On Sat, 24 Aug 2013 21:06:59 +0100, "gareth"
wrote:

I wonder if some more experienced and senior (in the literal sense) amateur
could explain to me one difficulty that I have in understanding single
signal
reception with the crystal phasing control?

AIUI, the phasing control is adjusted so that the frequency that would give
the audio image is phased out by being in the notch.

If that is true, how is it then possible to adjust the BFO to a
pleasant-for-you tone,
because such adjustment will alter the CIO frequency?

Surely the BFO has to be set in advance to be halfway between the serial
resonant
frequency and the notchable parallel resonant frequency?

This is a query stimulated by my current project which is to build a
boatanchor style
RX, with a flywheel-loaded slide rule dial like that of the Eddystone EA12


The filter is operating on the incoming signal. The BFO frequency is
applied to the output of the filter.

peter

"Peter" wrote in message
...
On Sat, 24 Aug 2013 21:06:59 +0100, "gareth"
wrote:

I wonder if some more experienced and senior (in the literal sense)
amateur
could explain to me one difficulty that I have in understanding single
signal
reception with the crystal phasing control?

AIUI, the phasing control is adjusted so that the frequency that would
give
the audio image is phased out by being in the notch.

If that is true, how is it then possible to adjust the BFO to a
pleasant-for-you tone,
because such adjustment will alter the CIO frequency?

Surely the BFO has to be set in advance to be halfway between the serial
resonant
frequency and the notchable parallel resonant frequency?

This is a query stimulated by my current project which is to build a
boatanchor style
RX, with a flywheel-loaded slide rule dial like that of the Eddystone EA12


The filter is operating on the incoming signal. The BFO frequency is
applied to the output of the filter.


Thanks, but I think that you may have missed the point.

"gareth" wrote in message
...

"Peter" wrote in message
...
On Sat, 24 Aug 2013 21:06:59 +0100, "gareth"
wrote:

I wonder if some more experienced and senior (in the literal sense)
amateur
could explain to me one difficulty that I have in understanding single
signal
reception with the crystal phasing control?

AIUI, the phasing control is adjusted so that the frequency that would
give
the audio image is phased out by being in the notch.

If that is true, how is it then possible to adjust the BFO to a
pleasant-for-you tone,
because such adjustment will alter the CIO frequency?

Surely the BFO has to be set in advance to be halfway between the serial
resonant
frequency and the notchable parallel resonant frequency?

This is a query stimulated by my current project which is to build a
boatanchor style
RX, with a flywheel-loaded slide rule dial like that of the Eddystone
EA12


The filter is operating on the incoming signal. The BFO frequency is
applied to the output of the filter.


Thanks, but I think that you may have missed the point.


IMHO, Peter's reply is the correct opening statement of a response to your
rather unstructured question. If you cannot then use this statement to seed
and to refine your own thought process, it might be more helpful if you
elaborated the point that you think he is missing.

PA

"Peter Able" stuck@home wrote in message
o.uk...
"gareth" wrote in message
...
"Peter" wrote in message
...
On Sat, 24 Aug 2013 21:06:59 +0100, "gareth"
wrote:
I wonder if some more experienced and senior (in the literal sense)
amateur
could explain to me one difficulty that I have in understanding single
signal
reception with the crystal phasing control?
AIUI, the phasing control is adjusted so that the frequency that would
give
the audio image is phased out by being in the notch.
If that is true, how is it then possible to adjust the BFO to a
pleasant-for-you tone,
because such adjustment will alter the CIO frequency?
Surely the BFO has to be set in advance to be halfway between the serial
resonant
frequency and the notchable parallel resonant frequency?
This is a query stimulated by my current project which is to build a
boatanchor style
RX, with a flywheel-loaded slide rule dial like that of the Eddystone
EA12
The filter is operating on the incoming signal. The BFO frequency is
applied to the output of the filter.
Thanks, but I think that you may have missed the point.
IMHO, Peter's reply is the correct opening statement of a response to your
rather unstructured question. If you cannot then use this statement to
seed and to refine your own thought process, it might be more helpful if
you elaborated the point that you think he is missing.

Thanks. but the subject matter seems to have WHOOSHED over your head.

gareth wrote:
"Peter Able" stuck@home wrote in message
IMHO, Peter's reply is the correct opening statement of a response to your
rather unstructured question. If you cannot then use this statement to
seed and to refine your own thought process, it might be more helpful if
you elaborated the point that you think he is missing.

Thanks. but the subject matter seems to have WHOOSHED over your head.

Mine too, I don't really understand what you're asking. The crystal filter
is a bandpass filter. The phasing control affects the symmetry of the
filter somewhat (but not really all that much).
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

In message , Scott Dorsey
writes
gareth wrote:
"Peter Able" stuck@home wrote in message
IMHO, Peter's reply is the correct opening statement of a response to your
rather unstructured question. If you cannot then use this statement to
seed and to refine your own thought process, it might be more helpful if
you elaborated the point that you think he is missing.

Thanks. but the subject matter seems to have WHOOSHED over your head.

Mine too, I don't really understand what you're asking. The crystal filter
is a bandpass filter. The phasing control affects the symmetry of the
filter somewhat (but not really all that much).
--scott

The crystal by itself has a natural 'blow-suck' signal throughput, with
a sharp notch just HF of the peak. The phasing control capacitor should
be able to move the notch to the LF side of the peak, and also (to a
limited extent) to move the notch a little closer to the peak (on either
side).
--
Ian

"Ian Jackson" wrote in message
...
In message , Scott Dorsey
writes
gareth wrote:
"Peter Able" stuck@home wrote in message
IMHO, Peter's reply is the correct opening statement of a response to
your
rather unstructured question. If you cannot then use this statement to
seed and to refine your own thought process, it might be more helpful
if
you elaborated the point that you think he is missing.

Thanks. but the subject matter seems to have WHOOSHED over your head.

Mine too, I don't really understand what you're asking. The crystal
filter
is a bandpass filter. The phasing control affects the symmetry of the
filter somewhat (but not really all that much).
--scott

The crystal by itself has a natural 'blow-suck' signal throughput, with a
sharp notch just HF of the peak. The phasing control capacitor should be
able to move the notch to the LF side of the peak, and also (to a limited
extent) to move the notch a little closer to the peak (on either side).

Ian, with your greater experience than mine, it is the concept of
single-signal reception in which I am interested.

Have you any clues about that, please?

"Scott Dorsey" wrote in message
...
gareth wrote:
"Peter Able" stuck@home wrote in message
IMHO, Peter's reply is the correct opening statement of a response to
your
rather unstructured question. If you cannot then use this statement to
seed and to refine your own thought process, it might be more helpful if
you elaborated the point that you think he is missing.

Thanks. but the subject matter seems to have WHOOSHED over your head.

Mine too, I don't really understand what you're asking. The crystal
filter
is a bandpass filter. The phasing control affects the symmetry of the
filter somewhat (but not really all that much).

A single crystal-plus-phasing-control is NOT a bandpass filter. It is
a SINGLE crystal that has a series-resonant peak and a parallel-resonant
notch, and it is most certainly not a symmetrical response curve.

The phasing control affects the frequency of the parallel-resonant notch.

The reason for my query is that googling threw up the instructions for
a Hallicrafters (SX42, I think) that suggested that the BFO could be
adjusted
AFTER the setting of the phasing control, when it seemed to me that such
action
would move the position of the notch AWAY from the audio image and thus
lost the single-signal facility.

But thanks for your contribution.

A single crystal-plus-phasing-control is NOT a bandpass filter. It is
a SINGLE crystal that has a series-resonant peak and a parallel-resonant
notch, and it is most certainly not a symmetrical response curve.

The phasing control affects the frequency of the parallel-resonant notch.

The reason for my query is that googling threw up the instructions for
a Hallicrafters (SX42, I think) that suggested that the BFO could be
adjusted
AFTER the setting of the phasing control, when it seemed to me that such
action
would move the position of the notch AWAY from the audio image and thus
lost the single-signal facility.

But thanks for your contribution.



Gareth,

The answer is quite simple; unless you move the VFO there will be no
need to change the BFO setting. Adjusting the phasing control is akin to
an IF shift control on a modern radio with the addition of a notch to
the side of the passband which you can move with the phasing control.
Adjusting it will have no effect on the frequency of the received signal
merely the range of frequencies in the passband or the notch.


The only reason that the BFO might need adjusting is pulling of the VFO
which was quite common on early receivers due to poor supply regulation
and the like.

73
Jeff