I have not checked the TR4 manual but in the T4 series they show the FSK circuit. I had 2 of them in mine as well. One was set for 850 cps shift while the other was for 170 cps shift. That was at the time when things were still at 850 but moving to 170. I was also in MARS and they were stuck on 850. I am sure you have a frequency shift keying circuit for 2 shifts on your pto. Good luck. Jim Pruitt
>>> On 4/26/2012 at 6:10 AM, <[email protected]> wrote: Ethan, It is certainly some sort of FSK circuit. Actually, it looks like 2 FSK circuits. Why 2? Well, if one is good, two must be better, right? Back in the day, it was common to use both normal shift (850Hz) and narrow shift (170Hz). Normally you just changed it by the control voltage but the DPO of yours didn't know that. OR, maybe he put in two so he could implement an RIT using one. The schematic looks wrong, they are in series instead of parallel (kinda sorta) and looks like it was uncompleted. Construction is uh... UGLY and HUGE, I would remove it and start over, IF you want FSK. My guesses only.... BTW, Drake issued actual drawings of FSK circuits. I know because the PO of mine installed it in my T-4X and included the memo (tech tip?) with the manual. You need a wire coming out somehow. Mine comes out on an unused connection on the power plug. 73, Gary WB6OGD ----- Original Message ----- From: Ethan Blanton <[email protected]> To: [email protected] Sent: Thu, 26 Apr 2012 04:11:57 -0000 (UTC) Subject: [Drakelist] TR-4 mystery circuit attached to PTO Hi all, As discussed a few times in #drakelist on IRC over the past few days, I have a TR-4 ("B" era) with a circuit hanging off the PTO that I don't really grok. I've put up a web page with some photos and a discussion of the circuit as I understand it here: http://kb8ojh.net/misc/TR-4-PTO/ I've heard two plausible theories for what this circuit is, but both theories have holes (admitted by their authors). It's always possible that the circuit was built wrong, or that I have captured it wrong, and one of these theories is still correct. I'll leave those theories out for just now, to avoid tainting anyone's creative process. I'm curious to hear what others think it may be. Ethan _______________________________________________ Drakelist mailing list [email protected] http://mailman.zerobeat.net/mailman/listinfo/drakelist
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