Mike, Although my Celwave catalog does not show the CD220 isolators, I believe that they were made for 220 MHz service. This seems logical, since the CD150 series is for 136-174 MHz, the CD280 series is for 250-285 MHz, and the CD460 series is for 406-512 MHz. However, the range of a specific isolator is very narrow, and can be tuned only a few MHz each side of the center frequency for which it was originally made. The catalog listing for the CD150 series, for example, means that Celwave is able to make an isolator for any center frequency in the 136-174 MHz range, but once made, it can be field-tuned only 2 MHz or so each side of the center frequency. To move the tuning more than a few MHz requires that the isolator be returned to the factory for rework.
A vector network analyzer should be used to properly tune an isolator, since certain critical adjustments are best displayed as return loss. A ferrite isolator may generate a substantial second harmonic, so it should be followed by a low-pass or notch filter. You may get lucky and find that your isolator can make the 220 Ham band, but don't be surprised if it requires rework. I have had two dual isolators remanufactured so far, moving them from the commercial VHF band down to the 2m band, at a cost of about $200 each- about a third of the cost of a new unit. Not only do they work perfectly, but they came back with a new-product warranty. The letter suffix indicates the maximum amount of reflected power the isolator can handle: A indicates 15 watts, AA indicates 30 watts, and B indicates 60 watts. 73, Eric Lemmon WB6FLY -----Original Message----- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Sunday, October 05, 2008 11:38 AM To: Repeater Builder Subject: [Repeater-Builder] Celwave CD220-B Isolator I've searched high and low but not found my Celwave catalogs. The RFS site was no help. Can someone confirm that the CD220-B is for 220 MHz? Their naming conventions appear straight forward. And if indeed for 220, has anyone used one in the ham band on a repeater? Thanks Mike/W5JR
