Decibel made a low band duplexer that used notches made from helical resonators and passes made from lengths of coax. The whole thing measured maybe 3.5 ft Hi x 2.5 ft wide x 8-10" deep and could mount on a wall. I suspect his Sinclair is the same sort of thing. I recall talking to an engineer at Decibel about retuning the notches and he said that large frequency changes would require opening the cans and doing major surgery.
Milt N3LTQ ----- Original Message ----- From: "Chuck Kelsey" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Thursday, October 02, 2008 8:06 PM Subject: Re: [Repeater-Builder] LMR-400 Cable >I suspect that he has notch cavity resonators. Each can is about two feet > tall, more or less. So, while eight of them take up some space, they are > not > likely as large as you envision. > > Chuck > WB2EDV > > > > ----- Original Message ----- > From: [EMAIL PROTECTED] > To: [email protected] > Sent: Thursday, October 02, 2008 7:14 PM > Subject: Re: [Repeater-Builder] LMR-400 Cable > > > Tom, > > With 65 feet of cable, your feed line is very close to a resonant length > at > 6 m. Actually > about 3 wavelengths. If you have enough extra coax length, try winding > some > of it into > a coil and see if that reduces your desense problem. Also, make sure your > antenna is > a good impedance match to your transmitter/duplexer impedance. > > A 6-cavity duplexer on 6 m has to be a HUGE duplexer and I suspect that's > where your > problem is. You have to have a VERY precisely tuned duplexer that > provides > at least > 85 dB of isolation between the XMTR and the RCVR. > > 73, > > Dick W1NMZ > > > ------------------------------------ > > > > Yahoo! Groups Links > > >
