The SSM300 is a smart squelch generator with exclusive four independent outputs of C.O.R. Unlike traditional circuits which closes the squelch immediately when the signal ceases, the SSM300 analyzes the quality of the signal and if weak adds a squelch tail, significantly improving the reception of mobile and portable stations.
The SSM300 needs only the receiver´s discriminator to operate. This signal passes through some filters, goes to an analog to digital converter and then is handled by software algorithms which decide how much tail, if any, will be added to the squelch.
When a received signal is strong, will be an immediate audio shut-off and no squelch tail. Not having a squelch tail on your repeater sounds great, plus you can tell your signal is strong because you are full quieting:
With strong signals there is no squelch tail
On the other hand, when a signal is weak or unstable, a tail is added, so there is no audio chopping under "flutter" conditions. If there is a tail, you are noisy:
With weak signals there is a squelch tail
In “flutter” conditions, typical from mobile operations, a regular squelch circuit will cut the audio immediately, causing seconds of interruptions plus a typical sequence of courtesy beeps over the mobile station:
“Flutter” condition with no squelch tail there is audio chopping
Now we have the same condition, but because there is a tail in the squelch we will be able to hear all the transmission, and more, you can tell the signal is weak:
No audio chopping under “flutter” conditions
With the SSM300 you will not have to worry looking for C.O.R. logic signals inside a receiver anymore. As manufacturers are not supplying schematics anymore, what used to be a simple task in the past can be challenge nowadays.
The SSM300 offers four different C.O.R outputs with negative logic:
C.O.R. - Regular negative C.O.R. output with no tail. Just like you find in any receiver;
C.O.R. + Regular positive C.O.R. output with no tail. Just like you find in any receiver;
SS C.O.R. SHORT – Output with 150ms of tail only if the signal is not full quieting. Ideal for repeaters with no CTCSS2 tones.
SS C.O.R. LONG – Output with 300ms of tail only if the signal is not full quieting. Ideal for repeaters with CTCSS tones.
1C.O.R (Carrier Operated Relay) or C.O.S. (Carrier Operated Switch) is a signal from the receiver which tells the repeater controller that the squelch is open and there is a signal there.
2CTCSS (Continuous Tone Coded Squelch System) is a series of sub-audible tones standard on today radios.