SSM200 - Super Squelch

SSM200 - Super Squelch
Improve the sensitivity of your repeater for weak mobile signals.

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The SSM200 is a smart squelch generator with exclusive three independent outputs of COR1. Unlike traditional circuits which closes the squelch immediately when the signal ceases, the SSM200 analyzes the quality of the signal and if weak adds a squelch tail, significantly improving the reception of mobile and portable stations.



The SSM200 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 SSM200 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 SSM200 offers three different C.O.R outputs with negative logic:


C.O.R. – Regular C.O.R. output with no tail. Just like you find in any receiver;


SS C.O.R. SHORT – Output with 300ms of tail only if the signal is not full quieting. Ideal for repeaters with no CTCSS2 tones.


SS C.O.R. LONG – Output with 600ms of tail only if the signal is not full quieting. Ideal for repeaters with CTCSS tones.


C.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.


Instalation and Operation Manual


Sper Squelch SSM200