Crystal phasing & single signal reception
 

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

Crystal phasing & single signal reception
 

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

Crystal phasing & single signal reception
 

On Sat, 24 Aug 2013, 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.

When I had an SP-600, I don't remember using the phasing control much.
I'd leave it somewhere, I'd set the BFO and all was generally fine.

When that type of filter came along, it didn't replace anything, it added
something (so there was a wave of commercial receivers where you could get
two models, one without the filter, the other with the filter). The
single signal was because it suddenly did get rid of the audio image.
Tghe phasing control doesn't really change that, it allows some level of
control and you also get a notch at the same time.

DOn't forget the crystal gave really quite high selectivity, the phasing
was simply to balance out the capacitance of the crystal holder. Since
this added some control, you'd see the phasing control on the front panel.
Most of those filters had a selectivity switch, which would vary the
amount of loading of the output of the crystal filter, which allowed for
varying selectivity (though since it was only one crystal, the skirt
selectivity wasn't that great). The wider the filter was, the less effect
the phasing control would have on it. Which is likely why I never saw
much use in the phasing control on that SP-600, I'd generally keep it at
3KHz

MIchael VE2BVW

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

Crystal phasing & single signal reception
 

"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.

Crystal phasing & single signal reception
 

"Michael Black" wrote in message
news:alpine.LNX.2.02.1308241914010.27526@darkstar. example.org...
On Sat, 24 Aug 2013, 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.
When I had an SP-600, I don't remember using the phasing control much. I'd
leave it somewhere, I'd set the BFO and all was generally fine.
When that type of filter came along, it didn't replace anything, it added
something (so there was a wave of commercial receivers where you could get
two models, one without the filter, the other with the filter). The
single signal was because it suddenly did get rid of the audio image.

I think that it can only do that if the CIO / BFO is half way between the
peak
and the notch?

Tghe phasing control doesn't really change that, it allows some level of
control and you also get a notch at the same time.

If the notch is variable, then it will be some other audio frequency which
would be
notched out (clearly you'd go for the most troublesome interference, but
that
would not necessarily be the audio image)


TNX FER contribution OM

Crystal phasing & single signal reception
 

"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

Crystal phasing & single signal reception
 

"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.

Crystal phasing & single signal reception
 

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."

Crystal phasing & single signal reception
 

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

Crystal phasing & single signal reception
 

"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.