TRX-1: Squelch Codes?

[jleslieiii]

I was out by the Hudson this evening trying to listen to the Marine Band and kept getting public safety dispatchers from two counties away. They share at least five frequencies with the Marine Band, but the dispatchers use squelch codes. I know how to set up a frequency FOR a specific squelch code, and how to EXCLUDE a single squelch code , but is there a way to exclude ALL traffic that has any squelch code?

The Marine Band doesn't use these codes, so to get only tugboat traffic, I'd like to exclude any transmission with any squelch code. Is this possible? How?

Thanks,
Jack

 

[doctordialtone]

I'd like to exclude any transmission with any squelch code. Is this possible? How?

Just program a code that's not in use.

 

[jleslieiii]

Will that allow a transmission that does not have a code?

 

[tvengr]

If you program a code, you would receive only transmissions using that code. Hopefully, you don't need the frequencies that the counties are using. In that case, lockout the frequencies you do not want. If is possible that you are picking up an image frequency or intermod. I don't see a way to fix that in the owner's manual. With Uniden scanners, you have the IFX function for problems like that.

 

[jleslieiii]

If I lock out a frequency of 161.950 with a CTCSS of 94.8 (Sullivan County PD dispatcher) would I still be able to receive a frequency of 161.950 that has no squelch code (Marine channel #27RX marine operator)?

While I know how to exclude a single CTCSS code (94.8 in this example), that would still allow another transmission with a different code. I want to block all codes and just allow codeless transmissions.

I don’t mean to be dense, I’m just not sure that I’m explaining my self understandably.

Thanks.

 

[tvengr]

If you lockout a frequency, you will not receive anything on that frequency. If you don't need that frequency, you will not hear anything on it while scanning. I know that some railroad frequencies are used in large systems where there is a shortage of frequencies. I don't know if the FCC would allow other users on a marine frequency. I can't imagine marine frequencies being used for other purposes within range of a waterway. You will always hear everything on any frequency programmed for carrier squelch.

 

[tvengr]

I don't know how the Whistler firmware treats a locked out frequency with a code. You can try locking out a frequency with a code and programming the same frequency again for carrier squelch. It's worth a try. Let me know what you find out.

 

[Ubbe]

It works if it is only one CTCSS being used on that marine frequency. If you select to lock that out it will be skipped but will monitor all other CTCSS tones and those transmissions that doesn't use any CTCSS.

I have asked Whistler, and Uniden, to have a mode where only non-CTCSS codes are monitored and all CTCSS codes are muted and skipped. That's the mode you'll need to use. A problem could be that it's probably easy for the CTCSS decoder in a scanner to breifly indicate that a subtone have been decoded and will then falsely mute and perhaps even start scanning. It needs clever firmware coding, probably something that isn't so easy for the coders at hand.

/Ubbe

 

[jleslieiii]

Dear tvengr:

Thanks, that may be a work around. I'll try it.

Stay safe,
Jack

 

[jleslieiii]

Dear Ubbe:

You hit the nail right on the head; that is exactly what I'm trying to do. It seems that as currently configured it isn't possible.

I will contact Whistler support and suggest the necessary change and maybe if both of us request it things will progress. "A long time ago, in a galaxy far, far away" I used to code, and it seems to me that if you have a routine to get and evaluate the CTCSS code, you can also test if there is no code. It depends how things are set up, but it seems as if it could be technologically simple.

All the best,
Jack

 

[Ubbe]

I used to code, and it seems to me that if you have a routine to get and evaluate the CTCSS code, you can also test if there is no code.

Yes, it's very easy to do. But you will need to check that during the whole time, if the marine guys might stop talking and the CTCSS guys starts talking. But it needs enough delay and retesting to not react if the decoder sends out sporadic CTCSS decodes, as all decoders do, during normal nonCTCSS conversations. Some repeaters sends out a carrier without any subtones but as soon as someone starts to transmit it starts to send out a subtone.

Whistler has some strange code in their firmware that if you have the subtones set to search it will use the first CTCSS it finds and use that for the rest of the conversation. I have some boats that use different CTCSS tones for each boat on their own channel when they talk to each other, and if I want to see what tone their use I will only hear the first boat. Uniden doesn't use the tone it decodes in search mode so that scanner will scroll thru the different codes as they speak.

Whistler also has some hardcoded routine that always mutes the beginning of an analog conversation, and at that time it tries to see if there's a P25 datasignal transmitted and after some 300mS it unmutes. It could be changed so it always start to unmutes but if it detects P25 it should mute. Uniden has that function as well but only if you program a channel as mixed analog/digital and you can set the mute time to 0 to get rid of it. Whistler also has some quirks during recording, that it records noise in the beginning of all analog recordings before the carrier appears. Their analog sound processing seems to have a delay in the DSP processes so that when the recording starts it records a delayed audio signal from the receiver. The noise burst isn't heard in the speaker due to the P25 delayed mute function. So it isn't so easy to code for a scanner.

/Ubbe