[Boatanchors] Low Pass Filter Comparisons

[Carl]

Thats my recollection also Eddy.

Carl
KM1H


----- Original Message ----- 
From: "EP Swynar" <gswynar at durham.net>
To: "Peter Markavage" <manualman at juno.com>
Cc: <boatanchors at mailman.qth.net>
Sent: Wednesday, November 12, 2008 2:11 PM
Subject: Re: [Boatanchors] Low Pass Filter Comparisons


> 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
>> _______________________________________________
>
> _______________________________________________
>