Hi Kevin, Just a quick question regarding your earlier email - I thought crystal oscillators were cleaner (as far as noise sidebands are concerned ) than PLL types.
Is this not the case in the GE Mastr II you mention below, as you indicate the PLL type of exciter is better? Is this particular to this design? Don't get me wrong here Kevin- I'm not trying to poke holes in what you are suggesting, I just thought xtals would be cleaner? Great info about the duplexers though. 73, Matt ----- Original Message ----- From: "Kevin Custer" <[EMAIL PROTECTED]> To: <Repeater-Builder@yahoogroups.com> Sent: Saturday, December 18, 2004 10:59 PM Subject: Re: [Repeater-Builder] Sinclair Q-202G Hi Paul, Paul Holm wrote: >Has anyone had luck using the Q-202G duplexers in the 145-148 range? > Yes, there are 4 repeaters close by my area that use them. > What needs to be done with them for use in the ham band? Just different cables? > Right, considering they may be fairly far from the destination frequency. It's accepted that a move of 3% or less of where the factory built them is okay without cable replacement, more than that, its usually a necessity. >What sort of isolation figure is possible? > At 600 kHz, you will see a typical notch depth of between 85 and 92 dB depending on how good the harness matches. The *sides* of this duplexer seem to interact more so than others I have tuned, so, you need to make sure both sides are fairly close in tuning before spending time making them perfect. Here is a document that will help you tune and understand them: <http://www.repeater-builder.com/sinclair/cm-1008.pdf> We have Micor repeaters on the 4 installations I spoke of earlier. Most are running solid state 110 watt PA's running full power and the receivers include the Micor helical resonator preamp that gives 12 dB sinad sensitivity at -122 dBm (.2 uV) or slightly better. These repeaters have no desense, but likely have very little reserve isolation as well. One thing that can be done to add more reserve isolation is to use better than average equipment. If you have a GE Mastr II two meter or highband repeater that has inadequate duplexer isolation, change out the exciter to a PLL type and take advantage of the 20+ dB less transmitter side-band noise. Another thing is to consider using a tube type PA deck, like the GE 4EF5A1, with a typical 'multiplier' exciter. This could allow power levels in excess of 200 watts or more without suffering from inadequate transmitter side-band noise suppression. Kevin Custer Yahoo! Groups Links Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
