From: "George Pritchard" <[EMAIL PROTECTED]>
Reply-To: amradio@mailman.qth.net
To: <amradio@mailman.qth.net>
Subject: RE: [AMRadio] DX-100 vfo
Date: Thu, 9 Jan 2003 09:49:41 -0500
I realized my misinterpretation of your VFO problem, with the "skewed" dial
indication, after I read the replies. Funny, the dial must have been that
way from day one. Have fun,
George KC
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] Behalf Of russ dworakowski
Sent: Wednesday, January 08, 2003 11:48 PM
To: amradio@mailman.qth.net
Subject: RE: [AMRadio] DX-100 vfo
Thanks for your input Geprge, but you don't get it- the VFO tracks
"tunes" reverse- it is not drifting. I think I have the dial out 180
degrees. Russ
>From: "George Pritchard" <[EMAIL PROTECTED]>
>Reply-To: amradio@mailman.qth.net
>To: <amradio@mailman.qth.net>
>Subject: RE: [AMRadio] DX-100 vfo
>Date: Tue, 7 Jan 2003 15:25:40 -0500
>
>DX100 VFO Troubles:
>Drifting up during transmission: Line voltage drop during plate voltage
>turn
>on with 600 watts pulled from the outlet may the problem. Check by first
>using the spot switch listening to the beat freq on the receiver. Then,
>turn
>on the plate voltage with transmitter fully loaded, and monitor the
drift.
>If the filaments in the oscillator drops in voltage and slightly cools
off
>the tube, the oscillator will drift! See if the oscillator returns to the
>original frequency when the plate switch is turned off. Cure: Use a
variac
>to keep the voltage at >115 VAC during transmit. Or create a DC regulated
>supply for the filament string. Anything much lower than 115VAC and the
>emissions on the 12BY7 / 5763 and 6146s drops also. You may see this as
>gradual drop-off of grid drive during transmit... especially on TEN
meters.
>I also rewired my VFO with heavy #14 copper. This was mechanically
>superior
>to the flimsy wiring that can cause drift and microphonics. Here is the
big
>stability problem: Jumping during VFO freq adjustment on TEM meters. The
>VFO
>main variable has a rear ball bearing to support the cap shaft. It
oxidizes
>and becomes erratic. I tried to clean it, but it was never perfect and
>always degraded again. I finally REMOVED THE DAM BEARING THING and the
>problem was solved. The bearing is not needed as I initially thought. The
>shaft is very stable without it. I hope some of this helps.
>George AB2KC
>
>-----Original Message-----
>From: [EMAIL PROTECTED]
>[mailto:[EMAIL PROTECTED] Behalf Of russ dworakowski
>Sent: Tuesday, January 07, 2003 1:53 PM
>To: amradio@mailman.qth.net
>Subject: Re: [AMRadio] DX-100 vfo
>
>
>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: amradio@mailman.qth.net
> >To: amradio@mailman.qth.net
> >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
> > > > AMRadio@mailman.qth.net
> > > > http://mailman.qth.net/mailman/listinfo/amradio
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> >
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