Hi there Skip
I'll address your input like you did: --- In [email protected], "skipp025" <[EMAIL PROTECTED]> wrote: > > > "rtoplus" <[EMAIL PROTECTED]> wrote: > > Hi > > I'm thinking about putting 1 or 2 bandpass filters > > on my repeater receiver...got some desense. System > > is: MSR 2000, VHF 2 meter, about 50 watts out of > > the duplexer, 1/2 in hardline, 1/4 in hardline > > jumpers, el cheapo antenna (I know, I know), stock > > pre-amp, etc. > > It would be better to find the source of the problem. > If it is desense and what's causing it. Some simple > checks could give you an idea of the problem source(s). My duplexer is a older Sinclair P-202G...the one with the di- electric tubes for notch adjusters. As per repeater-builder info, here are the specs: Q-202G (132-174 MHz) (in splits 132-150, 148-174) Type: 4 cavity pass-reject Minimum freq. spacing 0.5 MHz Insertion loss 1.5 dB Max. continuous power 350 watts Tx noise supp. at Rx freq. 80 dB Rx isolation at Tx freq. 80 dB Temperature range -40 to +60C VSWR 1.5:1 I'm thinking that along with my junk antenna, the duplexer doesn't have enough isolation. > > > Question is: > > 1. Is the jumper length from the pass filter to the > > duplexer or PA to the pass filter critical? > > Most generic repeater people will say no. But it > does make a difference. I say yes and follow rules > of thumb on certain repeater system cable lengths, > this specific cable being one of them. > Do you follow the same rule as duplexer interconnect lengths? i.e. ((234/frequency) * 12) * cable velocity = cable length in inches (or multiples thereof)? > > 2. If I use more than 1 filter, is the length of the cable > > between the added on filters critical? > > Yes and use the same formula as above? > > > 5. Would I be better off using notch filters as opposed to pass > > filters? > > You don't know what the problem is yet... and you > didn't indicate what type of duplexer you are using. > > Number 5 alive says... "need input?" > see above for duplexer info. The antenna I feel for sure is causing some desense and junk...dual band (144/440) Comet co-linear. The repeater is set-up in a historical district on a roof-top, so stealth is a concern as is the building owner who really don't want me to increase antenna height for example using a stationmaster so my choices are somewhat limited. > Do you have a isolator or circulator in line? > no, I don't have either at this time > > I'm at a somewhat low noise site...closest RF stuff is about 200 > > yards away with the exception of my micor GMRS UHF repeater (50 > > watts) that's co-located at the site. > > Nice to be at a low noise site. You might not need the additional > filters. You should find and address the desense problem first. > Thanks again! Bob, GMRS WPVV845, Amateur KG4WAD, LMRS WPXC892 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/
