End of radio transmission "click"

[mkm43057]

Hello out there,

I was wondering what the "click" or "tick" noise is at the end of a radio transmission. I hear it at the end of a 800 mhz radio transmission and some times the end of a VHF radio transmission. Its not MDC, MODAT, or DTMF. Just curious to what it is.

Thanks!!!

[nd5y]

It depends on the system. It could be the PTT button scratching on the mic housing, squelch tail, artifacts when then receive audio is muted, signal tones in a remote receiver, voter or tone remote system and probably other things depending on how well or poorly the system was engineered.

[jruta]

http://www.kb9ukd.com/digital/eot3.wav. Is that what you're hearing?

[W0JJK]

Motorola speaker Microphones have a click when you unkey.

[mikegilbert]

I'd wager you're hearing the voting receiver's idle tone come on a fraction of a second before the voting comparator clicks it shut. Our local analog Type II system exhibits the same behavior. Rail dispatchers here in the Northwest have two clicks when they dekey. Again, most likely from the microwave linking.

Does it sound like this: BNSF dekey - YouTube

Ignore the MDC1200 and ''hum" after dekey- it's a simulcast system, PGE VHF Simulcast - YouTube

[greenthumb]

Originally Posted by mkm43057

Hello out there,

I was wondering what the "click" or "tick" noise is at the end of a radio transmission. I hear it at the end of a 800 mhz radio transmission and some times the end of a VHF radio transmission. Its not MDC, MODAT, or DTMF. Just curious to what it is.

Thanks!!!

What system(s) are you hearing this on?

[GM]

Or is this what you are hearing: http://www.w2sjw.com/sounds/SpectraTac.mp3

[gtaman]

Maybe it's the trunking clicks like in an analog trunked type 2 system. Listen to Columbus ohio police your hear it.

[Anderegg]

He might be talking about the "click" you hear on linked (phased?) repeater frequencies........there is also the "ker-plunk" that Motorola mics make as the button is released........"PLUNK!". :-)

Paul

[greenthumb]

Originally Posted by gtaman

Maybe it's the trunking clicks like in an analog trunked type 2 system. Listen to Columbus ohio police your hear it.

So the system is the Franklin County Public Safety - which from the sound of the feed and the licensing appears to be a Motorola Smartnet simulcast system. The clicks at the end of transmissions from radios in the field as well as preceding transmissions from dispatch consoles originate from the Digitac comparators. These perform the voting from the sites as well as audio interrupt connection for dispatch consoles in the system. The click comes from an attempt at filtering the 2175 Hz tone that briefly makes it through to the comparator when radios un-key or a console keys up (console key-up 2175 Hz tone is not present in SmartZone systems). I can't recall if the 2175 Hz tone is responsible for keying and/or un-keying the comparator or if there is signaling that takes care of it. Regardless, that's where it's coming from. If you're a tech and flip the comparator into test mode, the 'chirp' of the 2175 Hz tone makes it through over the air and is not filtered.