Sweep Marker generator for IF alignments.

[Paul P]

Does any one use a sweep marker generator similar to
http://www.peacockcollectibles.com/test/test2/knight1.htm
to align 455 kHz IFs?

I don't think they range low enough for AM radio IF. If so what am I
missing?

I believe they cover FM IFs just fine. But I am trying to use them for AM
radios.

Paul P.

[Jeffrey D Angus]

Post by Paul P
Does any one use a sweep marker generator similar to
http://www.peacockcollectibles.com/test/test2/knight1.htm
to align 455 kHz IFs?
I don't think they range low enough for AM radio IF. If so
what am I missing?
I believe they cover FM IFs just fine. But I am trying to
use them for AM radios.

The problem with most sweep generators that will handle a 455
KHz IF, is that the center frequency, sweep width and linearity
leave somewhat to be desired as to accuracy. When used
(watching the AVC line) they will give you an indication of
higher or lower flat or ripple and wide or narrow. However, as
to the degree of accuracy, as I said, they leave a lot to be
desired.

Some will accuse me of over kill, but I use a Hewlett Packard
synthesized sweep generator. 3325A

Loading Image...

When you set the sweep width, level out and center frequency,
you know that you get exactly what you told it to do.

On the other hand, if the caveats I mentioned above are adequate
for your testing, if memory serve me right, Xray has an Eico with
a 455 KHz sweep circuit built in. I modified a similar vintage
signal generator by driving a varicap across the main tuning
capacitor with the filament voltage. Gave a fairly nice sweep,
when driving the Y-axis of a scope with the filament voltage.
But it's still in the semi-by guess and by golly mode.

Jeff

[nesesu]

Post by Jeffrey D Angus

Post by Paul P
Does any one use a sweep marker generator similar to
http://www.peacockcollectibles.com/test/test2/knight1.htm
to align 455 kHz IFs?
I don't think they range low enough for AM radio IF.  If so
what am I missing?
I believe they cover FM IFs just fine.  But I am trying to
use them for AM radios.

The problem with most sweep generators that will handle a 455
KHz IF, is that the center frequency, sweep width and linearity
leave somewhat to be desired as to accuracy. When used
(watching the AVC line) they will give you an indication of
higher or lower flat or ripple and wide or narrow. However, as
to the degree of accuracy, as I said, they leave a lot to be
desired.
Jeff

I have a Precision E400 sweep generator that does 455kHz and it has
provision for markers developed from the E200 test oscillator, so you
are supposed to be able to accurately mark the centre and band edges
for aligning the IF. I have not yet restored it, but I did do the E200
and it's calibration is pretty good. I have noted that for the up-
scale sets with autotuning you need to use a sweeper [or oscillator
with 'wobbulator'] for aligning the IF for the AFC to get the proper
response.
Speaking of those sets, has anyone restored one fully and, if so, how
well do they 'lock in' on a station and do they drift much as they
warm up?

Neil S.

[exray]

Post by Jeffrey D Angus
On the other hand, if the caveats I mentioned above are adequate
for your testing, if memory serve me right, Xray has an Eico with
a 455 KHz sweep circuit built in.

Drag me into it :)

The RCA WR-50B is a cute little signal generator that will do a 455 or
10.7 sweep. There's no markers in the unit and the sweep range is wide
enough to where it is not 'wrong'.

I don't find much (read: any) use for the 455 sweep but on the occasions
where I have tried it out I had pre-peaked all of the IFs by
conventional methods and subsequently you can see, and mark on the
scope, pretty much where the 455 center is displayed and work from there
to play with the bandpass to your liking.

You may wind up a kc or two off center but thats rarely an issue for
anything but a higher end set where you should be using a better unit
and markers from the get-go..

Post by Jeffrey D Angus
But it's still in the semi-by guess and by golly mode.

Yeah, what he said.

-exray
** Posted from http://www.teranews.com **

[cmdr buzz corey]

Does any one use a sweep marker generator similar tohttp://www.peacockcollectibles.com/test/test2/knight1.htm
to align 455 kHz IFs?
I don't think they range low enough for AM radio IF. If so what am I
missing?
I believe they cover FM IFs just fine. But I am trying to use them for AM

Why? Is a sweep generator all you have?

[Tio Pedro]

I just figured out my Boonton 102F has a DC coupled input for the FM
modulator. That means I can use a triangular waveform from a function
generator to accurately "sweep" the center frequency of the generator, and
to drive the horizontal input on my scope. It should work :)

Pete