[GreenKeys] HAL ST-6 - squelch?

[Duncan Brown]

Howard,

I used the term "squelch" (in quotes) as a generic term for muting the 
output when there was only noise (or not a desired signal) present.

The ST-6 has a fairly simple (all hardware) muting system that is part 
of the Autostart circuit. But other than the statement in the 
Introduction of the ST-6 manual that I stated below, the manual says no 
more about this feature.  It turns out that the ST-6 "AUTO - AUTO OFF" 
switch controls the mute/squelch feature, whether you are in Autostart 
mode or not.

73 & have fun,

Duncan'
K2OEQ




On 08-Sep-20 17:52, Howard Weeks wrote:
>
> I suspect that the function on RTTY that is being called "squelch" is 
> not entirely accurate. Being confused with squelch performance as in 
> the FM radio domain.
>
> In the RTTY domain, you want a capability that will keep the loop 
> closed and not printing on mechanical machines unless or until you 
> have a legitimate char or sequence to print.  The definition of what 
> defines that decision point in the demodulator is pretty broad.  It 
> can't be made on the basis of one bit or even a string of bits in most 
> cases.  It is a moving target most of the time.   The solution is 
> usually based on both analog as well as digital analysis.  There are 
> simple approaches to he subject and there are very complex ones 
> depending on what the data is being used for.
>
> My old school approach to RTTY tones is 2125 low and 2975 high for 850 
> shift.  2125 low and 2295 high for 170 shift.  Mark low and space 
> high.  Nearly all of the hardware based systems (non software 
> oriented) use this convention because of "fixed frequency" filters and 
> detectors.  I also use crystal derived transmit tones and they cannot 
> be easily changed nor would I. Everyone knew what to expect!
>
> In the software domain, you can play all the games you want with the 
> tones and their interpretation.  But, if you are going to include this 
> "old school" stuff above, you will have to limit your tones and 
> related protocol to something that is compatible with them.  Those 
> tone frequencies, filters, and tone detectors are "fixed" by design.
>
> Howard K5JCP
>
> On 9/7/2020 1:29 PM, Duncan Brown wrote:
>> The Introduction to the ST-6 manual states: "An automatic control 
>> holds the ST-6 in the mark condition when non-RTTY signals (such as 
>> voice, cw, or noise) are received."
>>
>> When monitoring ham RTTY/RATT QSOs, I get a lot of random characters 
>> printed (from noise) between transmissions, so I don't seem to have 
>> (or have working) the "squelch" function mentioned above.  I also 
>> don't see anything in the schematics that might be doing this function.
>>
>> Am I missing something?  Does the ST-6 have a "squelch" function? If 
>> so, where?
>>
>> Thanks & have fun,
>>
>> Duncan
>> K2OEQ
>>
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