[AMRadio] DX-100 vfo

russ dworakowski wb3fau at hotmail.com
Thu Jan 9 12:57:52 EST 2003 

Yes George,  its a jugsaw puzzle,  this is a complete basket case
rebuild,  been a lot of fun though.  Just a few more pieces to figure out- 
hi.  I have it on the air-  getting great audio rpts!  Just minor audio 
mods.  Russ.






>From: "George Pritchard" <gpritchard at comtechpst.com>
>Reply-To: amradio at mailman.qth.net
>To: <amradio at 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: amradio-admin at mailman.qth.net
>[mailto:amradio-admin at mailman.qth.net]On Behalf Of russ dworakowski
>Sent: Wednesday, January 08, 2003 11:48 PM
>To: amradio at 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" <gpritchard at comtechpst.com>
> >Reply-To: amradio at mailman.qth.net
> >To: <amradio at 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: amradio-admin at mailman.qth.net
> >[mailto:amradio-admin at mailman.qth.net]On Behalf Of russ dworakowski
> >Sent: Tuesday, January 07, 2003 1:53 PM
> >To: amradio at 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 <garyschafer at attbi.com>
> > >Reply-To: amradio at mailman.qth.net
> > >To: amradio at 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
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