At 10:02 AM 5/6/2007 -0700, you wrote: >Bob, > >I never knew that. Then the R-390 does have an honest Noise Blanker and >not a Noise Limiter as the SP 600 had. Now that is interesting. I wonder >what kind of circuit the R 390 uses? Anyone know? That diode set up in >the SP-600 never did anything much except distort the audio as you >mentioned. That was the only reason I sold the SP 600. It was one great >receiver and netted me a lot of great DX through the years. One thing I >really miss is the crystal phasing. I wish the crystal filters in the >SPR4 had phasing. >73, >Patrick >Patrick Martin
Patrick, AFAIK, the R-390's NOISE LIMITER is essentially the same as the R-390A's NOISE LIMITER. Neither are noise blankers in the proper sense of the term. All they do is chop off the audio at a predetermined level as set by the operator by adjusting the LIMITER pot. Like the SP-600, they tend to distort the audio. The R-390A is the result of a cost-reduction contract written by the US Army Signal Corps with Collins Radio Corp. The R-390A was a great deal cheaper per unit than the R-390. But the R-390A has the mechanical filters, and THAT, sir, is the important difference! Every receiver, w/ the exception of the R8B, that I have owned I've had to supply either a crystal lattice filter or a mechanical filter to supplement the selectivity characteristics. The lack of a good product detector and a good noise blanker are the prime drawbacks of the R-390 family. And the noise blanker of the R8B is "finicky" in that, if the incoming signal is above a certain level, the NB ceases to operate. I think that's because the R8B's NB has an AGC input to the NB. Now go climb a tree! Kindest regards, Charles Charles A Taylor, WD4INP Greenville, North Carolina _______________________________________________ IRCA mailing list [email protected] http://montreal.kotalampi.com/mailman/listinfo/irca Opinions expressed in messages on this mailing list are those of the original contributors and do not necessarily reflect the opinion of the IRCA, its editors, publishing staff, or officers For more information: http://www.ircaonline.org To Post a message: [email protected]
