6146 Replacement

[Glen Zook]

The 6146B/8298A is NOT the same tube as the 6146 and
the 6146A/8298.  The tube is rated at 33% more power
input on CW and slightly more than that on SSB (120
watts input for both CW and SSB whereas the earlier
versions are rated at 90 watts CW and 85 watts SSB).  

RCA originally said that the 6146B/8298A could replace
the 6146 and the 6146A/8298.  However, that did not
actually work out.  Often the 6146B/8298A will produce
spurious signals when substituted for the earlier
versions.

The 6146B/8298A is MUCH harder to neutralize in the
circuits designed for the earlier versions.

Now, depending on the tolerances of the components the
6146B/8298A will work without any problems in
transmitters designed for the earlier tubes generally
between 10% and 20% of the time.  But, I have seen
transmitters of identical models with serial numbers
within 10 of each other in which the 6146B/8298A would
work fine in one yet would not work properly in 3
others.

There are exceptions to this and in the Collins 32S-1,
32S-2, 32S-3, 32S-3A, KWM-2, and KWM-2A the
neutralization capacitor WILL burn up unless the
transmitter has the "new" neutralization circuit.  The
neutralization capacitor that burns up is a ceramic
trimmer.  Later production models of the 32S-3,
32S-3A, KWM-2, and KWM-2A had the neutralization
capacitor changed (and some slight other changes in
the neutralization circuit) so that the military could
use the 6146W tubes manufactured after 1965 (the 6146W
was changed from the 6146A sometime in 1964 depending
on the exact manufacturer).  A field conversion kit
was available for converting the transmitters with the
earlier version of the neutralization circuit so that
they would work fine with the 6146B/8298A.

For the article on the 6146 family of tubes that was
published in Electric Radio a while back go the the
K9STH website the URL of which is listed at the end of
this message.  "Click" on the K9STH links.  The 6146
article is listed first link in the article section of
the website.

Glen, K9STH


--- W5EUQ <w5euq at VERIZON.NET> wrote:

Okay guys.  Question.  Tell me again WHY to not use a
6146B in a DX-40?  Maybe I'm a slow learner on this
subject....   HI.
 
I know the 6146B's are not as good as the 6146A's, for
example.  I also understand they are built somewhat
different to the A model.... and may be the
characteristics are different.....
 
So tell me one more time...but please tell me what is
fact, not what is "wives tales"....   I promise to pay
attention this time...









Glen, K9STH

Website:  http://k9sth.com

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