[Boatanchors] Electronic T/R Switch vs Coaxial Type

[Carl]

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
>>
>> _______________________________________________
>>
>
> _______________________________________________
>