[Lowfer] Beacon Schematic

Tue Nov 24 16:35:24 EST 2020

Kasey,

I looked at the 4060 datasheet and it recommends the two resistors John D,
was referring to. I guess I should have looked over it before instead of
making an assumption it was like other things I have done. So, I updated
the schematic to show the two resistors. I am not sure exactly what values
to use, but if it doesn't work, we will just have to play with the values.
Without an oscilloscope, you won't be able to see what's happening, but it
shouldn't take but a few tries to get it right.

Regards,
John Hamer
Lowfer JH

[image: simpltx_mod2.gif]

On Tue, Nov 24, 2020 at 7:14 AM KA4SEY <ka4sey at gmail.com> wrote:

> So I just put like a 10M ohm resistor in parallel with the crystal and the
> two 27pf capacitors in series to ground?
>
> Kasey
>
> On Tue, Nov 24, 2020, 12:31 AM John Hamer <wilbur0611 at gmail.com> wrote:
>
> > John Davis,
> >
> > What is the purpose of the resistor between the crystal and pin 10? I
> > understand the one across pins 10 and 11. I mostly design microcontroller
> > circuits and go by the design recommendations in their datasheet, but I
> > have never come across that. Though, that crystal configuration seems to
> be
> > common in these lowfer transmitter designs.  When Kasey was having issues
> > with the oscillator over the summer,  I told him to go to the 2 capacitor
> > configuration so we could easily calculate the values from the crystal
> > datasheet.  I've never had issues with a crystal starting, but I also
> don't
> > have much experience with the 4060.
> >
> > Regards,
> > John Hamer
> > Lowfer JH
> >
> > On Tue, Nov 24, 2020, 12:18 AM John Hamer <wilbur0611 at gmail.com> wrote:
> >
> > > Kasey,
> > >
> > > John is correct about the resistor. I did not mean to omit that.
> > >
> > > John,  thanks for linking those messages. I was trying to find them
> > > earlier to show Kasey, but was having trouble.
> > >
> > > Regards,
> > > John Hamer
> > > Lowfer JH
> > >
> > >
> > > On Mon, Nov 23, 2020, 10:23 PM KA4SEY <ka4sey at gmail.com> wrote:
> > >
> > >> John D.
> > >>
> > >> John H. has helped me out a lot so I'm hopefully on a good path. With
> me
> > >> building a new transmitter with all the new things I have learned it
> > >> should
> > >> do well. I will still leave room for a LPF just in case but like you
> > said
> > >> with the high Q factor it should be fine without one. I'm still very
> new
> > >> so
> > >> any information is helpful. Thanks again
> > >>
> > >> Kasey
> > >>
> > >> On Mon, Nov 23, 2020, 10:16 PM J D <listread at lwca.org> wrote:
> > >>
> > >> > Kasey, I'd really recommend not omitting the 2.2 - 10 meg resistor
> > >> > between pins 10 and 11 of the 4060, and the series 1 - 1.8 K
> resistor
> > >> > between pin 10 and the crystal. Sometimes it'll work without them,
> but
> > >> > other times there is unreliable startup or instability to struggle
> > with
> > >> >
> > >> > Other than that, I thoroughly endorse John H.'s recommendations,
> > >> > particularly the output coupling arrangement and isolation of the
> > tuning
> > >> > coil from ground losses. His experiences with those issues are
> > >> > documented in our discussions of that topic on the LWCA Message
> Board
> > >> > last December and January. You can find them in these archives,
> > >> > particularly the one for January:
> > >> >
> > >> > https://lwca.net/mbarchiv/msg1219.htm
> > >> > https://lwca.net/mbarchiv/msg0120.htm
> > >> >
> > >> > The high-Q tank circuit formed by the properly tuned inductor
> (that's
> > >> > where an RF current meter will help) and the antenna capacitance is
> > >> > normally more than adequate to comply with harmonic and spurious
> > >> > emission limits for Part 15 operation at 1750 meters.
> > >> >
> > >> > I would include provision on your circuit board to add the LPF
> > >> > components later, just in case (1) you find harmonics are a problem,
> > and
> > >> > (2) you are able to actually measure the impedance of the antenna
> > system
> > >> > and adjust the LPF values to match. But otherwise, the filter is
> > likely
> > >> > to result in more problems than benefits.
> > >> >
> > >> > 73
> > >> > John Davis
> > >> >
> > >> > ______________________________________________________________
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