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SL30 digital lock indicator for repeaters

Posted: Sat Jun 15, 2013 11:24 am
by g8gtz
One of the challenges for repeater builders is finding a digital receiver with a reliable (and easy) signal lock detect line to drive the control logic when a digital signal appears.

There is an article on page 28 of CQ-TV 240 describing how to extract a lock line for the Comaq SL30 - but beware of the PID issues! (see previous post in this forum).

73 & P5


BTW - calling all repeater keepers - let's have you tips and hints to help others who probably have the same problem with their repeater as you did! And if you are struggling with something on your repeater - trying asking here ;-)

Re: SL30 digital lock indicator for repeaters

Posted: Thu Oct 31, 2013 9:13 am
by g8ajn
The Porty and derivatives do have a problem decoding some of the data from the MK808 version of the DigiLite encoder smoothly so we have been obliged to find an alternative receiver. The cheap BigSat is being used by a number of repeaters and copes well with the digital stream and as it has a lock light it would seem to be ideal although the main received signal info screen is not as easy to display as with the Porty. Another snag is that it is driven by the same scanning waveform that is used for the LCD display so it is not a clear dc on/off line and the circuit shown here copes with the 80/20 ratio of waveform. I have been using a the diode pump arrangement on our BigSat here at GB3SQ. By rectifying the changing mark-space waveform squared off by the switching FETs it gives about 0.5v with lock light off and 3v with lock light lit. More details and photos under RECEIVERS/DIGITAL on my website.
Dave G8AJN

Re: SL30 digital lock indicator for repeaters

Posted: Thu Oct 31, 2013 9:27 am
by G4GUO
Dave, we do know what the problem is with the MK808, it is the irregular PCR timestamps.
How to implement an elegant solution to this problem is what is taking the time.
The MK808 software is very simple and this issue has thrown a bit of a spanner in the
works as far as the programs design is concerned. When I gave it to Rob I didn't think
anyone would actually use it!

- Charles G4GUO

Re: SL30 digital lock indicator for repeaters

Posted: Thu Oct 31, 2013 4:15 pm
by g8ajn
Thanks for that Charles. I much prefer the single button-press Received Signal info screen on the Porty and the dc driven lock light so if you guys can sort the problem it will be a huge benefit especially for repeater use where it needs to be remotely operated.
Dave G8AJN