[Boatanchors] Electronic T/R Switch vs Coaxial Type

[Bob Macklin]

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
>
> _______________________________________________
>