Josh; You could also use a 2n7000 fet in place of the 2n2222 device in that circuit.. 2n700 FET's have an on trigger of between 2-4 volts. as the switch point and switch like an npn transistor for this app.. the input does not require a resistor ( the gate )as it can swing to ~12v before destruction becomes an issue. you can limit it if you want but the gate resistance is in the meg ohm region. it is all but a dc switch for this application.
I had 2 Spectras converted to a repeater I was working on last week and had the same issue of about .8 volt to 8. I put a silicon rectifier 1n4002 type diode in series, anode to the cor of the station, cathode to the controller and then put a pull down-to-ground resistor on the cathode end to really hard pull to ground.. about 1k or so.. switching at that point became effectively zero to 8v. My controller was happy Doug KD8B From: [email protected] [mailto:[email protected]] On Behalf Of James Cicirello Sent: Monday, June 21, 2010 12:43 PM To: [email protected] Subject: Re: [Repeater-Builder] Micor COS issues.... continuing Hi Josh, Instead of resistors, try diodes in series. Each Diode will drop your voltage. I have series a couple to get rid of standing voltage, especially if you are down to a half volt or so. 73 JIM On Mon, Jun 21, 2010 at 11:57 AM, Josh <[email protected]> wrote: I've been fighting this issue for a while now. I've tried some bandaids to deal with it, tried multiple repeater controllers (including one I designed myself with an ATMEGA328 Microcontroller (I'll probably be releasing this design as open source coming up)... and I'm fighting the same problem everywhere... My micor COS signal is weird. When the squelch is closed, I get right around 8 volts, taken from pin 8 of the modified mobile audio/squelch board - the tried and true process just about everybody uses..... When the squelch opens, I'm at not ground potential, but right about half a volt. This isnt really the sort of logic signal I want (I want this thing to be dead nuts zero, not half a volt). What is the deal here? I've tried adding resistors in series to fudge things and cause voltage drop, but thats not really even working that well. I've tried the 2n2222 circuit, but that doesnt really have a lot to do with this (although a variation of that might come into play I suspect) How do I best solve this so I can get my repeater on the air?? This is very close to the last issue I have remaining to solve. Help / advice is greatly appreciated. Josh -- Jim Cicirello 181 Stevens Street Wellsville, N.Y. 14895 (585)593-4655
