Avoid a ctss, but not the freq

beerzkool

Member
Premium Subscriber
Joined
Feb 13, 2002
Messages
266
Location
Los Alamos, New Mexico
Hello.

My county uses the same freq as an adjacent county (seems like a FCC screwed up - it is not a mutual aide issue). I know the tone of the adjacent county, but I have not found the tone for my county on the same freq because they rarely use it.

Is there a way to program the sds 100 so it will avoid a specific ctss tone for a unique freq in scan mode so I can discover the ctss tone for the same freq in my county?

Thanks in advance for being helpful.
 
Joined
Apr 18, 2009
Messages
4,111
Location
CT
Is there a way to program the sds 100 so it will avoid a specific ctss tone for a unique freq in scan mode so I can discover the ctss tone for the same freq in my county?
Sure.

If you avoid the entry with the known CTSS then keep scanning in CTSS search mode - you'll still hear the unknown CTSS transmission. Right?
 

cg

Member
Premium Subscriber
Joined
Dec 13, 2000
Messages
3,654
Location
Connecticut
it would still stop and search for the tone on the active channel, locking out one channel will not affect another. You can ignore the other CTCSS using tone L/O but then you cannot search for the other CTCSS. You might make two identical channels, one with tone L/O set for the problem tone and the other set for tone search. Set the second one to be avoided. If there is activity, HOLD and scroll up to the one that is avoided.

chris
 

ko6jw_2

Member
Premium Subscriber
Joined
May 18, 2008
Messages
1,071
Location
Santa Ynez, CA
CTCSS is a very old technology. The problem is that the decoding takes place in audio stages of the receiver and this means that although you don't hear the other signal it is still in the front end of the receiver and may desensitize or create phase distortion. Once the squelch opens for the desired signal, the other signal may be heard mixing with the signal you want. All of this is bad practice. Where were the frequency coordinators? This seems like it might have started out as a mutual aid channel, but was changed to the situation that you have now. There's not a lot that you can do about it.
 

ofd8001

Member
Premium Subscriber
Joined
Feb 6, 2004
Messages
6,948
Location
Louisville, KY
I'd think you would need to know both CTCSS values. You can find the unknown one by searching as noted above.

Once it is discovered, created two channels. One has the frequency and CTCSS for your home county and the second for your adjacent county's frequency and CTCSS. Then you can do a lockout or avoid on the one you do not want to hear.
 

kruser

Active Member
Premium Subscriber
Joined
Nov 25, 2007
Messages
4,079
Location
West St Louis Cnty, MO
I've used ProScan for this very scenario.
We had a user here that used the same frequency for local government stuff and then much less for a small public works crew.
They simply used different tones for the two departments.
This seemed to be pretty common within small sized rural agencies I learned.

Like the OP, I knew one tone but not the other for the seldom used public works users.
I set the radio on the frequency in tone search mode and let ProScan log the activity for that frequency for a day while at work.
When I came home, a quick sort on the Tone column in ProScan's log screen and my unknown tone was revealed.

This could take more than a day of logging though if the unknown tone users only use their radios a couple times a week!
 

n1chu

Member
Premium Subscriber
Joined
Oct 18, 2002
Messages
845
Location
Farmington, Connecticut
A common issue. The apparatus at my fire station had radios installed that when the mic was in its hangar, there was no PL. everything on the frequency was heard. When the tech was asked why this is he explained it was to be able to monitor ALL the users of the system before transmitting so as not to transmit until the frequency was not being used. It made for a noisy cab when the mic was not in its hangar. (The hanger was either attached to chassis ground, common to the radio, or, if it was mounted on plastic or other material, where it was not attached to ground, a ground jumper wire was incorporated. This method had some removing the mic from the hangar, incorporating our PL, so they were not bothered by other usage of the frequency... a practice that usually ends up with the mic being keyed up unknowingly when placed on the seat, becoming lodged between the persons buttocks and the seat... getting keyed up! After a period of time we asked that the hangar function be reversed where the mic, while in the hangar incorporating our PL was the norm and instructed all to first listen for other traffic on the frequency when they pulled the mic from the hanger to transmit. To this day I’ve wondered why the tech was hooking up the mic hangers as “open” to all traffic. I guess the commercial world of radio usage dictated the practice where the public safety world of radio usage did not. Most ignored the instruction to first listen for traffic before transmitting unless it was another “fire” radio doing the talking. One thing appreciated by all was the quiet on-scene radio operations, by hanging the mic back in its hanger all the unwanted traffic was muted.

Our radio system was (and still is) using one of the same frequencies as the FDNY, a busy organization to say the least! And although we were out distance-wise better than the 70 mile rule of thumb, they still made their presence known! Not so much these days, I guess NYFD has moved off their VHF high band systems?
 

n1chu

Member
Premium Subscriber
Joined
Oct 18, 2002
Messages
845
Location
Farmington, Connecticut
A common issue. The apparatus at my fire station had radios installed that when the mic was in its hangar, there was no PL. everything on the frequency was heard. When the tech was asked why this is he explained it was to be able to monitor ALL the users of the system before transmitting so as not to transmit until the frequency was not being used. It made for a noisy cab when the mic was not in its hangar. (The hanger was either attached to chassis ground, common to the radio, or, if it was mounted on plastic or other material, where it was not attached to ground, a ground jumper wire was incorporated. This method had some removing the mic from the hangar, incorporating our PL, so they were not bothered by other usage of the frequency... a practice that usually ends up with the mic being keyed up unknowingly when placed on the seat, becoming lodged between the persons buttocks and the seat... getting keyed up! After a period of time we asked that the hangar function be reversed where the mic, while in the hangar incorporating our PL was the norm and instructed all to first listen for other traffic on the frequency when they pulled the mic from the hanger to transmit. To this day I’ve wondered why the tech was hooking up the mic hangers as “open” to all traffic. I guess the commercial world of radio usage dictated the practice where the public safety world of radio usage did not. Most ignored the instruction to first listen for traffic before transmitting unless it was another “fire” radio doing the talking. One thing appreciated by all was the quiet on-scene radio operations, by hanging the mic back in its hanger all the unwanted traffic was muted.

Our radio system was (and still is) using one of the same frequencies as the FDNY, a busy organization to say the least! And although we were out distance-wise better than the 70 mile rule of thumb, they still made their presence known! Not so much these days, I guess NYFD has moved off their VHF high band systems?
Correction; Change “It made for a noisy cab when the mic was not in its hangar.” To “When the mic was in its hanger.”
 
Top