[ARC5] Some information...

[CARL HUETHER]

Ken, Im glad to see that old IC still in use.

Back in the mid 80's to late 90's when I was running RadioKit I sold a Product Detector kit to replace the poor one in the Drake R4C that used a TI IC (cant remember the designation,TL???) that became unobtainium and adapted the round can version of the 1496. I used my own R4C as the test bed.

I probably still have some in a parts cabinet.

For tube versions I like the Pullen (also in the mixer) but it is a bit more involved with bullet proof no overloading.

Carl



> On September 12, 2019 at 12:49 PM "Kenneth G. Gordon" <kgordon2006 at frontier.com> wrote:
> 
> 
> I thought I would bring to your attention some interesting information from the latest issue of 
> Electric Radio Magazine, and some "historical" info from my own experiences.
> 
> In that issue of ER, Pat Griffin AA4PG's article covers the addition of a product detector to 
> an Elmac PMR-7 receiver. He uses an MC-1496 quadrature detector chip as his external 
> PD.
> 
> This can be added to almost any receiver without doing any easily-unreversible mods.
> 
> Here is the interesting quote from his article:
> 
> "The first improvement I noticed with the product detector was increased sensitivity. Using 
> the method outlined by W8BTA on the Internet at www.youtube.com, the minimum 
> discernible signal (MDS) was 21 dB lower with the product detector. That is about a 10-fold 
> increase in sensitivity and made an enormous difference in performance." (!!!)
> 
> Some 50+ years ago, I modified the detector in my NIB BC-779 to a triode-product detector, 
> using the 6N7 noise limiter tube, and I also found the apparent sensitivity, and 
> much-reduced noise, to be hugely improved. 
> 
> That receiver, after that mod, became my very favorite receiver for RTTY and CW. The 
> addition of the PD made it very, very quiet, and I could hear things I didn't even know were 
> in there before the mod.
> 
> So, Mr. Griffin's results completely coroborate mine, and I am very pleased, since when I 
> have mentioned my results in the past, those have been doubted by some.
> 
> I tend to disagree with him on one aspect of this though: that is, what he calls "increased 
> sensitivity", I have always called "apparent sensitivity" since the real sensitivity of any 
> receiver is set by the RF amp stage(s), the mixer, and the IF strip.
> 
> So, I have never really understood where the increase in "recovered signal" comes from. 
> After all, any circuit-improvement like this cannot recover a signal which is not already there.
> 
> In any case, as I have insisted for many years, the proper addition of a good product 
> detector to our old receivers makes a tremendous improvement in both apparent sensitivity 
> and reduced noise.
> 
> Ken W7EKB
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