[AMRadio] Sp-600 JX-11 Diversity?


John Flood kb1fqg at yahoo.com
Tue Feb 19 14:33:21 EST 2008


Greetings Wise ones!
 
This weekend a SP-600 JX-11 followed me home (when I was young it used to be kittens and puppies with the odd reptile or amphibian mixed in.) along with an assortment dust, dirt, and seed shells from barn storage but at least the beasties didn't get into the undersides!    In any event this is a diversity version.  I'm trying to I.D. who did the work but I think that it was done by Northern Radio.  I say this as the label details for the int/ext. M.O. and int/ext AGC/BFO controls look identical to those on a National NC-183D/R Northern diversity version that had followed me home some years earlier.  I was wondering if the factory did a diversity version of the JX-11?  If so what did the front panel look like?  This unit has no Xtal freq control and in addition to an IF output on the chassis, there is a second IF out "in a can" with a SO-239 connector and it is attached topside at the rear of the radio.  Sound like a Northern job to youz guyz?
 
After a basic cleaning to remove crud, the variac run up produced no smoke signals and the local BCB stations were making noise.  A treatment of carefully placed high tech bike lubricant with Teflon started the transmission spinning again in true SP600 fashion as well as freeing the bandswitch needle indicator that was stuck up top.  A dose or two of Deoxit on the controls helped to greatly improve things and the same on the bandwidth controls contacts started it singing again.  Granted I have yet to touch a single piece of test gear to it but I did notice that the AVC could use a bit more "A".  It tended to overload on the BCB station a mile or so away from me.  Turning down the IF gain (that was maxed out) helped a bit but it seemed to still act as it had more gain than was needed.  Of course, having what look to be all orrigional components, could very well be the cause here with caps gettin old and such, but some time ago didn't someone here comment
 that the way the diversity mods were done gave this type of AVC results?  Strange enough, the dial accuracy was spot on in fact, as good as any analog dial I have seen.  More to do to it but another old girl brought back to life is good news! 
 
Thats the weekend report from here your comments and flames on this beast are welcome.
 
Thanks to Mr. Mike for the lead and see ya at NEARFEST!
 
John Flood
KB1FQG


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