?
Ron
?
In
case you are not aware of my very simple Huff & Puff VFO stabiliser designs,
you can read about them here: ?.
The 2-chip design uses common and cheap IC's 74HC4060 and 74HC74, an ordinary
32.768KHz watch crystal, and a 5mm red LED for tuning. This design works well
and has been successfully replicated by at least 5 different
constructors.
?
73
Hans G0UPL
http://www.HansSummers.com
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I really appreciate your quick reply Raj,
No you did not confuse me.
This forum is alive !
Yes I used the ceramic ones for initial trails. I have some polysterene
ones (old!! from Philips radios) in my junkbox and will do some trials coming
days.
What is your feeling about making the 2 transistor vfo as shown in the
original schematics working with a freq. drift of 10Hz or less (this is a
tough requirement for digimodes like psk31).
Is there experience with the bitx working with digimodes (rtty, psk31...)
as far as you know?
?
73 and again tnx fer advice!
Ron
Raj wrote:
Ron,
????????
This is probably because of ceramic capacitors being used the
oscillator
stages. Components that determine frequency must be ultra-stabe.
Use NP0
caps, brown ceramics with a black top. You can also use
polystyrene,
they are transparent plastic with a silver foil visible
inside. They
were only available in the old days in small pF values less
than
5Kpf.
???????? I usually pour
bees wax on top of oscillator components to keep
them thermally isolated
and keep them from
shaking.
???????? Avoid
ceramic caps in audio stages, it causes microphonics. Tap
them and you
will hear a thump in the speaker/transmission. Use
mylar/polyester.
????????
Do not ! use mylar/polyester type caps in RF stages for bypass,
instead
use ceramic. Polyester work well in audio for
coupling.
???????? Ceramic =
brown round disks
????????
Polyester/Mylar = green like a chewing gum with
leads.
???????? Hope I have
not confused you..
73 Raj
vu2zap
>MHz IF will give the
proper range) Frequency range seems to be ok but
>stability is bad.
After 20 minutes waiting freq shift of 1 KHz still
>exists. I think I
will order some components for a HuffAndPuff
>circuit for stabilizing
purposes.
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