Hi Lee, I just took a listen on my early 13 tube R-4A. I can't find any really strong signals today but my rx works like this: I DO hear scratchy clicky sound with NB turned on even on the correct sideband of moderately strong signals. I hear it even off the side of the moderately strong signal. It is worse on some signals, some sound fine. I believe this is what you are describing.
But, if I turn the NB off, all scratchyness goes away on mine. I only use the NB if I have noise to kill, at this new QTH, I don't think I have ever needed it.. At my old QTH years ago (and on another early R-4A) I had to use it all the time due to florescent lights in the next room.. made the difference of getting on the air or not. 73, Gary WB6OGD ----- Original Message ----- From: [email protected] To: [email protected] Cc: [email protected] Sent: Sat, 14 Jan 2012 17:32:26 -0000 (UTC) Subject: Re: [Drakelist] Interesting discovery/problem about R-4A & R-4B Still looking for some help/input as to this issue.. Please...if you have a R-4A or B...check this out & let me know how yours works...(Just read the thread details) Looks to me the later R-4B's should have fixed this...if so, it may be worth it to update a R-4A to eliminate the problem?? Or even give me a call. Thanks, 73, Lee, KC9CDT Lee Simmonds Summit DCS LLC 260-799-4077 Office 260-403-6936 Cell -----Original Message----- From: Garey Barrell To: kc9cdt Cc: drakelist Sent: Fri, Jan 13, 2012 9:44 am Subject: Re: [Drakelist] Interesting discovery/problem about R-4A & R-4B Lee - What is the serial number of your R-4B??? 73, Garey - K4OAH Glen Allen, VA Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line and TR-4/C Service Supplement CDs [email protected] wrote: > Gary, > Thanks for the information...yes,,,I get the clicking/static like sound as described. > Not distortion...that is of course normal when the opposite SB is heard. > > D3 is fine...Good F/B ratio.... > > If you are tuned into a strong signal kind of by itself, of course you won't be hearing the wrong > SB at all...BUT, If there is a adjacent strong signal and his 'wrong SB' is in the front end > PB...you hear the clicking and it is pretty bad. It is the worst (of course) when you listen to a > weak or moderate signal and a strong signal is nearby. > > The R-4A AND the R-4B here do exactly the same thing. My R-4C does not. I do not hink it is > something only wrong with THIS R-4A. > > It would be nice if others with a R-4A or B would see if they hear it to... > > From a tech. standpoint my last post here describes exactly what is happening. > > Be nice to find a solution so anyone wanting it could install it. > > 73, > Lee > > > > -----Original Message----- > From: Gary Winblad > To: kc9cdt > Cc: drakelist > Sent: Thu, Jan 12, 2012 10:53 pm > Subject: Re: [Drakelist] Interesting discovery/problem about R-4A & R-4B > > > I think what you are describing is perfectly normal. > Strong signals within the "roofing" 10Kc(KHz) filter WILL upset your desired > weaker signal. The NB works by detecting and killing sharp noise spikes > BEFORE they get lengthened by passing through the narrow IF filter. > > IIRC, it was a Drake innovation to limit the NB detection bandwidth to 10Kc. > > AVC is generated after the sharp IF filter, and the stronger the signal, > the more the AVC cuts gain starting with V1, just as you have described. > > The only problem seems to be that you say you get the strong signal > distortion even with the NB turned OFF, that is not right... IMHO. > Like Garey already suggested, problems near D3 and the NB switch is most > likely I would think, this is where the NB gets turned OFF, V9 should be > running the same with NB on or off. > > 73, > Gary > WB6OGD > > ----- Original Message ----- > From: [email protected] > To: [email protected] > Sent: Thu, 12 Jan 2012 20:18:38 -0000 (UTC) > Subject: [Drakelist] Interesting discovery/problem about R-4A & R-4B > > Drake Enthusiasts, > > While working on a Drake R-4A..(11 tube) .I discovered something that > bothered me...and thought for sure it was a problem needing fixing! > Yeah...I do like things to work well. > > OK...find a nice STRONG signal...maybe S-9 ++ (20 over) tune it in it > sounds great...OK...now carefully tune to the opposite sideband of that > same signal. > NB is off...not that it matters, now...listen carefully...of course you > hear the garbled opposite sideband...BUT also you hear a lot of > clicking/arcing like noise on voice peaks especially. > Loud enough to be a bother....IF you PULL the Noise blanker tube V9 and > or V10...the noise goes away! Huh! the NB is OFF, so why do we hear > that racket?????And why does pulling the tube fix it? > > Well go off looking to see what's wrong so I can fix it....spent quite > a lot of time....looked at lots of things with the scope. > Discovered what was going on is: > If you scope the grid or plate of V9 the 50 kc NB amp...you see a > relatively small signal when the signal is tuned into the correct > SB...BUT if you look at it when tuned to the wrong SB...WOW huge signal > level (maybe 5-10 times as strong) ...and that signal level is getting > through the NB amp, shaper and amp...and clamping the plate of V4 the > IF amp right before the PB tuning...thus creating the annoying clicking > sounds. That's why it stops when you pull the NB tube(s). > > So, got to looking at the AVC signals and how it works at the grid of > V9 the 50 kc amp going into the NB section....found out the AVC does > not throttle back as much with a wrong SB sigal as the properly tunes > one! So the signal. > > Why is this a problem since we don't really listen to the wrong SB? > Well, IF you are listening to a nice signal AND right next door a > signal is pounding in and the RX hears the wrong SB for it (and it will > based on the location as to the good signal you want) you get the > clicking etc that is loud because the interfering signal is strong. > > Now that I understood what was happening...I looked for a bug....not > easy to find for sure.... > > Ah Hah! I thought let's look at my R-4B I have here to compare the > scope patterns and voltages in question. Maybe I'll learn something > helpful? > And does my R-4C do this? > > Answer is: Oh no...the R-4B does exactly the same thing! (R-4C does not) > > This R-4A is not really broke! or both the R-4A and the R-4B I have > here are both broken?? > > Looks to me like a design issue in the AVC circuits. > > > 1) Hey gang...try iy out, let me know what you discover. Please. > 2) Anyone already fixed this with a MOD? > > Thanks, > 73, > Lee, KC9CDT > > _______________________________________________ Drakelist mailing list [email protected] http://mailman.zerobeat.net/mailman/listinfo/drakelist
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