[Boatanchors] Low Pass Filter Comparisons

[EP Swynar]

Hi Pete,

Well, I've got my 1990 cumulative QST (1945 - 1990) index before me here, &
I'll be darned if I can find the doggone reference, either!

It WAS definitely in QST, because after I read it I went out & bought a B&W
filter...but do you think I can find it now...? I checked under every
category in the index that made sense to me --- including product reviews...

...All to no avail.

Sorry!

~73~ Eddy VE3CUI - VE3XZ


*************************************

----- Original Message ----- 
From: "Peter Markavage" <manualman at juno.com>
To: <gswynar at durham.net>
Cc: <boatanchors at mailman.qth.net>
Sent: Wednesday, November 12, 2008 2:37 PM
Subject: Re: [Boatanchors] Low Pass Filter Comparisons


> I checked the archives again for B&W and Barker & Williamson, and the
> only archive article on B&W low-pass filter was a "Stray" from 1962 that
> someone was selling a B&W lowpass filter. Also checked the Product
> Reviews, which go back to 1980, and no B&W low-pass filter reviews.
>
> Pete, wa2cwa
>
> On Wed, 12 Nov 2008 14:11:35 -0500 "EP Swynar" <gswynar at durham.net>
> writes:
> > Hi Peter,
> >
> > I believe it was written-up in QST way before 2002 --- probably
> > sometime in
> > the early 80's, because after I read the piece, I went out & bought
> > a B&W
> > filter for a linear amplifier project that I was working on at the
> > time...
> >
> > As I recall, the piece even showed 'scope photos of the actual
> > cut-off
> > characteristics of each filter. It was a very good read.
> >
> > ~73~ Eddy VE3CUI - VE3XZ
> >
> >
> > ****************************************
> >
> > ----- Original Message ----- 
> > From: "Peter Markavage" <manualman at juno.com>
> > To: <boatanchors at mailman.qth.net>
> > Sent: Wednesday, November 12, 2008 1:33 PM
> > Subject: Re: [Boatanchors] Low Pass Filter Comparisons
> >
> >
> > > I just checked the QST/QEX/Ham Radio archives, and the only
> > write-up on
> > > various kinds of low-pass filters was done in August QST 2002,
> > page 62.
> > > B&W and Drake weren't covered. There were lots of homebrew
> > articles on
> > > developing low-pass filters. I did not check the 73 or CQ
> > magazine
> > > archives.
> > >
> > > Pete, wa2cwa
> > >
> > >
> > > On Wed, 12 Nov 2008 11:25:07 -0500 "EP Swynar"
> > <gswynar at durham.net>
> > > writes:
> > > > Hi Glen,
> > > >
> > > > The old Barker & Williamson low pass filters were supposed to be
> > one
> > > > of the
> > > > best made, too...
> > > >
> > > > Indeed, some years ago there was a very detailed writeup in QST
> > > > comparing
> > > > many different brands of LP filters, & B&W ranked right up
> > there, as
> > > > I
> > > > recall.
> > > >
> > > > ~73~ Eddy VE3CUI - VE3XZ
> > > >
> > > >
> > > > ************************************
> > > >
> > > > ----- Original Message ----- 
> > > > From: "Glen Zook" <gzook at yahoo.com>
> > > > To: <boatanchors at mailman.qth.net>; "Peter Markavage"
> > > > <manualman at juno.com>
> > > > Sent: Wednesday, November 12, 2008 10:08 AM
> > > > Subject: Re: [Boatanchors] Low Pass Filter Comparisons
> > > >
> > > >
> > > > > One thing that has definitely helped with the TVI complaints
> > is
> > > > the
> > > > widespread use of cable television these days.
> > > > >
> > > > > My main linear is a Tempo 2001 (pair of 8874 tubes) that,
> > > > unfortunately,
> > > > was poorly designed, at least in terms of physical layout.  I
> > was
> > > > traded my
> > > > 2001 brand new back in the 1970s and immediately found out that
> > it
> > > > had
> > > > problems.  Things like the final tank coil is right next to the
> > > > power
> > > > transformer with NO shielding between, almost no bypass
> > capacitors,
> > > > etc.
> > > > The only shielding was the cabinet cover and that did not make
> > > > physical
> > > > contact to the chassis because of heavy paint.  Now the TVI
> > problems
> > > > were
> > > > before cable television, but I leave the filters in place
> > because
> > > > there are
> > > > still a couple of my neighbors that don't have cable even though
> > it
> > > > has been
> > > > available for almost 30 years!
> > > > >
> > > > > It took a lot of work but I was finally able to completely
> > > > eliminate TVI
> > > > from the Tempo 2001.  But, it took 2 of the Drake filters (in
> > > > series) to get
> > > > rid of the last of the TVI.  I do have one on the output of my
> > Heath
> > > > HA-10
> > > > Warrior, on my Heath Apache, Heath DX-100, and a spare, or two.
> > All
> > > > of
> > > > those transmitters are "clean" with the Drake filters in place
> > but
> > > > do cause
> > > > slight TVI on my television sets without them.
> > > > >
> > > > > I tried the Yaesu filter on the Tempo linear and although it
> > does
> > > > help
> > > > some, it is no where near as good as a single Drake.  Now I
> > have
> > > > not
> > > > actually made any "real" measurements of the harmonic
> > reduction.
> > > > But, the
> > > > fact that TVI has been completely eliminated with the Drake
> > filters
> > > > is a
> > > > fairly good indication that they are doing the job.
> > > > >
> > > > > Glen, K9STH
> > > > >
> > > > > Website:  http://k9sth.com
> > > _______________________________________________
> >
> >
> >