[Boatanchors] Electronic T/R Switch vs Coaxial Type

[Peter Markavage]

The early one had two tubes.

Pete, wa2cwa

On Tue, 4 Nov 2008 17:15:07 -0500 "Carl" <km1h at jeremy.mv.com> writes:
> 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
> >>
> >> _______________________________________________
> >>
> >
> > _______________________________________________
> > 
> 
> _______________________________________________
> 
>