The FL1 and FL2 ferrite filters in my NC-190 will not adjust to 230kc as
specified in the manual. About 227kc is as close as I can get them.
I can't find any info on them. Are they just coils? How do they work? Should
I just align the whole I.F. to 227kc? Any thoughts?
I think when this radio was made, it was still kilocycles. I if I align it
to khz might not function right. (joke)
Remove 1 to reply
John

On 1/11/06 2:05 AM, in article 1M4xf.22507$em5.3806@trnddc05, "JOHN D"
wrote:

The FL1 and FL2 ferrite filters in my NC-190 will not adjust to 230kc as
specified in the manual. About 227kc is as close as I can get them.
I can't find any info on them. Are they just coils? How do they work? Should
I just align the whole I.F. to 227kc? Any thoughts?
I think when this radio was made, it was still kilocycles. I if I align it
to khz might not function right. (joke)
Remove 1 to reply
John



FL1 and FL2 are part of the variable bandwidth filter. Did you set the
bandwidth switch to the most narrow position for doing the alignment? Are
you sure your signal generator is on frequency and that you are injecting
the signal at the right location?
Don

The problem is that you were actually putting in 227 kHz rather than 227 kc.
You must multipy your measured 227 kHz frequency by 1.0132158 to get 230
kHz.

When kHz was adopted, the World Frequency Commision (WFC) included a tariff
of 1.4%, which is stored in the World Frequency Bank and dispensed during
emergencies - if any frequencies are running short. This is the reason
there is a difference. In your case, those 3,000 cycles must be sent in to
the WFC to the world headquarters at Berne, Switzerland.

K7FM

Yes, they are just coils that are enclosed in ferrite pot cores to
make them "Hi-Q". You have found the threaded rods sticking out each
side. This is how you vary the frequency of each coil.

The last time I fooled with it, I recall that it had a pretty wide
tuning range up and down from 230 kc. Each coil winding has a dipped
silver mica cap across it's terminals underneath. I can't imagine those
caps drifting in value.

I agree with Don that you should probably align it in the "narrow
"position. Is it .6 kc? I think.

How accurate is your test equipment?

John

Litzendraht wrote:
Yes, they are just coils that are enclosed in ferrite pot cores to
make them "Hi-Q". You have found the threaded rods sticking out each
side. This is how you vary the frequency of each coil.

The last time I fooled with it, I recall that it had a pretty wide
tuning range up and down from 230 kc. Each coil winding has a dipped
silver mica cap across it's terminals underneath. I can't imagine those
caps drifting in value.

It is probably seeing the same problem that has been showing up in VFO's
for R390's. It would appear that after enough time has passed, the ferrite
changes its characteristics, and the VFO can no longer be adjusted to be
linear across its whole range.

-Chuck

"Litzendraht" wrote in message
oups.com...
Yes, they are just coils that are enclosed in ferrite pot cores to
make them "Hi-Q". You have found the threaded rods sticking out each
side. This is how you vary the frequency of each coil.

The last time I fooled with it, I recall that it had a pretty wide
tuning range up and down from 230 kc. Each coil winding has a dipped
silver mica cap across it's terminals underneath. I can't imagine those
caps drifting in value.

I agree with Don that you should probably align it in the "narrow
"position. Is it .6 kc? I think.

How accurate is your test equipment?

John

I have a RCA WR-50B signal Generator which I checked against a BC-221
hetrodyne frequency meter set at 230Kkc. I had previously checked the
internal 2mc crystal in the BC-221 against wwv. I also have a old
Heath/Schlumberger counter with 2 ranges that are too high and too low for
230kc. The high range indicates .230 mhz with the zero flashing 1 and the
low range indicates overflow and reads 29.942
The manual does say to align at the narrow, 6kc, bandwidth position.
Maybe some other external component is affecting it. I also have a hard time
thinking any mica caps have changed value especially since it seems they
would have to increase in value to cause the problem. There's a couple
molded paper bypass caps in the circuit.
John

Hi John:

I have a 190 that probably needs alignment one of these days. I would
certainly check the paper caps. Years ago I had an old HT-32 that would not
null anymore. I replaced every component in the circuit, yet it was still
unbalanced. I finally put in an completely different circuit - which worked
great on ssb but gave up am.

Decades later, it suddenly dawned upon me while working on a different
circuit that there was a leaky paper cap just outside of the circuit that
caused all of my grief.

Sorry about the kHz / cycles bad joke - but you started it.

Good luck, Colin K7FM

John,
Your test equipment sure is classic. (Viva La BC-221). I use one
myself. Are you reading the freq directly from the vernier dial on the
221? Of course if you have the book and trust your 221, that should be
close enough. But a counter would be comforting.

I have an NC-270 and assuming that the filter circuitry is the same as
your 190.

Is your receiver working OK and you're just doing a fine alignment, or
are there other issues?

Where are you injecting the 230 kc signal?

Are the two threaded rods in the filter backed all the way out and
still won't hit 230 kc? I'm sure you're aligning the other 230 kc tuned
circuits along with the filter.

If there has been a change in the ferrite characteristics as Chuck
mentioned, possibly those two silver mica caps (3900 pf in the NC-270)
could be replaced with a slightly lower value. But I don't think that
type of change is likely here. An R-390 linear PTO would seem to be
much more critical.

John

"COLIN LAMB" wrote in message
ink.net...
Hi John:

I have a 190 that probably needs alignment one of these days. I would
certainly check the paper caps. Years ago I had an old HT-32 that would
not
null anymore. I replaced every component in the circuit, yet it was still
unbalanced. I finally put in an completely different circuit - which
worked
great on ssb but gave up am.

Decades later, it suddenly dawned upon me while working on a different
circuit that there was a leaky paper cap just outside of the circuit that
caused all of my grief.

Sorry about the kHz / cycles bad joke - but you started it.


Good luck, Colin K7FM

I enjoyed the joke. I suspect though, that the kc to khz conversion must
be done on a slide rule to get the correct answer cus the clock in a
calculator runs in khz's.
I was in school when they made the change. Some of the guys were afraid
their motorcycles would become motorhertzes.
John Aye Bee IX Jay Bee

"Litzendraht" wrote in message
oups.com...
John,
Your test equipment sure is classic. (Viva La BC-221). I use one
myself. Are you reading the freq directly from the vernier dial on the
221? Of course if you have the book and trust your 221, that should be
close enough. But a counter would be comforting.
The BC-221 was a recent eBay purchase. They used them in school in
the early 60's and I thought it would be fun to have. The shafts
slipped on 2 variable cap trimmers inside allowing the plated to short.
Fixed 'em with super glue.
I have an NC-270 and assuming that the filter circuitry is the same as
your 190.

Is your receiver working OK and you're just doing a fine alignment, or
are there other issues?
It was almost dead when I got it. wireing errors, wrong miswired
resistor in PS, bad 0B2, shorted coax under chassis. had to take a IF c
an apart and bust out a stuck slug, slipping dial. Now it's working but not
perfect. I've got the alignment better than it was. At first I just
peaked the IF's where they were and didn't touch the ferrite filters. Got it
to a point and let it sit for a few months. It seem like other
stations are trying to come in, other than what it's tuned to. I haven't
been able to tell if it's poor selectivity, images or overloading.
Writeing this and thinking about it is makeing me suspect those bypass caps.

Where are you injecting the 230 kc signal?
At the middle sec of the main tuning cap, the input of the 1st
mixer.

Are the two threaded rods in the filter backed all the way out and
still won't hit 230 kc? I'm sure you're aligning the other 230 kc tuned
circuits along with the filter.
They peak before the end of travel but at 230kc as I reach the
peak it's not at the end yet, and keep turning it out to the end it don't go
down. Its like the peak is at the point where the slug is so far out it's
not makeing any more differance. 227 is as close as I can get to
230 and peak both coils.. I'm gonna clip in some extra bypass caps and see
what happens.

If there has been a change in the ferrite characteristics as Chuck
mentioned, possibly those two silver mica caps (3900 pf in the NC-270)
could be replaced with a slightly lower value. But I don't think that
type of change is likely here. An R-390 linear PTO would seem to be
much more critical.

John