[Boatanchors] QEX Dec 1988 W3NQN Article

[Bill Cromwell]

Hi Bill,

I was really happy to have those with my old tube radios but now I use 
the DSP stuff. I don't what kind of DSP you have used. I am using 
computer sound card based DSP and I don't have the ringing with it. 
Specifically I use quisk (native Linux version) and Spectran. Spectran 
is a MS Windows application that runs happily in WINE with Linux. I use 
those with my RAK7, BC453, and R-23 along with other radios that have 
barn door passbands. Like the 80 and 40 meter command receivers.

73,

Bill  KU8H

bark less - wag more

On 7/12/20 12:43 PM, Bill Cotter wrote:
> I still have the CW and SSB filters from the Wetherhold article, and use 
> them to this day. Even though I have a K3S and OMNI-VI+ with DSP magic, 
> the W3NQN design doesn't have the ringing and digital artifacts that DSP 
> filtering introduces. However, they don't do anything for noise 
> reduction short of reducing the bandwidth. Using the W3NQN filters last 
> in the audio chain before the headphones seems to be ideal.
> 
> 73 Bill N4LG
> 
> PS: They do wonders for BA receivers that were before DSP.
> 
> 
> 
> At 12:30 PM 7/12/2020, Bill Cromwell wrote:
>> Hi, I once used a passive L-C audio filter built around those. I may 
>> still have it and may still have some more 88 mH toroids ( I once hade 
>> five of them). They did a nice job at the time but other filtering 
>> schemes run circles around them. They do what they always did and are 
>> good for nostalgia:) For on-air use I will take the DSP machines:) I 
>> could be talked into parting with my 88 mH toroids assuming I can find 
>> them:) 73, Bill  KU8H bark less - wag more On 7/12/20 12:09 PM, 
>> w5jo at brightok.net wrote: > Someone refresh my memory abut those coils 
>> Grant mentioned.  I have 10 > coils that, as I recall, are that type 
>> but am short on memory. > > These are toroid and a lot of wire on 
>> them, indicating a large > inductance. There are 5 with Red wire and 5 
>> with Green wire.  If I > recall they are 88 and 44 mH but I can't be 
>> sure. > > Does this ring a bell with anyone?  I inherited them in an 
>> estate from a > local ham who was prone to save things like that and I 
>> did not look at > them until just after reading message from Grant and 
>> Scott. > > Should they be of use, postage will get them. > > Jim > 
>> W5JO > > > -----Original Message----- > > While not Wetherhold’s 
>> filters, there is a Crud-o-ject filter in a 1972 > QST which looks to 
>> have a similar bandwidth. > > I built the later SSB Crud-o-ject which 
>> I wish I still had, but parted > with a long time ago.  I had it 
>> built into a Heath SB-600 speaker.  > These were both basically 
>> “noise and crud” filters, but the original > version for CW is 
>> relatively narrow.  Someone also produced commercial > versions of 
>> these.  It’s too bad that 88/44/22 mH coils have become so > 
>> seemingly scarce. > > Grant NQ5T > >> On Jul 12, 2020, at 11:12 AM, 
>> <whitebear1122 at comcast.net> >> <whitebear1122 at comcast.net> wrote: >> 
>> >> Hi, I'm trying to get my hands on an article from December 1988 
>> QEX.  >> It is >> not available through the ARRL's magazine 
>> Archives.  The article is by >> W3NQN >> titled "CW and SSB Audio 
>> Filters Using 88 mH Inductors. >> >> >> >> I'm looking to build LC SSB 
>> and CW audio filters for my homebrew HBR-13 >> receiver.  I'd like to 
>> narrow up the CW bandpass to something like >> 800-1000 >> Hz. >> >> 
>> Thanks.  73, Scott WA9WFA >> > > 
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