Hi Tim see my message, you really do need to check isolation with an analyser I had a look at a duplexer for a chap and there was just 30dB isolation so needless to say the desense was tremendous. It took an input signal of around 70 microvolts to overcome desense. I retuned it on my analyser and got >80dB and it worked
Steve ----- Original Message ----- From: Tim Sawyer To: [email protected] Sent: Friday, May 21, 2010 3:47 PM Subject: Re: [Repeater-Builder] Duplexer on the cheap worries RG-8 is not good for duplex. The braid will make TX noise and get into the receiver. Cheap antennas can make the same problem. Test into a dummy load right at the duplexer. If no noise then you know it's the feed line and/or antenna. 6.5 inch dia cans are big ones so you should have plenty of isolation specially for 2 watts. On Fri, May 21, 2010 at 7:28 AM, kc0mlt <[email protected]> wrote: Hello all. I am trying to figure out if the duplexer we have put together is up to the task or not. Here is the situation. We have four cavities 6.5" dia. one is a vari-notch the others are simple reject cans. Two rejects are on the TX side and one reject and the vari-notch are on the RX side. All set and tuned with rg-213 jumpers between cans and RG-142 from the cans to the Tee connector. We are doing some light testing with a cheap dual ban antenna on the garage. It is feed with RG-8 about 70 feet. We are having some issues with receive. It kind of sounds like desense but I think it is something wrong with the receiver. I was just wondering if the cobbeled together cans sound like thay are doing a good enough job as a duplexer or if we do have something to change on it. The repeater is only putting out 2 watts for testing. I would think I have enough separation for that power level. Any suggestions or thoughts woyuld be greatly appreciated. Thanks Wade KC0MLT -- :wq Tim
