I have heard this point argued for years. “Does trimming the coax affect the SWR?” If the length of coax has an affect on impedance, then how could it not affect power out? We strive to maintain 50 ohms at the tail of all devices to match the end load. GE puts matching networks in their Mastr II’s. I have taken a MFJ-259 and soldered a PL259 only at one end and then started trimming the coax down and watched the impedance change significantly with each cut. Duplexers come with precise lengths of cabling. I have heard that trimming coax only fools the meter. Not being an engineer with millions worth of equipment I can only make a SWAG (scientific wild ass guess) as to whether coax length makes a difference in power out.
Randy W4CPT -----Original Message----- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Jeff DePolo Sent: Saturday, August 25, 2007 12:30 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Duplexers > When you put the Bird between the TX and the duplexer, you > have changed the > length of the jumper cable, which upset the tuning. Adding a wattmeter or any other length of cable between the transmitter and the duplexer Tx input port has no effect on the tuning of the duplexer. It may change the load Z the transmitter sees, which may make the transmitter happier (or sadder) depending on the resulting Z, but in no way does it alter the tuning of the duplexer itself. Adding or removing cable lengths between the transmitter and duplexer also does not change the VSWR as seen by the transmitter (minimal cable loss effects notwithstanding)-. --- Jeff --------------------------------------------- Jeff DePolo - HYPERLINK "mailto:jd1%40broadsci.com"[EMAIL PROTECTED] Broadcast Sciences LLC, Valley Forge PA v: 610.917.3000 f: 610.917.3030 No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.484 / Virus Database: 269.12.6 - Release Date: 8/24/2007 12:00 AM No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.484 / Virus Database: 269.12.6 - Release Date: 8/24/2007 12:00 AM
