Terry, Yes, I tried using a Q2220E duplexer on a 2m repeater, with a 600 kHz split, but quickly realized that it was not up to the task. It simply does not have sufficient isolation at a 600 kHz split to be useful at 2m. It is specified to have 70 dB of isolation at a 500 kHz split, but you need 71 dB of isolation for a 1 (one) watt transmitter working with a 0.3 uV receiver- according to CommShop for Windows. Part of the problem is that the Q2220E duplexer uses the "Res-Lok" design, wherein the coupling between cavities of each pair is via a machined port between them, rather than a cabled coupling loop that can be adjusted. Although this particular duplexer is advertized as capable of 500 kHz splits, it is aimed for applications with at least a 3 MHz split. Quite a difference, there!
Although you may find significant desense of 3 to 10 dB to be okay, I shoot for zero dB of desense- and that means 95 to 100 dB of isolation with most practical repeaters. Choose wisely... 73, Eric Lemmon WB6FLY -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Terry Sent: Monday, March 23, 2009 11:29 AM To: [email protected] Subject: [Repeater-Builder] Sinclair Q2220E Does anyone have experience using this model on 2 meters? Do they provide enough practical isolation for single antenna, 600kc split? (Sinclair Q2220E 4 Cavity VHF BpBr Repeater)
