Laryn, That's a very good question! It was my intention to emphasize that a receiver that, by its design, is made to cover a relatively narrow range of frequencies, is perhaps better suited to fixed-frequency operation in a repeater than is a broadband receiver. Consider a classic Micor or GE front end that must be manually tuned for optimum reception on ONE frequency. In my (relatively limited) experience working with receivers, such manually-tuned receivers are almost always better performers than newer broadband models. Moreover, the latest offerings from Motorola (MTR2000 and Quantar) are broadband by design and depend upon optional preselectors for optimum operation as repeaters. In my (relatively limited) experience, they do not match the single-frequency performance of a Micor, unless equipped with the optional preselector.
The Micor and most GE radios have a helical resonator front end that may limit their usefulness in a multichannel system, but for a fixed-frequency operation as a repeater, they are excellent. A receiver equipped with a helical resonator front end MAY require less duplexer isolation than one without. 73, Eric Lemmon WB6FLY Laryn Lohman wrote: > --- In [email protected], Eric Lemmon <[EMAIL PROTECTED]> > wrote: > It also makes a big difference if your receiver has a helical > > resonator filter in the front end or not. > > Eric, I'm not disputing the statement above, just want to learn. > > Looking at the specs on a Mastr II base station receiver, I note that > the Maximum Frequency Separation for the 150.8-174mc version for full > specifications is 1.0mc. I read that also as +or- 500kc. The 3dB > Degradation Separation is 1.8mc. So if I'm thinking right here the > response of this receiver at +or- 600kc is only down maybe 1dB or so. > I don't see this receiver rejecting much energy at all at the TX > frequency. 99% of needed isolation is provided by the duplexer. So > why is a helical front end such a big advantage for a repeater > receiver? > > Laryn K8TVZ > > > 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/
