6146B Question & TVI

[Peter A Markavage]

I agree with the points than Glen presented but have you also considered
the "TV side". What channels are getting interference? What frequencies
are you operating on that creates the TVI? How close is the TV antenna,
if used (indoor or outdoor), is your antenna? Is the TV connected to
cable or satellite access? Is it a number of TV's in your area? Lots of
areas on the TV side of the problem that might need to be checked.

Pete, WA2CWA

On Sat, 15 Mar 2003 08:31:35 -0800 Glen Zook <gzook at YAHOO.COM> writes:
> What rig is it?
>
> If Japanese and designed for the 2001A tubes, then it
> was originally designed for the 6146B and use of them
> shouldn't be a problem.  However, if the rig was
> designed for the 2001 or if it is of US manufacture
> (very few US rigs were designed originally for the
> 6146B), then the finals could still be a problem.
> Tubes do change slightly with operation and spurious
> emissions are possible.  Have you tried a new set of
> finals?  If not, try them first.
>
> Check ALL of the hardware on the chassis including
> that which holds the printed circuit boards in place.
> Slightly loosen and then retighten ALL of the screws
> and bolts.  Almost all rigs make ground connections
> through terminals held in place by screws and these
> either become loose or build up corrosion (which you
> often cannot see).  Corrosion equals diodes which
> equals harmonics.
>
> If there are shielded areas, make sure that all of the
> hardware that attaches the shields is in place and
> tight. If shield uses the lugs that are attached by
> rivets to the shield, move those back and forth on the
> rivets to get rid of any corrosion.
>
> In many years of working on equipment I have found
> either the use of the 6146B in place of the 6146/6146A
> or else loose/corroded hardware to be the problem in
> virtually every case.  If the rig was designed for the
> 6146B, then loose hardware in every case where the
> station grounding was proper.
>
> It is possible to have problems in the supression
> circuitry go bad, but I have only seen this happen
> once in over 40 years of working on equipment (I
> started working on radios when I was a sophomore in
> high school in late 1959).
>
> Check your station grounding.  Corrosion often builds
> up even if you can't see it.  Loosen, "wiggle", and
> then retighten the hardware.  Check the wires for
> orrosion.  If any present, either "cut back" the wire
> or else take a knife, sandpaper, or something else and
> clean the surface of the ground wire.
>
> Check your antenna connections.  Again, corrosion
> builds up.
>
> Have you checked things using a dummy load?  If TVI is
> present using the dummy load then it is definitely
> coming from the rig or the grounding system.  If it
> isn't, then you have to include the antenna system as
> well as the rig and grounding system!
>
> If you have a grid dip meter use it to "sniff" around
> the rig looking for harmonics and spurious emissions.
> If you don't have a GDO but have a scanner, you can
> put the scanner into the search mode and go looking
> for harmonics and spurious emissions.  This often
> works, but not always due to the nature of spurious
> emissions (they can vary in frequency, often at a
> rapid rate).
>
> Since I present seminars on various aspects of
> grounding I have put a synopsis of my presentations on
> the two websites that are listed at the end of this
> message.  Of course those articles only hit the "high
> lights", but they do give a starting place.  There are
> other ways of doing grounding, my way isn't the only
> effective method.  But, what I recommend does work and
> is inexpensive to install.
>
> I do not recommend the "in-line" type of protection
> devices that are "pushed" by certain manufacturers.
> They don't usually hurt anything, but there are
> certainly other things that work just as well, if not
> better, that cost a fraction of the price.  Of course
> the recommendation articles on the websites pushing
> those types of articles just happen to be those
> websites of the people who make the devices!
>
>
> --- Fred Wittman <wittfa19 at EARTHLINK.NET> wrote:
>
> My old hybrid rig (not a Heathkit - sorry) has begun
> putting out horrendous TVI. I figure something in the
> supression circuitry has changed value.  How should I
> approach troubleshooting this?  The outputs are, BTW, 6146B's.
>
> =====
> Glen, K9STH
>
> Web sites

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