[Boatanchors] Low Pass Filter Comparisons

[Peter Markavage]

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
> > _______________________________________________
> 
> 
>