help on crystal filter circuits.

[abhilashj]

would any one give me circuit diagrams on crystal filters that would
work on 5ookhz range and very sharp cut of frequeccy so as to
eliminate lower or upper bandwidth of a double side band suppressed
carrier modulator. the band width is one khtz or less. thank u

 

[James Meyer]

On 7 May 2004 04:10:31 -0700, abhilashj@rediffmail.com (abhilashj) posted this:

would any one give me circuit diagrams on crystal filters that would
work on 5ookhz range and very sharp cut of frequeccy so as to
eliminate lower or upper bandwidth of a double side band suppressed
carrier modulator. the band width is one khtz or less. thank u

Present the entire signal to a phase locked loop. The output of the
circuit will be the signal you are seeking.

Jim

 

[Tom Bruhns]

abhilashj@rediffmail.com (abhilashj) wrote in message news:<73c54a84.0405070310.1608a6a8@posting.google.com>...

would any one give me circuit diagrams on crystal filters that would
work on 5ookhz range and very sharp cut of frequeccy so as to
eliminate lower or upper bandwidth of a double side band suppressed
carrier modulator. the band width is one khtz or less. thank u

Go to www.aade.com and download the free Filter Design program. It
will give you design parameters for crystal ladder filters. You must
get a number of nearly-identical crystals; that may be easier/cheaper
at a somewhat higher frequency. Also, search in
rec.radio.amateur.homebrew for articles on crystal filters. There
have been several, and they generally give references to helpful
articles in the ham radio magazines and manuals.

Cheers,
Tom

 

[Tim Shoppa]

abhilashj@rediffmail.com (abhilashj) wrote in message news:<73c54a84.0405070310.1608a6a8@posting.google.com>...

would any one give me circuit diagrams on crystal filters that would
work on 5ookhz range and very sharp cut of frequeccy so as to
eliminate lower or upper bandwidth of a double side band suppressed
carrier modulator. the band width is one khtz or less. thank u

Crystal filters usually work in the 2-10 MHz range.

The 500kHz range SSB filters are all mechanical filters. Collins
is a very well respected name in this area, with more than half a century
of experience:

http://www.rockwellcollins.com/about/additionalproducts/collinsfilters/page1907.html

Tim.

 

[Dbowey]

shoppa posted:
<< abhilashj@rediffmail.com (abhilashj) wrote in message
news:<73c54a84.0405070310.1608a6a8@posting.google.com>...

would any one give me circuit diagrams on crystal filters that would
work on 5ookhz range and very sharp cut of frequeccy so as to
eliminate lower or upper bandwidth of a double side band suppressed
carrier modulator. the band width is one khtz or less. thank u

Crystal filters usually work in the 2-10 MHz range.

The 500kHz range SSB filters are all mechanical filters. Collins
is a very well respected name in this area, with more than half a century
of experience:

http://www.rockwellcollins.com/about/additionalproducts/collinsfilters/pag
e1907.html >>

So what is your point?

Crystal filters work very well at 500kHz and much lower frequencies.

Don

 

[Michael Black]

Tim Shoppa (shoppa@trailing-edge.com) writes:

abhilashj@rediffmail.com (abhilashj) wrote in message news:<73c54a84.0405070310.1608a6a8@posting.google.com>...
would any one give me circuit diagrams on crystal filters that would
work on 5ookhz range and very sharp cut of frequeccy so as to
eliminate lower or upper bandwidth of a double side band suppressed
carrier modulator. the band width is one khtz or less. thank u

Crystal filters usually work in the 2-10 MHz range.

The 500kHz range SSB filters are all mechanical filters. Collins
is a very well respected name in this area, with more than half a century
of experience:

http://www.rockwellcollins.com/about/additionalproducts/collinsfilters/page1907.html

Tim.

The first single-signal selectivity came in the thirties, with a single
crystal filter operating in the 500KHz or so frequency range. Had a pahsing
control to knock out the capacitannce of the crystal holder, and if you
got fancy, various load resistors to get different bandwidths. Wasn't
a perfect filter, but it worked fine for CW where it was most needed.
But it's limitations was due to the single crystal, not the signal frequency.

In this case, something like that might be fine, since he only wants
to extract the carrier. (And he ought to have specified the real problem
because if he's regenerating the carrier there are other schemes.)

Actually, on second reading it's not clear if he's trying to extract the
carrier or select one of two sidebands. That "less than 1KHz" is ambiguous
since it is too narrow for most cases where selectable sideband is needed.

But, just to get back to the issue of filters. One could cascade a number
of those phasing filters to get a better shape factor. Oddly, such
circuits tended to show up as better filter choices came along.

I'm pretty certain the first crystal-lattice filters were at 455KHz.
Certainly in ham circles, they were first made there, using WWII surplus
crystals. I'm not sure if nobody knew how to make an HF filter, or it
just never occurred to anyone, since the standard IF had been down that low.

It was later that HF range crystal filters came along, both home made
and commercially.

Mechanical filters came along before HF crystal filters. But keep in
mind that that was at a time when most IFs were at 455KHz or 500KHz.
I believe it's impractical to make mechanical filters in the HF range,
though I can't think of a reference. On the other hand, at the time
mechanical filters did tend to have better shape factors than crystal
filters, at any frequency.

Michael

 

[Tim Shoppa]

dbowey@aol.com (Dbowey) wrote in message news:<20040508095910.16549.00000956@mb-m04.aol.com>...

shoppa posted:
abhilashj@rediffmail.com (abhilashj) wrote in message
news:<73c54a84.0405070310.1608a6a8@posting.google.com>...
would any one give me circuit diagrams on crystal filters that would
work on 5ookhz range and very sharp cut of frequeccy so as to
eliminate lower or upper bandwidth of a double side band suppressed
carrier modulator. the band width is one khtz or less. thank u

Crystal filters usually work in the 2-10 MHz range.

The 500kHz range SSB filters are all mechanical filters. Collins
is a very well respected name in this area, with more than half a century
of experience:

http://www.rockwellcollins.com/about/additionalproducts/collinsfilters/page1907.html

So what is your point?

Crystal filters work very well at 500kHz and much lower frequencies.

Indeed they do - I recently did a 60kHz filter using tuning-fork crystals
with a bandwidth measured as a few Hz.

That said, 500kHz and a bandwidth of a few hundred Hz to a kHz is
the "sweet spot" for mechanical filters. You can buy crystals in this
range to make your own filters, but your chance of finding the values
you need on the surplus market are pretty much zero, and you'll end up
shelling out a lot of $ to get them made.

If you know of a good supplier for custom-cut crystals in the 300-500kHz range
I'm all ears. Or where to find some already-cut ones in the surplus stream.

Tim.