Don, Do you know what band the radio was on when in service? If it was a 480 MHz radio it would tune to 460 but have major problems tuning to 440. If this was the case you need to lengthen the helical resonators about 1/2 turn to start with, that is if my memory serves me right.
That is a very good receiver, what does it look like, they had a couple different versions. Both had the same basic electronics but different housings. Does the exciter tune up? Paul -----Original Message----- From: [email protected] [mailto:[EMAIL PROTECTED] Behalf Of donlspivey Sent: Monday, February 27, 2006 9:48 AM To: [email protected] Subject: [Repeater-Builder] Help With EF Johnson CR-1000 Repeater Ok you Johnson ghuru's out there, please read this. I was asked by an area ARES group to lend a hand and convert an EF Johnson CR-1000 series UHF repeater to amateur use. This is, of course, free gratis on my part, I'll even chip in the ID'er since it's for a good cause. I cannot get the receive sensitivity where it should be. Initially when I received it, the JFET located inside the preselector was blown. I replaced it with a generic JFET but not an exact match. At first I couldn't get the sensitity any lower than about 50uv and several tuning screws were bottomed out in the row of helicals suggesting the new frequency is beyond the range of the preselector. I replaced the screws with a similar brass screw but about 3/8 in longer and I was able to get the sensitivity down into the 10-15uv range, obvioiusly a big improvement, but still way off. No screws were bottoming out at this point. I first retuned the receiver as per the factory manual. I did, however, note the suggested minimum voltage reading I should see were always lower. I've really never particularly paid strict attention to these "should be about" readings, but all increased after the machine screw changeout suggesting they could possibly increase more once the proper sensitivity is reached. Does anyone have experience with this repeater or the mobile chassis it's patterned after? I can assume the helicals will need modification, but that's why I asking the experts!!!! The group that will own/manage this repeater are buidling their shack this week and hanging hardline, so it looks like I may be the "holdup" here. Please point me in the right direction...Thanks...de N5MZQ Yahoo! Groups Links 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/
