Gary,
Oh no...this is without the NB ever on....
it occurs only if you have someone near and you are getting their loud
opposite SB ...ot if you tune slowly to the opposite SB on the STRONG
signal you are working.
It is a clicking or arcing kind of sound...like you described with NB
ON.
Happens here on R-4A and R-4B
73,
Lee
-----Original Message-----
From: Gary Winblad <[email protected]>
To: kc9cdt <[email protected]>
Cc: drakelist <[email protected]>
Sent: Sat, Jan 14, 2012 1:49 pm
Subject: Re: [Drakelist] Interesting discovery/problem about R-4A & R-4B
Ok Lee,
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..
This is absolutely NOT reproducable(?) here.
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.
Well turn off the NB. IF your desired signal is now covered in noise,
turn it back on and suffer ;-) Really, I have never gotten any
clicking
or distortion with the NB off, definitely DO get it with NB on.
73,
Gary
WB6OGD
----- Original Message -----
From: [email protected]
To: [email protected], [email protected]
Sent: Sat, 14 Jan 2012 18:23:35 -0000 (UTC)
Subject: Re: [Drakelist] Interesting discovery/problem about R-4A & R-4B
Gary,
Here is my original post:
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?
Lee Simmonds
Summit DCS LLC
260-799-4077 Office
260-403-6936 Cell
-----Original Message-----
From: Gary Poland
To: kc9cdt
Sent: Sat, Jan 14, 2012 12:47 pm
Subject: Re: [Drakelist] Interesting discovery/problem about R-4A & R-4B
I have all three “ TWIN “ lines, what is it you want tried out??
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