[Boatanchors] 6146B

[peter markavage]

I could probably rationalize in my mind that these Motracs operating
between 30 to 50 MHz, because of circuit design and being very compact,
space wise, could exhibit issues with a different design of tubes, even
though the tubes were stated to be interchangeable. However, many of our
boat anchor transmitters don't operate under the same constraints,
although I would concede that under certain design criteria and maybe, at
10 meter frequencies, some issues might prevail. Of course, in this part
of the amateur radio service using boat anchors, tinkering should be a
fact of life.

Pete, wa2cwa

On Thu, 8 Dec 2005 13:34:34 -0800 (PST) Glen Zook <gzook at yahoo.com>
writes:
> Collins used a ceramic trimmer in the neutralization
> circuit in the earlier S-Line equipment, not a
> compression trimmer.
> 
> It is just not amateur radio equipment that has
> problems with the "B" series.  For example, in the
> Motorola Motrac HHT series the "A" model through the
> "D" model will have major problems when the 6883B (12
> volt equivalent of the 6146B) is used.  The tubes will
> definitely overheat due to spurious emissions.  In the
> HHT "E" model, LHT, and MHT versions the transmitter
> was designed for the 6883B / 8032A / 8552 and work
> fine with the later tube.  However, to go back and try
> to eliminate the problems with using the later tube in
> the earlier models violates the type-acceptance of the
> transmitter and therefore cannot be done if the unit
> is used in the commercial services.
> 
> It is not even different models of transmitters in
> which problems occur.  I have seen like 3 transmitters
> of a particular model with serial numbers within 10 of
> each other.  The "B" worked fine in 1 and not in the
> other 2.
> 
> For a while Heath had specially selected 6146B tubes
> that they supplied with the HW-101 and SB-102 that did
> not have the problems that most "B" series tubes
> exhibited.  I don't know just what the difference was
> between these and the "normal" 6146B.
> 
> Anyway, there are those persons who have never had a
> single problem using the 6146B in place of the earlier
> versions and there are even more persons who have
> definitely had problems.  There is no "obvious"
> solution that does not require some modification to
> the equipment (in some cases minor, in other cases
> major).  It then becomes a question of just how much
> effort the owmer of the transmitter wants to go
> through just to be able to use the "B" series of
> tubes.
> 
> Glen, K9STH
> 
> 
> 
> --- Garey Barrell <k4oah at mindspring.com> wrote:
> 
> I think the problem with the early Collins
> transmitters was that they used a compression trimmer
> for the neutralization. The trimmer cap "burned up"
> because of RF current or ?.   The later transmitters
> used a small air variable trimmer and works fine.
> 
> Glen, K9STH