Folks, My Drake R4B now has the correct bandwidth, and it is not quite so deaf. Thanks to all who provided suggestions.
The problem was inside the xtal filter after T5. The metal cans of the two HC6/U crystals in the filter are soldered to a wire that goes to chassis - sensible. But just very slight pressure to the can of the 5642kHz xtal caused it internally to short its signal input to its can, and hence to chassis. The fit into the overall screening can was enough to do this when it was assembled. Equivalent pressure on the can of the 5645kHz xtal had no effect. So the problem is internal to the 5642kHz xtal. As a work around, I've removed the chassis wire from the 5642kHz xtal can and wrapped the xtal can in insulating tape. The bandwidth is now as expected, as determined by the 2nd IF LC filter. I'd welcome any suggestions as to where I could obtain a good 5642kHz xtal ... As a matter of record, there is a post by Joe Rafferty on Tue, 15 Jun 2004 11:30:39 -0700 where the cause of an R-4B with image problem was traced to a faulty 5642kHz xtal, but no note of what the actual fault was. 73s Gwyn _______________________________________________ Drakelist mailing list [email protected] http://mailman.zerobeat.net/mailman/listinfo/drakelist
