John. Lot of interesting stuff there. Well, it is always ABOVE the lower
frequency that doesn't track. That is to say: I will use the local
oscillator compression trimmer and set to the up frequency i.e. 5 mhz and
then go down to the lower frequency i.e. 1.8 mhz for that particular band
and in the case of this band (includes 80 meters) I will be approx 250 khz
ABOVE the 1.8 mhz frequency it should be at when I run the COMMERCIAL
digital readout signal generator. Then you are supposed to move a "loop"
around inside the inductance coil form to get on the lower frequency, in
this case, 1.8 mhz. But the best I can do in any direction is swing the
lower frequency about 25 Khz which is probably about right. Yes, on the
alignment regards being careful you are on the "right side" of things. In
fact in National's manual they send you down to another band to check to
make sure you can hear yourself on the image frequency and tell you if you
can't you are on the wrong side of things. As far as the IF's are concerned
they are exactly where they need to be on 455 Khz and align right up with
the crystal phasing control as they should. So don't believe it has
anything to do with the general alignment as it is pretty well described and
everything comes out like they say it should. The idea about the additional
trimmer on the other end has come to mind but you know the inductor forms
would be very hard to get to without a major disassembly project probably to
include removing their rather complex main tuning and bandspread capacitor.
It is hard for me to believe that the wire wound inductor coils have changed
as they are on a firm coil form and in no way distorted. If you followed my
first query you will see what I have checked so far. The tuning capacitor
is tied to ground in several places running down the base of the capacitor
and the chassis actually looks like new (no kidding) and was stored in a
house in a den and covered with a sheet for the last twenty five years or so
and is in excellent condition all around. I am just running out of ideas
and was hoping that someone out there has solved the problem. It's sure
over my head at this point. One fellow said he ran into the same thing with
his and fiddled with it for several months and finally just sold it. I am
not going to do that as I was able to get the tracking pretty close on the
80 and 40 meter bands by using their band alignment instructions and
worrying about the tracking from 3.5 to 4 mhz and 7 to 7.3 mhz only. It
sure it a beautiful receiver and the first one I saw belonged to
"Onie"...W1Z?? and her OM back in 53 or 54 when I belonged to the Framingham
Radio Club near Boston and had just got my novice ticket. National always
seemed to have some very attractive equipment that worked well. Now, of
course, they are sk.
73 Van, K7VS Medford, Oregon
----- Original Message -----
From: "John Coleman" <[EMAIL PROTECTED]>
To: "'Discussion of AM Radio in the Amateur Service'"
<amradio@mailman.qth.net>
Sent: Wednesday, September 26, 2007 3:55 PM
Subject: RE: [AMRadio] NC-183D Alignment questions help
Is the oscillator freq on the low end too high and needs to be lower or is
it to low and needs to be higher.
Some one mentioned that the oscillator may be running on the wrong side.
You may know this already but I will state it anyway, that the OSC must be
running above the RF that you want to receive. OSC = RF + IF. It is some
times possible to pull the OSC with the trimmer all the way down to where
the OSC = RF - IF. This will work where you set it but it will not track as
the manufacture did not design it that way.
Assuming that the culprit is ageing coil forms, not incorrect parts or IF
misalignment, there could be a number of quick fixes for this type of thing.
Padding capacitors can be added in series with the top end of the coils or
extra turns could be added to the coil assembly or just placed in series
with it. I have beat up some powdered iron and put it into the coil form
with glue to lower the frequency.
John, WA5BXO
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Van K7VS
Sent: Tuesday, September 25, 2007 11:04 PM
To: Discussion of AM Radio in the Amateur Service
Subject: [AMRadio] NC-183D Alignment questions help
I have a pristine NC-183D I picked up a year ago that I am finally getting
around to. Have replaced all the electrolytics and sound really good.
BUT...I cannot get it to track properly as I follow the alignment
instructions in the manual. I can set the top frequency on each band with a
small trimmer cap (this is the oscillator coil adjustment) but then
according to the instruction manual you adjust the low end of the dial by
moving a wire inside an inductor, which does move the lower frequency but
not nearly enough to get to the frequency they say you should see. Has
anyone else had that problem during alignment of this receiver, or am I
missing something. Have checked the voltages at the first and second
converter and they seem fine and have pulled off the mica cap across one of
the oscillator coils (1.8 to 5 Mhz) and it checked just fine (supposed to
be 1600 pf and reads 1615 pf). And have substituted a different 6BE6 in the
first converter and still can't get close to proper or accurate dial
tracking. I am 500+ Khz off no matter what I have tried. And thoughts on
this one! Thanks. Van, K7VS
PS I would like to hear from NC-183D owners that may have experienced this
problem or have some thoughts about what I am seeing. tnx
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