To the group: I am having difficulty witha different VFO- a VF-1
or same as used in a DX-100. I know you guys are talking CE20- just a
question- my VFO is tracking reverse in frequency- like when you go down
in frequency on the display, it is actually going up in frequency.
Is it possible that the end point adjustments are so far off that they
could cause this? Russ
From: Gary Schafer <[EMAIL PROTECTED]>
Reply-To: [email protected]
To: [email protected]
Subject: Re: [AMRadio] "Reply" button got me...
Date: Sun, 05 Jan 2003 14:46:35 -0500
Hi Larry and others,
I too have a 20A. Have had several over the years. I found that to get good
output on 40 meters that the 1625 has to be in very good shape. Being just
a
little weak makes a big difference.
Also you need to adjust the padding coil (miniductor stock) that is across
the
1625 tank coil in the vfo. You adjust it by spreading the turns on one end.
If I
remember right, the padding capacitor under the chassis needs to be peaked
on 80
or 20 meters. The other bands are adjusted by adjusting the miniductor
coils for
maximum output. (It doubles or triples for other bands) It takes some
messing
with to get them right as the Q is pretty high. When you replace the top
cover on
the vfo things change so you have to compensate for that when adjusting.
I watched the output of the transmitter (at less than full power) on a
meter
while adjusting the coils. Then watching how much it changes with the
cover, you
can get a feel for how much you need to adjust it in the opposite direction
so it
will be right with the cover on. Adjusting the coupling loop (knob on front
panel) will detune the tank a little too on 40 meters.
On one vfo that I have I tried slug tuned coils in place of the miniductor
stock
to see if they could be substituted. I found that the slug tuned coils in
place
of the miniductors did not give near as much output on the vfo so that was
abandoned .
I also tried to use a higher harmonic for 10 meters and shift the vfo with
an
additional padder capacitor (similar to what is done for 15 meters). I had
a
spectrum analyzer to watch all the harmonics at once but found that I could
not
get enough isolation. Some of the lower harmonics would end up in the
output. I
got it to work but tuning was very tricky and if not looking at the
spectrum
analyzer, the wrong harmonics would get right through the 20A. I gave up on
that
idea.
I do have a vfo with the 10 meter kit in it. The crystal oscillator in it
is run
directly from the 20A's high voltage. When keying the transmitter that
voltage
drops some and the crystal oscillator starts to drift. I think that I tried
running it from the regulated 105 volts one time but that dropped the
output too
low. I have never gotten back to it to try and solve the drift problem.
Other
than that it works pretty well on 10.
I also have a Phase master vfo that I have yet to hook up. It is built on
the 458
parts but rather than use harmonics they have separate crystals and
heterodyne
for the other bands. It may double on one band, I can't remember. The
schematic
of it is in Stoners SSB handbook.
73
Gary K4FMX
Larry Szendrei wrote:
> Mike et. al.,
>
> My CE20A has about 1/2 the output on 40M as it has on the other bands
> (160, 80, 20, & 15) in spite of the fact that the CE mods to cure this
> in the VFO-458 have been implemented. As I recall the VFO output is
> tripled for 40M, and only doubled or on the fundamental for the other
> bands. My VFO doesn't have 10M capability, so have no experience with
> 10M on this rig.
>
> 73,
> -Larry/NE1S
>
> MIke Wells wrote:
> >
> > I'm enjoying the 20A discussion. I have a 20A that I want to get on
the air
> > so keep the messages posted here for the benefit of others.
> >
> > Tell me more about the VFO, are you having good luck with it on all
bands?
> > I've only got mine working on the low bands, no oscillation on 40
meters.
> > Suggestions?
> >
> > 73,
> >
> > Mike W0FD
> >
> > Subject: [AMRadio] "Reply" button got me...
> >
> > Regarding the previous posting to the list: it was unintended. The old
> > "reply" button got me again!
> >
> > If you're interested, read it. It's part of a discussion Jim Candela
and
> > I are having about a vintage SSB exciter, the venerable Central
> > Electronics 20A. If not, the "Delete" button is much more predictable
in
> > its effects than "Reply." :>)
> >
> > 73, and back to AM...
> >
> > -Larry/NE1S
> >
> > _______________________________________________
> > AMRadio mailing list
> > [email protected]
> > http://mailman.qth.net/mailman/listinfo/amradio
> _______________________________________________
> AMRadio mailing list
> [email protected]
> http://mailman.qth.net/mailman/listinfo/amradio
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