[Lowfer] Beacon Schematic

[John Hamer]

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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