On Sun, 05 Oct 2014 19:30:43 +0100, gareth wrote:

Being somewhat of a polymath (just spent all day fence judging at a
horse trial) I find that I have a string of ideas faster than I could
ever implement them (rather unkindly described in one area as
vapourware), but I think it to be useful to punt them for a wider
discussion.

Musing upon the Huff-and-Puff technique, I wondered if there was a
better way to improve the frequency stability of older RXs,
because the Huff-and-Puff necessarily brings about a punctuated
frequency span (eg, multiples of 32 Hz), and this is what I came up with
...

Using the ubiquitous timers to be found en masse in most micros that
seem to sell for only a few pence / cents these days, implement a
frequency counter to measure the local oscillator. Then, when the user
presses a Lock button (yet to be provided) the same micro can program an
si570 to generate the same frequency indefinitely and to switch the
mixer stage from the original to this new oscillator.

If you are going to go to those lengths, why not program the micro to
recognise the difference between rapid changes of frequency (tuning) and
slower changes (drift) and apply a correctional voltage to a varactor in
the case of the latter. Capture range may be a problem if the radio is a
determined drifter.

On 10/5/2014 3:15 PM, Radiohead70 wrote:
On Sun, 05 Oct 2014 19:30:43 +0100, gareth wrote:

Being somewhat of a polymath (just spent all day fence judging at a
horse trial) I find that I have a string of ideas faster than I could
ever implement them (rather unkindly described in one area as
vapourware), but I think it to be useful to punt them for a wider
discussion.

Musing upon the Huff-and-Puff technique, I wondered if there was a
better way to improve the frequency stability of older RXs,
because the Huff-and-Puff necessarily brings about a punctuated
frequency span (eg, multiples of 32 Hz), and this is what I came up with
...

Using the ubiquitous timers to be found en masse in most micros that
seem to sell for only a few pence / cents these days, implement a
frequency counter to measure the local oscillator. Then, when the user
presses a Lock button (yet to be provided) the same micro can program an
si570 to generate the same frequency indefinitely and to switch the
mixer stage from the original to this new oscillator.

If you are going to go to those lengths, why not program the micro to
recognise the difference between rapid changes of frequency (tuning) and
slower changes (drift) and apply a correctional voltage to a varactor in
the case of the latter. Capture range may be a problem if the radio is a
determined drifter.

I'm not sure I understand the issue. But if you want a digitally
controlled oscillator for your mixer why not just make a digitally
controlled oscillator for your mixer? That is already there with the
Si570. Why the complex usage of using the existing oscillator and then
switching?

--

Rick

"rickman" wrote in message
...

I'm not sure I understand the issue. But if you want a digitally
controlled oscillator for your mixer why not just make a digitally
controlled oscillator for your mixer? That is already there with the
Si570. Why the complex usage of using the existing oscillator and then
switching?

The older RX, with its mechanical tuning, perhaps loaded with
a flywheel, is a much more ergonomic tuning mechanism than
anything that has come out of the semiconductor world.

Therefore, use the existing tuning dial in the first place, and then
lock with the 2nd oscillator.

On 10/5/2014 6:34 PM, gareth wrote:
"rickman" wrote in message
...

I'm not sure I understand the issue. But if you want a digitally
controlled oscillator for your mixer why not just make a digitally
controlled oscillator for your mixer? That is already there with the
Si570. Why the complex usage of using the existing oscillator and then
switching?

The older RX, with its mechanical tuning, perhaps loaded with
a flywheel, is a much more ergonomic tuning mechanism than
anything that has come out of the semiconductor world.

Therefore, use the existing tuning dial in the first place, and then
lock with the 2nd oscillator.

There are controls which can be just as nice to spin as any existing
tuning dial and can control a digital circuit.

What does the existing knob control, an air capacitor? That dial knob
can be connected to another type of control which can be read by the MCU
to control the Si570.

--

Rick

"rickman" wrote in message
...
There are controls which can be just as nice to spin as any existing
tuning dial and can control a digital circuit.
What does the existing knob control, an air capacitor? That dial knob can
be connected to another type of control which can be read by the MCU to
control the Si570.

How would you move the dial pointer in such cases?

On 10/5/2014 7:28 PM, gareth wrote:
"rickman" wrote in message
...
There are controls which can be just as nice to spin as any existing
tuning dial and can control a digital circuit.
What does the existing knob control, an air capacitor? That dial knob can
be connected to another type of control which can be read by the MCU to
control the Si570.

How would you move the dial pointer in such cases?

Why change that?

--

Rick

On Sun, 5 Oct 2014, rickman wrote:

On 10/5/2014 3:15 PM, Radiohead70 wrote:
On Sun, 05 Oct 2014 19:30:43 +0100, gareth wrote:

Being somewhat of a polymath (just spent all day fence judging at a
horse trial) I find that I have a string of ideas faster than I could
ever implement them (rather unkindly described in one area as
vapourware), but I think it to be useful to punt them for a wider
discussion.

Musing upon the Huff-and-Puff technique, I wondered if there was a
better way to improve the frequency stability of older RXs,
because the Huff-and-Puff necessarily brings about a punctuated
frequency span (eg, multiples of 32 Hz), and this is what I came up with
...

Using the ubiquitous timers to be found en masse in most micros that
seem to sell for only a few pence / cents these days, implement a
frequency counter to measure the local oscillator. Then, when the user
presses a Lock button (yet to be provided) the same micro can program an
si570 to generate the same frequency indefinitely and to switch the
mixer stage from the original to this new oscillator.

If you are going to go to those lengths, why not program the micro to
recognise the difference between rapid changes of frequency (tuning) and
slower changes (drift) and apply a correctional voltage to a varactor in
the case of the latter. Capture range may be a problem if the radio is a
determined drifter.

I'm not sure I understand the issue. But if you want a digitally controlled
oscillator for your mixer why not just make a digitally controlled oscillator
for your mixer? That is already there with the Si570. Why the complex usage
of using the existing oscillator and then switching?

He wants a big Eddystone dial, likely connected to a Command Set or BC221
variable capacitor.

Michael

"Michael Black" wrote in message
news:alpine.LNX.2.02.1410052133310.11722@darkstar. example.org...

He wants a big Eddystone dial, likely connected to a Command Set or BC221
variable capacitor.

Partially right, but after recent posts from me on that matter, I
acquired an Eddystone EA12, which is very stable, because, as
its handbook claims, its thermal capacity is large.

However, just before the acquisition, I finally put money where my mouth
is and obtained some heavy grade aluminium plate to form the chassis
of my projected retro rig, and, anticipating oscillator drift wanted to
discuss various ways of circumventing that. I am fully aware of the
huff-and-puff and how it functions, BTW, but the huff-and-puff is
not absolutely stable to suit reception of some digital techniques.

Yes, I do want RX facilities that have the human-friendly big flywheel
knob and moving pointer, an ergonomic appraoch with its visual
feedback that has never been equalled in any rice box.

Think of the difference between using a DVM and an analogue meter
such as an Avometer where visual tweaking is more usable!