I have about a half dozen 3.333mhz and 5.0688 crystals.
Each group is with in 100hz of the same frequency when
put into a simple oscillator. I also have a few 11.0592
crystals that are almost as close (probably should get
a few more of these). The 5.0688 and 11.0592 are in
HC49/U cans, the 3.333 are in a somewhat larger sized
can.

Wonder if any of these groups would make a good ladder
filter for a receiver IF strip? I would guess the 3.333
ones would be better for CW, the 11.0592 for ssb, and
the 5.0688 might be a compromise either way?

My general impression is that ladder filter terminating impedances tend to
be based on the general frequency range of the crystals.

I built some 5.000 MHz ladder filters that work best with 270 ohms
termination, while a filter I read about in an article which was at 12 MHz
had 50 ohm impedances.

Of course, one can work with either termination....

In my case, I had calculated that 5.000 MHz IF and 1.2 MHz VCO would
result in a 7 MHz transciever with VERY few mixing spurs anywhere near a
frequency that would bother my design.

So, in general, I think the frequency of a ladder filter can be low or
high, and used for either SSB or CW. But, mixing spurs and so on should be
considered when choosing an IF.


Jim Pennell
N6BIU

My general impression is that ladder filter terminating impedances tend to
be based on the general frequency range of the crystals.

I built some 5.000 MHz ladder filters that work best with 270 ohms
termination, while a filter I read about in an article which was at 12 MHz
had 50 ohm impedances.

Of course, one can work with either termination....

In my case, I had calculated that 5.000 MHz IF and 1.2 MHz VCO would
result in a 7 MHz transciever with VERY few mixing spurs anywhere near a
frequency that would bother my design.

So, in general, I think the frequency of a ladder filter can be low or
high, and used for either SSB or CW. But, mixing spurs and so on should be
considered when choosing an IF.


Jim Pennell
N6BIU

"Ken Scharf" wrote in message
. ..
I have about a half dozen 3.333mhz and 5.0688 crystals.
Each group is with in 100hz of the same frequency when
put into a simple oscillator. I also have a few 11.0592
crystals that are almost as close (probably should get
a few more of these). The 5.0688 and 11.0592 are in
HC49/U cans, the 3.333 are in a somewhat larger sized
can.

Wonder if any of these groups would make a good ladder
filter for a receiver IF strip? I would guess the 3.333
ones would be better for CW, the 11.0592 for ssb, and
the 5.0688 might be a compromise either way?

There's a good article about building ladder filters in QRP Power. Designing
and Building High-Performance Crystal Ladder Filters by Mahkinson, N6NWP.
Was originally in QEX for Jan 1995. QRP Power also reprints an article by
W7ZOI, Refinements in Crystal Ladder Filter Design, from June 1995 QEX.

Mahkinson says "Unfortunately, the required termination resistances of
filters built with [color-burst] crystals may exceed 10k ohms, which
necessitates an impedance transformation with a very high ratio (for a
50-ohm system.). As a result, very high voltage levels may be developed at
the filter input, which may cause an overload condition. In addition, the
required values of the coupling capacitors may be under 5 pF, making
construction difficult due to stray capacitances. For these reasons, crystal
filters with center frequencies under 6 MHz are not recommended."

"The usef ful upper frequency limit is determined by the influence of stray
capacitances at frequencies above 10 MHz and by the limitations imposed on
the VFO circuit for multiband HF operation. Consequently, the recommended
frequency range for an HF SSB crystal filter is between 6 and 12 MHz.: The
remaining criteria for the crystal frequency selection are the crystal Q and
the price."

73,

"PM"

"Ken Scharf" wrote in message
. ..
I have about a half dozen 3.333mhz and 5.0688 crystals.
Each group is with in 100hz of the same frequency when
put into a simple oscillator. I also have a few 11.0592
crystals that are almost as close (probably should get
a few more of these). The 5.0688 and 11.0592 are in
HC49/U cans, the 3.333 are in a somewhat larger sized
can.

Wonder if any of these groups would make a good ladder
filter for a receiver IF strip? I would guess the 3.333
ones would be better for CW, the 11.0592 for ssb, and
the 5.0688 might be a compromise either way?

There's a good article about building ladder filters in QRP Power. Designing
and Building High-Performance Crystal Ladder Filters by Mahkinson, N6NWP.
Was originally in QEX for Jan 1995. QRP Power also reprints an article by
W7ZOI, Refinements in Crystal Ladder Filter Design, from June 1995 QEX.

Mahkinson says "Unfortunately, the required termination resistances of
filters built with [color-burst] crystals may exceed 10k ohms, which
necessitates an impedance transformation with a very high ratio (for a
50-ohm system.). As a result, very high voltage levels may be developed at
the filter input, which may cause an overload condition. In addition, the
required values of the coupling capacitors may be under 5 pF, making
construction difficult due to stray capacitances. For these reasons, crystal
filters with center frequencies under 6 MHz are not recommended."

"The usef ful upper frequency limit is determined by the influence of stray
capacitances at frequencies above 10 MHz and by the limitations imposed on
the VFO circuit for multiband HF operation. Consequently, the recommended
frequency range for an HF SSB crystal filter is between 6 and 12 MHz.: The
remaining criteria for the crystal frequency selection are the crystal Q and
the price."

73,

"PM"

Hi Ken,

I have built a lot of crystal ladder filters over the years using
methods and tools provided by W. Hayward W7ZOI, J. Makhinson N6NWP and
others. Some filters are simple while others can be considered as high
performance ones.

Among the several papers dealing with the subject, I strongly suggest
you read the following :

- A Unified Approach to the Design of Crystal Ladder Filters, W.
Hayward, QST May 1982, pp 21-27

- Designing an Building High-performance Crystal Ladder Filters, J.
Makhinson, QEX January 1995, pp 24-29

- Designing and Building Simple Crystal Filters, W. Hayward, QST July
1987, pp 24-28

You can also have a look at my Web site : roland.cordesses.free.fr
where some designs are presented with their measured characteristics.

73's

Roland F2DC

==============================================

Ken Scharf wrote in message ...
I have about a half dozen 3.333mhz and 5.0688 crystals.
Each group is with in 100hz of the same frequency when
put into a simple oscillator. I also have a few 11.0592
crystals that are almost as close (probably should get
a few more of these). The 5.0688 and 11.0592 are in
HC49/U cans, the 3.333 are in a somewhat larger sized
can.

Wonder if any of these groups would make a good ladder
filter for a receiver IF strip? I would guess the 3.333
ones would be better for CW, the 11.0592 for ssb, and
the 5.0688 might be a compromise either way?

Hi Ken,

I have built a lot of crystal ladder filters over the years using
methods and tools provided by W. Hayward W7ZOI, J. Makhinson N6NWP and
others. Some filters are simple while others can be considered as high
performance ones.

Among the several papers dealing with the subject, I strongly suggest
you read the following :

- A Unified Approach to the Design of Crystal Ladder Filters, W.
Hayward, QST May 1982, pp 21-27

- Designing an Building High-performance Crystal Ladder Filters, J.
Makhinson, QEX January 1995, pp 24-29

- Designing and Building Simple Crystal Filters, W. Hayward, QST July
1987, pp 24-28

You can also have a look at my Web site : roland.cordesses.free.fr
where some designs are presented with their measured characteristics.

73's

Roland F2DC

==============================================

Ken Scharf wrote in message ...
I have about a half dozen 3.333mhz and 5.0688 crystals.
Each group is with in 100hz of the same frequency when
put into a simple oscillator. I also have a few 11.0592
crystals that are almost as close (probably should get
a few more of these). The 5.0688 and 11.0592 are in
HC49/U cans, the 3.333 are in a somewhat larger sized
can.

Wonder if any of these groups would make a good ladder
filter for a receiver IF strip? I would guess the 3.333
ones would be better for CW, the 11.0592 for ssb, and
the 5.0688 might be a compromise either way?

) writes:
On Fri, 23 Apr 2004 03:29:53 GMT, "Paul_Morphy"
wrote:

There's a good article about building ladder filters in QRP Power. Designing
and Building High-Performance Crystal Ladder Filters by Mahkinson, N6NWP.
Was originally in QEX for Jan 1995. QRP Power also reprints an article by
W7ZOI, Refinements in Crystal Ladder Filter Design, from June 1995 QEX.

snipped for brevity
"The usef ful upper frequency limit is determined by the influence of stray
capacitances at frequencies above 10 MHz and by the limitations imposed on
the VFO circuit for multiband HF operation. Consequently, the recommended
frequency range for an HF SSB crystal filter is between 6 and 12 MHz.: The
remaining criteria for the crystal frequency selection are the crystal Q and
the price."

Don't tell Elecraft their 4.9152mhz filters can't work.

We've seen so much about measuring the crystals and then doing calculations
in recent years, that it's easy to forget that hams started using crystal
ladder filters about thirty years ago. Make that a quarter century ago.
The fifth edition of Pat Hawker's "Amateur Radio Techniques" (copyright
1978) and references a number of articles in the France and the UK from 1976
on.

Memory tells me that when such filters started showing up in US publications,
namely QST, it referenced at least some of those articles, but then with
time the key articles have become the later onesin QST.

The synopsis in ART shows some standard designs, and you are supposed
to scale the components for your choice of crystal frequency. And no
mention there (though perhaps it was in the original articles) of
matching crystals. This is rule of thumb work.

Michael VE2BVW

) writes:
On Fri, 23 Apr 2004 03:29:53 GMT, "Paul_Morphy"
wrote:

There's a good article about building ladder filters in QRP Power. Designing
and Building High-Performance Crystal Ladder Filters by Mahkinson, N6NWP.
Was originally in QEX for Jan 1995. QRP Power also reprints an article by
W7ZOI, Refinements in Crystal Ladder Filter Design, from June 1995 QEX.

snipped for brevity
"The usef ful upper frequency limit is determined by the influence of stray
capacitances at frequencies above 10 MHz and by the limitations imposed on
the VFO circuit for multiband HF operation. Consequently, the recommended
frequency range for an HF SSB crystal filter is between 6 and 12 MHz.: The
remaining criteria for the crystal frequency selection are the crystal Q and
the price."

Don't tell Elecraft their 4.9152mhz filters can't work.

We've seen so much about measuring the crystals and then doing calculations
in recent years, that it's easy to forget that hams started using crystal
ladder filters about thirty years ago. Make that a quarter century ago.
The fifth edition of Pat Hawker's "Amateur Radio Techniques" (copyright
1978) and references a number of articles in the France and the UK from 1976
on.

Memory tells me that when such filters started showing up in US publications,
namely QST, it referenced at least some of those articles, but then with
time the key articles have become the later onesin QST.

The synopsis in ART shows some standard designs, and you are supposed
to scale the components for your choice of crystal frequency. And no
mention there (though perhaps it was in the original articles) of
matching crystals. This is rule of thumb work.

Michael VE2BVW