RE: [Repeater-Builder] Old duplexer tuning question
> I have been pulling my hair out (I don't have that much more > to go) over an > old Celwave 6 cavity 526-4 pass reject duplexer. I can get > the notches to > tune properly one by one but when I put it all back together > it just does > not seem to sum out right. Is there a procedure someone can > point me to? 526's usually tune up pretty straightforward. If it's an older 526, it may have RG-8 interconnects, which can get noisy (better to replace with RG214). As far as tuning the notches, they are generally a PITA to tune to begin with due to the mechanical design (almost as much fun as Motorola T1504's), but as far as tuning them up separately and then putting it back together and having it not work right, I can't say that I've seen that effect, but then again, that's not how I would tune it. You can get in the ballpark by doing it that way, but in the end, you'll need to look at return loss to know when the pass is really tuned right, and you may need additional amplification to really see the notches, since when it's properly tuned, notch depth will be over 100 dB (although if yours has RG8 interconnects, you may not realize that kind of notch depth). In fact, if yours has RG8, it wouldn't suprise me if some of the problems you're fighting are related to cable leakage coupling. Just to confirm, the one you've got was the 440-470 split model, right? If not, then the cable lengths will be wrong and you can expect to see problems like you're experiencing (notches won't "line up", insertion loss high, etc.). As always, isolate your test equipment from the DUT with pads when tuning. > Also, I am curious if I need to use the same high frequency and low > frequency ports which would be the opposite for ham radio out > here, or if I > need to keep the transmitter port for the transmitter and the > receiver for > the receiver. The 526 is symmetrical - you can use either side for high pass or low pass. --- Jeff 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/
Re: [Repeater-Builder] Old duplexer tuning question
I've got three of them. They're great! There's definitely a low-side and a high-side. You want to maintain that orientation regardless of which side is used for transmit or receive. The duplexer doesn't care - it'll handle 350 watts either way. If you orient the unit with the notch screws and connectors closest to you, or down towards the table, the LEFT side goes to the receiver (usually the higher frequency), and the RIGHT side goes to the transmitter (usually the lower frequency). High/Low refers to commercial repeaters; amateur ones can be oriented either way - mark the sides HIGH and LOW and connect your receiver and transmitter appropriately. The RG214 coax jumper lengths are critical. For 440-470 MHz, there are four that are 11-1/2 inches long and two that are 12 inches long. The two longest ones go from the TEE connector to the center-most N jacks, and the others go between the various sections. I received tuning instructions via e-mail from RFSystems some time ago. They don't really support these old things in a user-friendly self-serve way. As far as tuning goes, separate all the sections and tune each one. Do the bandpass first, then the notch. Make sure the notch tuning doesn't change as you tighten the locking nut. You should get about 0.5dB bandpass loss and at least 35-40dB rejection loss per section. When finished, cable it all up properly and you should be good to go. No further tuning should be required. I use a spectrum analyer with a tracking generator. I haven't seen any difference in tuning if I use 6-12dB pads in series with the input and output, but your equipment may need them if it doesn't present a 50 ohm impedance. I also use a return loss bridge, and a very good dummy load, to adjust the bandpass tuning. This gives a very sharp notch when the resonant frequency causes a 50 ohm impedance; this notch is just as sharp as what you'd get when adjusting the notch tuning on the duplexer itself. Make sure all of your cables are good. The old clamp-style male N connectors can become loose and bits of braid can get lodged inside the connector. A new set of RG-214 cables from RFSystems costs $250 (I had to buy one set) and uses crimp-on N connectors. For all that money, you don't get a new TEE connector with the cable set! Hope this is enough to get you through it. Bob M. == --- tony dinkel <[EMAIL PROTECTED]> wrote: > I have been pulling my hair out (I don't have that > much more to go) over an > old Celwave 6 cavity 526-4 pass reject duplexer. I > can get the notches to > tune properly one by one but when I put it all back > together it just does > not seem to sum out right. Is there a procedure > someone can point me to? > > Also, I am curious if I need to use the same high > frequency and low > frequency ports which would be the opposite for ham > radio out here, or if I > need to keep the transmitter port for the > transmitter and the receiver for > the receiver. > > I should really know all of this but the memory is > fading. > > td > wb6mie __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com 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/
Re: [Repeater-Builder] Old duplexer tuning question
At 02:59 PM 12/19/2005 -0800, you wrote: >I have been pulling my hair out (I don't have that much more to go) over an >old Celwave 6 cavity 526-4 pass reject duplexer. I can get the notches to >tune properly one by one but when I put it all back together it just does >not seem to sum out right. Is there a procedure someone can point me to? > >Also, I am curious if I need to use the same high frequency and low >frequency ports which would be the opposite for ham radio out here, or if I >need to keep the transmitter port for the transmitter and the receiver for >the receiver. <---Yes, you want to keep the same frequency relationship between the hipass and lowpass ports. In other words, if it was Tx high and Rx low before and that's upside down from your needs, you'd connect your Rx to the Tx port and your Tx to the Rx port. Also, it sounds like you made the common mistake of cavity tuning, in that you didn't guarantee a 50 ohm load at each port (you didn't say HOW you tuned 'em but I suspect you didn't use 50 ohm pads on both ports when you did). Ken -- President and CTO - Arcom Communications Makers of state-of-the-art repeater controllers and accessories. http://www.ah6le.net/arcom/index.html We offer complete Kenwood TKR repeater packages! We are now an authorized Telewave Dealer! AH6LE/R - IRLP Node 3000 http://www.irlp.net 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/
