Sounds like a plan. One thing about it, I can always either completely remove the helical extension or shorten as needed. Cutting that strip down will make working with it easier, that' for sure. That 220mhz project sounds interesting!! And yes, the very first think I noticed about this radio was the lack of a true 1st RF stage. I even called the mixer JFET the first RF until I looked at the schematic...Boy was I suprised!!! You could put a train load of these machines in the same shack and probably not get intermod between any of them. I'll probably give it a try this weekend. Thanks again Paul....Don
--- In Repeater-Builder@yahoogroups.com, "Paul Finch" <[EMAIL PROTECTED]> wrote: > > Don, > > It sounds like your close, I have had very good luck butt soldering the same > gauge wire to the top end of the coil and formed in the same shape as the > helical. I would start at around 1/2 turn and re-install the helical strip. > Cut a little off if necessary. Turn the screws up and see if it tunes. > > I have worked on a lot of the UHF radios, it really sounds like you have the > high split 480 to 512 radio. I have moved several 480 radios down to 440 > this way but I have never had to add anything to the 460 split radios. > > By the way, yes you will need to add to the multiplier/injection helical > resonators to get them to tune. That is unless you went to high side > injection and then you may still need some. > > A trick I learned, cut the metal strip where you have three strips, the > multiplier strip helicals on one end and the 5 helicals from the RF input on > the other. That leaves the middle strip where the mixer transistor is. Cut > right in the middle of the screw holes, when you screw them in the screw > make the ground connection for both parts. I have never noticed any > degradation in sensitivity doing this. You will find aviation shears work > the best. This makes it a lot easier to remove just the helicals that need > lengthened. By the way, you can't do that with a VHF 530 or 529, the strip > is a PC board. > > Another by the way, I am working on converting a Fleetcom 530 150-160 MHz > radio to 220 MHz. I have the exciter putting out 8/10 of a watt and the > receiver tuning except the last two helicals nearest the mixer. Something > else, I guess you see that these radios don't have a receive RF amplifier. > Pretty good, huh. Makes for less intermod! > > Hope this helps, > Paul > > > -----Original Message----- > From: Repeater-Builder@yahoogroups.com > [mailto:[EMAIL PROTECTED] Behalf Of donlspivey > Sent: Tuesday, February 28, 2006 8:06 PM > To: Repeater-Builder@yahoogroups.com > Subject: [Repeater-Builder] Re: Help With EF Johnson CR-1000 Repeater > > > Paul.. > > I have the manual, a nice clean one. The original crystal was indeed > an EFJ crystal and looked to be original. I've pulled the entire set > of helicals out one already to install the JFET mixer transistor, it's > a great radio to work with, very easy to get to everything. > > So, I take it you still think I still need to add a bit to the > resonators. How much to you suggest? Half a turn possibly (it's > always easy to cut them back it too long)? And do would the 3 mixer > resonators need extending too?? Thanks again Paul...Don > > --- In Repeater-Builder@yahoogroups.com, "Paul Finch" <dpaulfinch@> > wrote: > > > > Don, > > > > Do you have a manual? The 5 helical resonators together are the > front end > > and the three together are the tuning for the injection to the mixer. > > Really easy radio to work on. Are the 461.XXX crystals EF Johnson or > > another make. A 461 receiver really should come down to 440 OK. It > still > > sounds like you need to add some to the helicals. > > > > Paul > > > > > > -----Original Message----- > > From: Repeater-Builder@yahoogroups.com > > [mailto:[EMAIL PROTECTED] Behalf Of donlspivey > > Sent: Tuesday, February 28, 2006 12:58 PM > > To: Repeater-Builder@yahoogroups.com > > Subject: [Repeater-Builder] Re: Help With EF Johnson CR-1000 Repeater > > > > > > Thanks for the help Paul: > > > > Originally it was on 461.375, which appears to be from the factory. > > Both the exiter and receiver look to be a cast mobile radio chassis > > remounted for rack use with unnecesscary circuitry not installed. All > > looks original and non modified. It's very clean. The receiver has a > > row of 5 helicals then three more used in other ways, mixer..etc. The > > exciter chassis does not have the holes where the helicals screws > > would have gone threaded, so it's not a mobile converted to repeater > > service. > > > > Unless there's another issue as to why I the sensitivity isn't there, > > it looks to be in great shape. No repairs are apparant, nobody has > > butchered it. I mentioned that I went through the factory tune up > > procedure step by step and each time the voltage I found was below the > > range given in the service docs. I also mentioned after changing the > > helical screws/slugs the sensitivity increased a lot and those > > voltages did get a lot closer to the bottom end of the range it gives. > > I mentioned I changed the JFET in the mixer although a generic sub > > within the correct frequency range and voltages. > > > > With the exception of needing to change the compensating cap for the > > new crystal, I had the exciter tuned up in about 5 minutes. I believe > > it was putting out 15 watts with the original crystal and I had > > exactly the same after retuning it. > > > > Sure looks like it's still an issue with the helicals. Much like I've > > encountered with Micor receivers. However, this is my first EFJ > > repeater so any hints or tips would be greatly appreciated, the boys > > down here with ARES are appreciative too. Thanks again for your > help...Don > > > > > > --- In Repeater-Builder@yahoogroups.com, "Paul Finch" <dpaulfinch@> > > wrote: > > > > > > 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: Repeater-Builder@yahoogroups.com > > > [mailto:[EMAIL PROTECTED] Behalf Of donlspivey > > > Sent: Monday, February 27, 2006 9:48 AM > > > To: Repeater-Builder@yahoogroups.com > > > 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 > > > > > > > > > > > Yahoo! Groups Links > Yahoo! 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