Wonder if Radio Shack 21-543 uses switched capacitor filters as basis.

Google no direct help but does show Rad-Shack parts list that might
be plumbed for an answer.

Would like to move the CW center-freq. around the 750 hz place it's
currently located - per '95 Handbook wherein only a pot's needed with the
MF8CCNs in a design there.

Thnks for the read OMs

Marty aa4rm

PS... now that I've got ur attn, anyone know a 'filter' that hunts
out a hetrodyne freq. and nulls it automatically?



--

For direct reply, strike 3 letters to left of dot in sender address

Time flies like an arrow, fruit flies like a bananna / Groucho

Netnews Marty wrote:

Wonder if Radio Shack 21-543 uses switched capacitor filters as basis.

Google no direct help but does show Rad-Shack parts list that might
be plumbed for an answer.

Would like to move the CW center-freq. around the 750 hz place it's
currently located - per '95 Handbook wherein only a pot's needed with the
MF8CCNs in a design there.

Thnks for the read OMs

Marty aa4rm

PS... now that I've got ur attn, anyone know a 'filter' that hunts
out a hetrodyne freq. and nulls it automatically?




They exist. They've been described in QEX or QST, but I can't remember
the date. It requires making an adaptive filter on a DSP that looks for
highly correlated data and nulls it out. Supposed to work very well.

I think I've seen ads for such things, but my personal radio collection
only includes things that I built or things with vacuum tubes, so I
can't give you any specific information.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Hello, Netnews!
You wrote on Tue, 01 Jun 2004 11:01:35 -0500:

NM PS... now that I've got ur attn, anyone know a 'filter' that hunts
NM out a hetrodyne freq. and nulls it automatically?

- google for "auto notch" filter. Most modern HF rigs have them built in.
Datong FL1 and FL3 were popular add-ons a decade or so ago, you might find
one on ebay.

With best regards, g1lvn (Gareth).
Replace "mycallsign" to reply by E-mail
http://www.g1lvn.org.uk

PS... now that I've got ur attn, anyone know a 'filter' that hunts
out a hetrodyne freq. and nulls it automatically?

Yes, they are used for rock music to get the vocal monitors loud over loud
backline setups
They hunt constant frequency's and sharply notch them out, monitors
engineers best friend.
I personally never tried them on a radio, may not be enough cut like a good
receivers manual notch filter
http://www.samedaymusic.com/product--DBXAFS224
http://www.fitnessav.ca/detail.aspx?ID=11
give em a call

-Joe



"Netnews Marty" wrote in message
...


Wonder if Radio Shack 21-543 uses switched capacitor filters as basis.

Google no direct help but does show Rad-Shack parts list that might
be plumbed for an answer.

Would like to move the CW center-freq. around the 750 hz place it's
currently located - per '95 Handbook wherein only a pot's needed with the
MF8CCNs in a design there.

Thnks for the read OMs

Marty aa4rm

PS... now that I've got ur attn, anyone know a 'filter' that hunts
out a hetrodyne freq. and nulls it automatically?



--

For direct reply, strike 3 letters to left of dot in sender address

Time flies like an arrow, fruit flies like a bananna / Groucho

Netnews Marty aa4rm wrote:


PS... now that I've got ur attn, anyone know a 'filter' that hunts
out a hetrodyne freq. and nulls it automatically?


Hi, Marty

I'm the happy owner of a "Magic Notch" filter, which goes
between the receiver audio output and speaker. It has a
built-in 2 Watt audio amplifier, and requires a 12 VDC wall wart.

Per the manual -
"It has a switched-capacitor active filter which is scanned through
the audio frequencies, and stops scanning when the output drops.
The filter then phase-locks to the interfering signal and tracks
any varitions in its frequency until it disappears."

One nice feature is a green LED indicating power on, which turns
to steady red when the filter is ready to notch out a heterodyne.

The filter is a small grey box, with a bypass switch and a phone jack.
It was a product of "j-Com", but I bought mine from Ramsey
Electronics, Victor NY, who I think took over the j-Com line.

They also made the much more complicated "W9GR DSP II" audio
filter, which includes an automatic notching filter,
and was featured in Sept 1992 QST.

73,
Ed Knobloch

Edward Knobloch wrote:
Netnews Marty aa4rm wrote:


PS... now that I've got ur attn, anyone know a 'filter' that hunts
out a hetrodyne freq. and nulls it automatically?


Hi, Marty

I'm the happy owner of a "Magic Notch" filter, which goes
between the receiver audio output and speaker. It has a
built-in 2 Watt audio amplifier, and requires a 12 VDC wall wart.


Tnx Ed, et al.

Duly noted are the "magic notch,' the Datong FL1/3, & the "monitor's pal"
hetrodyne hunter-killers.

Tnx

But, still haven't got an answer about the Rad-Shark's guts & possible
mod. But perhaps that's a futile quest.

Why do I ask at all? Well to replace the lost adjustable-peak audio
filter in a Navy RAL regen. That's why.

Again, tnx

Marty

PS... now that I've got ur attn, anyone know a 'filter' that hunts
out a hetrodyne freq. and nulls it automatically?

Marty-

I'm not familiar with the part number, but years ago I purchased a Radio Shack
DSP unit. I consider it lousey for its intended purpose, but one thing it did
was remove heterodynes. It was so good at it, that it would also remove the
voice of someone who talked in a monotone!

73, Fred, K4DII