The preselectors I recall (e.g. the "R-9 er") had two major functions:
1 - Provide more attenuation of the image frequency only 910 kHz away from the signal frequency in 455 kHz I.F. systems. 2 - Provide low noise gain to overcome mixer gain in the receiver. These were critical functions in even the best of receivers in the 14-30 MHz range (including my WWII vintage National HRO-5). But, on the lower frequencies, it was completely unnecessary. I wonder if what people are seeing nowadays has to do with the typical multi-section, fixed-tuned filters in modern rigs that is designed for a 50 ohm antenna system? Is it possible that under certain conditions of input impedance they show excessive loss? Ron AC7AC -----Original Message----- On 3/29/2011 4:53 PM, Don Wilhelm wrote > > There was a time when pre-selectors were available for > receivers, but that was way back when dirt was young. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
