Just to echo previous comments, the LMR type cable (any cable with aluminum foil/braid combination) is suspect. This subject comes up here about every other week.
Chuck WB2EDV ----- Original Message ----- From: "Bill Wilson" <[EMAIL PROTECTED]> To: <Repeater-Builder@yahoogroups.com> Sent: Sunday, July 06, 2008 10:24 PM Subject: [Repeater-Builder] New Repeater Desense Problems Greetings Group, I had hoped to be able to purchase off-the-shelf components for a 2 meter repeater for our local club to use. I purchased a Maggoire HiPro R1VHF35, 35 watt version, and with their recommendation a set of FiPlex DVN-1533L Duplexers (6 cans). These were installed with LMR-400 cabling and a 50 foot run to a Diamond X- 50 Dual Band vertical installed about 40 feet above ground. We have a good ground, and the equipment is mounted in an open rack. The controller is a CAT-250, currently with COR receive only, although the CTCSS module is installed but not turned on at this time. I have been told however that the PL is being transmitted on the transmit signal for decode. I also had the Narrow Band IF Filter installed. Ever since we first hooked everything up, we have had receive desense problems. The cans have been retuned 3 times by two different radio shops in the area, and the problem still exists. With the exception of the duplexer and repeater itself, every other component in the system has been swapped out at least once. One observation by the first radio tech (ham) that came out was the "very sensitive" receiver on the order of 0.10 uv, versus the 0.20 uv as advertised. On the third tune-up of the duplexers, they "discovered" that the loops were 180 degrees out of phase, and when they turned them, the duplexers "came right in". However, the problem persists. Great for in town use, but that's about it. We have used varied lengths of cables between the repeater and the duplexers, without any significant change in results. Next weekend, I am planning on looking at the tuning myself with borrowed test equipment. I know what I'm looking for pretty much, and it's got to be close to correct to work as it does. Any thoughts ideas, etc., would be appreciated. Bill - KJ4EX ------------------------------------ Yahoo! Groups Links
