OK, here's one I haven't heard of before. I have an early TR7 on the bench that I have installed the resistor in an empty filter slot to fake an AM filter. I've never used this mod myself, since I've sprung for the AM filter in my rigs. In tuning around and listening to AM signals, I have observed that the "center" of the signal seems to tune 3 or 4 KHz below the dial reading for correct carrier frequency. That is, the signal sounds best when off-tuned. I've checked this with local longwave AM stations and various shortwave signals. A complete frequency alignment has been done on the radio, as well as the IF tanks checked for peak, so everything else is spot-on.
It seems like the only thing that could cause this is a skewed response of the 48 MHz filter on the upconverter board. Has anyone seen this before, or tried an alignment of the 48 MHz filter section? The service manual clearly states this requires magic mojo that I don't have, and not to touch it or my hair will fall out. I could possibly wrangle access to a tracking generator if absolutely necessary, but it's probably not a big deal. The owner doesn't do much AM, and it doesn't seem to be detrimental to sideband operation. WDYT? 73 -Jim -- Ham Radio NU0C Lincoln, Nebraska, U.S.S.A. TR7/RV7/R7A/L7, TR6/RV6, T4XC/R4C/L4B, NCL2000, SB104A, R390A, GT550A/RV550A, HyGain 3750, IBM PS/2 - all vintage, all the time! "Give a man a URL, and he will learn for an hour; teach him to Google, and he will learn for a lifetime." HyGain 3750 User's Group - http://groups.yahoo.com/group/HyGain_3750/ http://radiojim.exofire.net http://incolor.inetnebr.com/jshorney http://www.nebraskaghosts.org _______________________________________________ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
