Could you clarify whether qalqalah is always in a letter or whether it is only in saakinah letters?

Question
As salaamu alaykum
Could you clarify whether qalqalah is always in a letter or whether it is only in saakinah letters? Most books say it is in saakinah letters. But if qalqalah is because of shiddah and jahr, both of which are sifaat laazimah which are ALWAYS in the letter, then isn't qalqalah also always in the letter? It may be less prominent, but it should be present if it is a sifah laazimah.
Answer
Wa alaikum assalaam wa rahmatullahi wa barakaatuh
The qalqalah is only present when the letter is saakin.  The letter hamzah also has shiddah and jahr, but it is not to be read with a qalqalah.  The mechanism of the qalqalah is such as it can only be in a saakin letter. 
Some scholars add (when saakinah) the characteristic of the qalqalah is used for the group of letters which have the qalqalah. 
There are those who say the qalqalah is always present (as stated in your question)  but more apparent when the letter is saakin, but we and many others hold the opinion that it is only when the letter is saakin.  It is not a big issue since in the end the way it is read is the same, and we should respect both opinions. 
Wa assalaam