08:24:45 PM »

The other reason would be the (unfortunate) case the repeater has some PIM running around the site; in some cases, if the tone was the same (Tx-Rx) the repeater would talk to itself, thus, disabling the reason to have tone (RF suppression-or to ignore it). Of course a repeater owner would want to fix the PIM problem to begin with, but the point might not be realized by all.
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K6LCS
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« Reply #12 on: May 19, 2014, 08:07:47 AM »

Just an add: I have more than 100 repeater systems programmed in my HTs. Not a single system is programmed in "closed tone" mode for expecting to receive a CTCSS tone. They are ALL open tone on receive.

One might think that is crazy. But is has not proven problematic in the slightest for me here in Southern California.

Here is the scenario that could crop up: Two repeaters on the same frequency, although several miles apart. If I were closed-tone on my local system, and there was important comms occurring on the other system, I could key up and unintentionally interfere with legitimate comms on that distant repeater. I would be violating FCC rules by keying my mic on a frequency that was in use by others.

SO ... For me in this region - open one on receive has worked just fine. And if it doesn't cause me problems in this region - the most populous region of the nation's most populous state - I cannot see why it would be problematic for others.

Clint K6LCS
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Clint Bradford, K6LCS
http://www.work-sat.com
N0GW
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« Reply #13 on: May 19, 2014, 02:18:31 PM »

It may make more sense why public service might use different encode and decode tones if I give an example.  Here in Missouri, most rural fire departments use VHF analog.  In my county, it is necessary to have four repeaters to provide adequate coverage into all the gullies and hollows that are common in the Ozarks.  What has worked best is to have all of their outputs on the same frequency and CTCSS tone.  The output CTCSS is necessary because of county overlap on rural fire frequencies.  RF does not stop at a county line!

Each repeater has its own different CTCSS input tone so fire crews can operate through whatever one is usable from a fire scene.  Of course, the county dispatcher can operate through all of the repeaters simply by selecting the correct input tone.  There is really no need for or interest in linking all these repeaters together since all communications is either local to an incident or with the county dispatcher. Likewise, fire Incident Commanders will shift their operation to one of the national fire simplex frequencies if the incident would be creating lots of chatter between crews.
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K9MHZ
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Posts: 439




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« Reply #14 on: June 14, 2014, 05:37:07 AM »

If you ever decide to get on 33 cm, it's not only important, but downright vital.  902 MHz is shared (as is 70 cm) with other services, but is particularly littered with ISM digital garbage, and it will drive you nuts unless your radio is programmed for CTCSS receive.  Repeater owners know all about it and will CTCSS output their machines.

Someone mentioned above, start with open receive and see what happens, then go from there.

Enjoy.

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