AJ, the only suggestion that I have is to add a regular cavity on each side if you have some available....that 2220 is probably never going to work very well at 600 Khz.
If your PA is causing spurs....put an antenna tuner on the output of the TX between the TX and the Duplexer, and tune it for minimum VSWR...that should clean it up.... GE did this with a device they called a Z Matcher. John VE3AMZ ----- Original Message ----- From: AJ To: [email protected] Sent: Wednesday, March 25, 2009 7:35 PM Subject: Re: [Repeater-Builder] Re: Sinclair Q2220E Any suggestions for improving the situation with our existing Q2220E duplexer? We could turn the P/A down even further, but there's not much more room to work with with this 40 watt P/A from it's current 25 watt level without causing spurs... On Wed, Mar 25, 2009 at 3:44 PM, John J. Riddell <[email protected]> wrote: Re the Sinclair RES-LOC Q2220E Duplexer, they make a much better version, the Q2330E model. We use one here on VE3KSR, 146.970 It has 100 Db of Tx - Rx isolation at 500 Khz and midband isolation of 55 Db as opposed to 30 Db in the Q2220. Power rating is 350 watts on each unit. The Q2330E has three "cavities" on each side. 73 John VE3AMZ ----- Original Message ----- From: AJ To: [email protected] Sent: Wednesday, March 25, 2009 4:19 PM Subject: Re: [Repeater-Builder] Re: Sinclair Q2220E We have one in place right now on the 600 KHz split at 25 watts from a MastrII... Very noticeable desense... Not very happy with the setup... But we're doing the best we can with what was on the hill when we started... Oh well lol. On Tue, Mar 24, 2009 at 12:39 PM, ve7fet <[email protected]> wrote: Actually, the comment below isn't quite true. The Q2220E is a "Res-Lok" duplexer, but there are no machined coupling ports between the cavities. I just took the loops out of one to confirm. The coupling between the cavities is a function of the pickup loop inside the cavity, and the coax between them. However, in the C2034 type Res-Lok combiners, there ARE coupling ports machined between the bandpass section cavities (confirmed that too). Of interesting note on the Q2220E, the docs from Sincliar show two different harnesses available, presumably one for high split, and one for low. I have two Q2220E's here, one factory 143/148 and the other 152/157. They both have the same harness on them (320mm inter-cavity of RG400), and the pickup loops are the same size too (110mm). If you run the numbers for 320mm and a velocity factor of 0.695, you get a center frequency for the harness of 163MHz. If you wanted to optimize the tuning for the best response in the ham band, you may want to consider re-building the harness and changing the inter-cavity lengths to 355mm. I wouldn't change the lengths of the pickup loops as that is going to significantly change the response. Also note, the Q2220E makes a good candidate to modify for 220MHz... just ask Dave Cameron... http://www.irlp.net/duplexer Cheers! Lee --- In [email protected], "Eric Lemmon" <wb6...@...> wrote: > 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.
