Ron, Contact EMR and request a copy of the bulletin, "Field Tuning of Isolators." Be aware that typical circulators and isolators can be field-tuned perhaps +/- 2% from the frequency for which they were made. If you want to use it at a new frequency that is more than 3 or 4 MHz away, it probably will need to be remanufactured at about 1/3 to 1/2 the cost of a new unit. You should use a vector network analyzer, or at least a spectrum analyzer with tracking generator and a return-loss bridge, to properly tune a circulator or isolator.
73, Eric Lemmon WB6FLY -----Original Message----- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Ron Wright Sent: Wednesday, November 12, 2008 8:01 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] isolator Hi all, I have aquired a EMR Isolator, model 7450/4 for 150-170 Mhz and tuned to 155 MHz. It has 3 tuning adjustments so need to retune it. Can anyone give info as to how to tune it or where I can get info. EMR has good info on what it does and how it works, but found nothing at their site on tuning. Tune for low SWR, max power out, min smoke, etc??? 73, ron, n9ee/r
