I bought a bag of 2N6426 Darlington Pair transistors some time back. These work nicely for COS pick off because they do not load the existing circuit very much.
Say you have a point that goes between 1/2 volt and 5 volts for a cor source, (it will take around 1.4 V to turn on a dp cause of two cascade BE junctions) and you need to invert it. Take a 27K resistor from the cor source to the base of the npn darlington. Place 47k between the base and ground to reduce accidental turn on. Also, a 0.005 uf capacitor from base to ground won't hurt to keep some rf out. Ground the emitter of the darlington, and place a 27K between collector and 12 or 10 thereabouts supply and the collector of the darlington. You might have to add a 47k from the cos source to supply if the source is an open collector. If the circuit causes the squelch on the radio to quit working, it might be loading it too much, and the input swamping resistor, 27K might need to be a little bigger. Seems like the ARRL, FM and Repeaters book might have some good info. Also there a plenty of Elmers here willing to take a few minutes and help. 73, Steve NU5D -----Original Message----- From: jay_kruckenberg [mailto:[EMAIL PROTECTED] Sent: Tuesday, November 30, 2004 10:00 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Inverting COS I have a Motorola radio that has an active low COS signal. I need this to be an active high COS signal. Does anybody know how to build a simple circuit that will invert the COS signal from a low to a [Steve Bosshard (NU5D)] --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.802 / Virus Database: 545 - Release Date: 11/26/2004 Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
