A half wave length cable will act as an impedance transformer too. In this case it will be a 1:1 transformation and if the output of the transmitter is not 50 ohms then whatever impedance it is will be transformed to the cavity input.
73 Gary K4FMX _____ From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Friday, February 23, 2007 4:06 PM To: [email protected] Subject: Re: [Repeater-Builder] Re: 220 repeater receiver recommendations? In a message dated 2/23/2007 12:00:13 P.M. Pacific Standard Time, [EMAIL PROTECTED] writes: It probably isn't exactly 50 ohms, but should be close. And the cables from the duplexer to the radio do NOT *REPEAT* NOT need to be an exact length. This again indicates an impedance mismatch in the duplexer and it should be retuned. (or a bad antenna/load) I never suggested that the cable between the TX and the duplexer had to be an exact length and if the TX output is a true 50 ohms then any cable length produces no consequence at the cavity input. But if the TX impedance is not 50 ohms, I think any cable length other than half wave will make the cable a line transformer affecting the impedance presented to the cavity with a quarter wave producing the greatest impedance shift.
