[R-390] Re: My R390A

[Todd Bigelow - PS]

Hello Ken and group -

Thought I'd toss in a bit more about the KW-1 and Johnson Desk KW:

6' tall, 675 lbs. Runs a pair of 4-250s(can be swapped with 4-400s) modulated
by a pair of 810s. 150 production models and two prototypes(both of which still
existed last I knew). New price in 1952 was $3850. They started out as a
CW/AM/NBFM transmitter, but apparently sold only as CW/AM(although Collins
later offered a factory modification to the RF deck allowing it to be used as a
linear amplifier). ER put out an interesting KW-1 issue some years back, with a
very interesting story in it about the development of this transmitter and how
one was rushed to Art's house for a contest and the fellows finished
building/assembling it there for a weekend contest. Indeed a sight to behold,
built at least to broadcast industry-standards, a lot of extra shielding for
TVI, including feedthrough caps for any wires passing through the RF deck to
the outside and a hefty lowpass filter for the feedline. As their ads state,
the KW-1 'tunes as easily as the 32V transmitter'.

Desk Kilowatt was built later(late 50s/early 60s) - Johnson's response to the
KW-1, basically. Shares a very similar design (4-250s modulated by 810s) but is
an amplifier only. Even uses the same mod. transfomer. Not a surprise,
considering some parts in the Collins transmitters like variable caps are made
by Johnson. I think UTC made the iron. Something like 400 units produced, not
sure about prototypes. Pedestal(amp) alone weighs in at 403 lbs, desk at 151
lbs, for a combined weight of 554 lbs.

Both unit are rated for 1000w input. Both are superior in one way over the
other as well as lacking the opposite. KW-1 is a complete bandswitching
transmitter, Desk KW is capable of SSB linear amplification stock. Both are
built like the proverbial battleship and are very enjoyable to either use or
service(plenty of space to work inside). The Desk KW even rolls out of the
pedestal for easy service. Both give the term 'boatanchor' an entirely new
meaning!

Belated Christmas wishes and all the best for a Happy New Year -

de Todd/'Boomer'  KA1KAQ

Kenneth Crips wrote:

> RE: KW-1
>
> I have actually had My hands on one.  They where shipped in three
> sections, power supply, Finals deck, and exciter/modulator deck.
> They look just like a Collins AM broadcast band transmitter of the time
> except they where tunable.  I understand they where build so Mr. Collins
> himself would have the king AM signal on the air. As good as a KW-1 is, I
> still think the Johnson Desk Kilowatt was the most interesting. I have
> always thought the best looking equipment from Collins  was the 51J/75A....
> receivers, the 32V.../KWM-1 transmitters.
>
>                           Ken