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#1
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R2000 SSB "improvement"
A friend is making some PCB boards for my
AD607 synch detector project so I tried something else. Today was a REAL slow day at work. Someone had to be thre "just in case", and as new man I was bitten. So I took my original R2000 in to try an idea I hade for a while. The product detector isn't the best design. It uses a transformer to couple the IF to the mixer bridge and a set of resistors to couple the BFO. El stinkero. I cut the traces and put a minicircuit 1:1, secondary CT, between T18, removed the BFO feed resistors and fed the BFO to the center tap. I replaced the 1N60, (which where far from matched!) with some old HP hot carrier diodes (HP2800). The differnce between this uit and a stock unit was night and day. Very tedius work. But very worthwhile. I have both radios complete, I ended up staying an extra hour to complete this and a rather plain "improved AM detector". Before I reported that when I biased the AM detector diode I experienced some very odd happenings. I don't know what I did wrong, but when I re did the experiment, it offered a slight improvement. The AGC has it's own detector. Just for grins I tried a hot carrier and low voltage Shotky (zero bias) diodes. They both worked but really wasn't enough to bother with . The diode needs a negative bias voltage and that is a big hassle. Even though I have NO plans of ever taking either R2000 out in the field again, I decided to go on and add both these mods because they are very worth the "minor" efforts. And for this weekend I don't have my fancy synch detector. Terry |
#2
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Once you get all the upgrade mods to my old R-2000 done, I've decided I
want it back! :-p Frank |
#3
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fcath wrote:
Once you get all the upgrade mods to my old R-2000 done, I've decided I want it back! :-p Frank ----------------- Er, dream on! At best you aren't getting the Inrad fitler back. That fitler is MAGIC! Thanks for the positive response to my question on "capacitor effect on sound". That started this whole craze. That and the +95F +70RH have given me plenty of incentive to stay in where it is cool. While the simple op amp active detector is clearly not a synch detector,it is so simple to build and it is so much better then the stock single diode detector that every one who has a mid quality receiver ought to at least think about it. I have disassembled my bread board AD607 synch detector so I was forced to lsiten to RCI/CBC's Vinyl Cafe' today sans sycnh, but the active detector made it more then bare able. As I edited it down for archive I noticed that when the studio switched from the news to program the was a big jump in 60/120Hz noise. Their little problem was hidden until I got better equipment. It might be that I will have to have a synch detector for weak/noise and use the active detector for "high" quality SW. Terry |
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