[Boatanchors] Electronic T/R Switch vs Coaxial Type

Bob Macklin macklinbob at msn.com
Tue Nov 4 19:47:22 EST 2008


The Johnson T/R switch the 2 stages of 6BL7 is very similar to the 2 stages
of 12AU7 in the 62 ARRL handbook.

Bob Macklin
K5MYJ
Kent (Seattle), Wa,
"Real Radios Glow in the Dark"

----- Original Message ----- 
From: "Carl" <km1h at jeremy.mv.com>
To: "Bob Macklin" <macklinbob at msn.com>; <boatanchors at mailman.qth.net>
Sent: Tuesday, November 04, 2008 4:39 PM
Subject: Re: [Boatanchors] Electronic T/R Switch vs Coaxial Type


> Im not counting the rectifier and I should have said stages.
>
> The early Johnson had one RF stage and the 250-39 had two using a hefty
> 6BL7.
>
> Carl
> KM1H
> ----- Original Message ----- 
> From: "Bob Macklin" <macklinbob at msn.com>
> To: "Carl" <km1h at jeremy.mv.com>; <boatanchors at mailman.qth.net>
> Sent: Tuesday, November 04, 2008 6:13 PM
> Subject: Re: [Boatanchors] Electronic T/R Switch vs Coaxial Type
>
>
> > The Johnson T/R switch documentation on BAMA has two tubes.
> >
> > One is a 6BL7 dual triode. The second is a 6X4 rectifier.
> >
> > Mine is a 12AU7 dual triode and the 6X4 rectifier is in my HR-10.
> >
> > Bob Macklin
> > K5MYJ
> > Kent (Seattle), Wa,
> > "Real Radios Glow in the Dark"
> >
> > ----- Original Message ----- 
> > From: "Carl" <km1h at jeremy.mv.com>
> > To: "Bob Macklin" <macklinbob at msn.com>; <boatanchors at mailman.qth.net>
> > Sent: Tuesday, November 04, 2008 2:15 PM
> > Subject: Re: [Boatanchors] Electronic T/R Switch vs Coaxial Type
> >
> >
> >> There are 2 versions of the Johnson. The early one with a single tube
> >> is
> >> the TVI generator, the later 2 tube version is usually OK.
> >>
> >> Use a LPF with any rig, even a BC-610; the software for balanced and
> >> unbalanced lines is online.
> >>
> >> Carl
> >> KM1H
> >>
> >>
> >> ----- Original Message ----- 
> >> From: "Bob Macklin" <macklinbob at msn.com>
> >> To: "rbethman" <rbethman at comcast.net>; <boatanchors at mailman.qth.net>
> >> Cc: "Peter Markavage" <manualman at juno.com>
> >> Sent: Tuesday, November 04, 2008 3:28 PM
> >> Subject: Re: [Boatanchors] Electronic T/R Switch vs Coaxial Type
> >>
> >>
> >> > Do modern solid state TVs with cable connections have the same TVI
> >> > problems
> >> > the old tube TVs did?
> >> >
> >> > I have a 10 year old Sony that gets RF OVERLOAD when I use my 2M FM
> >> > RICEBOX
> >> > that is about 2ft from it with a 19" whip on it. If I turn the TV
> >> > sound off
> >> > there is no problem with the picture. If I tune to cable channel 18
> >> > I
> >> > do see
> >> > some RF TVI but not much. CH18 is in the 2M band.
> >> >
> >> > I need to try it with the new cable DTV converter.
> >> >
> >> > Bob Macklin
> >> > K5MYJ
> >> > Kent (Seattle), Wa,
> >> > "Real Radios Glow in the Dark"
> >> >
> >> > ----- Original Message ----- 
> >> > From: "rbethman" <rbethman at comcast.net>
> >> > To: <boatanchors at mailman.qth.net>
> >> > Cc: "Peter Markavage" <manualman at juno.com>
> >> > Sent: Tuesday, November 04, 2008 12:02 PM
> >> > Subject: Re: [Boatanchors] Electronic T/R Switch vs Coaxial Type
> >> >
> >> >
> >> >> I, like Pete have been running a Johnson TR Switch on the output
> >> >> of a
> >> >> BC-610.  NO TVI!  I monitor the output of the BC-610 with an
> >> >> SM-220
> >> >> w/BP-8.  I also feed my receiver's IF into the SM-220.  I observe
> >> >> NO
> >> >> TVI.
> >> >>
> >> >> I believe that those getting TVI are mistakenly relating the
> >> >> source
> >> >> as
> >> >> the TR Switch.  I only see TVI when over modulating an Apache.
> >> >>
> >> >> Bob - N0DGN
> >> >>
> >> >> Peter Markavage wrote:
> >> >> > I've run a Johnson T-R switch on the Johnson Thunderbolt for
> >> >> > years
> >> >> > and
> >> >> > not experienced any TVI related issues. I also have a Dow-Key
> >> >> > relay
> >> >> > on
> >> >> > the back of my Apache that's been there and working since around
> >> > 1960/61.
> >> >> > The Dow-Key on the back of my Viking II has been there and
> >> >> > running
> >> >> > since
> >> >> > 1955. These relays were some of my better investments.
> >> >> >
> >> >> > Pete, wa2cwa
> >> >> >
> >> >> >
> >> >> > On Tue, 4 Nov 2008 10:36:39 -0800 "BLIMPY" <blimpboy at sonic.net>
> >> >> > writes:
> >> >> >
> >> >> >> Biased vac tube T/R switches have bad reputation as TVI
> >> >> >> generators.
> >> >> >> Many
> >> >> >> in-line filters are not tolerant of impedence mis-matches
> >> >> >> expecially
> >> >> >> those
> >> >> >> with  reactive components.
> >> >> >>
> >> >> >> Run of the Mill Dow Key are second rate relays.. compared to
> >> >> >> Advance
> >> >> >> Coaxial
> >> >> >> Relays.. which are available for less money and will give no
> >> >> >> grief
> >> >> >> due to
> >> >> >> unscheduled liberation of smoke.  Some BNC commerical
> >> >> >> application
> >> >> >> surplus
> >> >> >> relays  with dc  may be contradict this generality.
> >> >> >>
> >> >> >> a vox type t/r switch might be a workable compromise, but not
> >> >> >> true
> >> >> >> break-in
> >> >> >>
> >> >> >> good luck
> >> >> >>
> >> >> >>
> >> >> >> _______________________________________________
> >> >> >>
> >> >> >>
> >> >> >>
> >> >> > _______________________________________________
> >> >> >
> >> >> >
> >> >>
> >> >> -- 
> >> >> Bob - NØDGN
> >> >>
> >> >> _______________________________________________
> >> >>
> >> >
> >> > _______________________________________________
> >> >
> >>
> >>
> >
> >
>
>



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